Tuning Results From An O2 Kit?

Posted By: RapidRobert

Re: Tuning Results From An O2 Kit? - 03/01/11 03:49 AM

Daytona thank you very much!. I've done all the guessing on the eddy 1406 I can & now it's time to b scientific about it

. I wont b doing any downloading/recording and I wouldn't necc keep it mounted permanently in a vehicle one I get the mixtures dialed in & would want to check several cars. Still the LC-1 kit? Would you suggest a source & a part # as I have no clue what all I need other than the gauge and a sensor of some sort

Posted By: DaytonaTurbo

Re: Tuning Results From An O2 Kit? - 03/01/11 05:19 AM

Robert, just go to ebay and type in innovate lc-1 or lm-1 and they will pop up.

The LM-1 is the bit more expensive one. It's a hand-held unit for around $300 on that auction site. If you want a unit to move between cars, it's the preferred choice. With that one you get a cigarette lighter power adapter, 9v battery, you can get an rpm converter so you can datalog o2 vs rpm and you can get a metal adater so you can stick the o2 sensor up the tailpipe instead of welding a bung into your exhaust system for it.

The LC-1 is the cheaper alternative. On ebay for about $170 you get the sensor/controller and a standard automotive type permanent mount o2 gauge. That unit needs to be properly wired in to power and ground. It would not be nearly as convenient to transfer between vehicles as the LM-1, but for the $ savings you could I suppose. I still needed to briefly hook up the o2 sensor to my laptop to configure it for my analog wideband o2 gauge, not sure if that would be necessary with the digital gauges most of the kits come with. For the price, I just chose to do a permanent install because I like having it. For the most basic setup you need a wideband o2 sensor, a sensor controller and a gauge so you can read the output. For around 170 on ebay you get a kit that comes with all that.

Posted By: RapidRobert

Re: Tuning Results From An O2 Kit? - 03/01/11 05:49 AM

Daytona w your advice I will get on it

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/09/11 01:35 PM

I have been doing some reading trying to take notes on what the correct A/F range should be with a carb'd "street" motor.
I know that this will be a little different across the board, but this is what I have found so far (+ many revisions of this). If you have any additions or changes, please let me know.

12's: Right after cold startup
13's: during the warmup (before actual running temp)
13.8-14.5: N idle (actual running temp)
Hi 13's: in D with foot on brake (example: stop light)
??.?: Stop light to light accel?
14.5: Cruise
12.5-12.9: WOT

Thanks

Posted By: Cudajon

Re: Tuning Results From An O2 Kit? - 03/09/11 02:26 PM

That looks good, however

I like to be lean while idleing it seems to keep the engine from loading up. I also believe with it lean at idle its just starving for me to tap the accelerator, i've never had a bog with a lean idle. I'm running 2X4's Carter comp AFB's and a bog is something you have to really tune out.

Added: Your cooling system needs to be good for a lean idle, some engines will try to overheat.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/09/11 02:45 PM

John,
Is yours a 4 speed or auto?
I am assuming that the 4 speeders can be setup a bit leaner in N than the auto guys due to the idle in D issue. Another variable is the outside temps. I am assuming that in the Summer, I can probably get into the 14's. But right now our temps are in the 40-50 range so I am running mid to high 13's on warmup.

What kind of A/F ratio from a stop (steady accel) ?

Thanks!!

Posted By: JimG

Re: Tuning Results From An O2 Kit? - 03/09/11 02:58 PM

Quote:

How can you achieve 14 plus in N and have it rich enough to get it to warm up?
I cranked my electric choke to the max setting and I left the ms's set at 1 full turn and I will try and restart it again once the engine is completely cold again and see what happens on the guage. If this does not do it, I may consider adapting a manual choke.

Holley-type electric chokes get no feedback from the engine. You just put 12 volts on a bimetallic heater, and the choke begins the process of opening. In an effort to make the choke stay closed longer, you can crank it richer, but then it might be too rich at first startup, and the choke might close when you turn the engine off for 20 minutes. Not good.

I copied (sort of) the factory choke arrangement from the 70's. I bought some normally open temperature switches (50 degrees C, if I remember correctly); they are approximately the diameter of a dime and about 4 times as thick) and put a power resistor in PARALLEL with the switch. Mine worked out to be 10 ohms, but a small rheostat would make it adjustable. I mounted this on a small rectangular piece of stainless steel (so it's purty) drilled a hole and mounted it under one of the intake manifold bolts. The power for the choke is fed through this circuit.

When the engine is cold (and the temperature switch is open), power to the choke flows through the resistor, making the opening rate slower. Once the engine wams up (and the switch closes) full 12 volts is applied to the choke heater.

You adjust the choke so that cold start is right. You tweak the resistor size and the location of the entire mechanism (some places on the engine warm up faster than others) to get the opening rate set properly.

If you're interested, send me a PM and I'll send you a temperature switch - I've got a bunch of them.

Quote:

I am wondering if 14+ in N is just too lean of a goal. I just read a thread where someone said that it is better to run the N reading in the 13.0-13.5 range. I am not sure where to aim for now. The 13.5 range would allow the cold startup to improve until the warmer outside temps get here.

Idle is an area where you should just ignore the meter and set it the old fashioned way, IMHO. Of course, use the meter as a sanity check, but idle is an area where some engines are happy richer or leaner than others.

I'm glad you got a wideband meter. Carb perfectionists such as yourself should have every possible tool at their disposal.

Good luck,

Jim

ETA - switch is wired in parallel with resistor, NOT series. That wouldn't work very well.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/09/11 03:21 PM

Jim,

""When the engine is cold (and the temperature switch is open), power to the choke flows through the resistor, making the opening rate slower. Once the engine wams up (and the switch closes) full 12 volts is applied to the choke heater.""

That is a great idea. I am fighting this right now in the cooler 45-50 degree outside temps. If I set my choke at #3 (3 marks from the back), it is too rich to start. If I set it at 3 marks from the front, then it opens too quickly and with the carb set leaner now (14.2-14.4), it is a fight to keep it running long enough to get some temp into the motor.
I am going to test a couple more positions on the choke and maybe a larger primary squirter and see if I can get the startup a little easier in the cooler weather. If this does not work, then I might get with you on your change. I am hoping that I won't have this much cold startup problems once the outside temps go back up.

Thank you.

Posted By: Mr340

Re: Tuning Results From An O2 Kit? - 03/09/11 06:05 PM

Good info I'm thinking of purchasing a kit soon. One question I have is these lc-1 and lm-1 kits are a single sensor correct/ which bank are you guys monitoring? Or Do you switch the sensor between banks or put the sensor in the H-pipe if so equiped?

Thanks
Gary

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/09/11 06:16 PM

Gary,
I have a O2 bung welded into both of my header reducers. I am currently learning with one sensor in the drivers side reducer. My plan is once I get some tuning time with one sensor, I would like to buy a second gauge for the passenger side just so I can watch both sides. Is it overkill for the second sensor? Maybe, but I would not know for sure until I install it or move my existing sensor to the other side.

Attached picture 6520354-170634GAGE.jpg

Posted By: DaytonaTurbo

Re: Tuning Results From An O2 Kit? - 03/09/11 08:25 PM

On a cold start with the choke on in park, my a/f was in the low 13's during the summer. When fall rolled around and the temps were not far above freezing, that a/f went to the low 14's. I would warm it for 30 seconds, kick it down and go. During that initial part of cold driving where my choke was still closed, I found my a/f didn't really change as the choke opened. However if I tried a cold start with the choke wired open, it would want to run very lean like 16-17:1. I was running a thermoquad at the time with the stock choke with the electric heating element disconnected. Headers, aluminum heads and a stock cast iron intake and I found it took a bit longer than necessary for the choke to open, especially compared to the stock heads w/ manifolds and a functioning exhaust heat crossover in the intake. Next time I would just do a manual choke instead.

Quote:

Good info I'm thinking of purchasing a kit soon. One question I have is these lc-1 and lm-1 kits are a single sensor correct/ which bank are you guys monitoring? Or Do you switch the sensor between banks or put the sensor in the H-pipe if so equiped?

Thanks
Gary

I just picked one bank and installed it. I jet both sides of the carb the same so I don't really see a reason to run two o2 sensors. Another thing I read was running an engine with an unpowered wideband o2 sensor can ruin it because soot/carbon can build up on it and without it being powered, it's heater isn't running to burn that stuff off.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/09/11 08:47 PM

If I go to two o2 sensors, they would both be permanently wired in.
My only thinking of running two was to be able to see if there was any issues with one side or the other.

Thanks

Posted By: DaytonaTurbo

Re: Tuning Results From An O2 Kit? - 03/09/11 09:01 PM

I've read that argument before, but IMO any issues that would cause an a/f variance from one bank to another is something I would notice without an a/f gauge. Unless a jet gets plugged or something it would have to be a mechanical failure of some kind to make one side get out of whack with another. I could see where having one o2 sensor per cylinder could be advantageous if you were hardcore tuning, but I'm skeptical as to the idea that one o2 sensor per bank would supply you with any new information over just a single o2 sensor.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/09/11 09:17 PM

Good point!!

Posted By: Mr340

Re: Tuning Results From An O2 Kit? - 03/09/11 09:54 PM

I guess the idea of monitoring both banks stem from when I used to run a Six pack and the outboard carbs required stagered jetting but now I'm running a 750 holley on an M1 single plane so the jetting should be the same side to side.
I will probobly do as your doing Y07 install a bung on both sides, tune to one, then swap the sensor to see if there is any diff.
I've heard of guys installing two sensors with a switch to one gauge but as you stated the unpowered sensor may foul out.

Thanks,
Gary

Posted By: superbyrd

Re: Tuning Results From An O2 Kit? - 03/10/11 02:13 AM

i picked up this balkamp exhaust analizer a few years ago at a pawn shop for $15. handy as heck for carb tuning......

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/16/11 05:30 PM

12's: Right after cold startup
13's: during the warmup (before actual running temp)
13.8-14.5: N idle (actual running temp)
Hi 13's: in D with foot on brake (example: stop light)
??.?: Stop light to light accel?
14.5: Cruise
12.5-12.9: WOT
-------------------------------------------------------------------------

I have read a few articles lately that show that 14.7 is a good goal for a steady cruising ratio. I have also read where this is too lean and it should be in the upper 13's. What ratio are you running at a steady 45-70mph or so.

Thanks

Posted By: DaytonaTurbo

Re: Tuning Results From An O2 Kit? - 03/16/11 06:31 PM

14.7 is the goal for cars with cat converters. Since we're not running those you can go leaner than that as long as your car will tolerate it without detonating, surging, etc. I tried running mine at 14.7 for a while, then went to 16 and I didn't get any difference in driveability or throttle response. With the thermoquad's easy to adjust primary metering rod tree, the cruise a/f ratio was very easy to tinker with.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/16/11 09:06 PM

I will aim for 14.7 as a target and see how it reacts. If all is well, then I will aim for the 15's and see what happens.
Thanks for the reply.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/17/11 01:35 PM

With a 4 barrel carb, would it be easier to disconnect the secondary side until I get the primary jetting/squirter/cam, pv/pvcr's, and primary WOT done?

Am I going to have any issues just running the primary side at WOT or do I need to test WOT with all four barrels?

Thanks

Posted By: DaytonaTurbo

Re: Tuning Results From An O2 Kit? - 03/17/11 07:32 PM

Do WOT with all 4 barrels. Would be pointless to try and tune the front 2 barrels for WOT considering you will never actually run it like that in the real world.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/17/11 08:52 PM

Daytona,

I can see it both ways.
I could tune the primary WOT only (once the main jets are tuned for cruise, then tweak the pvcr's and pv (2 door vs 4 door) to try and obtain the WOT number) and then hook up the secondaries and then finish the WOT tune on the secondary side, or I can leave it on 4 barrels and tune the secondary to suit. I was just curious which way would be best.

Thanks for the reply.

Posted By: radar

Re: Tuning Results From An O2 Kit? - 03/17/11 08:58 PM

Get the primaries sorted for cruising first then figure out what jets in the back once the front is done.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/18/11 01:49 AM

Are you guys still seeing the 6-10 jet size difference (Holley style carb) from front to back after tuning with the 02 kits?

I think that I have my choke setup about right and after repairing my font squirter threads, I got the car started back up with minimal problems during warmup. I was able to get the neutral idle to 13.8-14.2 which I am comfortable with in 70 degree temps. One more cold startup test and I should be ready to test drive it and check the jetting.

Thanks again.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/30/11 01:25 AM

I think that I have my cold startup problem cured with the Holley Choke Delay Kit. This choke delay allowed my much leaner idle circuit to richen up long enough to get some heat in the motor.

After the engine reached running temp, I leaned out the N reading a little bit more and now I am at 13.8 on the O2 gauge in low 40's outside temps. I will lean this out some more as I drive the car, but for now I am comfortable with that reading. I noticed something that confuses me and I am looking for an answer. In N, the car was showing 13.8 on the gauge, then I dropped the car into D (with my foot on the brake) and the rpms dropped down to 850rpms (which is typical), but the O2 gauge LEANED OUT to 14.2. I was guessing that the 13.8 reading was going to go richer once I dropeed it into D with the extra load, but I was surprised to see it go lean to 14.2. Why did it do this? Is this typical?
EDIT: Am I idling in N on the transition circuit and when I put it in D, it is idling on the idle circuit?

I am just trying to understand the readings a little more before I get it out on the street and start tuning the other circuits.

Thanks allot.

Posted By: radar

Re: Tuning Results From An O2 Kit? - 03/30/11 03:22 AM

To tune my auto trans car's Holley I warmed it up and put it in D with the E-brake on and tuned for a mix of best vacuum and idle quality. A stock cam will like 14:1 afr for idle, a wilder cam will want a richer mix all the way down to the high 12s because of reversion.

Don't tune the idle in N tune it in D. If it has to be 1500rpm in N just to idle at 750rpm in D look for more initial timing or a higher stall converter.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/30/11 11:29 AM

Radar,
I always get my N idle settings close and then fine tune in D with the brake applied.
I am currently idling at 1050rpms in N and it dropped to 850rpms in D. The only thing that I can think of is that I am idling on the transition circuit at the 1050rpms and when it drops to 850rpms in D, it is then on the idle circuit.
I am going to drop my N idle to 975 and see what the O2 readings are. If this is correct, the N O2 readings should lean out some more.

Thanks for the reply.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/03/11 08:54 PM

I got my first day out in the car with the O2 sensor. This is what I found (67 degrees):
N=1000rpms 13.4-13.6 15"hg (rich?)
D=800rpms 13.6 11"hg (rich)
light accel from stop = 13.8 (good?)
light accel with pv open = mid 13's (good?)
Cruise:
40mph= 2200rpms 15.8-16.0 (lean?)
45mph= 2400rpms 15.6 (lean?)
50mph= 2500rpms 15.4-15.6 (lean?)
55mph= 2700rpms 15.4-16.0 (lean?)

I did not test WOT. I was just out for a cruise for the first drive of the season.
Are the 15.4-16.0 readings too lean?

Is the 2200-2700rpms on the main jet circuit or am I still on the transition circuit? I believe that 2200rpms and up are my jetting but I am not sure.
I have read where 4 jets equal 1 full point on an O2 gauge. With my cruise reading high 15's, should I bump up my primary jets by 2 which might be equal to a half of a point on the O2 guage? This would put me in the low 15's if this works out right.

It was VERY windy (45mph + wind), but I did not notice any surging or pinging sounds.

Let me know what you think.

Thanks

Posted By: JimG

Re: Tuning Results From An O2 Kit? - 04/03/11 09:20 PM

Quote:

I got my first day out in the car with the O2 sensor. This is what I found (67 degrees):
N=1000rpms 13.4-13.6 15"hg (rich?)

I would still use the old tried and true vacuum gauge and tachometr method to set the idle, and I'd ignore the meter. The engine wants what it wants.

Quote:

D=800rpms 13.6 11"hg (rich)

See above.

Quote:

light accel from stop = 13.8 (good?)
light accel with pv open = mid 13's (good?)
Cruise:
40mph= 2200rpms 15.8-16.0 (lean?)
45mph= 2400rpms 15.6 (lean?)
50mph= 2500rpms 15.4-15.6 (lean?)
55mph= 2700rpms 15.4-16.0 (lean?)

Pull a few spark plugs after cruising at 16.0 and see if the engine is happy running that lean. Some are, some are not.

You appear to be going leaner as the RPM increases. Here's what I'd like you to do: stay out of the secondaries and stay out of the power valve, and run the car slowly up to, say, 4 - 5,000 RPM in 1st or 2nd gear and see if the AFR continues to climb lean. If so, you need to fix that. If the plugs aren't snow white, and it doesn't continue to go leaner at higher speeds/RPM than you've checked, you have a starting point that some people would kill for.

Quote:

I did not test WOT. I was just out for a cruise for the first drive of the season.

Good. Just be sure it's plenty rich, then tune it after you've got the everything else right.

Quote:

Are the 15.4-16.0 readings too lean?

Is the 2200-2700rpms on the main jet circuit or am I still on the transition circuit? I believe that 2200rpms and up are my jetting but I am not sure.

That is more dependent on throttle position than RPM. Do you have a good feel for how far the throttle plates are open? Are they much past the t-slots or are you just cracking the throttle 2 - 3%? If the throttle is barely cracked and the manifold vacuum is high, it's a sure bet it's the transition circuit.

Quote:

It was VERY windy (45mph + wind), but I did not notice any surging or pinging sounds.

Let me know what you think.

Thanks

Post some info such as primary jet size, MAB size, number, position, and size of primary emulsion bleeds, etc. This carb has 1 - 11/16" throttle plates, right?

If the thing stops climbing lean past 55 MPH/2,700 RPM, you're in VERY good shape!

Jim

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/03/11 09:57 PM

Jim,
I will test to see what the O2 gauge shows on my next drive past 2700rpms.
Current setup:
Quick Fuel SS-750 Annular DP, 66/72 jets, 8.5 hi flow pv (per QF), .028 IFR's, .075 IAB's, 4 metering screws out one full turn. I do believe the buttrtflies are 1 11/16". I think that I am far enough into the throttle to be on the primaries.
Thanks Jim.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/04/11 12:33 AM

These are my updated numbers after another cruise in 76 degree weather.

D=800rpms 14.6 11"hg (this was 13.6 in 64 deg.)
For unknown reasons, the car ran leaner in the warmer 76 temps then it did earlier in 64 deg temps.

light accel from stop = 15-16 (was 13.8 in 64)
Same as above. Leaned out in warmer temps.

Cruise: (Transition lean issue?)
30mph= 1700rpms 17.0 (added)
40mph= 2200rpms 15.8-16.0
45mph= 2400rpms 15.6
50mph= 2500rpms 15.4-15.6
55mph= 2700rpms 15.4-16.0

CHECK THIS OUT
CRUISE: (main jet a tad rich?)
3000rpms in 2nd gear= 14.8-15.0
60mph= 3100rpms 13.6-13.8 (added)
3500rpms in 2nd gear= 13.6-13.8 (same as 60mph)

It appears that the mains are starting in between 2700rpms and 3000rpms. My main jets (66's) might be a tad rich. I swapped out my .071 IABS to the current .075's after the first startup with the O2 kit. Should I go back to the 071's to bring the mains in quicker and to richen the transition?

TRANSITION:
30mph= 1700rpms 17.0
Off idle with a red pump cam and a 037 squirter, I am still getting a lean spike of 16 on the guage from a stop to light throttle. I believe that the 071 IAB's will help this too but I am not sure if my .028 IFR's are too lean too looking at the 30mph thru 55mph readings.

Thank you very much.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 04/04/11 01:46 AM

The IABs have a greater effect with higher air flow. However, the bigger IAB may also delay transition circuit flow. I don't consider myself an expert by any measure, but my thought would be to decrease the IAB size some since it is an easy change, and see how it affects the off-idle transition and low RPM AFR. If that doesn't adequately improve it, then come up a bit on the IFR.

I've been tinkering with my QF Q850PV; it has been rich all over the range (admittedly it is sold as a race carb), but I'm slowly getting closer to improving its street manners.

Dave

Posted By: JimG

Re: Tuning Results From An O2 Kit? - 04/04/11 02:14 AM

YO7:

At this point, I'm most concerned with the occasional 16 and 17 you're seeing. Even 16, where you are not reporting any misfire issues, "might" be on the hairy edge of too lean. Some engines will tolerate mixtures that lean, some will not. Plus, you're measuring 4 cylinders. One cylinder might be leaner than the rest. Before you go any leaner with the MJs, I'd really like you to pull all 4 spark plugs from whichever side of the engine the sensor bung is on, just to be sure everything looks OK.

I agree wholeheartedly w/DaveNC regarding the IABs...go back to the 71s (or smaller), it's quick and easy. You can always pop in larger IFRs if smaller IABs aren't doing it for you.

You're really not far from where you want to be. It appears from your last post that you aren't getting leaner as low-load RPM increases, something I was concerned about.

Keep us posted.

J

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/04/11 11:20 AM

I have .073, .071, and .067" IAB's. I will test the .071's (factory for this carb) and retest later on in the week.
I will shoot for my cruise numbers to be in the 14.5-15.5 range.

EDIT:
Notes:
- I spoke with QF this morning and they suggested that I try and have my main circuit active between 2,000rpms-3,000rpms as a general rule. So far I am right at the high end of that range (2,900rpms-3,000rpm). The smaller air bleeds should get me down lower into that range.

- I have read online where a general rule of thumb on changing jets due to the AF ratio is 4 jet sizes equals 1.0 point of AF change. I asked QF about this and they said that due to the different signals of all of the different engine combos, there is no general rule of thumb when trying to change jets. This is still a test and tune deal. Currently my mains are showing 13.6/13.8 so this puts me about 1 full point lean. I am just trying to think ahead but I need to finish my transition tuning first. I have plenty of jets to choose from but right now, I am guessing at a 2-3 jet size drop on the primaries.

Thank you very much for the replies.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 04/04/11 05:41 PM

Did the QF rep provide any more color to the statement about starting the main circuit between 2K and 3K? I'm still learning the fine points of carb tuning as well, but I don't believe the IABs will have an effect on the main circuit start.

On my car, it appears that due to limited throttle opening, the transition circuit continues to deliver a good bit of fuel, even up in the 3K range (highway cruise), where the mains are starting. The combined fuel leads to a pretty rich mixture. I have been debating on whether I should try and slow down the main activation.

Thanks for your thoughts!

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/04/11 06:07 PM

Dave,
I found this explanation on the web.

"Adjustable air bleeds, while usually found on high-dollar fuel mixers, can have a significant impact on A/F ratio. Not only will larger air bleeds lean out the mixture, they will also delay the effect of that circuit by weakening its signal.

Conversely, installing smaller (richer) air bleeds boosts the signal and speeds up the transition into that circuit. These factors have great influence over driveability."

In my case, since the mains are not starting until apx. 3000rpms, and I need to richen the transition circuit, by installing smaller idle air bleeds will do both. They will richen the transition circuit and also speed up when the main circuit (primary jets) come in to play.

This O2 kit is a great learning tool. I am finding out why I have made changes to my jetting in the past and not received the change that I was looking for. I thought in the past that the main circuit started around 2200rpms or so (per QF. But this is with the stock setup which mine is no longer.) and now once I chart out the rpms and the O2 readings, I can see the jump in the mixture reading that shows me where the main circuit now starts. I am curious how much lower the main circuit will now start when I change from the .075 IAB's to the .071's. I will show my changes once they are known later in the week.

Thanks for the reply.

Posted By: JimG

Re: Tuning Results From An O2 Kit? - 04/04/11 06:19 PM

Quote:

On my car, it appears that due to limited throttle opening, the transition circuit continues to deliver a good bit of fuel, even up in the 3K range (highway cruise), where the mains are starting. The combined fuel leads to a pretty rich mixture.

Dave

Dave, the transition circuit is dependent on manifold vacuum. If the throttle plates are open enough to expose some t-slot, high manifold vacuum will draw fuel/air mix into the engine. This happens ragardless of whether the mains are working or not; it's just that at higher main circuit flow this additional fuel, while still present, becomes becomes lost and insignificant in the much greater fuel being introduced by the main circuit. Conversely, if you're coasting down a hill at say, 22" hg. and crack the throttle open enough to expose some transition slot, there's a good chance you'll see the AFR meter dive rich. The mains aren't working much (if any at all) and you just introduced massive vacuum to the transition circuit.

Quote:

I have been debating on whether I should try and slow down the main activation.

Starting the main circuit sooner and limiting the transition circuit might be the hot ticket for you. I say this because the main circuit is not dependent on manifold vacuum; it's dependent on flow through the venturi.

Jim

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 04/05/11 03:04 AM

Y07_A66,

First, I didn't mean to cause a distraction on your thread. I have read all of these sort of threads in the archives, and was thrilled to see yours. Thanks for sharing the details of what you are doing. It really helps others such as myself to learn.

I do have a wideband and I think a reasonable understanding of carb theory. What I was trying to say was from what I understand the MAB will affect the main circuit activation point. I believe the IAB bleeds air into the idle well, with the idle well getting fuel from the main well via the IFR. As such I don't understand how the IAB could affect the main circuit activation. However, I'm still learning, and appreciate other thoughts on this. There are a bunch of knowledgable folks here, and I continue to gain the benefit of others posts.

In many ways, your are in a much better position than I since you need to add fuel, not take it away. I look forward to your results!

JimG,

I have read many of your posts on carb tuning in the archives, and appreciate your comments. Can you explain some more how the IAB change can affect the main circuit activation? I do have about 20" Hg during highway cruising, and believe even at 3K most of the fuel is still coming from the transition circuit. I didn't mean to get into the details of my setup on this thread (that seems like poor form!), but I would like to better understand your comments better.

How do you limit the transition circuit flow? As you noted, the main circuit is driven by flow. At 65MPH, you may need around 35HP?, which is not a lot of flow. Under these conditions, how can the transition circuit flow be reduced?

The only way I see is to have a greater throttle opening (lowering vacuum), but this will increase HP which will increase vehicle speed.

It seems like the transition is going to be providing most flow under light throttle, and the mains may be delivering just a little. Of course I can lean the transition via the IFR, which will get the cruise AFR into better shape but then the low end of the transition will be lean. I understand I need to get the best balance and shape of the AF flow on each circuit, it is just taking a lot of trial and error!

Thanks for your comments!

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/05/11 11:31 AM

Dave,
""First, I didn't mean to cause a distraction on your thread. I have read all of these sort of threads in the archives, and was thrilled to see yours. Thanks for sharing the details of what you are doing. It really helps others such as myself to learn.""

No distraction at all!! I too am learning about this process and I hope that Jim will use this thread to answer your questions.
I will continue updating this post with my results but Mother Nature is keeping me in the garage this week.

Posted By: JimG

Re: Tuning Results From An O2 Kit? - 04/05/11 02:50 PM

Hi Y07_A66:

DaveNC beat me to it. If you want us to start another thread for this discussion, we'll move on. I don't want to hijack your thread either. At this point, we're just discussing theory that sort of pertains to some of what you're doing. Just say the word and we'll start a new thread.

Hi Dave:

Where are you in NC? We might be next door neighbors. I'm on the southern border of NC in central VA.

Here's the essesnce of the battle being fought by many of us who are trying to tame high HP engines to drive them on the street with good manners at 1 - 2% throttle opening.

You've most likely got a very responsive engine that doesn't need much throttle opening to make the few horsepower it takes to move it down the street (or highway). You've probably got a carb with large throttle plates. Larger throttle plates = smaller opening angle to achieve a given airflow. Many times, this small throttle opening puts your throttle plates smack-dab in the transition slots. Note also that your plates most likely aren't open enough to get the main circuit flowing much, if any at all. So you're cruising down the road operating almost solely on a circuit that is dependent of manifold vacuum, not airflow.

Compounding this problem is the fact that you perhaps have a cam that produces low idle vacuum. So, you get out your box of drill bits and brass set screws and get the Idle Feed Restrictions (IFRs) and Idle Air Bleeds (IABs) sized just right. You've got that sucker idling great with 1 1/2 turns out on the mixture screws; the holy grail according to everybody. Life is good.

Problem is, out on the highway, you're tooling along running pig rich at 20 or 22" hg. Open up the throttle and the carb seems to behave just fine, but you want to drive this car on trips, and this simply won't do.

The problem here is twofold. One, you're driving on the t-slots and not the main circuit. Two, the transition circuit is rich because orfices that are propely sized for 8" hg are too large at 20" hg.

This is why the factory embraced spreadbore carbs when emissions laws tightened up. The smaller primaries allowed greater throttle openings, which ensured that the main circuit was working.

OK, on to your question. Fuel and air for the transition and idle circuits comes from the IAB and the IFR, as you know. After the fuel and air are mixed, there is a "fork in the road". The mixture flows unrestricted to the t-slots, while it flows to the curb idle discharge ports after being restricted by the idle mixture screws.

To limit the transition flow, use the smallest IFR/largest IAB possible and still get a decent idle. Your idle screws will most likely be more than 1 - 1/2 turns out, but as long as you still have adjustability and the idle doesn't suffer compared with what you have today, it's a compromise that we must endure. Once you reach the point where the idle screws have no response, you've gone as far down that path as you can.

Further, any effort that achieves greater idle vacuum allows you to further restrict the idle circuit (IFRs and IABs), thereby restricting the transition circuit. Note that you are still cruising on the transition circuit, but at least you've found a way to lean it out somewhat.

In a perfect world, we'd be able to adjust the length and width of our t-slots. Alas, our world is not perfect.

You can also make and install t-slot restrictors is the main body. This sometimes helps when engines have low idle vacuum/high cruise vacuum, but there are problems inherent with them that usually rear their heads before the problem is totally fixed. I'll elaborate later, but this post is long already.

Back to Y07_A66's results: he's got a very good starting point. He has a carb with annular boosters which is helping the mains get started at lower airflow. Y07_A66, when you get a chance, post your idle vacuum, cruise vacuum, and number, position, and size (if known) of your emulsion bleeds. Based on your data, you don't have any rich spots at light throttle/high vacuum. I'm curious how high your "high vacuum" gets.

Thanks,

J

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/05/11 04:37 PM

Jim,
Please keep posting Daves questions on this thread!! Your information helps us both.

Idle hg: 14.5" Neutral @ 1000rpms
11.5" in D @ 800rpms
30mph: 16"hg @ 1700rpms (.075" IAB's = 17.0)
40mph: 16"hg @ 2200rpms (15.8-16.0)
45mph: 17"hg @ 2400rpms (15.6)
50mph: 18"hg @ 2500rpms (15.6)
55mph: 20"hg @ 2700rpms (15.4-16.0)
Main Circuit starting:
60mph 3000rpms (14.8-15.0)
65mph: 17"hg @ 3300rpms (not measured)
70mph: 3500rpms (13.6-13.8)

Sorry, I do not have the emulsion bleed info.
I will update the info above once I test the .071 IAB's so that we have a comparison.

Please carry on.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 04/06/11 02:43 AM

Jim,

I live in the Raleigh area, a bit over an hour from the VA border but east of you.

I'm certainly in the battle for taming a high HP engine for regular street use. Your description is perfect. My situation is even further complicated by use of a stock 440 torque converter for the time being (started with a MP 175K converter behind my engine, but it was too loose for my taste during normal street driving), and use of a single plane intake manifold (M1) which really complicates the idle situation (more on that in a moment).

I found your comment on spreadbore carbs interesting. Obviously some stock racers can get great performance with ones like the Thermoquad but from a high performance standpoint, I wonder about potential fuel distribution issues with the biased flow in such a carb (ie cylinders 1&2 running leaner). The smaller primaries would be a great solution for my challenges though. Clearly a fuel injection setup would be easier to tune for the various conditions for a street/strip vehicle, but that is not in my budget at the moment! Besides I still feel my carb should be able to work better than it currently is, and I don't overly mind the challenge.

So, back to the theory. Your recommendation to use the smallest IFR and largest IAB possible makes a lot of sense, along with starting the mains early to overlap the transition circuit to cover the lean area. I have already explored that path a bit, and got to a state where I could not cure an off-idle (1200-1300) lean miss and had to come back up on the IFR some. I should probably invest more effort in this direction though but the cam timing certainly presents low RPM mixture challenges. My thinking is that the large IAB was delaying the start of the transition circuit.

I had heard mention of transition slot restrictors before, but don't have a good appreciation of the way to implement this. Also, I can see that it would be fraught with potential problems. Can you explain some more about this?

Currently I have been considering two different directions. One, as I mentioned, was to try to delay the main activation some. However, your comments are reinforcing my thoughts that the majority of the fuel is coming from the transition circuit, and as such delaying the mains would have a muted impact.

The other direction I am considering is switching to a dual plane intake (EBrock RPM). Many seem to be making good power with this. I believe this may help in two ways. First, it should improve the idle vacuum, which hopefully will allow a slightly leaner mixture while still maintaining a stable idle in drive. Second, because each cylinder would only see 1 barrel of primary, it seems to me that the throttle opening position would be increased relative to my current setup, with the benefit of lowering the highway cruise vacuum level, which should reduce the draw on the transition circuit. Would you agree that I could expect both of these benefits from a DP?

Thanks for the thoughts!

Dave

Posted By: JimG

Re: Tuning Results From An O2 Kit? - 04/06/11 01:56 PM

Hi Dave:

You're not far from me at all. Let me know when there's a good cruise-in down your way and I'll come by and we'll hoist our favorite beverages and talk cars.

Regarding t-slot restrictors: look here

http://www.carcraft.com/techarticles/ccrp_0807_holley_carburetors_basics_guide/carb_main_body.html

drill and tap passage "H" to 8-32. Buy some (preferably) brass set screws (McMaster-Carr) and some numbered drill bits, if you don't already have them. Drill an orfice in the set screw as required.

That's the how. Here's the "when should I".

As a last resort!

As I previously stated, this is a trick that's sometimes handy on cars with low idle vacuum and high cruise vacuum after you've reliably determined that the transition circuit is sucking too much fuel at cruise. If you've reached the end of the road with smaller IFRs, and you're satisfied that you've done everything possible to increase idle vacuum (which will allow you to further decrease IFR size) this might help.

I use an Excel spreadsheet to keep track of changes, and I let Excel do the following math. Measure the length and width of the primary t-slots, and get the area. Next, using pi r^2, figure out a hole size that has roughly 75% of that area. That's a good starting point. Do this math every time as a sanity check.

This is a far less than perfect solution, but for those of us working with basic tools in our basement, it's all we've got.

My personal experience says that t-slot restrictors will help in situations of low idle/high cruise vacuum, but not totally fix it. What happens is, the restrictors get small enough that you eventually create an off idle bog at the same 2 - 3% throttle position that's screwing you at cruise, and this bog shows up before the rich cruise problem is totally fixed. Remember my previous comment that orfices sized for 8" hg are too large at 20" hg.

I'll pass on your intake manifold question. Modern single plane designs have surprised me. Maybe you can find someone who has experience with both of the manifolds you're considering on the same engine.

And the big problem with spreadbore carbs (as I see it) is lack of manifold choice. Not much out there, comparatively speaking. But if your car is truly a street car, they deserve some consideration.

Take care, and post your progress.

Hey Y06, how are you coming along?

J

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/06/11 04:02 PM

""Hey Y06, how are you coming along?""

I am waiting on Mother Nature to allow me my next test drive. I have swapped out the .075" IAB's for .071" IAB's. I also have .067" IAB's if needed.

Thanks

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/07/11 12:55 AM

I got some time tonight to test the .071" and the .067" IAB's. The following show the results:

-.075" -.071" - .067"
30mph 1700rpms 17.0- 16.6 - 16.0/16.2
40mph 2200rpms 16.0- 16.0 - 16.0
50mph 2500rpms 15.6- 15.6 - 15.6/15.4
55mph 2700rpms 16.0- 15.6 - 15.0/15.2
60mph 3100rpms *13.8- 14.0 - 14.0/14.2
65mph 3300rpms N/A- 13.8/14.0 - 13.8

* This could have been a wrong note taken. All of the above tests were done during a windy day. I did my best to keep the throttle even.

.071/.067 notes: 67 deg.
These numbers are after I retuned the carb for best in D idle vacuum.

My light accel at all speeds was 13.8/14.0 with red cam and .037 squirter. This setup should change after I richen up the transition circuit.

My N and in D A/F numbers richened up to 13.6 (.071) and 13.4 (.067), but it seems to like those readings. I had smooth light accel from a stop on each IAB size.

I am still lean on the transition below 2700rpms but above 2700rpms, the 66 primary jetting is looking good.
Is it time to swap IFR's from the current .028" to .031's, or go up to .033's?
I only found three of my .031's, I need to dig some more.

Would it do any good to stick the .031 IFR's in the primary side only for a test since I only have three?

Thanks

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 04/07/11 03:14 AM

Jim,

I'm very impressed that you are happy to drive your ride significant distance just for a car gathering....I hope I get my car to that point some day!

Really appreciate the information on the T-slot restrictors. I guess there could be some value to it, but as you highlight it is likely to create a new problem at the low end of the transition. I don't think I'm going to head down that path.

The M1 can accommodate a TQ, but all I have is an old 800CFM one which is too small. I vaguely remember that there was a 1000CFM race unit, but then I have to worry about all of the tuning parts, and as I mentioned, my perhaps not well founded concerns on fuel distribution. So for now, that is also not a path for me.

My intake manifold question is likely one that no one else can answer from a empirical standpoint, since there are so many variables involved. At this point, I am committed to trying the experiment, and will need to gather enough data under various conditions to hopefully be able to come to a definitive conclusion. If I come up with anything interesting in the next month or so, I'll post again.

Thanks again for the food for thought.

Dave

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 04/07/11 03:20 AM

Y07_A66,

What is your goal for the light throttle AFR?

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/07/11 11:35 AM

Dave,
My current goal is to see the cruise A/F around 14.7-15.5 range. This is just a guess from the reading that I have done. This goal means that I still need to add about 1.2 to the transition circuit, so it appears that I need to work with the IFR's to make that large of a change.

I do know that I was getting light surging at 17.0 (30mph) and the car still feels a little strange with a 16.0 reading at 30mph too.
If I can get into the low 15's and get rid of the 16+ readings, then I think that would be safe enough to move on to the main jetting.

OOPS,
After all of that, you said light throttle. I have read where light throttle accel should be in the low 13's, so once I get my transition where I need it, then I will tackle the primary pump setup. But the current readings 13.8-14.0 seem fine for casual driving.

Thanks Dave.

Posted By: JimG

Re: Tuning Results From An O2 Kit? - 04/07/11 01:29 PM

Quote:

I am still lean on the transition below 2700rpms but above 2700rpms

YO7_A66:

I think you may have answered this in a later post, but please elaborate on this. Is there a lean spike when you tip the throttle in? Is is surging/missing at steady cruise below 2,700 RPM? Post all the details you can.

Based on your later post, it sounds like you need more primary IFR or less IAB.

Post back with a few more details when you get a chance.

J

Posted By: JimG

Re: Tuning Results From An O2 Kit? - 04/07/11 01:42 PM

Quote:

I guess there could be some value to it, but as you highlight it is likely to create a new problem at the low end of the transition. I don't think I'm going to head down that path.

Hi Dave:

I didn't mean to scare you off from the TSRs. I just didn't want you to think you'd found the magic bullet that would fix everything. I can say this...with low idle/high cruise vacuum engines with rich cruise such as the one you're describing, I've never failed to make some improvement with TSRs. I've also never totally fixed the problem with them either, for reasons previously described.

And really, you don't even have to drill passage "H" - it's already so close to 8-32 that all you need to do is tap it 1/2" deep or so. If the TSRs don't work out for you, you just remove them and go on about your business. No harm done whatsoever. I don't want tyou to think installing TSRs means butchering your carb.

You also talked about delaying the start of the mains, which is another option that might work. Personally, I'd like to see the transition limited first, and mains working as early as possible. I think the end result will be better that way.

So far, we've talked theory and generalities. What are the specifics of your setup?

Yes, I'd drive to Raleigh for a good cruise-in, recommended by a local who's in the know. I finished installing a Keisler TKO 600 in my sig car JUST before they announced a better option, and just before Jamie Passon announced his new bolt-in overdrive tranny. Sigh. Talk about great timing, huh?

J

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/07/11 02:04 PM

""Is there a lean spike when you tip the throttle in?""
When I had the .075 IAB's and my metering screws were not dialed in, the answer was yes.
The 071's (MS dialed in) and the 067's did not show a lean spike at tip in. The light accel from a stop and cruise to light accel both showed 13.8-14.0 on the guage with the red/037 primary pump setup.

""Is there surging/missing at steady cruise below 2700rpms?""
30mph [1700rpms] (.067"=16 / .071"=16.6) there was a slight surge.
40mph [2200rpms] (.067"=16 / .071"=16) there was a slight surge.
50mph [2500rpms] (.067"=15.6 / .071"=15.6) there was no surge felt. It seemed that once the cruise was richer than 15.6 or so, there was no surge at any rpm level. It appears that 15.6 might be my lean limit.

My thoughts are to test .031" IFR's front/back and go back to the .071" IAB's (stock for my carb) and see where the readings go.
Note:
I need the gauge to read about 5-7% richer between 1700rpms and 2700rpms. If I swap out the .028 IFR's to the .031 IFR's, that will give me about 10% more fuel available in the transition circuit.

I called QF and they suggest that I do not go richer than .067" on the IAB's with a gasoline setup. So my current IAB's are .067,.071,.073, and .075 IAB's. I will also have the current .028 IFR's, plus .031 and .033 IFR's to test with.
The next five days show storms, so I won't be able to give any updates for a while. This will give me some time to get the lost .031 IFR's on order.

Since I am going to have the front metering block off, I am thinking of swapping out the 66 jets for some 65's since my reading at 60mph (3100rpms) is down around 14.2 and it goes lower at 65mph (3300rpms) to 13.8.

Thank you very much for your time.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/01/11 09:13 PM

UPDATE:
The weather allowed me to test drive the car again with the following changes:
.028" IFR's to .031" IFR's [lean trasition circuit, 15-16+]
66 main jets to 65 main jets [60mph/65mph was in the mid to upper 13's]
.071 IAB's [back to stock setting]

I started out after a short drive tuning the in D idle A/F ratio and I got it to 13.8-14.2 which made it idle nice at 850rpms. Then I started the test drive.

The following shows the last test drive (first) and todays results second. The 028" to 031" IFR's made a big difference (no more 16+'s) and they put me right about where I am guessing that I need to be for cruise.

64 degrees:
25mph ----------------14.0
30mph 1700rpms (16.2) 14.6
35mph ----------------14.6
40mph 2200rpms (16.0) 14.6
50mph 2500rpms (15.6/15.4) 14.6
55mph 2700rpms (15.0/15.2) 14.0
60mph 3100rpms (14.0/14.2) 13.6
65mph 3300rpms (13.8) 13.8

Then I tested my WOT from a cruising 40mph to WOT and it showed 12.2 and then slowly climbed to 12.5 before it shifted into 3rd.
Then I tested my WOT from a cruising 55mph to WOT and it showed 11.8 and then slowly climbed to 12.5 before it shifted into 3rd.
I am guessing this rich WOT reading immediately at WOT kickdown, might be from my secondary pump cam combo which is a red/031. I am going to retest with a smaller cam, maybe the pink/031 to see if the number keeps from dipping down to the 11.8-12.0 mark. If this does not work then I will look at the secondary jetting. It is currently at 75.
Is 13.6/13.8 too rich for 60/65mph? I could drop another main jet from 65's to 64's and retest. The outside temps are still fairly cool at 64 degrees today, so Summer may have me leaning it out anyway. I am surprised that my 60/65mph A/F ratio did not change since going from 66 to 65 main jets. I am wondering if I am still not on the main jets at these speeds. REF: My only 70mph test showed 3500rpms @ 13.6-13.8.

When I got back from my drive, the in D reading stayed at 14.0 and then I watched my N reading and it richened up to about 13.4 from when I initially left the garage when it was about 14.2. The car did not like the leaner N reading of 14.2 and it showed lean while driving until I got to stop and retune my in D A/F ratio as shown above.

Posted By: JimG

Re: Tuning Results From An O2 Kit? - 05/02/11 03:16 AM

The weather is breaking! Everybody's out with their cars. 3 cheers for springtime!

Can I talk you out of changing 3 things at once? It obviously worked, but I'm just sayin...

If you can get a leaner cruise than 13.8 without upsetting the balance (and you're pretty darn close now) sure, go for it! It seems to be going richer as you go faster (14.6 to 13.8). Any way you can safely cruise it faster than 65 MPH and see what happens? (IE, does the curve continue toward rich) You might try a larger MAB, which will lean it out at higher airflow. What size do you have now? (I searched this page for the answer and nothing came up). Hopefully, you have some that aren't a huge jump up from what you have now. As I said, you're close.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/02/11 11:34 AM

Jim,
Now that I have had a few hours to think about it, I don't want to open up the carb just yet. I am currently running the stock .033" MAB's and I "think" that I have a set of .036". I will check tonight. Once I swap out the MAB's, I will test it up to 70-75mph to see what the curve does.

Thank you very much for your help.

Posted By: radar

Re: Tuning Results From An O2 Kit? - 05/02/11 01:05 PM

Wow great stuff here.

I tried to post fishing for experienced answers about these issues here and got nothing. I'm currently trying to dial in my 750 dp for street driving and the tuning is starting to involve wires in the idle feed restrictions. I already ditched my main body for a HP version for the bleed tuning.

My issues are similar- I have a strong motor with a race carb that is a pain in the butt in traffic. The carb cruises super rich on the t-slots and the transition to the mains is jerky as the proper mix takes over and good power hits

I already switched from a single plane to an air gap and put a four hole spacer (secondary opened up now a three hole) in an uneducated attempt to boost the signal to the carb. I was thinking more vacuum would give me the street performance of a smaller carb but it probably just sucked harder on the rich mix in the t-slots.

Thanks for all the in depth tuning results. It seems like most guys just live with a bad street tune as long as wot is good. I moved close to work in a congested area so I need to get dialed in.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/02/11 05:01 PM

""Thanks for all the in depth tuning results.""

My main reason for posting all of the details is because I ran into the same problem as you. I could not find allot of information or any articles that showed the progression of the tuning with actual results. I could find some reading here or there, but not any from beginning to end. Hopefully this will help others that run into the same questions that I have had trying to tweak in their carb.
So far, I can't think of a better tuning tool for a carb than these A/F kits!!

FOR REFERENCE:
I still can't get over what 1/12 of a turn on the metering screws will do to the A/F ratio.
If I turn all four of mine from 11:00 to 12:00 positions (for reference), this could be .5 difference on my guage. I would have never guessed that before this process started.
.028" IFR's to .031" IFR's showed a 1.4 to a full 2.0 change in my cruising A/F ratio at the same speeds.
.075" IAB's to .071" IAB's showed .4 to .6 change in my cruising A/F at the same speeds.

Posted By: JimG

Re: Tuning Results From An O2 Kit? - 05/02/11 10:58 PM

Quote:

Wow great stuff here.

I tried to post fishing for experienced answers about these issues here and got nothing. I'm currently trying to dial in my 750 dp for street driving and the tuning is starting to involve wires in the idle feed restrictions. I already ditched my main body for a HP version for the bleed tuning.

My issues are similar- I have a strong motor with a race carb that is a pain in the butt in traffic. The carb cruises super rich on the t-slots and the transition to the mains is jerky as the proper mix takes over and good power hits

I already switched from a single plane to an air gap and put a four hole spacer (secondary opened up now a three hole) in an uneducated attempt to boost the signal to the carb. I was thinking more vacuum would give me the street performance of a smaller carb but it probably just sucked harder on the rich mix in the t-slots.

Thanks for all the in depth tuning results. It seems like most guys just live with a bad street tune as long as wot is good. I moved close to work in a congested area so I need to get dialed in.

Radar:

I suggest starting another thread so this one doesn't get confusing. I'll be happy to chime in. There are other guys on this board who know their Holleys but but they've not posted. Perhaps I'm bogarting the discussion; I'll leave your thread alone for a day or two and see who else shows up.

Jim

Posted By: JimG

Re: Tuning Results From An O2 Kit? - 05/02/11 11:04 PM

Quote:

I still can't get over what 1/12 of a turn on the metering screws will do to the A/F ratio.
If I turn all four of mine from 11:00 to 12:00 positions (for reference), this could be .5 difference on my guage.

That would normally be a hint that you need smaller IFRs/larger IABs, but I think you've proven they produce other problems. It is a pain to have mixture screws that are so sensitive, yes?

Quote:

.028" IFR's to .031" IFR's showed a 1.4 to a full 2.0 change in my cruising A/F ratio at the same speeds.
.075" IAB's to .071" IAB's showed .4 to .6 change in my cruising A/F at the same speeds.

Just goes to show how much the idle and (mostly) the t-slots are working at cruise. That's really not good, because those circuits are dependent on manifold vacuum, not airflow. But you're making it work! Good job!

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/03/11 12:52 AM

""There are other guys on this board who know their Holleys but they've not posted.""

Jim,
I do not know why the others have not chimed in but we appreciate your opinions!!

I found my .036" MAB's and they are in. Now I need to wait again for the weather to clear.

Thanks again.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 05/03/11 05:03 AM

Y07_A66

The MAB experiment will be very interesting to me. I am doubtful that you are moving much fuel thru the main jets at 65MPH, and suspect there will not be much of an impact at cruise. It may have a bigger impact on WOT at high RPM though, so you might want someone running shotgun to keep an eye on the AFR if you run it up to redline.

The IFR change from .028 to .031 is a 22% change in area, which is a pretty big jump. Your current results look pretty good though. A change from .028 to .030 is around 15%. At light throttle you could probably run leaner than 14.6 but going to .030 might make too much of a change (you can always add that jet to a future parts order if you want to try it!).

As JimG said, there were 3 changes at once. With the bigger IFR, you may be able to go a little bigger on the IAB. This could help with the 65MPH+ cruise, since I suspect most of your fuel delivery is still from the transition slot. I think you indicated you only had .075, .071, and .067 IABs. Again, if you are really wanting to fine tune it, getting a set of .073 IABs would give you an intermediate step to try.

If your MAB experiment doesn't bear fruit, then you could try the .075 IAB, and if that is too much then time to consider that parts order! It is a little expensive, but I ended up getting a QF IAB jet kit to let me experiment to my hearts content.

I look forward to your next update!

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/03/11 12:04 PM

Dave:

- MAB .033" to .036" swap: Once I can test drive the .036 MAB's and write down any changes at cruising speeds, then I am going to test the cruise to WOT affects. I did not change any jetting, only the secondary pump cam change from red to pink (due to the rich spike right at WOT kickdown. The pink should lean that spike out). This test should help me decide if I need to make any changes on my secondary jetting.

- I am content with the .031 IFR swap. I think that it puts me right on the richer limit for the cooler Spring and Fall temps. I would like to lean out the 14.6 cruising readings from 25mph to 50mph just a tad, so I might try swapping out my .071 IAB's to some .073's after my MAB test. But the combo of .031" IFR's and the .071" IAB's might be my cool weather ticket. (I currently have .067's, .068's, .071's, .073's and .075's to play with.)

Thank you for your reply and I will post my results once the weather breaks.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/14/11 09:05 PM

Next Update:
Issue: Lean out the rpms above 55mph.
Changes: .033 HSAB's (MAB's) to .036
Weather: Was 66 now 72 degrees.

The 036 swap leaned out the A/F ratio above 55mph. I added the new A/F ratio at the end (/). My 35 & 40mph A/F leaned out some but that might be from the temp change. But I am now aiming for 14.5-15.5 cruise and I am as close as I think that I can get.

64 degrees:
25mph ----------------14.0/ 14.0
30mph 1700rpms (16.2) 14.6
35mph ----------------14.6/ 15.4
40mph 2200rpms (16.0) 14.6/ 15.4
50mph 2500rpms (15.6/15.4) 14.6/ 14.6
55mph 2700rpms (15.0/15.2) 14.0/ 14.4
60mph 3100rpms (14.0/14.2) 13.6/ 14.4
65mph 3300rpms (13.8) 13.8 ----------
The following was a 2nd gear test to see what the A/F ratio was doing at higher rpms:
3000rpms @ 14.4 (same as above 60mph)
3500rpms @ 13.6 (not sure why richer)
4000rpms @ 14.6

The above was with the carb setup: 65/75 jets, .071 IAB's, .036" HSAB's, 8.5 high flow pv, .031 IFR's, red/037 primary cam and pink/.031 secondary cam, 40% secondary linkage delay.

I was able to get my cruising a/f raio into the 15's by leaning out the four metering screws but I was not comfortable with the 15-15.8 readings so I richened them back up. Plus I found that my in D/brake applied A/F ratio needs to be about 13.6-14.0 or my cruise A/F numbers start to change.
I made one WOT run from 50mph and it shows the same as before with an A/F reading at 12.5 then it leans out slowly to 13.0 at the shift point. I am assuming that this 12.5 reading right at WOT is due to the pumps dumping the fuel (DP carb) and then the leaning out to 13.0 is the engine using the extra fuel. Is this a good number for the WOT stab?
Note: I swapped my red secondary cam for the pink cam and found no difference in the A/F ratio.

Thanks to all. The car is running great!!!

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 05/15/11 01:44 AM

Y07_A66,

Your fuel curve is looking sweet! Looks like JimG's recommendations were right on the money.

I haven't tinkered with MABs yet, and your results provide encouragement that this may be viable approach to cure some of my street tuning issues as well.

Your WOT numbers look pretty good to me as well but the final authority on what the motor wants best would be chassis dyno or drag strip MPH numbers.

Thanks again for sharing all your details. This has been a very educational thread.

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/15/11 01:25 PM

Dave,
When you change your MAB's, let us know the results.

I am going to test some more WOT runs but from a stop and from lower speeds to see what the pump cams are doing. I also want to see how lean it goes from the lower speeds up to my shift points istead of cruise speeds to WOT.

Thanks for the reply.

Posted By: dOrk !

Re: Tuning Results From An O2 Kit? - 05/15/11 02:27 PM

INTERESTING read guyz...... It is my intent to join the 02 crowd when I get motorhome project on-the-road. A couple of Q's .....

How many choices are there for a wide-band 02 combo-kit? Anyone tried to add water-injection to enable going HIGHER UP on the A/F numbers? I knew a guy who worked at Ford who said that either Ford or Mazda tried WI ...and were able to get the A/F #'s out to 25 to 1. IIRC ... but if you ran the car out of water ... the motor was toast.

What are your combo's ....stock type or mild HP?

Posted By: JimG

Re: Tuning Results From An O2 Kit? - 05/15/11 08:39 PM

Doc, I'm partial to the Innovate stuff. You can datalog multiple discreet and analog inputs (TPS is especially helpful, RPM, manifold vacuum, etc.) with their auxbox and a laptop. You don't have to buy everything at first, either. You can buy the basic LM2 kit (or used LM1) and add the auxbox later if you so desire. This setup is something you probably wouldn't want to leave in your vehicle permanently. The basic kit will allow you to read (or datalog) the AFR; the addition of an auxbox will allow you to add other data to the graph.

In your case, you might want to permanently mount an O2 gauge in the cockpit of your motorhome. An Innovate LC1 along with a gauge of your choice would be good in that application.

I look at it this way - the LM2 (or LM1) lives in your toolbox, much like a scan tool or dwell tach. An LC1 lives in your vehicle as an add-on gauge, such as a tach or oil pressure gauge. The first thing to decide is if you want a tool for diagnosing multiple vehicles or an O2 gauge for your motorhome.

The guys here are also having good results with other brands of equipment.

I hope that helps.

J

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 05/16/11 03:00 AM

Y07_A66

I have been dealing with multiple engine issues, with the carb just being part of it. I had a bad problem with rotor phasing (resolved a few months ago), and most recently I have been dealing with pulling oil into the intake at the valley pan gasket (BB). The weather was good today, and I was inspired to take the car out and tinker. I loaded my tools and IAB and MAB kits and hit the road.

Unfortunately, increasing the MABs didn't help; in fact it appeared it made the situation worse. At this point I can get reasonable numbers at 2K cruise (45MPH), but at highway speeds it still goes pretty rich. Today I increased the MAB from .033 to .035 and at 3K (@65MPH) the AFR was swinging more wildly than in recent memory, moving almost 2 full AFR (from high 11's to mid 13's).

Earlier experimentation lead me to believe my mains are over-emulsified, so I have change my emulsion jets to .028, blocked, .028, blocked (was .028, .028, blocked, .028). With the MAB at .033, this helped control the wild swings. However, the MAB at .035 has brought this problem back. It seems I am getting too much air into the main jet mixture at small throttle openings.

I then reduced the MABs to .031, and this reduced the AFR swings at 3K. Right now, I left it here.

Previously I had convinced myself that the motor was only getting fuel from the transition at 3K cruise, but your experience made me question that. I came to this conclusion because changes in the main jets didn't seem to be having an effect on the cruise AFR, but in hindsight expecting to see the effect of a couple jet size changes with the AFR swings that are occurring is a little foolish.

Anyway, after reducing the MABs, I tried a second experiment of increasing the IABs from .069 to .072. This did help the 3K cruise AFR some but it still bounces from the high 12's to the mid 13's.

How steady is your AFR at highway cruise? Do you use vacuum advance? Have you ever checked to see what difference there is with the vacuum advance hooked up and plugged, with no other changes?

Hopefully I will get a chance to check the plugs during the week. If I solved my oiling problem, then I should be able to fully concentrate on the carb setup. I am pondering with the idea of hooking up an in car video so you guys can see what happens at highway cruise. I'm also stewing on whether my problem is in the emulsification, and whether to try reducing at least the size of the first emul jet.

Doc,

I use an AEM 4100 setup. It is very entry level but seems to work well enough for basic tuning. I have an O2 bung in each bank, and move the single sensor from side to side while testing. I figure once I get everything dialed in, just leaving it in one side to monitor the motor should be fine.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/16/11 12:02 PM

Dave:

""How steady is your AFR at highway cruise?""
- At a steady throttle, the reading is very smooth (exp: 14.4-14.6) and I take the average to write down. I have seen a larger swing but that was when I was running leaner on the transition circuit. Overall, I would have to say that the guage reading is smooth. Sorry that I can't help you out on the guage swing, but do you have any air leaks on the exhaust "before" the bung?

""Do you use vacuum advance?""
- No. I have a FBO distributor and he plugs them up.

""Previously I had convinced myself that the motor was only getting fuel from the transition at 3K cruise, but your experience made me question that. I came to this conclusion because changes in the main jets didn't seem to be having an effect on the cruise AFR, but in hindsight expecting to see the effect of a couple jet size changes with the AFR swings that are occurring is a little foolish.""
- I can't give you an answer but I can tell you that I read an article to help find how to tell when your mains are coming in. The answer was to raise the main jetting by at least 4 sizes so that you will see a dramatic change in A/F ratio once you hit the mains.
I have found in reading about different brands of carbs, that each manufacturer may have a different opinion on if the carb should be running on the main circuit or on the transition circuit at cruise. My QF carb appears to be running on the transition circuit at cruise.

Doc:
I run the FAST #170634 analog unit. My exhaust is setup as two separate sides (no h or x pipe) and each side has a bung in the header reducer. I am only running one sensor and I have only tested it on the drivers side.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/16/11 04:05 PM

After my last test drive, I was looking over the new A/F numbers and I am curious about the A/F dip at 3500rpms:

40mph 2200rpms (16"hg) 15.4
50mph 2500rpms (18"hg) 14.6
60mph 3100rpms 14.4
65mph 3300rpms (17"hg)14.4
70mph 3500rpms 13.6
75mph 4000rpms 14.6

Is this A/F dip showing when the main jetting is starting in or is there something else? It seems weird that it takes almost a 1.0 dip in between the 3300rpm and 4000rpm range.
If this is the main jet, should I lean out the main jets by one or two sizes and restest?

Thanks

Posted By: dOrk !

Re: Tuning Results From An O2 Kit? - 05/16/11 04:33 PM

Hay guys ... more interesting stuff ...

YO .... do you have corresponding vacumn readings with those MPH, RPM and A/F #'s ?

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/16/11 04:49 PM

Doc,
I updated my last response with the hg numbers that I have.

Thanks

Posted By: dOrk !

Re: Tuning Results From An O2 Kit? - 05/16/11 05:02 PM

So YO ....

Why do you think the A/F #'s are better at a faster speed ....70 vs 75 mph ?

Better vehicle aero at a faster speed? ... better efficiency of the motor at a higher RPM ?

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/16/11 05:24 PM

""Why do you think the A/F #'s are better at a faster speed ....70 vs 75 mph ?""

Honestly, I do not know. I am thinking that if the mains are starting at the 3500rpm mark, then maybe at 4000rpms more air is being pulled into the main circuit which is leaning it out to the 14.6 AF.

Thank you.

Posted By: GomangoCuda

Re: Tuning Results From An O2 Kit? - 05/16/11 05:42 PM

I think you guys may be way overthinking this. Carburetors are not perfect. If they were, nobody would have spent the money to develope EFI. If you are going to agonize over every data point then you need EFI instead of a carb and you can expect to spend many hours tuning it to get the perfection you are shooting for.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/16/11 05:50 PM

I understand that a carb is not perfect. I also understand that certain areas of the fuel curve will be better/worse than the other areas. I am just trying to figure out how much of it I can tune out and how much of it I need to live with. I have a feeling that I am probably to that point.
Plus, I am learning more about tuning a carb as I go thru this process, which I enjoy.

Thank you for your perspective.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 05/16/11 06:00 PM

Y07_A66

"do you have any air leaks on the exhaust "before" the bung?"

I can double check this, but the AFR appears to swing to the rich side. There are some interesting posts on Innovates forums, and I speculate that I may have some fuel "spitting" from the main booster, due to too much emulsification. This loosely fits with my experience of changing the emulsification, and reducing the MABs. However, given the other problems such as pulling oil into the intake, it is hard to be definitive.

"I read an article to help find how to tell when your mains are coming in. The answer was to raise the main jetting by at least 4 sizes so that you will see a dramatic change in A/F ratio"

I have had from 76 to 71 main jets in it. Again, I am cautious to make any firm conclusion, but I did not see any major change in the AFR or swing. Of course there could be some small change, with that change buried in the swing. If I have fixed the oil issue, then perhaps I should re-do that experiment.

It is still my general belief that my engine is running almost exclusively on the transition at highway cruise (22" vacuum) but it is not clear to me why the fuel mixture gets so unstable. Perhaps there is another, non-carb, issue with the engine. I'm pretty confident the ignition is in good shape now (Mopar Distributor, 6AL-2 box).

Posted By: radar

Re: Tuning Results From An O2 Kit? - 05/16/11 06:03 PM

I wonder if the top of the transition could be leaned out with the idle air bleed?
Maybe the mains could be delayed with the high speed bleeds?

Either way, if that is not a common cruising rpm for mileage concerns I would leave it alone and drive for a while. 12-13:1 is rich but shouldn't foul plugs or cause a dead or jerky spot in the revs right?

Good luck and thanks again for the tuning log

rdr

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/16/11 06:20 PM

""Either way, if that is not a common cruising rpm for mileage concerns I would leave it alone and drive for a while.""

Good point Radar.
Thanks for the response.

Posted By: AndyF

Re: Tuning Results From An O2 Kit? - 05/16/11 06:27 PM

Nice job of documenting your tuning process. One item that jumped out at me was you saying that you did not have vacuum advance. Is that correct? It appears that you have basically a street car and that you're spending a lot of time cruising at highway speed. That is the perfect application for vacuum advance so I'd recommend that you go back to a stock type distributor. Adding in a bunch of ignition advance at cruise can really help the engine run more efficiently.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/16/11 07:12 PM

Andy,
That is correct, I am not running a vacuum advance distributor. Several years ago when I sent in my dist to FBO, I got it back with the VA plugged and I have always just left it that way because it was working. I thought that if I had any issues with it than I would change it back out for a VA unit. Now I have a better reason to reconsider that.
Thank you for your reply.

Posted By: JimG

Re: Tuning Results From An O2 Kit? - 05/17/11 07:49 PM

Quote:

It is still my general belief that my engine is running almost exclusively on the transition at highway cruise (22" vacuum) but it is not clear to me why the fuel mixture gets so unstable. Perhaps there is another, non-carb, issue with the engine. I'm pretty confident the ignition is in good shape now (Mopar Distributor, 6AL-2 box).

Dave, perhaps a non-carb issue yes, but I wonder if, after changing your e-bleed configuration, your fuel level is even with one of the upper e-bleeds at light cruise, causing it to alternately suck air, suck fuel, etc. as the fuel level slightly fluctuates. Easy to test - just raise or lower the float level a tad and go for a ride.

Based on what you've said, I agree that you're cruising mostly on the t-slots, but I'd be surprised if the mains weren't working enough for this scenario to play out, IF the fuel level was just right...or in your case, just wrong, in comparison to the upper e-bleeds.

Just a thought.

J

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 05/18/11 03:47 AM

Jim,

That is a very interesting thought. Hopefully the weather will be good this weekend, and I will play with the float level and see if it has an effect on behavior.

Prior to changing the emulsion jets the AFR swings were larger than they are now. There was a .028 in the first and second bleed, and now I have a blank in the second hole which seemed to help. As you say, perhaps the fuel level is sitting right at the first bleed. On the sight glass, the fuel level is in the middle which maybe is too high.

What sort of gaskets do you use in your carb? The reason I ask is that I have wondered whether under high vacuum there is fuel being pulled from somewhere where it should not. My carb is a QFT Q-850-PV (vac secondary), and have had trouble with the blue "non-stick" gaskets that it came with. They were sticking really bad all the time, and the aluminum of the carb main body was getting some oxidation on it. The guys at QF said it was from water (apparently the gaskets dissolve with water), but I suspect it was from the E-10 fuel that we have here. I wonder if the fuel additive can carry more moisture. Any way, I now use the Buna-N rubber gaskets which don't stick and I think they seal well but there is always that concern in the back of my mind.

Thanks very much for the thought. I'll report back as soon as I can try that experiment.

Dave

Posted By: JimG

Re: Tuning Results From An O2 Kit? - 05/18/11 01:22 PM

Hi again Dave:

I re-read your last couple of posts. Can you confirm that your current two e-bleeds are in the same position as the "old" Holley setup? I'm more familiar with the 5-e-bleed blocks, and am not sure how 4 positions work out WRT the the old Holley setup. That's always a good place to start, regardless.

Since your cruise is so rich, you might have better results lowering the float level below the top e-bleed. That way the top e-bleed will suck air at low main circuit flow. If testing confirms that your engine likes this, you could always move the upper e-bleed to the top position and reset the float level back to the sight plug.

Have you ruled out t-slot restrictors?

J

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 05/19/11 04:14 AM

Jim,

I have an old Holley 750 and even older 780 that I can pull the metering block off of, and see how well the height of the e-bleeds match with my current metering block. The QF block has 4 holes, drilled at .028 and tapped at 6-32. When new, only the 3rd hole from the top was blocked. I guess it is reasonable to assume they had a reason for leaving the top 2 .028 holes unblocked. Does that seem like a lot of bleed air to you?

As I mentioned, changing the setup reduced the AFR swings, but did not eliminate it. And the cruise AFR was still pretty darn rich.

To add insult to injury, tonight I pulled spark plugs and although my oil sucking problem is much improved, it appears there are still a couple of plugs with signs of oil getting into the chamber. So, I'm going to have to take another attempt at the pan gasket sealing. Given that it is pulling oil, it must also be pulling some air, but perhaps it isn't enough to really upset the AFR (or this thing would be even richer than it is!).

You may yet talk me into the transition slot restrictors, but I'm still trying to get my off idle transition right just with the reduced IFRs. My concern is that the t-slot restrictors will just make this task harder.

BTW, here are the details of my setup:
70 Cuda, 400/470, E-head, 10.8:1, 248*@.050, 112LSA in at 109, RPM intake (recently switched from M1 SP), 1 7/8 TTIs, full 3" exhaust with X pipe and Ultraflows. Carb Primary setup: IFR .034, IAB .072, jet at 73, 6.5" PV. Motor pulls close to 15" vacuum in park at 1000, and bounces a bit between 9-10" in gear at 700 (factory 440 convertor at the moment). The M1 use to bounce 8-9" in gear. Secondarys are disabled via adjusting screw on the QF vacuum pod since I'm trying to tune the primaries only at the moment.

At one time, I did check the fuel level relative to the top bleed, and felt it was below it. But I will definitely double check as you suggest, since it was hard to make a great measurement.

I should get a chance to tinker over the weekend, and will report back.

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/19/11 01:07 PM

Dave and Jim:
Nice info. Keep it coming.

I now have a problem with my O/2 sensor. It only reads 14.6 on my A/F gauge. This just started two nights ago when I started the car. It just quit taking the readings. It does not fluctuate at all with the accel pedal now, and it just reads the 14.6.

Last night, I checked the voltages at the gauge electrical connector and it showed (engine off, key @ RUN position):
Blue: 12v (12v ignition switched)
White: 0 (or 12v when lights are turned on, light source)
Black: 0 (ground)
Green: 2.5v (analog output)
Brown: 12v (12v constant battery)

I asked in another thread, what can make an O2 sensor go bad and the answers did not apply to my setup. So I am assuming that I might have a bad sensor already after just eight test drives and a few start ups. I am going to get under the carpet to make sure that the sensor has not come disconnected and I will also check the wiring as it comes thru the rubber boot in my floor pan.

Note: Rich says that a 14.6 reading usually shows the O2 sensor is not hooked up or the O2 heater has gone bad. He gave me a test to run to see if the problem is in the sensor. I will check back when I know more.

Can Autozone test an O2 sensor "off of the car"? If so, then I will take the sensor in to them to check it out. UPDATE: My local store said that they can not test O2 sensors.

Any thoughts?

Thanks

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 05/20/11 03:46 AM

Y07_A66:

I don't know that much about the O2 sensors themselves. The two things that I have heard that kill them are operation with leaded fuel and running the engine without the cable connected to the sensor (I believe because the heater is not operational). I guess they could get totally fouled by carbon as well. I recently swapped my sensor from one engine bank to the other, and it did have a lot of carbon on it (since under some conditions my engine still runs pretty darn rich), but not of the holes where clogged or anything. I just wiped the carbon off before re-installing it.

Did you pull your sensor and examine it? Does your system have any sort of power on check routine that occurs when first starting your engine?

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/20/11 11:35 AM

Dave,
I was told to do a test last night to check the heater on the sensor to see if it was heating properly. I turned the key to the "run" position for at least 30 seconds, and I was told to touch the body of the sensor for some heat. I did that and the sensor was still as cool as it was when I moved the key, even after about a minute with the key in that position. I made this test twice with the same result, so I pulled the sensor. The sensor does have carbon on it, but like yours, the holes are not covered and it can wipe off.

Note: I do not have any power on check routine unless it is built into the FAST system. I run unleaded pump gas and the sensor is plugged in full time. I may have just gotten a bad sensor.

Thanks for the reply.

UPDATE:
I talked with FAST tech support and I need to ship them the unit back for full inspection. It looks like I am out of the O2 game for a while.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 05/20/11 05:56 PM

Sorry to hear of the trouble, but it's good the manufacturer will look at the unit for you. Hopefully you'll get it back together soon!

Dave

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 05/23/11 04:29 AM

JimG,

I am impressed and greatly appreciative of your insights. This weekend I ran the experiment which you suggested. I dropped the float a whole lot...about 1/2" or so, and the fuel level was noticeably below the bottom of the sight glass. The motor ran much leaner, in fact so lean that I was worried. At 2K RPM, I was seeing AFR in the high 15's to low 16's at light throttle. At 3K highway speed the AFR was richer but still in the 14's. The really lean mixture worried me some, so I switched the IABs from .072 back to .070, and this helped; I didn't see excursions of AFR into the 16's anymore.

The question is "why did help so much". Check out the attached image. The original fuel level is at the bottom of the top piece of tape (mid-sight gauge). Just as you suggested, the fuel level was right at the bottom of the first e-bleed. Given the motor vibration and road quality surface, it is easy to imagine that the fuel was at times covering and uncovering this bleed hole. This is likely the cause for the AFR swings.

The very low float level is marked by the top of the bottom piece of tape. This would have put the fuel level a little above the 3rd e-bleed. Note that the jets you see in the picture are blanks.

But now there is still a mystery. I was not happy with the float as low as it was, and decided to raise it up some. I moved the adjuster 1.5 flats, and that brought the fuel level right to the edge of the bottom of the sight glass. This had a very noticeable effect on the AFR, with 2K cruise now in the low to upper 14's. So it changed the AFR by at least 1 point. Highway speed is now solidly in the mid-13's. The mystery is why did it have such a big effect? It looks like the 3rd bleed would have been covered with the very low float, and now the fuel level should be right in the middle of the blank e-bleed. Perhaps with fuel slosh, the very low float setting was allowing some bleed air in???

As I mentioned before the factory setup had the top 2 e-bleed open (drilled to .028), with a blank in the third, and the fourth open. Having the upper 2 allow some bleed air now seems reasonable, but I feel that 2 .028 bleeds is too much. At the moment, I am considering drilling the second bleed to allow some air in, perhaps something like .020.

In my next post, I will show the comparison of the QF 4 e-bleed metering block with an old Holley one.

Dave

Attached picture 6646301-MeterBlock_small.JPG

Attached picture 6646301-MeterBlock_small.JPG

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 05/23/11 04:34 AM

OK, here is a view of metering block from an old Holley 780VS. If the fuel level was set to the bottom of the sight glass, then it would have been covering both e-bleeds. The only bleed not covered is the kill bleed. Does the kill bleed affect the AFR?

On my QF metering block even though the top e-bleed was not anywhere near covered with the second and third float level I tried, the carb still ran noticeably rich at highway speeds.

Next up, a comparison of the two metering blocks.

Attached picture 6646307-HolleyMeteringBlock_small.JPG

Attached picture 6646307-HolleyMeteringBlock_small.JPG

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 05/23/11 04:40 AM

Here is the comparison between the two. It appears the top e-bleed is in almost the same position (height). The 3rd e-bleed on the QF block appears to line up with the 2nd e-bleed on the Holley. I think my current setup is darn close to the old Holley setup.

The kill-bleed on the QF is lower than the Holley. Would that have an effect? The kill-bleed is also smaller on the QF.

As I mentioned, I am now considering adding some bleed air on the second e-bleed by hand drilling a jet. Do you have any thoughts on this?

Thanks,
Dave

Attached picture 6646315-MeteringBlockCompare.JPG

Attached picture 6646315-MeteringBlockCompare.JPG

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 06/27/11 12:49 AM

I have the FAST kit back and I have been running it for a couple of weeks now and I have a quick question.
I noticed that when I take my foot off of the accel pedal at a cruising speed (A/F readings 14.4-15.4) and the A/F gage goes richer into the mid to low 13's. What causes the richer A/F reading on decel?

Thanks

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 06/27/11 03:24 AM

Y07_A06

Glad to here your wideband is back in action!

Can you remind us what your AFR at idle? When the throttle closes, the vacuum level is likely going very high, and pulling more fuel thru that circuit. I doubt there is much that can be done about that on a carb.

Question for you....how much does your AFR change immediately following a gear shift?

Regards,
Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 06/27/11 11:45 AM

Thanks Dave. I am glad to have it back.

I have been able to do plenty of testing with my N idle/in D idle and what I have found is that my setup idles best in the 13.5-13.8 range in D. I had the D idle setup to 14.0-14.2 (couple of times with different outside temps) and it idled too choppy and the rpms were moving around too much at a stop sign/light. I have also found that my N idle numbers are usually in the same range as the in D A/F ratio once I move the gear selector from D to N after it has been driven and up to temp. The rpms still go up once it has been changed from D to N, but the A/F stays pretty close.
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""When the throttle closes, the vacuum level is likely going very high, and pulling more fuel thru that circuit. I doubt there is much that can be done about that on a carb.""
- That is what I was assuming but I was not sure. Thank you.
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""how much does your AFR change immediately following a gear shift?
- During light accel to cruising speed, I do not recall much of a fluctuation in A/F readings. From gear to gear at WOT, I have not tested that one. I have only tested WOT from cruise until the car shifts at the WOT shift point, then I let go and take my notes. Once I get my pumps dialed in, I will check that out.
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Speaking of getting my pumps dialed in, what A/F number should I be aiming for under light accel and medium accel (before the power valve kicks in)? I am currently getting 13-8 to 14.2 depending on the cruising speed. The idle accel (from a stop) seems to be in the 13-8-14.0 range and my cruising accel seems to be in the 14.0-14.2 range. This seems a little lean to me, what do you members suggest?

Thanks to all.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 07/09/11 09:01 PM

Guess what? After 7 more drives after re-installing the A/F kit, it died,,again. It is now back at FAST and they say that they have never seen this trouble with one of these units before. Last time they said that they did not find any issues with the unit and it was due to my wiring. But when I told them that I had power at both of the 12v leads, they said that it was still by wiring. So I wired it back in and it ran fine for a short time again. Anywho, the same problem happened again this time as it did four weeks ago. So I am waiting on them to call me and it is still under full warranty. I am waiting patiently to see if they find anything wrong with it this time.
But during the seven drives, I was testing the cams/squirters trying to get my off idle accel and my cruise-WOT A/F ratios to fall into place. I did not finish before the kit took a dump, but what I did notice was that the different pump cams that I was using sure do make a huge difference in the A/F ratio. I was running a pair of Red cams and from 50-55mph cruise to WOT, the A/F ratio dropped to 12.5 for a second and then leaned out to 13.0 at my shift point. I wanted to lean this out to the upper 12's and started changing out squirters. The squirters did not do anything to the A/F number (secondary side: 25, 31,35,37) so I started swapping out cams. I tried swapping in the secondary cams and retesting and found a minor A/F change from red, black, and pink which all gave me about a 12.0-12.2 A/F reading with the red primary cam. So, for the fun of it, I swapped out the primary cam to an orange and found a huge A/F change that showed a dip to 11.0 at the cruise to WOT. These changes do reflect the Holley pump cam chart that I have been referencing for the past 3-4 years. I know that there are a few of these charts on the internet and now I have proof that I am using the correct chart.
I am finding out that I need the smallest black cams to keep my cruise-WOT spike in the upper 12's. I am now using a black/.037 on the primary and once I get the kit back installed, I will be testing with the black cam on the secondary side with a 031 squirter. I am hoping that this change gets me into the upper 12's but if it does not, then I am going to test with a scondary linkage change that Quick Fuel provides with their DP carbs. I am currently using the linkage that allows the secondaries to come in at 40% throttle and if I have too, then I will delay it with the 60% throttle link. I remember when I ran a vacuum secondary carb that this combo liked the heaviest brown spring. Maybe it will like having the secodaries coming in later with the 60% delay too.
I will check back in when I get my A/F kit re-installed and I have more tuning time.
If any of the members have some A/F numbers to provide along with their pump cam tuning, please feel free to tell us how the tuning came along.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 07/15/11 04:08 AM

Y07_A66

The target AFR during light acceleration is a great question, and one which I don't have any firm thoughts on. It should certainly be leaner than WOT AFR. There is not much load during light acceleration, and I would be too surprised if keeping it around 14.7 is acceptable. The best answer is probably to see what a modern factory EFI system does. Does anyone have insight into that?

I asked about the AFR immediately following a gear shift because on my car I have noticed a significant transitory lean condition after a shift on light acceleration. Its almost like the carb looses its metering ability for an instant when the RPMs drop. I'm not that concerned about it, but when the motor is not to full operating temp, I can actually feel it go lean (besides seeing it on the wideband).

I'm sure you're frustrated with the wideband problems. I know a guy whose LC-1 went wacky during a road race, but hadn't heard what the final resolution was.

I'm not sure if the different progressive ratio on secondaries will make much difference on the AFR. When going to WOT, the difference in opening time between primary and secondary is going to be pretty darn close. I thought the advantage of the different ratio was during moderate throttle conditions, where avoiding hitting the secondary accelerator pump can help. The VS secondary carb likely had a much more noticeable difference in timing of opening between pri and sec, and obviously doesn't have the extra fuel from a secondary accelerator pump.

Your accelerator pump cam tests sound like they are going in the right direction, and this "knob" will likely get you to where you want with sufficient experiments.

I don't have a lot of info to share on pump cam affects. On my motor, virtually all of the cams have been insufficient, with a big lean spike on the WOT transition. I have had to go to the biggest cam (blue) and currently have a 0.035 squirter. I purchased a 50cc pump, but unfortunately it has interference with the RPM DP, so for now I am sticking with the 30cc pump. My WOT AFR still needs tuning, and is a bit on the rich side. I'm trying to strike a balance between high speed cruise and WOT mixture and am still playing with the PCVR and main jet relationship.

Hope you get your wideband sorted out soon!

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 07/15/11 01:51 PM

""I purchased a 50cc pump, but unfortunately it has interference with the RPM DP, so for now I am sticking with the 30cc pump.""

I tried a 50cc on my RPM intake with a different carb. I found the same interference so I added a heat spacer under the carb which gave me enough space to run the 50cc unit.

I had my light throttle accel around 14.0 but it seemed lazy and the exhaust sounded funny. As soon as I richened it back up into the mid 13's, it ran better. I am currently getting 13.4-13.6 for my light accel from a stop and it feels right (black/037 primary).
FAST found the problem this time and they are sending me a new kit. Their warranty manager said that he has not seen an analog kit fail like this one before. The processor was overheating causing the system to read 14.6 which is a typical reading if there is a fault in the kit. It also appears that their first repair on this unit was not performed properly and they sent it back to me and that it why I found the problem for the second time. I should have it back in the car next week and I can continue on the cruise to WOT rich spike.
Your thought on the secondary rate sounds correct. The linkage moves pretty darn quick during a WOT change and the secondary delay may not help. Good point.
I have a feeling that if the two black cams together (leanest cam setup) does not work, then I might test what a standard power valve does versus my current High Flow power valve which QF suggests to use with their carbs. The current opening rate is a 9.5 which works well under all of my cruise conditions and the WOT transition, but maybe the four door design is dumping too much all at once when the valve opens.

Thank you Dave.

Posted By: kilroy

Re: Tuning Results From An O2 Kit? - 07/15/11 09:55 PM

GREAT STUFF GUYS PLEASE KEEP IT UP!!!!!

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 07/16/11 04:12 AM

I may try a spacer to allow the 50cc pump, but my hood clearance is pretty darn close, so I have been doubtful that it would still close, at least with my current air filter. I don't like running too short of a filter with a drop base since the lid gets sort of close to the top of the venturi. At the moment, I still have some hope that the 30cc pump will just be enough.

If you still have a rich dip after going to two black cams, then you might want to try decreasing the squirter size again. Now that the cam is about right sized, you may be able to see more sensitivity to that. You may be right about the PV having an effect on how quickly that extra fuel gets introduced, but I don't have any experience to draw on there.

Look forward to hearing more!

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 07/20/11 03:09 PM

Dave,
I have another thought on my 50/55mph to WOT rich spike. After reviewing my latest chart, my primary jets are still a little rich. This is what I show with the same outside air temps:
70mph (3500rpms) = 13.6 A/F with 65 primary jets
70mph (3500rpms) = 13.8 A/F with 64 primary jets
I am going to swap in some 62 primary jets to see if I can lean out the 70mph cruise to get into the 14's. If this works, this should lean out my 50/55mph to WOT rich spike a tad. Then I will make a secondary squirter swap (currently Black/031") to lean it out some more if needed. I have .028", .025", .021", and .019" squirters to test.
If this does not fix it, then I will pull the high flow pv and swap in a standard pv of the same rating.
Our outside temps are now in the mid 90's so the A/F may not lean out enough.

Note:
FAST found an internal heating issue with my last A/F unit and they sent me a new complete kit. I have it installed and now I just need to get my tale out in the heat and test some more.

Thanks for the reply.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 07/21/11 04:00 AM

Y07_A66:

I wonder if that rich dip in your fuel curve is due to overlap of the transition circuit and the main. At 3500 the motor may be pulling decent amount of fuel thru the mains while the transition is still flowing a noticeable amount. Above that point, the transition may be flowing less and the mains more. Leaning the main jet will cause your 4K RPM to be leaner as well, and some care may be needed to balance between getting it perfect at 3.5K and having it too lean above that.
The main jet change will obviously lean up the WOT AFR as well.

Sometime back I realized my motor is also pulling fuel thru the mains at 3K cruise, contrary to my original thoughts. If I went really lean on the mains, the 3K cruise AFR can be improved. Geting the right balance is going to be some work though. However, last weekend I pulled the intake again, and confirmed I am still getting oil into the runners, so I need to resolve that before tinkering any more.

I'm glad you are back in business with the wideband. Your motor seems like it is running like a fine clock. My wideband has been fine so far, but I'm lacking on the motor side. Hopefully soon we will have both motor and wideband working well at the same time!

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 07/21/11 11:45 AM

""I wonder if that rich dip in your fuel curve is due to overlap of the transition circuit and the main. At 3500 the motor may be pulling decent amount of fuel thru the mains while the transition is still flowing a noticeable amount.""
- You may be right. I never thought of both circuits still pulling at the same time.

""Above that point, the transition may be flowing less and the mains more. Leaning the main jet will cause your 4K RPM to be leaner as well, and some care may be needed to balance between getting it perfect at 3.5K and having it too lean above that.""
- My chart shows that the higher up in the rpm range the richer the carb is getting:
64 jets, 2700rpms: 14.6 A/F
64 jets, 3000rpms: 14.4 A/F
64 jets, 3500rpms: 13.8 A/F
64 jets, 4000rpms: 13.6 A/F
I changed out the primary jetting last night to the 62's from the 64's. The 4000rpms A/F could use less fuel too. I also swapped out the 9.5 Hi Flow power valve to a 8.5 Standard power valve too while I had the metering block off. I want to see how rich it gets at 50/55 cruise to WOT with the standard pv in it. My standard 9.5 felt a bit too strong versus my Hi Flow 9.5, so I opted for the next lower unit of 8.5. (I know, one thing at a time. But the wideband is showing me two different issues to fix. I believe that the leaner primary jet will help out the 3500-4000rpm cruise while the standard pv will help lean out the rich spike at a cruise to WOT.)

""The main jet change will obviously lean up the WOT AFR as well.""
- I currently have 75's in the secondaries and my WOT with the 64's in the primary side did not go leaner than 13.0. I will keep an eye on the WOT AFR now with the 62's in front.

Thanks a bunch for your response. I might wait until the weekend to test it out due to our current heat wave of upper 90's.

--------------------------------------
""However, last weekend I pulled the intake again, and confirmed I am still getting oil into the runners, so I need to resolve that before tinkering any more.""
- Is this just a gasket or is there more to the problem?

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 07/22/11 03:58 AM

Y07_A66:

The oil in the intake runners is hopefully only a gasket issue! As you probably know, the big block uses an integrated valley cover and intake gasket made of metal. This works fine with with cast intakes and heads, and the higher torques applied when those are in use. With the aluminum intake and heads and lower torque values, there appear to be mixed results. Some will state they have had no issues with just the tin gasket, others will say you need to use paper gaskets in addition on one or both sides of the tin. To add to the situation my block has been decked which slightly changes alignment.

The other variable is gasket sealer, and again there are lots of opinions and testimonials to what works and what doesn't, with no clear consistent results. Originally I had paper gaskets on both sides of the tin gasket, because I was concerned about the effect of the block decking. Last weekend I redid the intake, and now just have a paper gasket on the intake side of the tin. Hopefully that will do the trick. Next step would be to just try the tin by itself. The final step would be to use a separate valley cover, but that would entail doing some clearancing on the bottom of the intake (trying to avoid that). My old M1 SP would clear but the RPM DP would not.

It is going to be smoking hot here this weekend as well, but I will still complete putting everything back together and take the car out for a spin to try it out. At least my motor doesn't run hot!

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 07/23/11 02:13 PM

Update
The new FAST wideband is working fine and I was able to take a test drive with the 62 primary jets (versus 64's) and the 8.5 "standard" pv (versus 9.5 High Flow).

30mph (1800rpms) @14.4 A/F
40mph (2200rpms) @15.4 A/F
50mph (2500rpms) @15.0 A/F
60mph (3100rpms) @15.6 A/F
2nd (3500rpms) @14.2 A/F (64 jet = 13.8)
2nd (4000rpms) @14.0 A/F (64 jet = 13.6)

The 64 to 62 primary jet swap brought the A/F range up into the low 14's above 3500rpms. I think that I will leave it alone for now. I keep changing the range that I would like to be driving in but for right now, I like the 14.0 - 15.6 cruising A/F range.

The 9.5 HF PV (high flow per Quick Fuel) swap to the Standard 8.5 power valve did not help my 50/55mph to WOT rich spike like I was hoping. The rich spike stayed in the 11.8 to 12.2 A/F range. The 62 jets did not hurt my WOT A/F number, it was still at 13.0 at my shift point. It also took away from my low end power at WOT. I am going to swap back in the 9.5 HF unit and then swap my secondary squirter from the current .031" all the way down to a .018" and see how the rich spike acts.
The above was done in 80 degree temps with very high humidity. We are supposed to get into the mid 90's with high humidity, so I am done for the day.

Posted By: lokalik

Re: Tuning Results From An O2 Kit? - 07/23/11 02:52 PM

this has been a great post. thanks for all the info. my question is a/f ratios are controled by the jets correct? and the idle mixture screws are only for the idle circuit? thanks again.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 07/23/11 04:48 PM

The metering screws do control the idle mixture but their settings also affect the transition circuit too.
The main jets are in the main metering circuit which help control the A/F when the main circuit is working.
You have a few circuits to deal with, idle then the transition and then the main metering circuit, then the secondary or WOT. All need to be tuned to the correct A/F range, and depending on the carb, they have replaceable jets for each circuit for tuning.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 07/24/11 02:58 PM

Another update:
82 degrees HIGH humidity. I swapped back to the 9.5 High Flow power valve and the bottom end power came back. This carb definately needs the HF unit per QF's recommendation. The 50/55mph cruise to WOT did not change but the response was excellent at all driving rpms.
I also swapped the .031" secondary squirter for my smallest .018" squirter and found no change on the 50/55mph cruise to WOT rich spike. I think that I will live with this since the spike only happens for a second before the A/F starts to rise.
This was the first attemp from an idle at a stop to WOT all the way up to the 2-3 shift and I was surprised to see both 1-2 and 2-3 WOT A/F readings showed 13.0 in the same run from a stop all the way up thru the shift points.
Do you think that the 13.0 is a safe WOT reading at the shift point?
Each 50/55mph to WOT showed apx. 12.0 spike and then climbed to the 13.0 mark. I am wondering if delaying the secondary pump cam from #1 to #2 position might help but I think that I can be happy with this number since so many different changes never affected this spike. I wonder if a vacuum secondary unit drops to this level and this is a DP issue. I would rather be safe than sorry at the WOT transition.
I also lowered my in D idle A/F ratio from yesterdays 13.8 to 13.6. This engine really likes the 13.6 in D A/F reading. Even after changing the in D A/F reading, my cruise readings were still in the 14.0 to 15.4 range.
The current setup was very responsive in the light throttle reaction and the WOT transition. My 195 thermostat kept the engine temp right at straight up on my stock engine temp gauge.

I am sold on these wideband kits. The following is a review of where I started (Spring time) on the carb setup to this morning.
Spring: 66/75 jets, 8.5 HFPV, red/037 primary pump, red/031 secondary pump, .071 IAB's, .033 HSAB's, .028 IFR's.
This combo showed way too lean transition circuit and too rich main circuit cruise.

Current: 62/75 jets, 9.5 HFPV, black/037 primary pump, black/.018 secondary pump, .071 IAB's, .036 HSAB's, .031 IFR's. I would have never guessed that I could get away with 62 primary jets.

I am very pleased with the current tune of the engine especially in the high humidity this morning. Unless the 13.0 seams too lean at WOT, I think my only decision is whether to buy a second wideband for the passenger side of the engine or not.
Thank you very much for the responses as I have learned so much from everyone.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 07/24/11 03:19 PM

"The rich spike stayed in the 11.8 to 12.2 A/F range. The 62 jets did not hurt my WOT A/F number, it was still at 13.0 at my shift point. It also took away from my low end power at WOT."

Can you explain what you mean by "took away from"? Are you saying that the jet change to 62s reduced the low end power? Was the AFR different after the rich spike clears? I would think that the rich spike is definitely impact power on the initial transition to WOT.

If the smallest squirter doesn't tame the spike some, I wonder if increasing the AP clearance on the secondary side only might help slightly decrease the total pump volume and the discharge onset.

Dave

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 07/24/11 03:38 PM

Y07_A66:

OK, looks like you posted an update while I was typing my last response. So the low end power change was due to the PV. Where you able to observe a difference in the low RPM AFR at WOT with the different PV in place?

" Do you think that the 13.0 is a safe WOT reading at the shift point? "

I have always heard that the typical motor will like somewhere between 12.8 and 13.2 at WOT. At this point, I think the only way to really refine the best WOT number would be on a chassis dyno or dragstrip. You are likely very close though, and only you can answer if further tweaking would be worth the effort. If you have screw-in PCVRs you could increase your WOT AFR without further disturbing your cruise setup.

With respect to a second wideband, here is something to consider. I have two bungs but only 1 wideband. I move the sensor from side to side periodically. This made some sense when I had a single plane manifold on it since one side of the carb will have more influence on one side of the motor but now with a dual plane, one side of the motor is already feed from both sides of the carb so it is hard to really know whether the motor wants a staggered jetting. Best bet is probably to check the plugs and see if all the plugs on one plane look the same or different from the other four.

I am very impressed with how well you have done with your tune. Well done!

Dave

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 07/24/11 03:59 PM

Y07_A66:

I also meant to comment on this -

"I am wondering if delaying the secondary pump cam from #1 to #2 position might help"

The squirter experiment showed that delaying the fuel delivery is not having a positive effect. Clearly the issue is with too much volume. As I remember, using the #2 pump cam position increases the volume, in addition to delaying the start. This is not what you need.

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 07/24/11 05:14 PM

Dave,

""As I remember, using the #2 pump cam position increases the volume, in addition to delaying the start. This is not what you need.""
- Good catch, you are correct.

""If the smallest squirter doesn't tame the spike some, I wonder if increasing the AP clearance on the secondary side only might help slightly decrease the total pump volume and the discharge onset.""
- BINGO!! I did not think of this before, but turning in the screw should do the trick. I will pull the black cam which has a more aggressive lobe up to about 50% travel than the pink cam, and put the pink cam in there with the additional clearance. Thanks!

""So the low end power change was due to the PV. Where you able to observe a difference in the low RPM AFR at WOT with the different PV in place?""

- Yes the change was definately from the HF power valve swap. In this carb, the two door pv did not have much response once the vacuum dropped below the rated level. As soon as the HF unit was back in, I could definately feel the difference. No, I did not observe the low end A/F ratio. I waited to watch once I got higher up in the rpm range.

I was thinking of adding one more jet size to the secondary side to see if that would bring the WOT A/F down into the high 12's. I might try that if I get bored. That would take my 75's to 76's.

Thanks allot for your help Dave.
Are you thinking of testing a high flow pv to help with your lean spot?

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 07/25/11 04:01 AM

"thinking of adding one more jet size to the secondary side to see if that would bring the WOT A/F down into the high 12's."

Yes, that could be worthwhile. It is easier to try that, then mess with the PCVRs. One thing I think about on my motor is primary to secondary balance. I have been tuning my carb (unsuccessfully I might add!) with the secondaries disabled, so that the primary behavior can be directly observed. Most say that 8-10 jet sizes difference keeps a good balance (assuming PV up front, not in rear). You could add up the area of the mains+PCVR versus secondaries, although this is not exactly the same as flow. If you are a racer, it is something to consider. I don't see that going up one or two jet sizes is going to make your balance much different from what it is today.

"Are you thinking of testing a high flow pv to help with your lean spot? "

I do run a high flow PV. My lean spot is just off idle. I have been trading issues with an ugly rich highway cruise for an off idle lean stumble I can't get rid of. My carb (QFT 850-PV) was designed as a race carb and sold as a race carb, but I have been trying to get better street manners for my street/strip ride (mostly street). It's probably a bit foolish of me. The carb does not have very good low speed airflow behavior. I think I might have mentioned that at light throttle, there is a huge lean dip on a shift, and the carb takes a moment to recover good metering. I still need to get a looser converter (running a stock 440 unit right now), and that will make this less of an issue.

I had the car out this weekend, and sometime during the week I need to pull all the plugs to look for signs of oil. It seems the motor is running a little smoother, so I am again hopeful that I have solved that problem. Also found an ignition problem today (bad rotor) that was causing a slight miss. At the moment I changed the IFR/bleed/main jet combo to get good off idle and low speed operation, and good WOT AFR. The nasty highway (3K) cruise AFR is back, with the wild AFR swings with rich dips into the 11s. I wonder whether the mains are "spitting" fuel at 3K and 22" vacuum. I realize now that the mains are flowing some fuel under these conditions and I am again pondering the emulsification jets.

I'm open to suggestions if anyone has them!

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 07/25/11 11:42 AM

""Most say that 8-10 jet sizes difference keeps a good balance (assuming PV up front, not in rear)""
- My carb setup came with a 14 jet spread front to back from Quick Fuel. My current jet spread is 13. I have noticed a .2 A/F change on the primaries with only a one jet size change. This carb is very sensitive.

I was looking back thru my charts and I found that this 11.8-12.2 A/F spike from cruise to WOT was not as bad of a problem when our outside temps were in the 60's-70's. I was getting A/F readings at the 12.5 A/F mark before the Summer heat hit. Maybe I just need a leaner cam adjustment during the Summer time.

""I wonder whether the mains are "spitting" fuel at 3K and 22" vacuum. I realize now that the mains are flowing some fuel under these conditions and I am again pondering the emulsification jets.""
- Have you tried delaying the mains to see if the problem moves up in the rpm range beyond your cruising speed?

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 07/27/11 02:11 AM

"- Have you tried delaying the mains to see if the problem moves up in the rpm range beyond your cruising speed? "

I played with the MAB only a bit so far. At the time it appeared that smaller MAB helped. At the moment I have .031 in the primary down from .033. However, it makes sense to explore that again. Thanks for the thought!

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 07/31/11 02:33 PM

Dave,
I took your suggestion about adding clearance to the secondary pump cam to try and lean out the 50/55mph-WOT rich spike.
Ref:
Was: 11.8/12.2 with WOT shift point at 13.0
Now: after a couple of times of shortening the secondary cam screw (larger gap), this worked great! I am now at 12.4/12.6 and my WOT shift point leaned out to 13.4 but a few jet sizes on the secondary side should fix this issue. I was concerned about not having the pump cam gap tight but it was very responsive to the gap. I have to say that it might be a touch quicker in response now at cruise to WOT.
I am going to delay it a little more and then get my WOT A/F around 12.8 or so, then I am going to play with the stop/WOT to see where it is at. I am one step closer!

Note:
I have been using the black cam on the secondaries since it is the smallest volume cam. I tested an .018" squirter and found that the 50-55mph to WOT A/F ratio went lean first (mid 14's) and then dipped to the previous 11.8. Now since I have the gap (apx 1/8") and with a .031" squirter, the A/F ratio goes straight into the 12's instead of going lean.
I think the tricky part will be tuning the idle to WOT tuning. This might require partial throttle then to WOT from a stop instead of 100% throttle from a stop with the DP style carb. But, with delaying the fuel on the secondary pump, I might be surprised.

Thanks a bunch Dave!

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 08/01/11 03:44 AM

Y07_A66:

Fantastic! I'm glad loosening the secondary AP helped. It looks like you have a decent convertor in the car, so the standing start might not be any problem at all. Traction is likely to be the first problem you encounter with street radials!!

I didn't do anything on my car this week. The temps have been into the low 100s here, and it doesn't really make sense to try to tune under those conditions. Last weekend I had the car out when it was in the upper 90s, and the more I drove it, the more of a problem the off-idle stumble was (as the motor got heat soaked). Today it finally rained here, so no option for taking a spin. Hopefully it will be a little cooler next weekend.

Please keep us posted.

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 08/03/11 01:58 PM

I have a small tuning issue that I am trying to decide how to fix.

I have my cruising A/F range between 14.5 and 15.5 below 65mph or so. When I am cruising and I let off of the pedal, the A/F drops down into the mid 13's. I am assuming that the vacuum goes up which pulls more fuel making it rich. How do I correct this?

I am currently running a distributor with out a vacuum advance canister. If I had a vacuum advance distributor, would this correct this issue?

Thanks

Posted By: mrob

Re: Tuning Results From An O2 Kit? - 08/03/11 02:56 PM

Y07,
It sounds to me like the transition circuit is still contributing to the overall AFR under those conditions. As you correctly observed, the AFR goes richer because of the high engine vacuum caused by letting off the gas. This pulls extra fuel out of the transition slots which makes the AFR richer.
One way of limiting it is to install restrictors in the transition circuit. But don't expect miracles, because the restictors can only do so much before they limit the fuel flow to the point of causing a bog. Another method is to find a baseplate with smaller transition slots.
Honestly, an AFR of 13:1 doesn't sound so bad to me. Many Holley carbs have AFRs in the 11-12's during deceleration.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 08/04/11 01:29 AM

Martin,
I am running on the transition circuit up to about 70mph with my current setup. I just assumed that mid 13's was rich. Thank you for your response.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 08/07/11 02:09 PM

UPDATE:
My last issue was the WOT shift point was showing 13.4 A/F with the 075 secondary jets and my 50/55-WOT rich spike was getting better at 12.4-12.6 after adding more gap at the secondary pump cam/arm.
I swapped out the 075's for some 078's and now my WOT A/F is good at 12.8 but my rich spike from 50/55-WOT came back rich around 11.8-12.0.
I will add some more gap at the secondary pump cam and see what happens.
I also tested a rolling start to WOT and found a 11.8 A/F spike reading at the rolling start and it leaned back out the the 12.8 mark at the shift point.
So back to leaning out the secondary pump. I am still wondering if swapping out the 40% secondary linkage to the 60% delay may help a touch.

This is my latest carb setup:
62/78 jets, black/037 & black/031 (+ gap), 9.5HFPV, N=1000rpms @ 14.5"hg & 13.0/13.2 A/F
D=900rpms @11.5"hg & 13.6/13.8 A/F
Notice how much richer the N idle is compared to the tranny being in D with the foot on the brake. I tune the idle in D so I let the N reading fall where it ends up.
30mph= 14.0 A/F
40mph= 14.6 A/F
45mph= 15.4 A/F
50mph= 15.0 A/F
WOT = 12.8 A/F

I have always noticed a lean jump at 45mph for several test drives now. It is usually my leanest cruise reading. I did not check it today but my 3500/4000rpm cruise has been in the 14.0-14.2 range with the 62 primary jets.

Back to secondary tuning.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 08/08/11 04:28 AM

Y07_A66:

"I am still wondering if swapping out the 40% secondary linkage to the 60% delay may help a touch."

I have never played with mods to the secondary linkage, so take what I say with a grain of salt. My understanding has been that the secondary opening progression tuning was for part-throttle racing such as road racing.

It seems you have a nice bag of tricks to get the WOT AFR were you want it. One more thing you may want to consider is decreasing the secondary MAB, instead of increasing the jet. You could go back to 75 or 76 jets, and try decreasing the MAB a few steps. This will change the slope of the fuel curve, and could be useful if the AFR is good at lower RPM but not where you want it at higher RPM.

Update on my problems: I tinkered some this weekend trying my smallest MAB (.025) and the largest (.035), just to see the effect. The big AFR swings were still present under all tests at highway speed. The smallest MAB moved the range of AFR lower (centered about 12.3) as expected, and the largest moved it up (centered about 13.1). At this point, I am thinking there is still some sort of an ignition problem, and the rich dips are the result of a miss. My wideband is a little slow, so it is hard to correlate what is shown on the meter with other sensory input. If I really focus it seems I can hear some subtle farts in the exhaust note at highway speed.

At first I thought it might have something to do with my 6AL-2, since highway speed (3K) is right when it drops the multi-spark. However I need to do more experiments to see if I can determine if it happens at a specific RPM or conditions. I haven't been able to notice anything at speeds in the 45-50MPH range. Any thoughts on what could cause a light throttle miss at higher RPM?

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 08/09/11 12:29 AM

I am not sure about the 40% to 60% change either but it is an easy swap on the linkage.

""One more thing you may want to consider is decreasing the secondary MAB, instead of increasing the jet.""

I increased the size of the secondary MAB to keep my transition circuit active during my upper cruising speeds. My curve starts to go richer above 70mph so I want to keep the MAB's where they are. I don't mind the jet spread and I am giving it what it wants.
-----------------------------------------------

""Any thoughts on what could cause a light throttle miss at higher RPM?""

What conditions are your wires and distributor?
I wish that I could give you some help on this but I am not sure what to say.
Where did Jim go? Any ignition guys want to give this a try?

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 08/09/11 04:17 AM

"increased the size of the secondary MAB to keep my transition circuit active during my upper cruising speeds."

I would have guessed that the secondaries are closed during high cruise conditions, but if not, the secondary linkage change you are considered would likely guarantee plenty of margin to not activating the secondaries during cruise conditions. Just something to keep in mind during further tinkering.

"What conditions are your wires and distributor?"

The wires are MSD 8.5 super conductor, and are about 2 years old with a little over 1000 miles on them. The distributor is from a MP electronic ignition conversion kit, and it probably 11 years old, but with less than about 3000 miles on it. The control box is a 1 year old MSD 6AL-2 (replaced a MP chrome box). Plugs are NGK 6's.

I have been wondering about the distributor. However, I have been hoping to retain the vacuum advance for later experimentation, and the aftermarket distributors I have looked at so far don't have that feature. My shopping criteria is easily adjusted mechanical advance, vacuum advance, compatibility with the 6AL, and use of stock style plug wire ends. I could change over the wires if I had to though.

The distributor has been disassembled lots of time, while I have been tinkering with the advance curve. I don't think I did anything bad to it, but I guess it could be something subtle. The reluctor gap has been checked multiple times and seems fine. One or two of the tines are a little bigger than the others (insert generic statement about quality here...), and I use those to set to the gap. The distributor did have a noticeable problem with rotor phasing but I corrected that by adding shims under the vacuum canister to reposition the advance plate.

I also have wondered whether JimG still visits here. I have not had as much time to visit this site either in the last month or two, but I can't remember seeing any recent posts from him. Hope he is just busy enjoying his ride!

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 08/27/11 02:26 PM

Seondary Pump Tuning Results:
I have been chasing a 50-55mph to WOT rich spike (10.0 to 12.2 A/F spike) and I have finaly made some progress. I was also trying to tune my idle to WOT rich spike of 10.0 to 12.0 A/F which was making the car a dog off the line with the DP carb.
With my backup DP on the shelf, I started playing with the secondary pump/cams/arm trying to limit the fuel from the secondary side to try and limit the rich spike. After grinding down a black cam, I noticed the A/F spike getting leaner but not nearly enough. Then I added an air gap at the black cam and pump arm screw and it got a little better. So I knew if I could limit the secondary side more then I should see the results.
Then I grabbed a pink cam which has a very slow lobe and I rotated the cam CCW as far is it would go to get the least amount of fuel from the secondary side as possible at WOT. I was not sure that it would work because it did not produce much of a pump shot at WOT.
So I went out this morning for a test drive and I am so suprised at the result. Limiting the secondary side of the DP gave me instant tire spin from idle to WOT. Of course I wanted to test this over and over and over again to make sure but after several idle to 100% WOT shots, it was immediate tire spin each time.

My idle to 100% WOT A/F showed an immediate lean spike to 16.0 but the tires still spun like mad. The 16.0 spike then richens up very quickly to about 14.2 during the tire spin and then drops down into the 13's as the mph comes up. The lean spike does not appear to hurt the performance but I am going to test a larger primary pump cam to see if this helps. The larger primary cam will also help my light throttle A/F which is now into the 15's with the cooler weather. The warmer afternoon temps may show a richer A/F too.
Note: this was with the secondary linkage set at 60% delay.
Then I tested my 50mph to WOT rich spike and I was again surprised. My rich spike is now at 12.4/12.6 right where I was hoping. After a 50mph to WOT run, the rich spike starts at 12.4/12.6 then then slowly rises to the 12.8 WOT shift point.
Then I tested idle to WOT thru both shift points and they both showed 12.8. I am very pleased!!
I am very surprised at the idle to WOT response since the secondary cam has been delayed.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 08/28/11 03:51 AM

I suspected you would be reaching the point of pondering the topic of traction.....

The lean spike on idle->WOT is pretty high, and wonder whether it should be tamed some. I would suspect that with really good traction, the motor would bog.

Do your comments about being surprised by the results imply that the car would not have as much tire spin with a lower AFR on the WOT hit?

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 08/28/11 05:27 AM

""The lean spike on idle->WOT is pretty high""
- Yes it is and I am already working on that one with a larger squirter on the secondary. If that does not fix it then I am going to change the secondary linkage from 60% to 40% to see if that helps. I just don't want to change the volume.

""Do your comments about being surprised by the results imply that the car would not have as much tire spin with a lower AFR on the WOT hit?""
I have beeen fighting an over-rich Idle to WOT A/F reading which made the car a dog. I have read where others were having great response at idle to WOT with their DP's but I was having to raise the rpms a little bit to see the same results. Now it is instant tire spin with the delay in fuel from the secondary pump.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/03/11 08:53 PM

UPDATE:

I fixed my 50mph-WOT throttle lean spike with a larger squirter on the secondary side. Now I have no lean spike at idle to WOT (which was spiking to 16.0) or 50mph-WOT (which was also spiking16.0). Now my A/F goes richer as soon as I hit WOT.
I need help on this next one. I ran into this ealier into this thread but now I am ready to fix it. My A/F ratio from 60mph (apx 3100rpms) up to 4000rpms is too rich for my liking (14.0-14.4). So I tried to lean out the HSAB's to lean it out. I tested with my .036's and then swapped in .039's with no change at all in A/F reading in this range.
I am guessing that I need to lower the front jets a couple and see if that helps it out. This is my latest A/F readings taken on the same day but one was at 75 degrees and the other at 92 degrees.
Note: I was having cruising readings at 40-45mph at the 15.5 range so I wanted to richen that up just a bit and I swapped my .067 IAB's for a set of .064's and that richened up my cruise quite a bit. But for now I am going to just lower my floats a tad and recheck my readings.
75 deg (.036 HSAB's, .067 IAB's, "D" A/F=13.6-13.8 & solid idle)
30mph=14.0, 40mph=14.2, 45mph=14.4, 50mph=14.8
55mph= 14.8, 60mph=14.4, 3500rpms=14.4, 4000rpms=14.0.
92 deg (.039 HSAB's, .064 IAB's, "D" A/F=14.0-14.2 & rough idle)
25mph=13.6, 30mph=14.2, 35mph=13.8, 40mph=14.2, 45mph=14.4, 50mph=14.6, 55mph=14.6, 3500rpms=14.0, 4000rpms=14.0.
So you can see I need to lean out the cruise just a tad (lowered floats) and then I need to lean out my 3100-4000rpm range with what I am guessing a primary jet change.
Let me know what you think.

Something that I have noticed is that my in D idle A/F is richer than what I have read on the net. When I have my in "D" A/F set at 14-14.2, the idle gets rougher and my vacuum drops. But if I have it set in the 13.4-13.6 range, the vacuum is solid and it idles smooth.

Thanks

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/05/11 10:12 PM

Y07_A66:

Your setup is pretty darn good!

A primary main jet change may help but be careful of creating a lean "hole" at part throttle before the PV opens. At cruise there is not that much fuel flowing thru the mains, but at part throttle there can be much more flow. A change which provides a small improvement at cruise may end up being too big of a change in the wrong direction under part throttle.

Another thought to consider is to try using your vacuum advance. This should provide for a smaller throttle opening at the same cruise RPM, and therefore move the slight rich dip up in the RPM band a little more. If the mechanical advance has been tweaked, the vacuum advance may also need to be limited.

I would not worry about the idle AFR that much; the engine is telling you what it wants. Optimal tunes are never "one size fits all". In addition to all of the variables in the engine (cam specs, exhaust sizing, intake manifold type, carb characteristics, etc), there is also the variable of how much load the converter is placing on the motor, and what sort of torque the motor makes at idle. In setup's like yours (and mine) a moderately rich idle is typical (IMHO).

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/06/11 01:31 AM

""A change which provides a small improvement at cruise may end up being too big of a change in the wrong direction under part throttle.""

That is what I am afraid of. I am so close that I can make a small change and my A/F cruising numbers will be:
A) in the mid 14's to mid 15's
Or
B) in the lower 14's to the low 15's

So I keep going back and forth trying to decide what cruising range(30mph-60mph)I want to be in. Right now I am comfortable in the "A" range.

I have most of my setup figured out (jetting, pv,cams/squirters and bleeds) and I am just playing with the 40% and 60% delay on the secondary linkage and the float adjustment. The float adjustment can really dial in the cruising A/F without having to change any bleeds. I am going to leave my A/F at 3500rpm and 4000rpm at the 14-14.2 mark for now.

Over the long weekend, I was lucky enough to drive the car with the same setup in 60 degree, 75 degree, and 92 degree outside temps and the only change that I made was with the in "D" A/F adjustment. I was able to keep the cruise A/F between 14.2 and 15.6 as long as I keep the in "D" A/F between 13.4-13.8 and it drives great within those outside temps if I keep the in "D" A/F in that range. If I did not keep "D" A/F in that range, then the cruise A/F range would go leaner or richer than the 14.2-15.6 range which I do not want.
A Vacuum advance distributor might be in my future but probably not before Winter.

I am probably going to stop updating this thread because I am so close on the setup. I have learned allot from the information that a wideband can give and also from the responses from this thread. I want to that you again and to everyone else for your help.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/06/11 03:44 AM

Yes, I think you have your carb setup as good as could possibly be expected.

If you do try a vacuum advance distributor in the future remember to check the rotor phasing. I recently put a new MP unit into my motor, and it needed significant correction to the phasing.

This has been a great thread, and thanks again for posting all of the detailed results along the way!

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/11/11 02:45 PM

I need some more help.
My last issue was having a cruising A/F ratio of 14.0 at 3500-4000rpms. I changed my primary jetting from 62's down to 60's and now I am seeing 14.4 at both cruising rpms. I can be happy with this for now. After discussing this issue with QF, the tech thought that it was strange having 62 jets in the primary side and still getting a rich number of 14.0. But after a long discussion about my A/F numbers (cruise, WOT, bleeds, etc.), it was decided to test the 60 main jets. That appears to be working.
Now I have created another issue. At any cruising speed (30mph-60mph) and I press the accel pedal for light to medium accel, my A/F goes lean (16.o+) and the car is surging under these accel conditions. What I have noticed is that once the vacuum drops below my pv rating (9.5 high flow), that is when the A/F goes into the 16.0+ range. Since I have leaned down the main circuit to the 60 jet, I am assuming that the pv does not have the flow to keep the engine happy now. This to me sounds like a PVCR issue (too lean) but I do not know anything about them except that they supply the fuel to the pv when the pv is open. I do not know what the stock PVCR's are in the SS-750-AN carb, but I am assuming that I need to open them up.
The following is my setup and A/F number as of this morning. As you can see, I am very close all over the range and I do not want to make a change that will affect the rest. I do know that I have a little bit to spare at WOT and my in D A/F was rich this morning at 13.0.
60/78 jets (stock spread was 14 sizes), .064 IAB;s, .039 HSAB's, 9.5HFPV, 40% linkage delay on secondary side, front float at 1/2 mark and secondary float at bottom of glass. (cool weather at 63 degrees):

35mph=14.6
40mph=14.4
45mph=14.8
50mph=15.0
55mph=15.2
60mph=14.6 (3100rpms)
3500rpms=14.4 (was 14.0 w/62 jets)
4000rpms=14.4 (was 14.0 w/62 jets)
0-WOT thru shift points: 13.0/13.0
50-WOT was 13.8 at shift point (lean)
50-WOT showed "0" on vacuum gauge with the 750 DP (actual 735cfms per QF)

If my PVCR's got richer, this might help the WOT number too with no other changes.
Is the PVCR the next change?

I am thinking of dropping the main jetting again to 58's and then sizing the PVCR's from that. This might lean out my 3500-4000rpm A/F into the mid to upper 14's. Then resizing my secondary jetting to suit. This might reduce the front/back jetting spread to get me a little closer to the stock 14 jet spread.
QF did say that the annular booster pulls more fuel than a downleg, but my jetting surprised him.

Thanks again.

Posted By: AndyF

Re: Tuning Results From An O2 Kit? - 09/11/11 05:22 PM

I'm not sure I can help since I don't know much about the carb that you are working with. It sounds like you only have a PV on the primary side? If so, you might consider adding one on the secondard side also. For the type of driving that you are doing a PV on both sides would be the best setup.

Are the metering blocks fully adjustable? If so, when you remove the PV there will be two jets under there that can be changed. I posted a picture earlier of a billet metering block with jets in all circuits. The fully adjustable metering blocks make this kind of work much easier.

One minor point, the PVCR add fuel to the main well when the PV opens. So it basically just adds jet size when the PV opens. You can figure it out with some simple math. A 60 main jet plus a 30 PVCR gives you a 67 jet for example.

Another thing that you should do at this stage is to double check your measurements. Get another wide band sensor and swap it in and double check your numbers. You are making a lot of assumptions based on your measurements. Double check your measurement equipment before you go to far. You might be shocked at what you find out.

I've tuned myself into a corner a bunch of times and then found out that my measurement equipment was bogus and my tune was way off.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/11/11 06:13 PM

Andy,
The metering blocks are fully adjustable and I will be pulling the PVCR's later today to confirm the size. My current rear block does not have a pv provision though.
Can you give me the formula for figuring the main jet and the PVCR total jet size?
I am going to pull a couple of plugs on the side where the sensor is on to see what the plugs look like. I pulled a couple about four weeks ago and they looked real good.

Thanks Andy.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/11/11 07:37 PM

I do not know the exact diameter of my current PVCR's but they are in between .037" (sloppy) and .062". These were the closest drill bits that I had. The .062 was closer in size.

When opening these up, how much do you open them up when testing (.001", .005", etc.)
Thanks

Posted By: AndyF

Re: Tuning Results From An O2 Kit? - 09/11/11 08:17 PM

For this type of tuning you'll want to invest in a set of pin gauges. They are fairly cheap for a small set.

I'd highly recommend buying a new metering block for the secondardy side that has a PV. Does your carb have four corner idle? That is another handy tuning device.

If you are going to drill the PVCR then you'll need to buy a set of small drills and a pin vise drill. (You'll do that once and then you'll decide to buy an adjustable metering block!)

Fully adjustable metering blocks aren't very expensive. BLP has them as well as all of the jets that you need.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/11/11 08:25 PM

I just pulled #3 and #7 plugs and they both were very similar. The porcelain was clear with slight brown color. Both of the plugs had a full ring of color on the bottom of the plug thread. They both looked good.
I do have fully adjustable metering blocks. I also have the small chuck with a small assortment of smaller drill bits for my air bleeds and my IFR's. But I do not have any precision bits for the PCVR's (.050's-.060's or so).
Can you give me some information as to why I should be looking at a pv in the secondary side of the carb? How do I choose the pv for the secondary side?

Thanks

Posted By: bonefish

Re: Tuning Results From An O2 Kit? - 09/11/11 11:02 PM

nothin to add YET just savin the thread

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/12/11 12:25 AM

I found the formula for tuning the PVCR's.
Take the stock jet diamter and the stock PVCR diameter, (2) each = 4:
3.1415 x jet x pvcr /4 = total area
Then take your new jet size x new pvcr until the new combo equals the area of the original combo.
Ref: 3.1415 x .068" original jet, .058" original pvcr = 003"
Ref: 3.1415 x .058" new jet, .069" new pvcr = .003"

I need to get me some more drill bits.

Using the new smaller main jet will allow me to lean out the primary A/F ratio (currently at 14.4) at the 3500-4000rpms range. Then by using the corrected pvcr's (larger) will allow me to tune the A/F of the fuel delivered by the pv to get me back into the 14 range (currently 16+). Then I will need to rejet my secondaries to get my WOT corrected to the 12.8/13.0 range.

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 09/13/11 01:50 PM

Hi Dave,

You posted on my thread on dodgecharger.com, thanks again for the advice.

I have measured the PVCR, they are approximately 0.056"

Not done any more tuning on the carb; I've had some overheating issues that were caused by a defective thermostat.

Thanks all, for the great advice in this thread!

Frederick

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/13/11 02:21 PM

Hello Frederick,
I have been checking in on your thread and I did not see any activity, so I was wondering how your tuning has worked out. It is good to hear from you.

UPDATE:
I am waiting on my new jets and pvcr's to get here. After discussing this with QF, the stock pvcr's that came in my carb were .059". So they gave me a list of their next larger pvcr's and I chose the .065", .069", and the .071" to test. After looking at the area of my existing main jets and pvcr's, and knowing that I am currently lean, I am going to test the .065" pvcr's with the new .058 main jets. This combo will be richer than my current 060 main jets and .059" pvcr's when the pv is open. If this combo does not bring my light throttle 16+ readings down into the low 14's, then I will test the .069"' pvcr's and so on.
Plus I can retest my 3500(70mph)-4000rpm(apx 75-80mph) A/F to see if it comes up into the mid-high 14's with the 058 jets. If not, I also ordered 056 main jets too for testing if needed. Then I will have to retest my WOT A/F and adjust the secondary jetting again.

Posted By: AndyF

Re: Tuning Results From An O2 Kit? - 09/13/11 11:57 PM

You don't need to use Pi or divide by 4 or any of that. Just add the sum of the squares and take the square root.

If you have 60 jets and 30 jets then that is 3600 + 900 = 4500. Sq root of 4500 is 67.

So a 67 jet is equal to a 60 main and a 30 PVCR.

If you know how to use Excel it is easy to make a little spreadsheet that adds the jets together. That way you can quickly see if a 58 main plus a 65 PVCR is richer or leaner than a 62 main with a 59 PVCR.

You're on the right track. If WOT is lean but the main circuit is fine, then keep opening up the PVCR until the AF is correct. Most people are too lazy to do it this way, but it is the only way to dial in a Holley type carb for both economy and performance.

Once you get this carb dialed in you'll be ready for a real challenge such as a three circuit Dominator!

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/14/11 01:18 AM

"If WOT is lean but the main circuit is fine, then keep opening up the PVCR until the AF is correct."

Andy,
If the main circuit is fine, why not just go up on the secondaries to achieve the required WOT A/F?

Thanks allot,

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 09/14/11 01:54 AM

Quote:

Now I have created another issue. At any cruising speed (30mph-60mph) and I press the accel pedal for light to medium accel, my A/F goes lean (16.o+) and the car is surging under these accel conditions. What I have noticed is that once the vacuum drops below my pv rating (9.5 high flow), that is when the A/F goes into the 16.0+ range.

Is the issue you are trying to solve now the lean surging? If so its not clear as I read it whether this is under light to moderate throttle (usually 12 - 14" Hg vac), or only when pushing below 9.5" vac?

Its possible that (especially below 60 mph) that cruise is still on the idle/transition circuit. Then as the throttle moves up the transition slot and the mains come in, they might be causing the lean surge. Retest at 70 mph and light to med throttle. If its surging above the power valve opening, you'll know its the main circuit. If only when the PV is opening, you'll know your on the right track.

As far as richening the secondaries goes, the better tuners on the innovate forum like to get the primaries correct first (disconnect the secondaries) then work the secondaries. Otherwise some of the cylinders wil probably get different AFR mix when the secondaies open.

Quote:

3.1415 x main jet x pvcr = volume

???
volume of what?
The flow is most dependent on Area of the restriction. Other factors are length and shape of the entry and exit of the restriction. If the other factors are the same (and they are in this case) then just compare areas as Andy suggest.

Posted By: AndyF

Re: Tuning Results From An O2 Kit? - 09/14/11 01:55 AM

Guess that depends on the throttle position during "normal" driving.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/14/11 11:30 AM

Mattax

Sorry about typing the ""3.1415 x main jet x pvcr = volume"" because I was in a hurry and I typed it wrong. The formula that I found was "3.1415 x jet x pvcr /4 = total area" but then I found that just multiplying the main jet and the pvcr gave me what I was looking for.

The only time that I am seeing the 16+ A/F is during medium accel "only" when the vacuum falls under my pv rating. So when the pv is open is when I was seeing this 16+ on the A/F meter. This is why I am changing to the richer pvcr's.

My main jetting is still a little rich at 14.4 and that is why I am dropping the main jet by 2 to see where the A/F falls. The mains were showing 14.0 then I dropped the main jet by 2 to give me the current 14.4. So now I am dropping the main jet again by 2 hoping to get me in the 14.6-14.8 range.
This is the same chart that I showed above. It appears that my mains are starting in around or after 60mph (referencing my past charts)
- 35mph=14.6
- 40mph=14.4
- 45mph=14.8
- 50mph=15.0
- 55mph=15.2
Above rpms can be changed with transition circuit tuning changes.

- 60mph=14.6 (3100rpms) [mains starting?]

Below rpms can be changed with main circuit tuning changes.

- 3500rpms=14.4(60 jets) [was 14.0 w/62 jets, was 13.8 w/64 jets]
- 4000rpms=14.4(60 jets) [was 14.0 w/62 jets, was 13.6 w/64 jets]
As you can see by the jetting progression, the 58 main jets should get me to where I want to be for the upcoming cooler air temps.

Thanks

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 09/14/11 01:34 PM

Good morning!

Quote:

Sorry .. I was in a hurry and I typed it wrong... but then I found that just multiplying the main jet and the pvcr gave me what I was looking for.

No apology needed..this way you know who is paying attention

(and admitidly I only check in sporadicly)
not sure about the multiplying, it's what AndyF wrote, its the areas that need to be compared. PI*r^2
but as Andy pointed out, its the square of the radius thats different.

Thanks for reposting the chart summary. That's really good.

Quote:

The only time that I am seeing the 16+ A/F is during medium accel "only" when the vacuum falls under my pv rating. So when the pv is open is when I was seeing this 16+ on the A/F meter. This is why I am changing to the richer pvcr's.

So my question is this whether the lean surge also occurs above the PV opening vacuum?

It's normal for the AFR to get leaner as the throttle opens. This is fine as long as load on the engine is not too high. Somewhere around 80-90% load (depending on the engine design) it needs to be richer. The vacuum where each engine-drivetrain combo hits the load that requires enrichment can vary quite a bit. Maybe you'll have to go to a 10.5 PV.

However when the PV does open, the AFR should not get suddenly leaner if the carb is already on the mains (even partialy). Check the AFR at 12" and 10". If its already around 16:1 or higher, then 16:1 at 9.5"vac at least makes sense. If AFR is richer at 10 and 12"Hg than at 9", then something is not right.* If its continuing to get leaner below the PV opening vacuum then the PV is probably not opening when it should be.

*one possible but unlikely scenario is that the fuel level is below PV

Hope that helps some.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/14/11 02:13 PM

Mattax,
""So my question is this whether the lean surge also occurs above the PV opening vacuum?""
- No it does not.

==============================================================

""However when the PV does open, the AFR should not get suddenly leaner if the carb is already on the mains (even partialy). Check the AFR at 12" and 10". If its already around 16:1 or higher, then 16:1 at 9.5"vac at least makes sense. If AFR is richer at 10 and 12"Hg than at 9", then something is not right.* If its continuing to get leaner below the PV opening vacuum then the PV is probably not opening when it should be.""

- I will check that out once I get the carb back together.

Thank you for your response.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/19/11 02:12 AM

I got some time this weekend to test a few different main jet/pvcr combinations and I am now more confused than I was when I started.
I tested the following (main jet/pvcr/hg below my 9.5 pv/cruising A/F 30mph-55mph):
62/.059/16+ (13.8-15.0)
58/.065/17+ (14.4-16.0)
64/.065/13.8-14.4[target] (13.6-14.4)
60/.069/16+ (14.0-15.0)

What I found was that the larger the main jet the richer the A/F with the pv open. This makes sense but the richer the jet, the richer my A/F was at cruise. The 064/.065[target] worked great at accel but the cruising A/F was too rich. The 060/.069 worked great at cruise (14.0-15.0 from 35 to 55mph) but the accel was 16+ with pv open. I am going to test a more aggressive pump cam to see if the 16+ readings will get richer (low 14's) but if not, then I have a .071 pvcr to test too.
This is how the current 60jet/.069pvcr/.060iab combo showed in 70 degree weather:
30=14.0
35=14.6
40=14.6
45=14.6
50=15.0
55=14.4
60=14.4
3500rpms=14.4 (best so far but too rich)
4000rpms=14.4 (best so far but too rich)
I was real happy with the small A/F spread but when the pv kicks in, I am getting an A/F ratio of 16.0 plus.

Note: I achieved almost the same A/F readings with 62/.059 combo but slightly leaner which is my goal, but the 3500/4000rpm A/F showed 14.2 though. This combo still showed 16+ below the 9.5pv rating at low speeds.

I am testing with a white primary pump cam and I might jump to an orange to see where the A/f goes too during accel. The next larger pvcr that I have is the largest QF had which is a .071.
The above is still slightly rich for my liking but I will swap the .060" iab's for a set of .064" to see if that leans it out just a tad.

Any ideas other than the larger pump cam and the richer pvcr to increase the below 9.5hg reading?
Note: I did make a couple of 12hg readings they were all sligtly richer than the above 9.5 readings.

""If its continuing to get leaner below the PV opening vacuum then the PV is probably not opening when it should be.""
This IS what is happening at low speeds (30-45mph or so) before the tranny kick down. It appears that the mains are not helping at lower speeds and this is why I am thinking of using the pump cam.

Thanks again.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/19/11 03:09 AM

Y07_A66:

How long does the lean AFR last? Does it persist for more than 1 second while accelerating? How are you controlling the vacuum level the engine encounters? Are you loading the engine with the brakes or up a long hill? Lastly, do you know if the secondaries are starting to open during your acceleration runs?

The AP should only cover a short duration lean period immediately following the throttle opening, unless it dumps too much fuel, which will then require the motor some time to recover from. It is possible that the total volume from the pump is correct, but the timing is not optimal. This could be particularly true on the secondary side if those throttle plates are starting to open, since you did a bunch of work to limit the accelerator pump volume coming on that side.

I might be influenced by your answers above, but the other thought I have is that the lean spot is actually occurring before the PV opens. The PV might not be opening at the right point, and the wideband also has a bit of latency in it, so the AFR will be a lagging indicator.

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/19/11 11:41 AM

Dave,
* How long does the lean AFR last?
- Until the 3-2 downshift occurs.
* Does it persist for more than 1 second while accelerating?
- It stays lean during accel.
* How are you controlling the vacuum level the engine encounters?
- I have a guage inside that I use to observe the vacuum. I am not sure that I answered your question though.
* Are you loading the engine with the brakes or up a long hill?
- No. Just a slow steady increase of speed from a stop but not enough for the 3-2 downshift to occur.
* Lastly, do you know if the secondaries are starting to open during your acceleration runs?
- Not for sure, but I am trying to stay out of them to tune this issue. I am going to disconnect the seconds on my test drive and test a couple of changes on the primary side.

* The AP should only cover a short duration lean period immediately following the throttle opening, unless it dumps too much fuel, which will then require the motor some time to recover from. It is possible that the total volume from the pump is correct, but the timing is not optimal. This could be particularly true on the secondary side if those throttle plates are starting to open, since you did a bunch of work to limit the accelerator pump volume coming on that side.
- Good point. Maybe while I am trying to stay out of the seconds, they are actually starting in and causing the lean period. Once I retest with my seconds disconnected, maybe I should go back to the 60% secondary delay (currently 40%) and see if this changes.

* I might be influenced by your answers above, but the other thought I have is that the lean spot is actually occurring before the PV opens. The PV might not be opening at the right point, and the wideband also has a bit of latency in it, so the AFR will be a lagging indicator.
- The lean spot is definately happening before the PV opening. I am using a 9.5 but I also have a 10.5 to test with. But with the lean spot happening upwards of 12hg, I am assuming that it is somewhere else. Now that you pointed out the secondaries opening, I might just need to delay the seconds to the 60% point or speed up the secondary cam by one hole.

EDIT: After thinking about what you wrote about the secondary throttle plates opening at my current 40% delay mode, and since I delayed the timing of the secondary cam so much to delay the volume, I bet that is creating a lean spot at 40% throttle. I am pushing down a bit on the throttle to make the 9.5pv open up. That has to be the cause!!!!!!!!!
I don't want the secondaries opening that quick, so I am going to swap the secondary linkage back to the 60% and retest.

Thank you very much for your responses. They help to pull the blinders off when I am trying to test so many different combos!!

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 09/20/11 03:12 AM

Yes, increasing the main jet effects highway cruise (approx 60 mph plus) and also wide open throttle. It continues to feed when the power valve opens, The power valve is allows additional enrichment to the main circuit through the PVCR.

If the main jets are much bigger than the idle restrictions (they usually are) they will not effect idle-transition circuit.

The accelerator pumps are there to cover the delay in fuel responding to the throttles opening suddenly. Get the main jets based on cruise. Get the main jets + PVCR based on 3rd or 4th gear run at WOT. Accelerator pumps usually are most needed at when the throttle starts nearly closed. The main circuits respond pretty quick to throttle changes an often need little or no AP shot.
Pick up a copy of Ulrich and Fisher's Holley Carburator and Manifolds book if don't have a copy already.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/21/11 02:51 AM

* How are you controlling the vacuum level the engine encounters?
- I have a guage inside that I use to observe the vacuum. I am not sure that I answered your question though.
* Are you loading the engine with the brakes or up a long hill?
- No. Just a slow steady increase of speed from a stop but not enough for the 3-2 downshift to occur.

Typically the vacuum level with increase as the car picks up speed (and the load is reduced). If you are attempting to maintain a constant vacuum level, I assume you are continuing to increase the throttle opening when the vehicle picks up speed. This makes me more suspicious that the secondaries may be opening during your test. Another way to increase the load on the engine is to do the test on a long uphill, or by applying the brakes while applying throttle.

Given the duration of lean period, and on the assumption that the secondaries are beginning to open, it seems the problem may be more than just the secondary AP. What are the current values of IAB and IFR on the secondary side? You may need to ponder the transition circuit behavior on the secondaries.

Dave

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/21/11 02:59 AM

"if the main jets are much bigger than the idle restrictions (they usually are) they will not effect idle-transition circuit."

It might be picking nits, but in my opinion, I feel "not much effect idle-transition" is a more correct statement. I have heard many folks state that main jet or premature PV opening cannot affect the idle or transition but this is not strictly correct, at least based on carb theory (and actual personal experience).

Anything that increases the amount of fuel in the main well can affect the idle well because the rate of fuel flow thru the IFR can be increased. I would agree that this can just be marginal increase but it is an increase to some degree.

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/21/11 11:32 AM

""Given the duration of lean period, and on the assumption that the secondaries are beginning to open, it seems the problem may be more than just the secondary AP. What are the current values of IAB and IFR on the secondary side? You may need to ponder the transition circuit behavior on the secondaries.""

- Since I have the secondary pump cam delayed so much, this is my guess on the long lean spot. I have delayed the secondary opening rate to 60% and I have made a few other changes and now I just need to find some time to get out and drive.
This lean spot is not an issue during most of my normal driving time. It only happens when I try to accel and not have the tranny kickdown. When I accel harder and the tranny kicks down, the A/F is fine. I am just trying to tune the bugs as they come up and this one got my attention.
I am going to test the secondary delay and see what happens.

""What are the current values of IAB and IFR on the secondary side?""
- .031" IFR's and .064" IAB's. (Same on front)

Thank you both for the replies.

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 09/21/11 01:25 PM

Relationship of jets to restrictions:
If there are two restrictions in series, and one restriction (main jet) is approximately 4 times the area of the second restriction (IFR), then there should be little or no effect. I agree that's not always absolute as other variables play a role and area is not the only determinant of flow (especially on Holley Main jets). There are some good discussions on this relationship if you dig back through the Innovate, Speedtalk, and Motorsports Village forums.

Secondary Accelerator Pump Cam:
That needs to be providing the fuel when the secondary throttle is on the transition. It needs to start moving as soon as the secondary throttle starts to move. It is needed because the fuel coming out the transition flow is based on the difference between the atmospheric pressure and the manifold pressure (in other words, vacuum). That flow not going to respond to a quick movement of the throttle (which reduces the vacuum at least momentarily)

Disconnecting the secondaries for testing purposes is the other option.

IFR, IAB:
Interesting. Compared to what I've seen, and waht people post on forums like Innovate's, that's a pretty small idle air bleed relative to the idle feed restriction. However I can't recall anyone else really spending the time you have with an annular boostered carb. The carb I'm currently working with also has annular boosters (installed by QF) in the primaries. Right now it has .028 IFRs and .073 IABs. Next chance I get will be to try .026 IFRs and then that's probably the end of my experiments with that carb.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/21/11 02:45 PM

""Compared to what I've seen, and what people post on forums like Innovate's, that's a pretty small idle air bleed relative to the idle feed restriction. However I can't recall anyone else really spending the time you have with an annular boostered carb.""

I have spent many hours searching the other sights looking for a good tuning reference on an annular carb. They are out there, but there is not much detail in how they tuned the carb and how they ended up in the tuning process. I have not found anyone that is using the smaller 60 main jets. I have found some using the .031 IFR's though. Mine came stock with .033" IFR's so I am fairly close. My carb cam stock with 068 main jets, but this just proves that with some tuning, the A/F numbers can be achieved. I have tried larger main jets but I had to use the larger IAB's to compensate for the cruising 30-60mph A/F. Then when I used the larger jets, the 60mph+ cruising A/F numbers went way fat. So my current .064" IAB's are just a tool to lean out my A/F numbers slighty to keep me in the upper 14's to low 15's. Actually, the last numbers that I posted were with 60 main jets and .060" IAB's. I want to lean those numbers out slightly so I put in some .064's and that should do it.

I started my tuning with the .028 IFR's and using the stock .071" IAB's and found my 30-60mph cruising A/F from 15.5-16.5. That is when I changed to the .031's and have been using them since. Then as I change the main jets, I then compensate with the IAB's to get my cruising A/F where I want it. I talked with QF about the 60 main jets, and they were surprised to see such a low jet but they also said that the annulars do pull allot of fuel and as long as I am getting the A/F numbers, then tune away. My vacuum gauge shows "0" at WOT, so the motor appears to be happy.

Note: My stock main jetting and stock pvcrs sizes were .068 and .059. I am now using the .060 main jet and .069" pvcrs which equate to the same volume.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/22/11 01:56 AM

Mattax,

Am I understanding your statement regarding the IAB size to imply you expect the booster type to have an effect on the transition circuit behavior?

Dave

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/22/11 02:02 AM

Y07_A66:

One of my theories was that the transition circuit on your secondaries was very lean, and so when you first tip into the secondaries the AFR rises a bunch. However, given your current IFR and IAB sizes, that does not seem like the most likely culprit.

The secondary AP can certainly be part of the issue if the secondaries are starting to open, but given how long the leanness persists, it seems there may be something affecting fuel flow in the secondaries with small secondary blade openings. At the moment though, I don't have a good theory.

Look forward to your further testing! Will you test with the secondaries disabled?

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/22/11 02:08 AM

"but given how long the leanness persists, it seems there may be something affecting fuel flow in the secondaries with small secondary blade openings."

Dave,
I delayed the secondary cam a BUNCH! The secondary blades were difinately opening way before the cam was sending fuel. Once I get the curve set back up, I will retest the secondary cam timing to fix that issue.

Thanks

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 09/22/11 02:12 AM

Quote:

Mattax,

Am I understanding your statement regarding the IAB size to imply you expect the booster type to have an effect on the transition circuit behavior?

Dave

I beleive it's a possibility because the main circuit may contribute sooner with an annular booster than a straight leg. Another factor is the size of the booster. The boosters that Quick Fuel installed on the 3310 that I'm working with are huge. So that should induce the mains to start sooner but of course the high speed air bleed and emulsion holes can effect that. Bottom line is that I'm just curious about what other people have found with annular boostered carbs.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/22/11 03:14 AM

Mattax,

I have never tinkered with an annular carb. I can see how the main circuit behavior will be different with such a booster and should activate sooner and pull more fuel. I'm not sure about the transition circuit itself but perhaps the booster changes the operating vacuum levels (since the transition circuit is driven by vacuum level) under the same conditions (ie downleg pulls 15"hg at 2K but annular pulls 16"hg). An interesting thought to ponder...

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/30/11 06:44 PM

The weather has not allowed me to test any changes, so until then, I wanted to discuss this chart. Every since Spring when I installed the sensor, I have been tuning to get my WOT at the 12.6/12.8 range while thinking that 14.7 was my stoich target. Then I read this chart and I am running 10% Ethanol.
It appears that I should be aiming for 12.2 WOT and thinking that 14.1 should be my stoich (Neutral/In D target) which is allot closer to what my engine wants versus the 14.7 target.
It appears that I need to rethink my tuning by .5 A/F or so. I will still tune to what the car wants but this chart makes me rethink my numbers just a tad, especially my WOT target.

Attached picture 6849337-6738904-EthanolPercentageAirFuelratiotable.JPG

Attached picture 6849337-6738904-EthanolPercentageAirFuelratiotable.JPG

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 10/01/11 05:10 PM

Hmmmm...that is a very interesting insight. I had never considered that. All of the pumps in my area indicate "pump may dispense E-10" and I assume they do but it is hard to be certain.

What is the reference for this table? The numbers do make sense, so I am not really questioning this, but am curious as to how reliable the source is.

Given the uncertainty on what you are getting from the pump, what do you do? Tune for somewhere in-between (E-5)?

It seems this would also be a problem for production cars, unless they had some fairly accurate way to determine the mix of the fuel. I know there are "FlexFuel" vehicles that can handle different fuels on the fly but I don't know the technique to do that. It is likely easier to distinguish between gas and E-85 than gas and E-10.

I know some people complain of how their motor runs on E-10, and in essence the tune may be leaner with the E-10. I still feel the proof of the ideal WOT AFR is going to be on the strip or a dyno, not one specific number.

Dave

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 10/02/11 12:34 PM

""but am curious as to how reliable the source is.""

I tried to find it but I am pretty sure that a FAST rep showed the chart in another thread.
The chart is an interesting reference and now that thy are talking about E15, this would give us a good tuning reference if this takes place.

While trying to get to the magical 14.7 number, I have found that the engine wants what it wants. I know that I can not go any leaner on E10 than 15.8 on cruise, but after seeing this chart, I see why people are aiming for different numbers. I may shift my A/F range down from 14.5-15.5 max to 14.0-15.0 based on this chart. Or, not worry about my low 14 number during cruise thru out the temp changes of the year.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 10/09/11 06:32 PM

The last issue was trying to find out why my light to medium accel was showing 16+ on the A/F meter. I delayed the seondary from 40% to 60% and also added a more aggressive primary pump cam and this helped a little but was still showing mid 15's to low 16's and the car does not like the upper 15's and started surging under accel.
Since I need more fuel under accel and since reading more about the A/F ratio of E10, I decided to richen my existing 30-70mph cruising A/F range that was showing 14.2-15.4. Since my driving season is quickly coming to an end, I decide to make a few changes at the same time:
60 primary jets to 62's
.069" PVRC's to .071's
9.5HFPV to a 10.5HFPV
green primary pump cam to an orange
With these changes there was only about 20 minutes and 2 degrees difference in outside temps (high 50's) and what a big difference in power!! My light/medium accel was now showing 13.8-14.4. I could feel the difference in power while the A/F gage was in this range. My cruising range richened up by about .5 on the gage. The E10 chart shows stoich at 14.1 and I am happy with mid 14's instead of low 15's from 30mph to 4000rpms.
What really surprised me is how flat my A/F range is now.

30mph = 14.2
35mph = 14.4
40mph = 14.2
45mph = 14.6
50mph = 14.6
55mph = 14.4
60mph = 14.2
3500rpms = 14.2
4000rpms = 14.2
I am done with the primary side!!!!! (62 jets, .064 IAB's, .039" HSAB's, .031" IFR's, .071 PVCR's,)

I then looked at my 50mph to WOT and found a spike to 12.2 and then it leaned out to 13.0 at the shift point. After reviewing the E10 chart, the WOT should now be 12.2 instead of the gasoline 12.6. I am going to richen up the secondary side by 2 jets and see if that keeps the A/F in the low 12's.
I also made a rolling start to WOT and my A/F spiked to 12.4 and then leaned out to about 13.4 at the shift point. This is too lean so I am hoping that the secondary jet change takes care of this.
The last thing that I tested was the overall hard acceleration with the 62 jets and the .071" pvrc's and I was surprised. The car pulled harder now with this combo than it ever has. It likes the .071" pvrc's with the 62 jets.
I have no issues with the main side of the carb and now I just want to tweak the secondary jetting with the 60% delay.
Note: I still have the secondary pink pump cam turned counter-clockwise as far as it will go which creates a gap between the pump cam and the pump arm screw. There is no drivability issues with this setup during my normal driving which is fairly aggressive and my WOT A/F is 90% there.

UPDATE:
75 degrees: 80 secondary jets made my 50mph to WOT show 12.8. The 78 secondary jets made a 13.4 WOT run, so it looks like I need to try some 82's next.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 10/10/11 03:24 AM

Sweet!

If the AFR increases thru-out the RPM range, you might want to think about decreasing the HSAB a bit.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/17/12 08:43 PM

First drive of 2012 with the following changes:
Swapped FBO ECU for MSD Steet Fire ignition box
Swapped old FBO dist for FBO dist with VA
Cool Carb heat shield

Last year, I finished up with A/F readings from 30mph to 60mph in the 14.2-14.6 range. 3500/4000rpms was consistant at 14.2. 50mph-WOT showed rich spike into the low 12's and then my WOT shift points leaned out a little to 12.6. My cruise to decel showed rich into the 12's. A couple of you suggested swapping to a vacuum advance distributor and that leaned out the cruise to decel A/F reading into the upper 13's.

My main goal this year is to get my 30-60mph cruising into the mid 14's to low 15's. I also want my WOT shift points around the 12.8/13.0 range.

I got two test drives in today in 65 degree weather. Once I retuned the carb to 13.6/13.8 in D, then I took notes at the following mph.
30:14.2
40:14.6-15.2
50:14.6/14.8
60:14.0
3500/4000rpms: 13.8
50-WOT: spiked to low 12's then leaned out to 12.8/13.2 at shift point
Light accel mid to upper 13's
Heavy accel high 12's

Something made my numbers go rich and my idle at a stop was acting up. When I got home I found my rear float WAY too high and it ended up have a piece of crud in it. I opted to change the primary jets from 62's to 60's and my pvcr's from .065" to .069's. I mainly wanted to lean out my cruising just a tad more and lean out my 3500/4000rpms into the 14's.

My second test drive showed the following changes after retuning my in D A/F to 13.2/13.4:
30: 14.2
40: 14.6-14.8
45: 15.4-15.8
50: 15.2-15.6
60: 14.4
3500/4000rpms: 14.2
50-WOT: No rich spike, A/F went directly to 13.0 and stayed at 13.0 until shift point
Light accel 13.8-14.2
Heavy accel low to mid 13's

I like most of what is shown above except for the readings leaner than 15.4 which gave me some slight surging. I am going to swap out my .065" IAB's for some .060"'s to see if it will richen up the 45-50mph cruise just a touch. The car loves the extra timing at idle (was 24, now 32 with VA hooked up to manifold vacuum) and it idles much smoother in the 13.2/13.4 range in D with foot on the brake (like at a stop).

Carb Review: QF SS-750-Annular Double Pumper: 60/80 jets, .031 IFR's, .065 IAB's, 10.5 HFPV/.069 pvcr's, 60% secondary linkage delay, fuel level 1/3 up the sight glasses.

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 03/18/12 05:48 PM

Hi Dave,

Don't know if you're still having trouble with the mixture leaning out before the PV kick in.
But like Davenc was saying, that might be the cause of the 0.039 HSAB's you're running. Standard HSAB's are much smaller at 0.033.
A too large HSAB leans out the mixture at higher flows.

Have a look at this graph.
Pics are always clearer than words.;)

So you might have to go with smaller HSAB's to keep it from going lean at medium acceleration.
The lean mixture should also show up at cruise with higher loads or rpm.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/18/12 06:41 PM

Frederick,

""Don't know if you're still having trouble with the mixture leaning out before the PV kick in.""

Not anymore. The first two drives looked really good except for the cruising went lean on me after the latest jet change. I decided to just richen up the front IAB's and then see if that changes the A/F ratio enough to get me back down to the low 15's. I only need to take out about .5 on the gauge (between 40mph and 50mph). If it does not, then I will even it out and change the rear IAB's too.

My light and medium acceleration looks good. Medium is in the mid 13's and light is right around 14.0. When my pv is open (10.5 HF), the .069" pvcr's look like a good combo with the leaner main jets.

""A too large HSAB leans out the mixture at higher flows.""

That is what I found when I swapped out the stock HSAB's. I have already made two HSAB changes, and each time my 60mph+ A/F leans out a little at a time. Since my A/F numbers from 60-75mph are in still in the 14.2 range, I am considering leaning out my .039 HSAB's again

. I would really like to get the 60mph+ into the upper 14's.

Once I get the 40-50mph richened up a tad, then I will test some on the HSAB's.

Thanks for the response.

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 03/18/12 06:52 PM

Just out of curiosity, what size did you go to on the front HSABs?
I'm also experiencing lean out at medium acceleration, AFR goes to around 16 before the PV kicks in. I'm considering going with smaller bleeds; just the opposite of where you're going.

But won't know more 'till I replace the sinking float.

What rpm is 60-75rpm?

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/18/12 06:56 PM

So far, all of my HSAB's have been the same. I have tried .033's, .036's and now the .039's.

""I'm also experiencing lean out at medium acceleration"".

What front pump cam and squirter combo are you running?
I am running red/.037 on the front and that gives me the mid 13's from cruising speeds to medium accel.

My 60-75mph is 3000rpms to 3600rpms.

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 03/18/12 07:05 PM

Pink cam and 0.031" squirter.
But the lean condition is after the accelerator pump.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/18/12 07:11 PM

That pink cam should last most of the throttle position. That is a loooong duration cam. Try testing a red or an orange cam to see if you see any changes.

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 03/18/12 07:19 PM

Ok will try to see if that cures it.
But like I said this is after the pump shot.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/18/12 07:44 PM

No it is not. Depending on which pump cam you are using, the pump shot will last between 50% throttle blade rotation and even up to 80% throttle blade rotation.
If you are cruising, you are only at 20-30% throttle rotation as a guess. The pink cam has the least amount of volume at 30% throttle position. As a reference, the orange pump cam has 30% more volume than the pink cam at the same 30% throttle blade rotation (depending on which pump cam chart you go by). The orange cam has allot more fuel volume and it lasts up to 70% throttle blade rotation.
To test this, with your engine off, just rotate the throttle and watch how far you have to move it until the pink cam quits shooting fuel. The pink cam is a 80% cam but it is in the middle on the volume chart, but it is very lean for most of its duration.

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 03/18/12 08:45 PM

You misunderstand, I meant after the pump shot has phased out, it only last a second or 2.
It's after this that I'm experiencing the lean situation.
It's like this:
cruising, press throttle to accelerate and hold throttle at that position, pump shot, lean condition.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/18/12 09:19 PM

Sorry about that. Now I understand why you are going to try the richer air bleed.

Is there a certain rpm range that this happens or is it after any accel transitioning into cruise speed?

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 03/18/12 10:55 PM

No apologies neccesary, sorry for not explaining it better the first time.

Well like I said, I've got a sinking float, so no guaranties. But when cruising at higher rpm's than before I did notice the mixture going leaner.
If I had to pick a specific rpm I would say above 3500-4000. It doesn't go as lean as when accelerating, but the trend is there.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/18/12 11:17 PM

""If I had to pick a specific rpm I would say above 3500-4000.""

From what I have tested, that is the range for the HSAB's. The last two jet changes that I made, I went leaner by 2 sizes and my 3500/4000rpm range only leaned out by .2 each time. Not allot of A/F change for 2 sizes and my lower rpm range can't go any leaner. So this rpm range is where I need to lean mine out while you are trying to go richer.
I need some small drill bits in the .045-.050" range for my next HSAB test. What size are you going to test?

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 03/19/12 12:58 AM

I've still got the 0.031 the carb came with, so I'm going to try that first.
If I need any other size I will drill them.
Already got the blanks, much cheaper.

From what I know the jet affects the whole curve; shifting it up or down.
A bigger HSAB affects the shape of the curve; richer at lower flows, leaner at higher flows.
Like the graph I posted shows.

Just be careful it doesn't go lean at higher flows with the smaller HSABs.
Can't remember where I read it but there's a range where changing a main jet has much more effect than elsewhere.

I still like going smaller on the jets better than going with a bigger bleed even if you take bigger steps with the main jets.

"From what I have tested, that is the range for the HSAB's"
Not sure what you mean? AFAIK the HSABs have an effect upto max flow?

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/19/12 01:26 AM

My testing has shown that the HSAB's affect the upper rpm range and the IAB's affect the lower rpm range.

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 03/19/12 02:03 AM

Yes, but they also affect the shape of the curve.
They don't just shift the whole flow range leaner or richer.
Also the idle air bleeds serve a much different purpose than the HSABs. While the HSAB feeds air into the well to emulsify the fuel within the well, changing the fuel flow differently at different areas in the flow curve, the idle air bleeds are for the most part simply a vacuum leak, that controls the amount of vacuum pulling on the idle well and idle jet.

Here's another pic to clarify what I'm talking about.
http://www.innovatemotorsports.com/forums/attachment.php?attachmentid=1803&d=1177457666
D is the HSAB
A and B are the emulsion bleeds.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/19/12 02:37 AM

Thanks for the info

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 03/19/12 03:38 AM

Y07_A66:

It looks that your target WOT AFR is 13.0. Some time ago you posted the chart that indicated that with E10 the target should be around 12.2. Do you have E0 where you live, or is there some reason you are discounting the chart? I thought it was an interesting insight when you originally posted that.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/19/12 11:33 AM

Dave,
Good catch. I am only targeting 13.0 for the short term leanest WOT reading, just like I know that my leanest safe cruise limit is 15.6.
I do not get any pinging at that 13.0 reading and then I will work my way back down into the low to mid 12's once I get the cruise back in line.

Thanks Dave

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 03/19/12 01:33 PM

Quote:

Yes, but they also affect the shape of the curve.
They don't just shift the whole flow range leaner or richer.
Also the idle air bleeds serve a much different purpose than the HSABs. While the HSAB feeds air into the well to emulsify the fuel within the well, changing the fuel flow differently at different areas in the flow curve, the idle air bleeds are for the most part simply a vacuum leak, that controls the amount of vacuum pulling on the idle well and idle jet.

I think the primary author of that thread where you took those illustrations would rather disagree with your fourth sentence. One of Tuner's points is that emulsification is not a primary goal. Also the top emulsion-hole and 'kill bleed' hole are used in the main circuit to vary the initial pressure drop. Here's the thread, Mr Tuner sir, Holley emulsion holes? you can decide for yourselves. Motorhead's graphic will show up in the second thread linked at the end of that one.

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 03/19/12 01:46 PM

Quote:

Just out of curiosity, what size did you go to on the front HSABs?
I'm also experiencing lean out at medium acceleration, AFR goes to around 16 before the PV kicks in. I'm considering going with smaller bleeds; just the opposite of where you're going.

But won't know more 'till I replace the sinking float.

What rpm is 60-75rpm?

Fredrick,
I think what you and Dave have been discussing is basically correct. And agreed you have to get the float fixed because that's effecting the pressure head and everything in the wells.

My only additional recommendation is to determine the HSAB based on the wide open throttle acceleration through the top of the RPM and load range. Your engine may be perfectly fine going to 16:1 AFR before the PV kicks in. It depends on the engine and the load. If you hold it at that point and it goes flat and loses power, then its too lean. In that case, adjust the main jets or open the power valve sooner.

Also take a look at your the spark plugs after doing that.

PS. As you may have seen on the Innovate forum, I found it useful to do testing with the secondaries disconnected.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 03/20/12 01:48 AM

Mattax,

Thanks for putting that link in this thread. I think there are a number of knowledgeable folks on that forum. I'm no expert but at times I am surprised that what I believe are basic carb principles are not taken into account. For example, in that entire emulsion discussion I don't see any mention that the fuel level in the bowl drops as the fuel flow thru the carb increases. This lowering of the bowl fuel level has several consequences such as exposing lower E-holes directly to air and reducing the "head" pressure which is a factor in lowering the fuel level in the main well and impacting flow rate thru the main jet. An emulsion hole may change from "below" to "at" to "above" fuel level.

I don't say this to discount any of the information there (there are certainly great items) but perhaps to just caution that any information on the net may have slight problems or gaps.

Posted By: Dadrules

Re: Tuning Results From An O2 Kit? - 03/20/12 03:22 AM

Just a big thank you to those of you in this thread.

I am new to this party, close to the end of a 7 year build/restoration/resurrection/conversion of a 65 Barracuda. grew up on 57 and 64 Chevy's. then later Datsuns and Toyotas. 7 years ago i didn't know squat about Mopars. I'm now recently retired, shop expanded, lift installed and i'm finishing up the Barracuda with hopes of beginning to learn to race this summer. I'm 62 and battling cancer, anyway i just wanted to say thank you for this dialog. i knew enough to put in an O2 sensor last year, haven't run it yet but this thread and the "corners are best" forums have been hugely educational. i really thank you guys for sharing this information in a digestable fashion.

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 03/23/12 11:29 PM

Quote:

I think the primary author of that thread where you took those illustrations would rather disagree with your fourth sentence. One of Tuner's points is that emulsification is not a primary goal. Also the top emulsion-hole and 'kill bleed' hole are used in the main circuit to vary the initial pressure drop. Here's the thread, Mr Tuner sir, Holley emulsion holes? you can decide for yourselves. Motorhead's graphic will show up in the second thread linked at the end of that one.

Mattax,
Thanks for clearing that up.
I'm no expert, didn't know anything about Holley's until a year ago. But trying to learn more everyday.
Can't find it anymore, but the statement I made came from the innovate forum too.
Agreed lot's of good reading there.

Quote:

Fredrick,
I think what you and Dave have been discussing is basically correct. And agreed you have to get the float fixed because that's effecting the pressure head and everything in the wells.

My only additional recommendation is to determine the HSAB based on the wide open throttle acceleration through the top of the RPM and load range. Your engine may be perfectly fine going to 16:1 AFR before the PV kicks in. It depends on the engine and the load. If you hold it at that point and it goes flat and loses power, then its too lean. In that case, adjust the main jets or open the power valve sooner.

Also take a look at your the spark plugs after doing that.

PS. As you may have seen on the Innovate forum, I found it useful to do testing with the secondaries disconnected.

Thanks, good to know I'm on the right track.
Am I correct in understanding that with a flat fuel curve of say 12.5 at WOT the mixture will still go lean on medium acceleration before the PV opens?
And that if you get problems you can't fix them with a different air bleed?
I'm genuinely interested in this and I haven't been able to find anything on this on the innovate forum.
Only that Tuner said the it's normal the mixture would go lean before the PV opens, but not why or how to solve it.(if it becomes a problem)

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 03/24/12 04:01 AM

You're welcome. Glad I could help on that one. Let's face it. This is a tough subject to explain clearly, and then sometimes even the most knowledgable ones either misunderstand or mistate, or just jump in their thinking in way its hard to follow.

Quote:

Am I correct in understanding that with a flat fuel curve of say 12.5 at WOT the mixture will still go lean on medium acceleration before the PV opens?

Correct. That is the way fuel delivery is normally set up. Perhaps the best graphic of that is the one from Obert in Tuners post.

Quote:

And that if you get problems you can't fix them with a different air bleed?

If you're asking about part throttle problems, I wouldn't say can't, but it didn't fit the description of the problem you described.
As you saw in both those charts that you referenced, the main air bleed has the most impact on the mixture when the circuit starts to operate and as it gets toward maximum flow. My experience and observations has been that the main circuit is providing most of the fuel when holding a steady speed around 60 mph (3000 rpm). In otherwords, around this point it has just fully taken over from the idle circuit. Changing the main air bleed (MAB) will likely start the mains a little sooner or a little later. But it will also effect the mix at the top of the rpm range.

So if you've got a nice flat AFR at WOT, and you change the MAB, it will effect the AFR at the top of the WOT. In my thread A little Dyno Fun: Disconnecting Secondaries you can see that the Primary MAB is pretty close but the Secondary MAB (and or e-holes) are not a good match.

The situation you described was that getting maybe 70% into the throttle, the load was too much for the lean AFRs. Looking back at Tuner's post #17 linked above, see the pages from Larew and Taylor have need to go richer at different loads. The one engine needs richer mixture at near 90% maximum load where the other somewhere around 70%. So your PV is opening by 90% load, but maybe not at 70% load. A higher power valve woild take car of that.

I'll also attach an AFR table (using E10 pump gas) from my own setup last September. It's not perfect by any means but gives you an idea of the relationship with vacuum and rpm. It includes only data from when the throttle was steady. The larger vacuum numbers for any given rpm are when the engine is light coasting and very light (nearly closed) throttle. [right click to see it full size}

Somewheres in the Innovate forums you can find some discussions of PV tuning. Some practical, some informative but unless you have access to a 4 or 5 gas analyzer, just informative. I've spent hours there digging back to the begining. Slowly I've absorbed some of it.

Attached picture 7132899-750-M1-SteadyTable.jpg

Attached picture 7132899-750-M1-SteadyTable.jpg

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/24/12 11:45 AM

Mattax

""you can see that the Primary MAB is pretty close but the Secondary MAB (and or e-holes) are not a good match.""

When do you know (per the chart) when to tune the PMAB versus the SMAB?
(Is it at the 3400rpm per your chart?

Thank you

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 03/24/12 01:49 PM

I seperated the Primary MAB (aka HSAB) from the Secondaries based on the dyno runs posted in A little dyno fun . The above table is mostly idle/transition circuit and primaries. It's possible that secondaries could have been cracking open at 3400 rpm or less, but I don't think they are in this particular chart.

So first lets go to the dyno runs. Below is one of the pdfs from logworks. [You can see it better in Logworks but it also shows on the Dynojet's data, see the pdfs in the Dyno thread for these.]
In this particular pair of runs, full throttle was applied just above 4000 rpm (so the transmission would not downshift). Notice the primary only run has a fairly flat AFR curve. HSAB is fine.
However the run with the secondaries has an AFR curve that goes lean to rich at the start and then trends lean. (Side note: Start is around 4000+ rpm due to the test, if you look at the tests with full throttle starting in mid 2nd gear, secondareies are partially open when 3rd gear hits.)

Since we know the primary WOT fuel curve is flat, the issue here is mostly if not all in the secondaries. Just based on the trending lean, the it would seem the secondary HSAB is too large. Further, its possible the lean then rich start of the secondaries is due to the secondary HSABs being too large.

Then, if the secondaries are starting to open on the highway (possible with a light spring or a mechanical linkage set to open early) it would show up in the table above. In my case, when running the yellow secondary spring, it looked to me like the secondary main circuit might have been effecting normal high speed (65 mph) highway driving a little bit. In my case, it was a little lean because as we can see from the WOT run, the secondaries mains are having trouble starting up. Based on the numbers, the table above is not from a light secondary spring configuration but I'd have to check my notes.

However, the heavier spring is not a solution to the secondary circuits AFR curve. Its just changing when the secondaries open, it doesn't address the curve. Once the curve is right, the opening should be seamless and then it will be easier to determine how quickly they can be brought into play and still help performance (good rsponse, more torque and power).

Bottom line is that both primary and seconday HSAB should be set based on track or dyno data.

edit: jpg rather than pdf attached. X axis (bottom) is Time, Vertical axis is RPM , AFR, and Vacuum.

Attached picture 7133204-N2-Reconnect-Secondaries-log.jpg

Attached picture 7133204-N2-Reconnect-Secondaries-log.jpg

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/24/12 02:09 PM

Thanks allot Mattax.

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 03/24/12 02:29 PM

Here's a pair of runs where we went to WOT a bit earlier and let it auto-shift.
This is a slightly different carb configuration than the above pair. Details in that Innovate thread but the point is the lean - rich hump starts in 2nd gear and the trend rich doesn't become apparent until mid third gear. However by comparing with the primary only run, it indicates the same issue, secondary HSAB too large.

Also you can see how the Dynojet data differs from an Innovate logger, both with WBO2.

Attached picture 7133240-N1-Discon-Secondaries.jpg

Attached picture 7133240-N1-Discon-Secondaries.jpg

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/26/12 02:09 PM

Since I was showing some mid-high 15's in my last test drive, I decided to swap the .064" IAB's for some .060" IABS and give it another test drive. The first A/F number is with the leaner .064" IAB's and the second A/F number is with the new .060's (all four in each case). This is a good reference as to what one IAB swap will do to the A/F reading. This one change made a .6-1.0 change in the cruise A/F readings with the outside temps only 8 degrees difference between tests:

In D (foot on the brake): 13.2-13.4 // 13.0-13.2
30: 14.2 // 13.6
40: 14.6-14.8 // 14.0
45: 15.4-15.8 // 14.4
50: 15.2-15.6 // 14.6
60: 14.4 // 14.6
3500rpms (70mph): 14.2 // 14.6
4000rpms:(apx 75mph): 14.2 // 14.4

The .060" IAB's richened the 40-50mph cruising A/F numbers away from the mid-high 15's and brought them back down to the 14's where I want them.

Since my local gas station is E10 and the Stoich for E10 is 14.1 (gasoline 14.7), it looks like I have the cruise numbers in good shape. My in D (foot on brake) numbers show the best vacuum results when I am reading 13.2/13.4. So my 30mph reading will probably stay in the 13.6-13.8 range which I can live with. The 60mph+ numbers leaned out a bit but that might be because I lowered my primary float about 1/8 turn. Both of my floats are now about 1/8" above the bottom of the sight glass for reference.

My 50mph to WOT and my 55mph to WOT (cruise to WOT) are still showing a 12.8-13.0 reading until the WOT shift point occurs at 5700rpms. I was also getting a lean hesitation at the WOT downshift which I can easily fix with a pump cam adjustment on the secondary side.

My next test is to get the cruise to WOT readings back down into the low to mid 12's (E10% Stoich=12.2). Once I see what the secondary pump adjustment does to the WOT A/F number, I may reduce my secondary HSAB's down from the current .039" to .036" to see if I can "sneak-up" on the low to mid 12's. I decided to go this route instead of changing the secondary jets because I have leaned out the HSAB's as part of my primary tuning, and now I might be able to reduce the secondary HSAB's back down closer to stock (.031").

Would changing the "Secondary" HSAB's be a better choice or should I just go with the secondary jet swap?

Thanks

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 03/26/12 04:30 PM

@Mattax

Thanks a lot for explaining.
To be honest I'm not yet sure if there is a problem or not, but I always like to think ahead.

Until now I've only been tuning at different cruise rpms. But what I haven't noticed before(not paying attention to) is that on acceleration the mixture goes lean. 15-15.5 AFR on perhaps 40-50 percent of throttle and the faster I accelerate the leaner it goes. Didn't get any stumble or pinging(I think) but it got me scared enough not to go push it any further before doing some more research and getting AFR's right at all cruise rpms.

I'm going to try a smaller HSAB on the next run and cruise at higher rpms first before doing a WOT run. (HSABs from 0.033 to 0.031)
Hope the float will arrive soon.

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 03/26/12 10:49 PM

Hope you're not letting the AFR numbers scare you. But when you write 'right AFRs' it seems like you're chasing numbers. Think of AFR numbers not as goals, but reference points, clues that help you figure out what is going on. Every engine will have slightly different needs. Your goals should be most economy and most power.

Urich & Fisher's Holley Carburetors and Manifolds provides a small section on part throttle tuning. It's aimed at road racing but the test methodology is to hold a vacuum in 3 or 4rth gear and measure the time it takes to accelerate over a set distance. Then do it again at a lower vacuum (more throttle) and again lower yet. Take it down to the PV opening. Then do it all again with richer or leaner jets until you get the best times. If the best jets don't match the jetting for best WOT, then adjust the PVCR.

That's pretty tricky to do safely on public streets even with a data logger, at least around here. However a dyno that can apply an eddy current load can work toward a similar test program. I tried it on inertia only but I don't think its terribly valid and its hard to control the throttle because the load isn't higher enough. There aren't too many dyno operators that are going to be this sophisticated about dyno testing and know carbs.

Simplest approach is to get best mph on the 1/4 mile. The nice thing about AFR monitoring is you can see if its changing during the WOT top gear. If it is, look at the HSABs. Then see if you can go leaner for highway cruise with the primary main jets. It won't ping at light throttle, it will lose power or rev up and down. At that point, you got to slow the car down to 50 or 55 mph and when you get back, jet richer. If you're doing WOT on an inertia dyno, jet a step or two richer before going out to the real world. I didn't one time, and thats how I got to experience what too lean feels like.

- I'm not sure if it the table I posted was clear. Throttle position is roughly a diagonal line on that table. A throttle position sensor is certainly another good tool in the datalogger arsenal. I'd like to add one.

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 03/27/12 10:24 AM

With right I meant pretty even at all rpm's not leaning at higher rpm's.

But you're right, 14AFR at cruise and leaning out more the more you step on it do scare me.

Yes, the graph was clear(Higher vacuum = lower load, Closer to 0 = higher load)
However it doesn't show the leaning out at the level I'm experiencing. (15-16)

4 speed manual, so I think 1/4 mile will vary too much.
But the Ulrich method would be a great idea. Thanks for that.

Finding a quiet road is much easier here than finding a drag strip. Think the nearest is about 100 miles.

Do you use a throttle stop to accelerate at the same rate every time?

I know logging would be a great and I've tried logging rpms with the LM1 but it's very unstable and it screws with the AFR as well.

I might have a fix for it, but not tried it yet.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 03/27/12 12:59 PM

My next test is to get the cruise to WOT readings back down into the low to mid 12's (E10% Stoich=12.2). Once I see what the secondary pump adjustment does to the WOT A/F number, I may reduce my secondary HSAB's down from the current .039" to .036" to see if I can "sneak-up" on the low to mid 12's. I decided to go this route instead of changing the secondary jets because I have leaned out the HSAB's as part of my primary tuning, and now I might be able to reduce the secondary HSAB's back down closer to stock (.031").

Would changing the "Secondary" HSAB's be a better choice or should I just go with the secondary jet swap? Note: My current secondary jets are 80's. This is the easy swap but I am not sure that it is the correct swap, mainly because I would be changing out the secondary HSAB's only.

Thanks

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 03/27/12 01:38 PM

Quote:

With right I meant pretty even at all rpm's not leaning at higher rpm's.

You may be on the right track. It depends on throttle position. If you are opening the throttle a bit at higher rpm, then the leaner AFR is normal. More throttle is needed to hold higher speeds steady so this is a tough variable to nail without a TPS.

Quote:

But you're right, 14AFR at cruise and leaning out more the more you step on it do scare me.

Yes, the graph was clear(Higher vacuum = lower load, Closer to 0 = higher load)
However it doesn't show the leaning out at the level I'm experiencing. (15-16)

Thats only due to the peculiarities of my setup. With more dynamic (and static) compression the motor would have more heat and more effecient combustion. It was OK on pump gas 10 years ago but now is marginal. The trend and pattern is prtty univeral, but the numbers and the PV location will vary considerably.

Quote:

Do you use a throttle stop to accelerate at the same rate every time?

Throttle stop is an interesting idea. I think the way to do it on a dyno may be to hold the throttle steady against a load and let the vacuum vary. The way I was trying it was to watch the vacuum gage and vary the throttle to 'crowd' 14"Hg then 12" then 10".

If you can get the rpm working with your logger, and maybe an extra set of eyes and ears, you can probably do this safely on pavement rather than rollers. Put it in 3rd gear and start the acceleration from 30 mph each time. Urich was recommending 30-80 mph but you could cut that top speed down if needed. You'll have the advantage of the rpm rise logged vs a stopwatch. Could it be done with throttle stop instead of vacuum gage? Don't know. I'd have to think about that. If you hold the throttle steady, the vacuum will rise with increasing rpm. So you'll not get the high load/low vacuum data in the higher rpm range.

Here's the post with dyno log of part throttle runs. When I've done crowds on the street, they are often short and not repeatable enough to compare. But it sounds like you may have the right situation to do it.

The Mike Urich and Bill Fisher Holley book is definately worth buying. There's a newer edition with Fuel Injection but you don't need that one. Urich was VP of engineering at Holley. I think that gives him a technical edge of the majority of authors.

Not sure what is up with your RPM logging. That's the big downfall of the Innovate stuff. Its not that user friendly and its a little flakey. I'm using an LM1 with the LMA3 (aka Aux box). I'm no longer using the rpm input, but the frequency channel set for rpm.

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 03/27/12 02:26 PM

I was suggesting the throttle stop because I thought trying to keep a constant vacuum would mean working the throttle and hence engaging the accelerator pump.
But in your logs I don't see this problem, AFRs are pretty constant.
Did you disconnect the accelerator pump?

Quote:

If you hold the throttle steady, the vacuum will rise with increasing rpm. So you'll not get the high load/low vacuum data in the higher rpm range.

Not even at WOT?
I was thinking you could vary the throttle stop from 10%-100% throttle.

The problem I have with connecting rpm is that it's impossible to read, it's incredibly spikey.
And it also makes the AFR spike.
I think it's electrical interference and the rpm converter not being able to handle it.
There are some threads on how to solve it on the innovate forum. I'm sure you've seen it, it involves making a pre-conditioning board to make sure the input voltage doesn't go above 5.0 Volts.
But like I said I have not tested it yet.

Quote:

I'm no longer using the rpm input, but the frequency channel set for rpm.

Any reason for using the frequency channel instead?

Quote:

The Mike Urich and Bill Fisher Holley book is definately worth buying.

I've got the Ulrich & Fisher book on Carburetors, Manifolds and Fuel Injection as well as the one by Dave Emanuel.

The Ulrich & Fisher is better for tuning.

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 03/27/12 03:02 PM

Well you're right about WOT. The vacuum rise at WOT is very small especially with a four barrel. I didn't think of that.

Oh I think the throttle stop idea has potential. Its a different approach but not wrong. My thought for doing this type of testing on a dyno was similar. The dyno would need a load on it. My best low speed testing (idle circuit) was very gentle accelerations from dead stop holding the throttle steady.

I'm using the frequency channel because the rpm input died. This was after they fixed the Auxbox's built in MAP. They offered to repair but I needed to continue testing. Maybe I'll send it back now that I'm not using it for at least a few weeks.

Does the Urich version with FI still have the section on Road Race Tuning?

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 03/27/12 04:33 PM

Accelerator pump was not disconnected. I think it is not apparent in the part throttle dyno logs for two reasons. First is that the throttle is already far enough open that the pump is little needed. In theory, pump shot is mostly to help the 'idle circuits' which can't respond to changes the way the mains can. Second reason is the throttle movements were gentle and relatively small. Any pump shot contribution would be spread out over the time of the throttle movement.

Attached is a screen shot of some part throttle crowds going uphill. Its a different carb, a 650 vacuum secondary that I was mucking up, err, learning on. Here it is set up with an 8.5 PV and the primary jets are too rich. But the main point is you can see a very brief lean pike with the begining of each increase in throttle. Could be the accelerator pump (or lack of it). Its a less than a second, and doesn't show on the accelerometer nor was it felt.

Only for the light part throttle was the vacuum held steady or 'crowded'.
-
edit. The few seconds notiicbly richer in the begining of the Light Part Throttle probably is from accelerator pump. Since I had lifted just before, the throttle position was starting from nearly closed. Thats a longer period than I normally see when logging the for pump shot tuning. Usually its all done in a second give or take a little.

Attached picture 7137907-650-85PV-Bridge-crowds.jpg

Attached picture 7137907-650-85PV-Bridge-crowds.jpg

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 03/27/12 04:53 PM

Quote:

Well you're right about WOT. The vacuum rise at WOT is very small especially with a four barrel. I didn't think of that.

Oh I think the throttle stop idea has potential. Its a different approach but not wrong. My thought for doing this type of testing on a dyno was similar. The dyno would need a load on it. My best low speed testing (idle circuit) was very gentle accelerations from dead stop holding the throttle steady.

One thing which might be a problem with the throttle stop idea is that at the same throttle position you can't put different loads on it.
A hill would give more load options, but we're kind of short of them here.

Quote:

Does the Urich version with FI still have the section on Road Race Tuning?

I think it does, but I'll check when I get home.

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 03/27/12 10:07 PM

Looked through the Ulrich & Fisher book but they don't mention the 30-80Mph anywhere.

But in the chapter "Performance Tuning" there is a paragraph titled "Tuning in the vehicle".
It starts with that you need a place that you can always use.
Also need a vacuum gauge and a stopwatch.
Start the watch as you accelerate past a certain rpm point, stop the watch when you reach the rpm where you want to be at the top end. Use the highest gear.

Is that about the same as in your version?
Which one have you got by the way?
This one:
http://www.amazon.com/Holly-Carburetor-Handbook-4150-Hp473/dp/0895860473/ref=pd_sim_b_2
Or this one:
http://www.amazon.com/Holley-Carburetors-Manifolds-Mike-Ulrich/dp/B001263G70
Or perhaps this one:
http://www.amazon.com/dp/0895864339/ref=rdr_ext_sb_pi_hist_3

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 03/27/12 11:31 PM

The last one in your list matches the cover. copyright 1987

The section I was refering to is titled "Road-race Tuning" on p. 123
- in it it suggests 30 or 40 mph to 80 mph, and specificly to crowd the vacuum readings down to the PV opening. This is to get the best main jets.
It follows a section titled "special Procedures for 'Wild' Camshafts. That section has diagrams showing the proper transfer slot to throttle relationship.
The chapter is titled Carburetor & Performance. There's a drawing of a 413 long cross ram in cut-away view on the chapters first page. Very cool picture.

(I also have the little 4150 book but its redundent to the big book. I keep the little one in the garage for reference.)

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/02/12 12:14 AM

I decided to leave the HSAB's alone and just change the secondary jetting to get my 50mph-WOT number richer than my previous 13.0 A/F. I swapped my #80's for some #82's and then my 50mph-WOT A/F ratio went down to 12.2-12.6 to the shift point. Then I wanted to test what would happen if I lowered the rear float only by 1/4 turn and that chage made the same 50mph-WOT A/F go to 12.4-12.8. So it appears that using the rear float can "tweak" in the WOT a/f number if needed.
I then decided to lower the primary float by 1/4 turn and it leaned out my cruise A/F by about .4 points on the gauge. This is where I ended up after several drives today in 75 temps.
D (foot on brake) = 13.2-13.4 (this number can go as lean at 13.6-13.8 before I start to have idle issues)
30mph = 14.0
40mph = 14.6
50mph = 14.8-15.0
60mph = 14.6-14.8
50-WOT shift point = 12.6-12.8
I achieved the above cruising numbers with 60 main jets, .060" iab's, .031" ifr's, and .039" hsab's.

I did find that the 50mph-WOT felt quicker with the A/F ratio in the 12.6-12.8 range than it did in the richer 12.2-12.4 range. The half a point was felt in my seat.

My primary cam/squirter is good with a Red/.042" combo. This gives me a smoooooth light throttle take off from a stop to cruise in the 13.8-14.2 A/F range. This combo also helps keep my medium throttle A/F into the 13.5-14.0 range which feels strong. This is with a 10.5 high flow power valve, .069" pvcr's, and small #60 main jets.

Now I am testing my secondary cam position and linkage delay (40% or 60% delay for the mechanical secondaries). Like last Summer, I have found that adding an "air gap" on the secondary pump linkage (between cam and bolt) helped lean out the WOT stabs at lower speeds. I started out with a 11.0 A/F reading from idle to WOT and now I am down to a 12.0 reading by increasing the gap which limits the extra fuel of the secondary pump. I have a couple more tests to run (enlarging the gap about one full turn at a time) before finishing my pump cam testing. Making this "air gap" did affect my 50mph-WOT reaction but adding a larger squirter on the secondary pump fixed that issue.
I now know that for my setup, that my in D A/F, my cruising A/F, and my WOT A/F numbers are close enough to leave alone. Now for the timing of the secondaries.
I have learned that just 1/4 turn on either float and 1/12 of a turn on each metering screw can affect the A/F ratio by .4/.6 on the gauge.

For those of you who are thinking of getting an O/2 sensor for your carb tuning, I can't think of a better tool that you can buy. They sure help show where you have been and where to go next on your tuning.
I started this thread with the idea of learning what each change can do to the state of tune. I had no idea how involved this thread would get after a year of tuning. This shows that even a DP carb can be tuned to work well on the street. I look back and kick myself for not getting an O2 sensor earlier.

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 04/03/12 01:54 PM

Quote:

My primary cam/squirter is good with a Red/.042" combo. This gives me a smoooooth light throttle take off from a stop to cruise in the 13.8-14.2 A/F range. This combo also helps keep my medium throttle A/F into the 13.5-14.0 range which feels strong. This is with a 10.5 high flow power valve, .069" pvcr's, and small #60 main jets.

Now I am testing my secondary cam position and linkage delay (40% or 60% delay for the mechanical secondaries). Like last Summer, I have found that adding an "air gap" on the secondary pump linkage (between cam and bolt) helped lean out the WOT stabs at lower speeds. I started out with a 11.0 A/F reading from idle to WOT and now I am down to a 12.0 reading by increasing the gap which limits the extra fuel of the secondary pump. I have a couple more tests to run (enlarging the gap about one full turn at a time) before finishing my pump cam testing. Making this "air gap" did affect my 50mph-WOT reaction but adding a larger squirter on the secondary pump fixed that issue.
I now know that for my setup, that my in D A/F, my cruising A/F, and my WOT A/F numbers are close enough to leave alone. Now for the timing of the secondaries.

Hi Dave,

Up to know I have understood and agreed with the steps you took.
But I honestly don't understand why you'd want an air gap on the secondary accelerator pump.
It just sound like you are working around the problem rather than curing it.
Also I don't think you can tune the accelerator pump without logging capability; things just happen too fast.

0.042 nozzle looks huge to me?

Frederick

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/03/12 03:23 PM

Frederick,
""things just happen too fast""

EXACTLY!! When you watch the linkage on the carb go from a steady cruising position to WOT, the secondary linkage moves so fast that the air gap is taken up in a flash. With the correct secondary squirter, I can not feel any hesitation at all with a large air gap.

I am currently testing the secondaries with the pink cam which has a very slow ramp speed (& medium sized volume) and I am using a .048 squirter on the secondary side to help speed that back up. If I was to use a quicker ramp speed cam (maybe a black), then the squirter will prabably be smaller. What I am trying to achieve is to lessen the amount of pump shot given by the secondary cam to lessen my idle-WOT A/F and my cruise-WOT A/F rich spike that I currently have without screwing up my other A/F readings. Since my cruise and my WOT A/F's are very close, I know by the A/F gauge that the secondary cam is giving too much extra fuel when I go to WOT.

Since I know that the pink secondary pump cam is too much volume, I could use a smaller pump cam or just shorten the adjusting bolt to create this air gap on the pink cam. The overall amount of the pump cam is reduced with the air gap (shorten the bolt) and since I had a slight hesitation at 50-WOT with a .037" squirter, I changed the .037" to a .040" to get rid of the hesitation. Since the pump cam is just a "band-aid", that is all that I am using it for. I do not need the entire pink cam's volume, so I am going to make the air gap larger by one full turn and retest. Then if that is still to much volume, then I will make the air gap larger by one more turn and retest again. Then if I run out of bolt adjustment, I will drop down to the smallest pump cam and retest. I did this several times last year and I have charted some of the changes. Since I made some ignition changes over the Winter, I am now just re-tweaking the rear pump cam to finish the tuning process.

I agree that the .042" primary squirter "seems" huge but I am using one of the smaller pump cams (red) and the Red/.042" combo keeps my acceleration A/F numbers in the range that I want. The squirter just speeds up or slows down the volume created by the pump cam. Since I do not want to increase the overall volume of the primary pump cam, I just want to adjust the speed of it by using a larger squirter until my A/F numbers are where I want them for accel. If I was using the stock #68 primary jets, then I would guess that I would be able to use a much smaller primary squirter. But since I have dropped my main jets from the stock #68 to now #60's, and I am able to use a smaller red pump cam, then I need the larger squirters to help tune the speed. I am running 30 of timing at idle. This might be some of the reason that a .042" primary squirter gives me a better A/F than a .037" primary squirter on light - medium accel.

I have found that since I have done so much tuning on the other circuits, that now I am down to just juggling the secondary cam and squirter to keep my A/F in check. The .042" squirter is not what "everyone else" is running, but neither are #60 primary jets. This is exactly why these O/2 sensors are such a great tuning tool.

I now totally understand why some people say "do not use a DP carb on an auto car on the street". They can be a bear to get the mechanical secondaries tuned. But I can now see exactly what my A/F is doing from idle-WOT and from cruise-WOT and I can correct the amount of fuel that the secondaries are adding which is causing my rich A/F spikes at WOT situations. I have found that in my case, limiting the secondary pump cam volume is the key.
Is "everyone" tuning their DP like this? NOPE!! Can "everyone" running a DP see what I am seeing? NOPE!!

Thanks for the response and get that new float installed!

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 04/04/12 10:47 AM

I now see what you're trying to accomplish; less volume.

WOT may be fine with the smaller pump shot, but doesn't the air-gap give hesitation on less than wide-open throttle?
Just seems the opposite of what you want, no pump shot when you most need it; when the mains aren't flowing yet.
Have you thought about shaping a cam to you needs?

Quote:

I agree that the .042" primary squirter "seems" huge but I am using one of the smaller pump cams (red) and the Red/.042" combo keeps my acceleration A/F numbers in the range that I want.

Are you sure you're tuning the right circuit. I'm not sure you can judge the pump shot on a gauge.
From what I know the shot doesn't last more than a second or so.
With the engine off and looking down the throat, you should be able to see how long a WOT pump shot actually takes?

I'm sure you've seen this one?

This is the correct one, according to tuner.

Negative on the float

I did take the car for a spin on Saturday and Sunday.
Everything fine on Saturday, but on Sunday the AFRs were much leaner, right from starting?
Went from the normal 13.5 to 15.
Any idea? Blocked jet perhaps?

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 04/04/12 01:49 PM

Are you saying after sitting overnight, the same driving condition read leaner on the meter?
If so, gasket sealing is my first guess, metering block to body.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/04/12 02:14 PM

""From what I know the shot doesn't last more than a second or so.""

That is the chart that I use. Per the chart, the pump cam can deliver fuel UP TO 50% or UP TO 80% throttle. At WOT, I am not sure how long the shot would last (in seconds pending on the pump cam).

Have you tested between the 40% secondary delay and the 60% secondary delay? If so, what have you noticed?
I have been going back and fourth between the two and I am still not sure which one to do my final tuning with. It may depend on the outside temps. Maybe using the 40% in the cooler temps and then using the 60% delay in the Summer months.

Posted By: Frederick

Re: Tuning Results From An O2 Kit? - 04/04/12 02:27 PM

Quote:

Are you saying after sitting overnight, the same driving condition read leaner on the meter?
If so, gasket sealing is my first guess, metering block to body.

Yep, one day to the next. Only very short drive on Sunday, because it was popping from being lean when you placed it under load.

Thanks, I'll check the gaskets.
Good thing I've also ordered the gaskets at the same time as the float.

Quote:

Have you tested between the 40% secondary delay and the 60% secondary delay? If so, what have you noticed?

No I have not tested the different linkages.
I will have to get the carb tuned better before I can start on that.
I can only guess at the effects the 60% delay has.
But I would only try the 1:1 linkage with a powervalve in the back.
What effects have you noticed with the 60% vs the 40% linkage?
Better part throttle response?

Quote:

At WOT, I am not sure how long the shot would last (in seconds pending on the pump cam).

I don't know either, which is why I suggested the test.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/10/12 01:31 PM

Last year I tested allot with the 60% delay and found it good for casual cruising. I am now testing the 40% delay and it appears to be a bit more aggressive which makes sense.

Last year, I was testing the "air gap" on the secondary pump cam and it actually worked great with the 60% delay linkage. Last year, I was also using a non-vacuum advance distributor which gave me 34 degrees total timing. I started out a couple of weeks ago trying to use the same "air gap" on the secondary side but this year I added a vacuum advance distributor which gives me more time from idle and up. I have not been able to make the "air gap" work so I have gone back to the standard gap setting. I think that the extra cruise timing this year has made the biggest setup change.

So far, I have been testing with the 40% linkage and I am swapping around the pump cams to see what works best. The extra timing is making me go with larger pump cams this year. My initial timing from last year was 24 degrees and now with the manifold vacuum advance setup, I now have 32 degrees timing at the same rpm. So this is wanting a little more cam on the front side. Now I am trying to select the correct rear pump cam and the interesting thing is that I am seeing an A/F change on the meter with the different size pump cams at accel and especially at WOT. I am now trying to get my light acceleration A/F down in the 13.6-14.0 range and then get my medium acceleration A/F in the low 13's and before the pump cam swaps, my WOT was 12.4-12.6. Last night after some larger pump cam changes, my WOT A/F spiked into the 11's. So I will keep adding to the P side and then reduce the cam on the S side to try and get my WOT numbers back into the 12's while richening up the accel A/F numbers.
Note: When my accel A/F numbers were in the high 13's to low 14's, the accel power was down. Now that I am approaching the mid to low 13's under different accel conditions, the car definitely feels much more responsive.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 04/11/12 02:12 AM

Y07_A66:

It makes sense to me that the acc pump shot will need to be quite different between the 40% and 60% progressive linkage settings. The amount of additional airflow when the secondaries first open will be different on a percentage basis between these two cases. With the 60% linkage it appears that the initial crack of the secondaries did not cause a significant lean hole before the secondaries mains starting flowing since the additional CFM was a small percentage of the total CFM. With the 40% linkage, this transition happens at lower total airflow thru the carb and therefore the impact of the secondaries opening is bigger.

That's my theory at least!

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/11/12 11:34 AM

Dave,
Thanks for explaining that. I wasn't coming up with any good reason for such a difference except maybe the extra timing at cruise. Your description makes allot of sense. Once I added more fuel to the secondary pump with the 40% delay, the throttle response increased allot as the seconds started in. (I was previously using the pink cam with the "air gap", then I added the red pump cam with standard gap for more fuel.)

Thanks allot for the reply.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/15/12 11:24 PM

I now have my cruising A/F numbers from 14.0-14.8 (40mph-70mph). I found that it was surging a little bit at 45-50mph at the previous 15.2, so I richened up the front float just a touch. I think for now on I need to keep my cruising A/F in the 14's.

I also have my pump cams/squirters close. I was using red/042 on the P side and red/040 on the secondary side but at 50-WOT, it gave me a rich spike at 11.8 or so. I was still only showing about 13.5 or so under a strong accel, so I wanted to richen up the Pside just a bit.
I am now running orange/037 on the P and the smallest black/031 on the secondary. This combo was VERY close to what I am looking for. My light accel was very smooth from a stop and it showed 13.8-14.0 under very light take off and no hesitation. I was showing mid to high 13's under medium accel and 12.8-13.4 under aggressive accel (not WOT) with the pv open. I also tried a rolling start (around 15mph to WOT) and the A/F dipped to the 12.4 again and hit 12.8 at the WOT shift point. My 50mph-WOT spike is 12.4 and it leans to the 12.8 mark at the shift point.

I am very happy with how the car runs today. All of my A/F numbers are in and the "Seat-of-the-pants" is fun all around. Now I am going to try and get some cruising miles on it.

EDIT:

I do have a lean spot at cruise when I go to a medium accel. My A/F goes from the low 14's to 16 then back down to the low 14's. This must be from when the secondaries are opening with the BLACK/031 cam/squirter combo. I am going to test a 037 squirter to see if that fixes the lean spot.

My next test will be to see what A/F numbers I have from idle in D (with foot on the brake, like at a stop light) to WOT with the DP carb.

Then I am going to try to see if I can switch from 91 octane to 89 octane once I have everything dialed in.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 04/16/12 01:37 AM

Excellent! Thanks for continuing to update this thread.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 04/30/12 01:49 AM

""I do have a lean spot at cruise when I go to a medium accel. My A/F goes from the low 14's to 16 then back down to the low 14's. This must be from when the secondaries are opening with the BLACK/031 cam/squirter combo. I am going to test a 037 squirter to see if that fixes the lean spot.""

I have been chasing this lean spot and I found something that I did not know. This lean spot is when I am cruising about 50mph or so and then I slowly apply pressure to the pedal. I keep adding pressure until I get up to about 70mph or so. The gauge stays in the 14 range (which is my current 40mph-70mph cruise reading) and then the gauge jumps to 16 for a second and then comes back down into the low 14's again. Since my secondary linkage is setup with the 40% delay, I was first thinking that when the secondaries come in, then I am getting the lean spike to 16 until the secondary circuit catch's up to return the A/F back down to the 14's. But now after some testing I am not sure. I started out with the secondary pump cam/squirter at black/037. Then I swapped in a .047" squirter and had the same A/F lean spike into the 16 range. Then I swapped out the black pump cam (smallest cc) for the white pump cam and kept the .047 squirter and I had the same lean spike into the 16 range. Then I jumped up to the orange cam and I still had the lean spike. Apparently the lean spike might be on the primary side instead of the secondary side. So I will swap the squirter on the P side to see if this helps.
But what I learned thru all of the cam swaps today was with each pump cam swap on the secondary side, my 50mph to WOT A/F reading stayed at 12.4 and leaned to 12.8 at my shift point. Even though each cam has a larger cc rating (black, then white, then orange), the cam size did not affect the overall A/F reading at WOT. I though for sure that I would have seen an A/F change after each cam swap. The outside temps only changed by 2 degrees during the swaps so the weather did not affect the outcome.
The overall A/F was not affected by the cam swaps but the performance (seat of the pants) was definately felt. The black cam was a little lazy when the secondaries kicked in under medium to heavy accel. Then the next larger cam I tried was the white cam. This cam brought in the power a little better over the black cam. Then I moved up in cam size again to the orange cam. This cam really woke up the motor when the secondaries kicked in. The orange cam made a big difference in performance over the little black cam from a rolling start to my 50-WOT acceleration.
So even though I felt the performance difference from the black cam to the orange cam on the secondary side, my WOT A/F number did not change.
EDIT:
The weather changed by 20 degrees and I upsized both sets of squirters and now I am seeing an A/F change with both orange cams. In the hotter weather, the orange cams are sending my idle to WOT into the 11's along with my 50-WOT A/F into the 11's. So my previous statement did not work for the cooler months but the cams sure start affecting it in the warmer temps.

This lean spike might also be when the carb is transferring from the transition circuit to the main circuit. So I might have to look at the front pump cam/squirter for some help, or richen my HSAB's up a tad to start the mains a little earlier.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 06/15/12 02:03 PM

I have been doing some WOT tests and after several attempts to find what my combo likes, I now know the answer.
Since this is a street car, I decided to make all of my WOT attempts from a steady 50mph cruising speed (14.2 A/F) and let the car go thru the first shift point which is 5800rpms. Then I write down what the richest spike is right when I go to the floor with the pedal (DP carb) and then I also take notes on what the A/F reading at that WOT shift point.
Note: All of these tests were taken with the outside temps between 75-85 degrees.

I started out with 82 rear jets and I was getting rich spikes into the high 11's with the 50mph cruise to WOT A/F showing 12.2-12.4. I ran this way for several weeks and the car felt good at WOT but not great. The car was also showing low 11 spikes at a stop to WOT too which is waaay rich with my auto/3500rpm flash/3:91/27" tire setup.
I then lowered the rear float and got the WOT A/F showing 12.4/12.6 with spikes still in the high 11's. The car felt about the same so I wanted to lean it out again.
I then swapped out the rear jets from 82's to 80's and then reajusted the rear float to achieve 12.8 A/F at WOT and what a huge performance response this gave. My WOT spikes were in the 12.4 range while the WOT shift point was at 12.8 at both WOT shifts. My idle to WOT response was excellent with my spike around the 12.0-12.2 range. This was my best WOT setup to date.
I still wanted to test a leaner WOT A/F so I swapped out my 80 rear jets for 78's and then adjusted my rear float to achieve a 13.0-13.2 WOT A/F reading. This felt good but I could tell that the power faded, but I did not hear any detonation.
I then lowered my rear float again and got a 13.2-13.4 WOT A/F reading and the power went down. My idle to WOT reaction was not as good and my overall performance went down and I started hearing detonation at hard throttle and WOT.
So after testing my rich WOT number (12.2 A/F) and then my lean WOT limit (13.4 A/F), I have now rejetted to go back to the 12.8 WOT A/F number. This is leaner than a chart that I have for 10%E (12.2), but I have found what the best performing A/F needs to be for my combo.

All of my testing has been done with one FAST #170634 A/F sensor kit on the drivers side exhaust header collector. I have now talked myself into a second A/F sensor kit to start looking at the passenger side numbers. I could have just moved the existing sensor to the passenger side, but I want to beat myself to death by added a second sensor and see how close I can get both sides to read. They should both be close but I know from my experience that a small movement in one metering screw can sure make the A/F gauge move. Since I have one side of the carb setup per the gauge and I only "eye-ball" the second side, and I also found the rear passenger side header hotter than the front of that same header, I want to add the second sensor to dial in the idle A/F and also see what I need to do to get the header exhaust temps closer to each other on the passenger side.

I just wanted to give an update for those who need a reference.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 06/24/12 04:30 AM

I bought a second FAST analog O/2 kit for the passenger side exhaust. (My exhaust is setup as true duals with no crossovers.)
I found that even though I marked all four metering screws in the full inward position (12 o'clock position with permanent marker), and I backed them all out the same amount, and I used the drivers side sensor as a reference. Even though I setup the passenger side the same as the drivers side (existing O/2 sensor), the idle was different from drivers side to passenger side once I had the dual O/2 sensors installed. This surprised me because even though I had both sides set the same, that the passenger side gauge was now showing about .4/.5 difference in the readings. It didn't take long to have both gauges reading the same, but the metering screws are different from the drivers side to the passenger side to achieve the same reading (within .2 on the gauge).
Another thing that I found was that when adjusting the passenger side metering screws, they mainly affected the passenger side O/2 sensor, but they still affected the drivers side O/2 sensor too. It took a few tries to get both sides balanced out, then I took the car for a drive. Overall, the two gauges were within .2 of each other with the carb setup the same from side to side, except for the metering screws. Cruise and WOT were also within the .2 or so which is close enough for me.
So after adding the second O/2 sensor, the main surprise was that setting the drivers side metering screws exactly the same from side to side did not show the same reading on the gauges. But cruising and WOT were mainly the same (passenger side was always .2-.4 leaner with the carb setup the same side to side). If I get enough energy, I might try adding slightly richer IAB's on the passenger side just to see if that brings in the passenger side O/2 reading at cruise a little closer to the drivers side.
The attached picture shows the difference at idle in P before I shut off the car for reference.

Attached picture 7262903-DualAnalog.png

Posted By: BigBlockMopar

Re: Tuning Results From An O2 Kit? - 06/24/12 11:57 AM

I've been playing around with an Innovate MTX-L gauge in my daily '73 Dart for a couple of months now. It's great fun being able to 'see' what's happening inside the combustion chambers.

Only difference is my car runs on Propane/LPG.

I've learned a lot aswell, but mainly how to tune a simple IMPCO propane system where the main tuning items are only a mixture screw and max-power screw on the LPG-mixer.
A lot of factors play a significant role in mixture-quality, especially with propane. As propane expands when heated, it also increases in pressure but mainly when it's a liquid state. When it's heated as a vapour under a controlled pressure/vacuum, it will lean out. Temp-differences with propane play havoc with your tune.
But with playing around with different springs in the propane vaporiser and the mixer, I've achieved a (I think) a very good tune now.

Pic below shows an AFR-number while idling from a while back.
The engine currently idles with an AFR of around 17 when warmed up.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 07/01/12 09:38 PM

PROPANE! That is cool. Thanks for sharing.

Now that I have had some more time with the twin O2 sensors, I have found that my idling in N, idling in D, and my cruise A/F readings from one side to the other are fairly the same now after a few adjustments. The passenger side usually runs about .2-.3 "leaner" during the above and I am good with that.
My current issue is that I have found my WOT readings from side to side are farther off than my idle/cruise numbers. My drivers side is right at 12.6 (aiming for 12.8) at WOT but my passenger side is richer at 12.2. I tested three different times from 50-WOT and a rolling start to WOT and my passenger reading is always .4-.5 richer at WOT.
My only tuning guess is to lean out the "passenger secondary main jet" by two sizes to see what happens. This means stagger jetting the rears.
Any other suggestions before I try this?

EDIT: http://www.popularhotrodding.com/tech/04...tech/index.html

I have now found two articles that show that the RPM intake required staggered jetting on the drivers side front corner and the passenger rear corner by 2 jet sizes. Reference #6 in the article for the diagram. The other article mentioned any four corner idle carb.

Thanks

Posted By: fuzzman

Re: Tuning Results From An O2 Kit? - 08/03/12 03:52 PM

Y07_A66
Do you have any results from trying your staggered jetting? I'm curious and have been following your thread for quite some time. I have about the same set up except my carb is a SS750 quick fuel stock jetting it came with 74 primaries and 80 secondaries and I also am using the same gauge as you but I have my sensor mounted in the Y part of my exhaust. I'm curious what your reading is at a steady cruising speed down the highway around 65 to 70 miles an hour. I'm running right now at about 13.5 to 13.8 and at idle my reading is 13.9 to 14.2. My jetting is set at 69 primary and 76 secondary. Keep up the great updates. Thanks
Pat Faley
67 Notch back Barracuda
408 stroker 4-speed
Peoria IL

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 08/03/12 04:32 PM

Hello Fuzz,

When I started out, my goal was to get my 40-70mph cruising in the 14.6-15.4 range and my in D idle A/F appeared to be good in the 13-2-13.4 range. I am now running my 40-70mph (70 = 3400rpms) cruise in the 14.0-14.4 (.039" HSAB's, & .033" IFR's) range and my in D idle at 13.8-14.0 (.060" IAB's). These numbers are based on 10% E and 91 octane.

My main jetting is now 62's and my secondary jetting is now 74 (passenger) and 80 (drivers). The 62 main jets still show 14.0 at 4000rpms, so I know that my mains are in good shape. Note: both A/F sensors are within 0-.2 of each other during cruise conditions.
As of last weekend, my D side WOT is 12.8/13.0 and my P side WOT is 12.6/12.8. I just made a secondary float change this week to try and get the D side down to at least 12.8 at the leanest reading.

It appears by your part number that you have the downleg boosters which might be why you and I are so far apart on primary jetting, along with the engine size difference. But as long as the A/F is where you need it, then I say give it what it wants.

Have you messed much with the adjustable secondary linkage? I have tried both the 40% and the 60% and I like the 40% better so far.

Are you having any issues at a steady cruise then slowly accelerating creating A/F swings?

Are you able to control the rich spike when transitioning from cruising speed to WOT with your DP?

How is your cold start now that your in D A/F is leaned out to 14?

Thanks Fuzz

Posted By: fuzzman

Re: Tuning Results From An O2 Kit? - 08/03/12 08:01 PM

I don't have all my numbers with me on my carb right now because I'm at work but I do know that I called Quick fuel about my rich problem at idle and they had me up the size of my air bleeds at each corner. I have noticed that this carb is very touchy when it comes to setting the four corner idle ajustments. When I adjust it with the vacuum gauge it ends up a bit rich when done aroud 13. So I just screw those in until I get it close to read 14.1 or so. It's been way to hot this summer so I haven't done alot of messing with the car. I noticed last week when I drove it to a car show that was about 20 miles one way that the cruise reading was right at 13.8 to 13.9 and I know I could jet down to bring that reading a little closer to 14. The plugs have been showing good color with these readings so far.
When I rebuilt the motor I just ran it with that carb right out of the box and it was so rich that it washed out the rings or what ever it did. I had a issue come up over winter when I changed out my stock heads to run edlebrock performer aluminum heads. The pistons where slapping against the bottom of the heads so, I had to tear the motor apart again and thats when the engine builder found the problem with the rings. Thats when I decided to buy the air fuel gauge and learn how to dial in the carburator. Like I said before I've enjoyed reading your post and it has helped me alot on setting up my carb.Thanks again
Pat Faley

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 08/03/12 09:17 PM

"" I noticed last week when I drove it to a car show that was about 20 miles one way that the cruise reading was right at 13.8 to 13.9 and I know I could jet down to bring that reading a little closer to 14.""

If you need to "tweak" the cruising A/F ratio, you could change your IAB's or raise/lower your front float. This might be easier than swapping the jets, especially if you are only looking to change the A/F by less than .4 or so. If you do either one of these, then remember to reset your idle A/F mixture again.

""I have noticed that this carb is very touchy when it comes to setting the four corner idle ajustments. When I adjust it with the vacuum gauge it ends up a bit rich when done aroud 13. So I just screw those in until I get it close to read 14.1 or so.""

I found the same results. 13.0 at idle can really smell up the garage in a hurry and 14.0 really cleans it up. My metering screws are very sensitive too. It only takes a fraction of a turn from any one of them to see the results on the meters.

Thanks for the reply.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 08/27/12 02:51 PM

I am continuing my testing on stagger jetting for WOT. As previously mentioned, I was able to stagger jet my secondaries to give me a .2 difference in my WOT readings from the drivers side to the passenger side. But this Summer, I am now back to seeing a .4 difference side to side at WOT.
Since my drivers side is the lean side at WOT, I decided to keep my jetting the same (I am just trying external adjustments to see if I can correct this) and try testing with different HSAB's on the drivers-secondary corner only. I was running with .039" HSAB's (all around) and found the .4 difference. Then I dropped down to a .036" (drivers-secondary only) and the difference became .2 again side to side. So I tried to go down again to a .033" which I thought would be perfect, but the .2 spread stayed the same. I do not have any .030/.031" to test with, so I was thinking of dropping both the front and the rear drivers HSAB's to the .036's to see what happens, but I am 99% sure that will change my cruising A/F which is already dead on.
I am also thinking of dropping both of the secondary HSAB's down to .036 or to .033 to see if the passenger side will help richen the drivers side. I am ok if the passenger side richens up just a hair, but I am mainly concerned with dropping the A/F of the drivers side.

Review:
I would like to alter the drivers side A/F by .4 at WOT.
I want to keep my primary side the same since my cruise A/F (and all the way up to 4000rpms) is right at the 14-14.2 which is my current goal.
I have a feeling that I may be opening up the carb and adding another 2 jet sized to the drivers secondary though.

Any additional thoughts?

Thanks

EDIT:
I have decided to stay with my .039" HSAB's (all around) and go up on my secondary jetting. I need to richen my drivers side by .4 and my passenger side by .2 (it is close!). So I decided to go up two jet sizes on both secondaries (the stagger in the rear is still 6 jet sizes) and retest.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 08/29/12 03:19 AM

Y07_A66:

Have you ever watched your AFR while power braking? I have a very tight convertor behind my motor, and my motor will go dead lean (17.x) when trying to bring the RPMs up against the converter. If I bring up the IFRs (.035) I can reduce the affect and at some RPM point the mains start and the AFR drops back down. My cruise is ugly rich, so I don't want to raise the IFRs, and am also reluctant to drop the HSABs (current .035). In general my QFT carb is possessed, and is off the motor again, but I am wondering if you have any experience under these sort of conditions, particularly with the large HSABs in place.

Thanks for continuing to update your thread!

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 08/29/12 11:43 AM

Dave,
I have not watched the AFR while power braking to witness a lean condition. The only lean condition that I have right now is when I am cruising and I very slowly get into the throttle for a few seconds (before the seconds kick in). Then I see the AF going into the high 15's during this situation. I was lean into the 16's until I raised my front jets up by two and then it richened up slightley. I am going to see if the .033" IFR's helped with this issue. If not, then I will bring up the main jets by another 2 sizes.
My A/F gets rich quick when I drop down the HSAB's. The .039's work great on mine. My cruising A/F is always in the 13.8-14.4 range with .062 main jets, .060" IAB's, and I just recently changed the IFR's from .031 to .033's. My WOT numbers are in the high 12's and I am working on bringing that down to the 12.5-.6 range.

""My cruise is ugly rich, so I don't want to raise the IFRs, and am also reluctant to drop the HSABs (current .035).""

I have been tweaking my cruise A/F with my IAB's and my front float level. Since my HSAB's are leaner with the .039's, and my main jets are leaner with the 62's, I am using .060" IAB's to keep my cruise A/F as mentioned above. I also had to go richer on my PVCR's to .071 to help out on the acceleration.
If you go with the .035/.033" HSAB's, can you lean out your cruise with leaner IAB's?

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 08/30/12 03:58 AM

"My A/F gets rich quick when I drop down the HSAB's. The .039's work great on mine."

My biggest HSAB is .035, and I hadn't considered trying to go bigger because it seems I already have an issue with the mains not flowing enough soon enough, with an increasing load on the motor. As mentioned, it is hard to bring up the RPM against the converter without causing a nasty lean miss. Vacuum is a around 10" and there is no way for the transition circuit to deliver enough fuel, at least up to a .035 IFR. Perhaps I should try bigger HSAB but it just seems that I am moving the problem around and I don't know a good way to cover the hole between the transition and mains.

If I had a looser converter, then I know the load would be less at lower airflow (which would help), and I may have to change the converter sooner than I wanted. I have been hoping to get the motor running decent, and then get it on a chassis dyno to get some numbers to better judge future converter characteristics. In general, I just don't like a loose converter on a primarily street driven car. I'm an old 4-speed guy, and I still miss the fun of throttle responsiveness under small "gooses" when going thru the gears, and I have been hoping the tighter converter would help with the fun factor.

"If you go with the .035/.033" HSAB's, can you lean out your cruise with leaner IAB's?"

I have tried as high as .075 IAB, and it helps the cruise some (getting into low, low 13s) but it causes a problem with the low end of the transition circuit (too lean) while putt-putting thru the neighborhood.

Over the past two years I have been all over the map with carb settings. I've found various other issues as well, but still cannot obtain a setup where all of the carb circuits work well at the same time. My motor seems to be possessed at times!

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 08/30/12 11:49 AM

Are you using a High Flow PV?
Have you tried increasing the IFR's (beyond .035") all around? You may not be able to cruise on the transition circuit very long with your setup.
I would not go leaner on the HSAB's in your situation. You are correct, this would just delay the mains.
What is smallest HSAB that you have tried?
My "guess" would be to go smaller on the HSAB's and larger on the IFR's to richen up the transition circuit to main circuit lean spot.

How much testing have you done with the front jets? It is hard to pin point when the mains start (even while watching and charting off of an A/F meter), but have you tried going up on your main jets with the smaller HSAB's to see if this helps down low in the rpm range?

Would you mind reminding me which QF carb you have?

Thanks allot for your replies.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 08/31/12 03:59 AM

Y07_A66:

My carb is the QFT-850-PV. It is advertised as a race carb but has vacuum secondary, and I am using for a street(mostly)/strip vehicle. The carb is on my 400/470, with E-Heads, RPM Manifold, and a 248@.050 solid flat tappet cam. The 727 has a stock 440 converter in it at the moment, and the rear has 3.55s. The converter needs to change at some point, but as I said I was hoping to get a solid tune before deciding exactly what to get. My car is a 70 Barracuda, and given its weight, the CI of the motor, dual plane, and a vacuum secondary carb, I felt I could get the combo going decent.

I know most folks first response is that I should be using a big DP and lots of stall in the converter. However, I am just not convinced that is right for me. When I first put the car together I had a MP 175K converter in it, and it was like slush. I know folks rave about the more modern converters. The thing I miss is the ability to goose the throttle and get the instant response like with a 4-speed. When I had the MP 175K in it, I would goose the throttle and all that would happen is the RPM would jump and the exhaust note would rise. You had to push deeper into the throttle to get past the flash point before it would get fun. For example at highway speed, the motor turns around 3K. I could use the throttle and move the RPM from 3-almost 4K with little change in instantaneous speed. The thing was too loose for my taste, at least given the torque of the motor.

--Are you using a High Flow PV?

Yes, I use the ones from QF. Currently it has a 7.5" one in it. Original one was a 4.5".

--Have you tried increasing the IFR's (beyond .035") all around? You may not be able to cruise on the transition circuit very long with your setup.

The original IFR when new was .036. I have not tried above that. I have tried as low as .031 but the off idle problems were fairly bad. If I move the IFR down, I can at least get the low speed (say 30-40MPH) AFR somewhere reasonable. At times I have had this in the mid-14s. Out of the box, the low speed AFR was in the high 11 to low 12 range.

--I would not go leaner on the HSAB's in your situation. You are correct, this would just delay the mains.

Factory was .033 HSAB.

--What is smallest HSAB that you have tried?

I have not tried smaller than .035 with my power brake test. This behavior was something I recently discovered. However, it possibly explains why I felt I could not go below 72 primary jets (factory was 76) because of the lean miss when I tipped into the throttle. My smallest HSAB is .025. During the past 2 years, I have had as small as .030 HSAB in there but I would have to review my records to see what pri jet was in at that time.

--My "guess" would be to go smaller on the HSAB's and larger on the IFR's to richen up the transition circuit to main circuit lean spot.

Good thought, although I would likely start going back down in the HSABs before coming up further on the IFR, just because of AFR in the 1500-2000 range.

--How much testing have you done with the front jets? It is hard to pin point when the mains start (even while watching and charting off of an A/F meter), but have you tried going up on your main jets with the smaller HSAB's to see if this helps down low in the rpm range?

I'm sure that might help in the low RPM range, but at cruise that would be a real killer. At times, I worry about washing out the rings. I have had AFR as low as in the 10s under light throttle. The funny thing is that the motor wants LOTS of fuel at WOT. At one time I removed the PCVR and run 72 pri, and the AFR was 12.2 at WOT. With .061 PCVR and 74 jets, the WOT AFR is in the low 14s (secondaries disabled).

I still believe there is something wrong with the carb. Besides being pig rich, the AFR will have wild swings (to the rich side) during highway cruise. This does not occur in the 1500-2000 range. The motor is getting extra fuel from somewhere but I can't find it. I have spoken to QF a few times on it, and tried everything they suggested to no avail. I know this problem is carb related because my 30 year old 3310 does not do it. The 3310 is on the motor right now, but of course it is not so adjustable and it has its own AFR problems.

With respect to seeing the mains start, the power brake test is a very easy way for me to learn this, at least given the current gap between transition. I keep a vacuum gauge in the car, and you can see it go down as the RPM goes up (standing on the brakes) with the AFR going up, until the mains start and the AFR drops back down. If I get adventurous I might put the QF back on the motor, and shoot a video of it!

Sorry for the length, and thanks for your thoughts. I have a friend in the neighborhood, and he keeps trying to talk me into FI. After all the time and frustration, he is starting to sway me! I don't know if JimG is still around, but we use to discuss the difficulties of getting a good highway tune on a street driven BB, and I don't think he ever got to a satisfying point in his efforts either.

Posted By: Jerry

Re: Tuning Results From An O2 Kit? - 08/31/12 03:27 PM

with wild swings of aft at cruise is to possible fuel is puddling in the manifold and then being evaporated into the mixture every now and again? ultimately i would believe that the air fuel charge is falling out of suspension in a dual plane or maybe there is some reversion going on in the intake, valve not sealling all the way, etc? there is a reason port efi is the way to go to minimize variances like this.

i do however applaud your stick-to-itiveness on getting the carb working. i will be following suit shortly and am eagerly following your progress.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/01/12 02:18 AM

--with wild swings of aft at cruise is to possible fuel is puddling in the manifold and then being evaporated into the mixture every now and again? ultimately i would believe that the air fuel charge is falling out of suspension in a dual plane or maybe there is some reversion going on in the intake, valve not sealling all the way, etc? there is a reason port efi is the way to go to minimize variances like this.

Jerry, this is an excellent thought and one I had not considered before! The AFR at cruise is certainly very rich. The motor turns 3K at 65, and I'm not sure if fuel would drop out at that point or not. Have you seen this before?

I don't see the same effect with the AFR swing with my 3310 but it may just be that it is not quite as rich as the QFT carb at cruise.

There is also definitely reversion as well, and I often see small amounts of raw fuel if I pull a vacuum cap off one of the vacuum fittings on the throttle plate. My cam is in at 109, and I have been toying with the idea of advancing it some over the winter. That would reduce the reversion some.

I don't think it is a valve sealing issue since I have adjusted the valves many times, and have run both compression and leakdown tests, and don't see anything odd.

EFI certainly has big advantages, but it does come at quite a cost, at least to support the type of HP levels the motor should be capable of.

Posted By: Jerry

Re: Tuning Results From An O2 Kit? - 09/01/12 10:24 PM

i personally have not witnessed it but it doens't have to have any outward signs either. i don't know what kind of dual plan your running but dual planes have the really long runners with narrow ports usually that have alot of curves. it doens't take much for fuel to fall out of suspension and create a wet wall. are you running your heat crossover or is it blocked off? really you won;t be able to identify fuel puddling runner issues unless you sample egts at each cylinder. your o2 sensor won't tell you enough.

advancing the timing and running a cam with less overlap will help with the reversion as well.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/02/12 04:30 PM

I run the Edelbrock RPM intake; it doesn't have a heat cross over. It was into the 90s yesterday though. The motor is a low deck big block, currently at 470CI. I am really warming up to the idea of some sort of fuel pooling, and I appreciate the thought. The AFR swings don't occur at low RPM, nor at WOT regardless of RPM. It only seems to occur at a certain RPM range. Advancing the cam timing looks to be in my future; hopefully that will help.

Yesterday I tinkered some with the carb using a thought from Y07_A66. I dropped the main jet down significantly (to 69s). To my surprise, this really leaned out the low RPM range, even causing a lean miss from off idle and up. I switched in my biggest IFR (.036) and it was still lean. Then I dropped the IAB from .070 to .065 (the smallest I have), and it improved some to the point where the car was just driveable, but still way too lean (16-17 AFR). Never had this problem before! So, now I am going to need to buy some bigger IFRs. I didn't want to drive it much, given the AFR, and didn't get a chance to take it far enough to try highway speed.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/03/12 01:36 AM

Dave,
Please keep us posted and thanks for sharing.

Ref: From what I have found so far, swapping all four IFR's from one stock size to the next will net the largest cruise AF change, around .6-1.0. Swapping all four IAB's from one stock size to the next will net around .4-.6.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/03/12 02:38 AM

Y07_A66:

I plan on buying each larger IFR from 037 to 040. That should cover me. I'm only planning on swapping the primary IFR since the goal is to improve the off-idle and low RPM mixture. Did you ever try just changing the primary IFR? To me, it seems the secondary IFR really shouldn't be delivering incremental fuel in the 1K-2K RPM range but I could be wrong.

Hope to have more results next weekend.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/03/12 02:55 AM

Yes. I ran .033 IFR's in the front for several weeks with .031's in the rear. It was just for testing purposes, so the next time I pulled the rear metering block I added the .033's to the rear just to keep them even so I did not forget what setup I had.
My theory was I only needed a small change, so I only did it on the primary side. I have been told to keep them the same front to back, but it did help me at the time. When I had the .033's in the front, I did only adjust the front metering screws to make up the difference in idle tuning. I did have to lean the fronts after adding the larger IFR's, which makes sense.
I would suggest buying enough to do both front and back, then add them to the front to see if it gets you where you need to be. If you still need more, then add them to the back and retest.

Note: I do like to see my metering screws set the same front to back (same side) and I can do so with the same IFR's front to back. Since I added my second O2 sensor, my side to side metering screw settings are a little different but they are the same setting per side.

"" it seems the secondary IFR really shouldn't be delivering incremental fuel in the 1K-2K RPM range but I could be wrong.""

I still struggle with,,, why are there IAB's on the "secondary" metering block?
They still affect the idle circuit, so I am guessing that the IFR's on the secondary side are still affecting the idle circuit the same way as the primary IFR's are too.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/03/12 01:51 PM

"I would suggest buying enough to do both front and back, then add them to the front to see if it gets you where you need to be...."

Good approach. The QFT IFR jet packs come with a set of 4 so I will be good there.

"why are there IAB's on the "secondary" metering block?
They still affect the idle circuit, so I am guessing that the IFR's on the secondary side are still affecting the idle circuit the same way as the primary IFR's are too."

Yes, I agree the function is exactly the same as on the primary side. On a mechanical secondary carb, it is feasible that the throttle is open just far enough to crack the secondaries. On a vacuum secondary carb, I am doubtful that such a state could be obtained but even there it may be possible. Even when in such a state though I don't think the secondaries would operate on the transition circuit since the airflow demand of the motor should quickly start the mains. I'm not certain about this, so the advice to keep the IFR square is reasonable. For now though, I don't want to have to keep pulling both fuel bowls.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/08/12 06:00 PM

I was working on my stagger tuning to get both sides to show 12.5-12.6 from 50mph cruise to WOT. As I may have noted earlier, my drivers side was leaner than my passenger side by .4. So in order to change this, I stagger jetted my secondary jetting. I started at 74 per side and found the drivers side to be lean. So I tested 76(D) and 74 (P) and it helped a little. Then I tried 78/74 and it stayed the same which did not make sense. Then I tried 80/74 and it stayed the same and then I tried 82/74 and both sides still read the same.
Now I am thinking that something is not right. This much stagger jetting towards the drivers side secondary should have made the car run RICH at WOT, but it did not. Then on my next drive I noticed that my cruise was going lean on both sides, my idle was going lean on both sides, and when I slowed down to a stop the car would want to shut off and was leaning out into the 15's in D at a stop. I just reset my idle in D to 13.8/14.0 but then when I came to a stop it would lean out again to the 15's.
I found out that my fuel pump was going out on me and I put in a new one and now my A/F numbers are back on track.
One of my previous issues (besides the 50-WOT readings beeing different) was when I was at a steady cruise and I would slowly push down on the throttle, the sensors would lean out into the 15's. I had this about a month ago and it was leaning into the 16's during the same situation so at that time I raised my main jets from 60's to 62's and this issue started showing the 15's. I rejetted the mains again and now I am running 64's up front and with my new fuel pump, I am no longer seeing the cruise to light accel dropping into the 15's. I am showing mid 13's at cruise (will be leaning this out to low 14's) and my light throttle stayed right around 14-14.2 before the seconds kicked in. This was good!
Now I am going to lean out my IAB's from .060's to 064's to get my cruise (40mph-70mph) back into the 14.0-14.2 range.
My secondary jetting: now that I have the new fuel pump and 064 main jets, I will swap out the secondary 78/78 for 76 (D) and 74 (P). This should get both sides right around the 12.5-12.6 number.
So my secondary stagger issues were getting worse because my fuel pump was not keeping up with the larger jetting on the drivers side. Now that I have the new pump, my 78's are too rich (12.4 (D) and 12.0 (P)) and I will rejet and retest.
UPDATE:
76 (D) and 74 (P) gave me a 12.8 (D) and a 13.0 (P) side 50-WOT. So I am now within .2 again from one side to the other. I am going to raise the rear float and see if I can bring the WOT number down about .2-.4 on both sides.
The IAB swap now give me a 13.4-14.0 cruise A/F. I just noticed that my mains appear to start in right around 55mph. My 50mph showed 14.0/14.2 and my 60mph showed 13.4. I might have to try something to lean this out again.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/09/12 12:11 AM

Y07_A66:

How did you isolate your fuel pump problem? Flow test?

I also had a chance to tinker today. I went from .036 to .037 IFR, which helped improve the low speed behavior. However, I discovered that some instances of my lean miss (AFR>17) are when pressing a little on the throttle. Vaccum is dropping to the 12-10" range, and I suspect the main are starting to flow at this point. My conclusion is that the 69 pri jets are way too lean, and I don't think further increasing the IFR is going to help under this condition. The motor was running well enough that I decided to take a quick highway run, and to add insult a WOT from 60MPH started with AFR in the 12's but then I watched as it dropped into the 11's then into the high 10's! This was from about 3K to 4.2K in high gear. Obviously my HSABs are also too small. So I have to go back up in size on both the pri jet and the HSAB.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/09/12 02:21 PM

I am not sure that I actually isolated my lean problem before I fixed it. I first thought that I might have had a vacuum line come off but after checking them, they were either new or had tight connections. I did hear a ticking noise coming from the pump area, so after going thru my notes and seeing what the A/F outcome was after changing my drivers-secondary jet (farthest jet from the fuel pump) from 74,76,78,80, then 82 with no change, and after all of the weird lean issues during my previous drive, I took a stab at replacing the fuel pump.

""I discovered that some instances of my lean miss (AFR>17) are when pressing a little on the throttle. Vaccum is dropping to the 12-10" range""
- Main jet sure sounds correct to me too. You are currently using a 7.5pv, what about using a higher rated unit? Your mains might just be starting which means your pv might help being higher once the mains are full on.

""a WOT from 60MPH started with AFR in the 12's but then I watched as it dropped into the 11's then into the high 10's!"
- The first dip into the 12's sounds good. What about the rear jetting? Could it be too rich? If you go up on the primary jetting, this issue will get even richer. What about a 4-6 jet drop on the secondary side? The HSAB swap would be a quicker test though.

Note: I just make a 4 jet swap on the passenger secondary side and a 2 jet swap on the drivers secondary side and it netted me 12.0 to 13.0 on the passenger side and a 12.4 to 13.0 on the drivers side for reference. One full point with four jet sizes and about half of that with 2 jet sizes.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/09/12 03:38 PM

"You are currently using a 7.5pv, what about using a higher rated unit? Your mains might just be starting which means your pv might help being higher once the mains are full on."

7.5pv is about as high as I can go right now. My in-drive idle vacuum bounces in the 8-9" range. As I mentioned, the torque converter is really tight, which puts quite a load on the motor. I know a looser converter would result in higher vacuum, but I'm not there at the moment.

"What about the rear jetting? Could it be too rich? If you go up on the primary jetting, this issue will get even richer. What about a 4-6 jet drop on the secondary side? The HSAB swap would be a quicker test though."

Currently I am testing with the secondaries disabled. On my carb, I can just turn a screw to adjust the secondaries, and closing it down should stop the vacuum signal to the pod, disabling them.

Between the two issues, I am thinking I need to try going up in pri jets from 69 to 71, and perhaps bump the HSAB from .025 to .027 and try again. Factory HSAB is .033.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/10/12 12:24 AM

UPDATE: After moving the pri jets to 71, the lean miss on light throttle is much better. Unfortunately it will still occur when hitting 10" vacuum, with the AFR in the high 15's, low 16's. I am going to have to go back to 72s. This is the jet I had previously determined to be the smallest I could use on the primaries, and in some ways it is reassuring that I came back to the same place.

With the HSAB, .027 didn't help much, so I increased some more to .029. It is better now, but the AFR on WOT still goes rich into the low 11's. Next step will be .031, and I suspect I may end back at the factory size of .033 when it is all said and done.

My low speed cruise (45MPH) was in the mid-13s, so I upped the IAB from .065 to .067 which seems to have helped, with numbers now in the high 13 to mid 14 range. I don't have a lot of flat roads around me so it is a little hard to be precise.

On the highway, the AFR was not jumping around like it has in the past which is interesting since I'm not sure why that has changed given that I am slowly working back towards my old settings. The AFR was in the mid-13s which is the best it has been in a long time.

In general, it seems I have finally made some progress. On the negative side, it seems that I have a light throttle miss that does not appear to be AFR related. I don't know if it was always there but I couldn't notice it because of how the motor was running with other issues. It doesn't occur under WOT. I long time ago I suspected a vacuum leak (at the manifold) but I could never find anything. The vacuum advance is not hooked up so I know it is not over-advanced.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/10/12 01:29 AM

I did not realize that you disconnected the secondaries. Now I understand the HSAB changes. Nice job!! Even if you end up back at the original .033's, you would have never known what the lean limit was without trying.

High 13's to mid 14's is excellent in my book. I have been told that I may not find the perfect setup on the primary side only (with seconds disconnected), but I hope to see how close you can get yours. You are definately getting closer with each change. That is what I love about the A/F gauges. You can see where you were and where you are now.

I am going to test a lower float setting on the primary side to see if I can lean out my new 64 jets above 55mph. I have now dipped down to 13.4 at 60mph (.039 HSAB's). My 62 main jets gave me 14.0 at 60mph with the .039 HSAB's, and I want to see if I can get into the upper 13's with the front float change. If not, I might drill out some old bleeds to make (2) .042" HSAB's just for the front to see if that gets me back on track.

I am going to try and richen up my 50-WOT A/F which is now 12.8 (D) and 13.0 (P) down to 12.5/12.6 with just a rear float change. I hope to test this out this coming week.

Please keep us updated on your progress!!

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/10/12 01:54 AM

"That is what I love about the A/F gauges. You can see where you were and where you are now."

I agree. I only have one though, and given my light throttle miss, I am now wondering if the other bank is significantly different. At light load and light cruise (perhaps 40-45MPH) I don't notice the miss. Going up a hill under the same conditions will show it though, even though the AFR is generally in the 14s (when I feel the miss I also see the AFR jump lean, as you would expect). First up, I think I will replace the plugs since perhaps the really rich WOT trials have fouled them a little.

"drill out some old bleeds to make (2) .042" HSAB's just for the front to see if that gets me back on track."

You probably know this but be very careful drilling jets. The flow is a function of the hole diameter and the length of the restriction. When you drill a jet, the hole gets bigger, but the length also increases. For a while I was trying to increase my PCVR by drilling some blanks but I always ended up leaner than the biggest QFT jet I had purchased. Finally it dawned on me that I had stumbled into this trap.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/10/12 11:36 AM

Good point on the air bleeds. I will not drill any of my existing pieces.

I have seen members on board say that buying a sensor for each side is stupid, dumb, waste of money, etc.. But I know first hand that "on my motor", there is a difference from side to side.
When I have the car in N and I am balancing out the metering screws, I can move the drivers side main metering screw and watch the P side O/2 gauge move. I have a dual plane intake, so that makes sense. So I have to take my time and go side to side to get the result that I am after for both sides. When I added the second sensor, the cruise was real close side to side and the WOT was off by .5/.6 side to side. Now I have the idle, cruise, and the WOT within .2 side to side.

I would suggest that you move the sensor to the other side to check your thoughts. You may be correct.

I separated my exhaust (straight thru each side) so that I could run the dual sensors without the exhaust contaminating the other sensor. I am glad that I did because I can set here at my keyboard and smile when I see someone say that the second sensor is worthless, especially on a dual plane intake.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/11/12 01:15 AM

Lowering the front float to the bottom of the sight glass helped lean out the 60mph A/F by .2. Raising the rear float to the middle of the sight glass helped richen the 50-WOT by .2 also.
Last year my 30-70mph A/F readings were 14.0-14.6 and I was not running vacuum advance.
After this last test, I am now:
Idle in D: 13.6-13.8
40mph:14.0
50mph: 13.8
55mph: 13.6
60mph: 13.6
4000rpms (apx 75mph): 13.2
50mph to WOT: 12.8(D) 12.6(P)
You can see by the 4000rpm A/F reading that my .039" HSAB's are not leaning out the main circuit. So this setup should be good.
So this year while running with vacuum advance, my cruising range is apx 13.4-14.0. I feel surging aroung 14.4-14.6 or so with the VA hooked up. So this setup gives me some room before the surging starts. The car feels strong at cruising speeds to any accel. I am no longer leaning out into the 15's and it stays no leaner than 14.0.
I might try raising my rear float to about the 3/4 mark to see if I can richen up my 50-WOT readings to around the 12.5-12.6 range on both sides. 3/4 up is all the higher I want to raise the float to allow fuel expansion during heat soak and not have the fuel expand and want to come out of the boosters when shut off.
I have found that the floats are a real quick external adjustment to get about .3-.4 change in the A/F readings. I would like to find a happy medium with the internal parts of the carb so that all I need to do year around is tweak the float level as the outside temps rise/lower.

EDIT:
I have decided to keep the rear fuel level to the middle or below, so this means rejetting the secondaries. 78/78 rear jets gave me 12.0 (D) and 12.4 (P). 76/74 rear jets are currently giving me 12.8 (D) and 12.6 (P). I am going to stagger the rear jetting slightly more and test 78/74. I am thinking that since I am running a dual plane intake, that the 78's on the drivers side will richen the drivers side 12.8 reading and hopefully help richen the passenger side slightly too. The larger jet will allow me to keep my rear fuel level under the half way mark which allows more room for the fuel to expand during shut down.

EDIT:
The gas stations are allowed to start selling the Winter blend this coming Saturday, September 15. What does this do to our current A/F ratios, if any?

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/15/12 03:18 PM

Previous results with 64 p jets and 76 (D) and 74 (P) secondary jets:
""Idle in D: 13.6-13.8
40mph:14.0
50mph: 13.8
55mph: 13.6
60mph: 13.6
4000rpms (apx 75mph): 13.2
50mph to WOT: 12.8(D) 12.6(P)""
--------------------------------------------

I could not stand it that my 50mph+ A/F went as rich as shown. So I decided to drop my primary jetting from 64's to 63's. I knew that this would cause my WOT numbers to go lean so I swapped my rear jetting to 78/76.
My new results in cooler weather (53-59 deg.):

Idle in D: 13.6-14.0
40mph: 14.0
50mph: 14.4
55mph: 14.2
60mph: 14.2
4000rpms (apx 75mph): 13.8/14.0
50mph to WOT: 12.8(D) 12.8(P)

As you can see, the main jet swap from 64's to 63's brought my 50mph+ numbers back up about .6-.8 in the cooler weather. This is where I want to be for cruising.
Now I have a question about the secondary HSAB's and their function.
I would love to just swap out something external when the outside temps go up and down. I am still very close on my 50-WOT A/F numbers (12.8's & aiming for 12.5-12.6). My current stagger jetting on the rear looks good but instead of opening up the rear bowl again to add 2 more jet sizes per side, what about swapping my SECONDARY HSAB's ONLY from the current .039's to .036's?
Would this change mess with my 50mph+ A/F cruising numbers?
I would love to just swap out secondary HSAB's as the temps go up/down since they are so easy to get too.
What do you think about this change and it's affect on my cruising A/F?

Thanks

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/15/12 04:12 PM

"Now I have a question about the secondary HSAB's and their function.
I would love to just swap out something external when the outside temps go up and down."

First, I would not expect the secondary HSABs to have any effect on the 50MPH cruise AFR since I can't imagine that the secondaries are operating on the main circuit at that point.

With respect to their function, my understanding is that the HSABs are tightly coupled with the boosters. The booster design will produce a particular "signal" for the main circuit. The booster signal by itself is non-linear though, with a non-proportional increase with air flow. The high speed air bleed acts as a "trim" for that signal. When the booster and air bleed are properly matched, then the AFR curve should be linear with air flow. If the air bleed is too small, then not enough booster signal is trimmed, and the result is more fuel flow, and as seen in my recent experiments, a AFR that gets richer with RPM. If the air bleed is too big, then the opposite happens, with a AFR that gets leaner with RPM. What I don't know is the exact sensitivity to the bleed size, and whether the secondaries operate in a narrow enough region to allow a measure of variation in bleed size around the ideal point. On a race motor that operates in a somewhat narrow region (say 5K-7K) the bleed might be an easy way to make an external adjustment. On a street motor, the situation may be different. Worse case, you will need to experiment. However, some sort of data logging would really be helpful with something like this.

All that said, I thought you were a proponent of using the float level to fine tune the AFR via external means. That sounds like a good idea to me, particularly on the secondaries. Are you concerned that does not give enough adjustability?

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/15/12 07:19 PM

""All that said, I thought you were a proponent of using the float level to fine tune the AFR via external means. That sounds like a good idea to me, particularly on the secondaries. Are you concerned that does not give enough adjustability?
""

I do like to use the floats as an external fine tune, but my rear float is already at the halfway mark. At that level, I know that I can get +/- .2 but I am not sure about taking it up higher than that mark. I think that I need a few ticks richer before I can be comfortable with that float height.
I might try the smaller rear HSAB just to see and report back. I know for a fact that making this same HSAB swap on the primary side changes the A/F a bunch. But as you wrote, the seconds are not active at this rpm level but I am not sure that if there is any residual affects on the main circuit.

Thank you for the reply. That explains it very well.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/16/12 02:49 PM

""I would not expect the secondary HSABs to have any effect on the 50MPH cruise AFR since I can't imagine that the secondaries are operating on the main circuit at that point.""

You are EXACLTY correct. I swapped the rear .039" HSAB's for .036" HSAB's and went for a drive. No other changes and the outside temp was 61 degrees vs 59 degrees yesterday.
Yesterday I showed my 50mph to WOT as 12.8 (D) and 12.8 (P)sides. Today I tested this three times and found 12.6/12.6, 12.6/12.4,& another 12.6/12.4. I have hit the 12.5 mark!! The car felt strong and I am happy with this.
My 40mph, 50mph, and my 60mph cruise A/F numbers WERE NOT AFFECTED by the secondary HSAB swap.

I had the exact same numbers as yesterday on cruise!!

Thank you Dave!!!!!

Note: My float levels are right at the mid line on the bowls. This allows me some tweaking to lean it out. Since I drive in 50-95 degree weather, this gives me some room on both the main and the secondary float adjustments for leaning it out in warmer temps. Now that I know that I can gain/lose .2-.4 on the secondary WOT reading with the HSAB swap, this is another external (quick) change that I can make during a normal driving year.
The metering screws handle the idle to off idle A/F changes and the IAB's handle the transition circtuit changes, I need to test to see if my existing internal carb setup is good. I am at 63's for front jets, .039" HSAB's up front, 9.5 HFPV/.071 PVCR's, .065 IAB's (all), .033" IFR's (all), 78 rear drivers and 76 rear passenger jets with the .036" HSAB's in the rear.
Time will tell.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/16/12 04:30 PM

"Today I tested this three times and found 12.6/12.6, 12.6/12.4,& another 12.6/12.4. I have hit the 12.5 mark!! The car felt strong and I am happy with this."

Excellent! Were you able to observe the AFR over a range of RPM? Notice any difference between the low end of the range and the top?

I see you list .071 PCVRs; did you purchase those or make them?

I bumped up my main jets from 71 to 72, and my light throttle stab AFR is now much better, so at least that is one improvement. However, my WOT is still way over rich (low 11s) and I tried .031 and .033 HSABs. Given that .033 HSAB is factory I am thinking I was wrong to assume that my over rich mixture was due to using the very small HSABs. Something else appears to be going on. I plan on going back to my .061 PCVRs and see what happens. Unfortunately rain today so it will need to wait for another day.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/16/12 04:57 PM

""Were you able to observe the AFR over a range of RPM? Notice any difference between the low end of the range and the top?

I watched it from in D idle, all the way to WOT shift point. The ONLY change was the WOT A/F went richer as noted.

""I see you list .071 PCVRs; did you purchase those or make them?""
I bought them from QF. I have four to chose from and those are the richest that I have. Since my cruise is 14.0-14.2, I tested with all four sets and found that these had the best "seat of the pants" feel from cruise to heavy accel.

""I bumped up my main jets from 71 to 72, and my light throttle stab AFR is now much better, so at least that is one improvement.""

I found the biggest improvement in cruise to light throttle accel when I swapped the 62 jets for the 64's. The 62's were showing a lean spike into the 15's from cruise to light accel. Then when the 64's were installed, the light accel stayed right around my cruise A/F (13.8-14.0). That felt good but the 64's were too rich on cruise. So when I moved the mains back down to 63's, my 50mph+ cruise is now 14-14.2 again but the cruise to light accel is now mid to high 14's which I can live with.
I am trying to come up with a way to richen this cruise to light throttle back up (like the 64 mains showed) but without richening my 50mph +. The only guess that I have is with larger PVCR's which I think there is only one more step richer than the .071's from QF (.073's). I tried going with a larger front accel pump cam but that did not seem to help enough (white to orange).
Any guesses? This issue is so small to the rest of the setup, but I don't mind testing to try and clean up this area too. I basically have my carb setup the way that I feel it needs to be, except for this small issue.

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/16/12 05:29 PM

"So when I moved the mains back down to 63's, my 50mph+ cruise is now 14-14.2 again but the cruise to light accel is now mid to high 14's which I can live with.
I am trying to come up with a way to richen this cruise to light throttle back up (like the 64 mains showed) but without richening my 50mph +. The only guess that I have is with larger PVCR's which I think there is only one more step richer than the .071's from QF (.073's). I tried going with a larger front accel pump cam but that did not seem to help enough (white to orange).
Any guesses?"

In my opinion, light accel in the mid- to high-14s isn't going to hurt anything. My suggestion is to check with a vacuum gauge under your light throttle conditions to see how close to the PVC opening point you are. If vacuum is hitting that point, a bigger PCVR may help, but then it will also richen the WOT which will require another round of other optimizations. You're lucky to be worrying about such small nuances!

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/16/12 05:54 PM

""My suggestion is to check with a vacuum gauge under your light throttle conditions to see how close to the PVC opening point you are. If vacuum is hitting that point, a bigger PCVR may help, but then it will also richen the WOT which will require another round of other optimizations.""

My vacuum at cruise is in the upper teens, so my thought of the larger PVCR will not work. The cruise to light throttle is minimal and it is time to start worrying about how to slow this car down a little quicker now. Front brake upgrade is next.

Posted By: fuzzman

Re: Tuning Results From An O2 Kit? - 09/17/12 10:37 PM

I hate to sound stupid here but I have been following along with your post and when you guys use all these acronyms and abbreviations I get lost so could you spell out some of them for me like I know PVR (power valve restriction) but what is PCVR and, where are these things located in the carb. Sorry just trying to learn.
Thanks
Pat Faley

Posted By: noplanb

Re: Tuning Results From An O2 Kit? - 09/18/12 12:13 AM

From one lurker to another

Attached picture 7383475-HolleyCarbbodypassages.jpg

Posted By: davenc

Re: Tuning Results From An O2 Kit? - 09/18/12 02:02 AM

These pictures are great references. Studying them can pay dividends!

You may still need to work a bit to figure out some of the acronyms because of minor variation in name or order of words in the acronym. Here is a cheat sheet:

IFR: idle feed restrictions, sometimes called the idle jet. #4 on the second picture, although some metering blocks have them at the top and others at the bottom of the idle down well.
PVCR: power valve channel restriction. #17 on the second picture.
PV/HFPV: power valve/high flow power valve which is a different style PV. I used PVC but that was a typo. #16 on second picture.
MS: mixture screws. #13 in third picture.
IAB: Idle air bleed. This is in the top of the barrels, and controls the amount of air admitted to the idle well which is fed with fuel by the IFR. This circuit controls the fuel/air mix sent to the idle circuit (controlled by the MS) and the transfer circuit.
HSAB: High speed air bleed. This is in the top of the barrels, and controls the amount of air admitted to the main well which is fed with fuel by the main jets and the PV via the PVCR. The HS part is to distinguish it from the idle system, and because it has the most effect at high air flows. The HSAB are closest to the squirter on Holley-like carbs.

QF/QFT is for QuickFuelTechnologies which is a carb vendor.

Posted By: Pyper70

Re: Tuning Results From An O2 Kit? - 09/29/12 09:18 PM

So what did we ultimately find as the ideal numbers?

I am running my Charger tomorrow for the first time in about a year on a 100 miles round trip. I was gonna jot down the numbers as I went through my stages. It's gonna be fun playing with the numbers because this time around, there are two Carb's instead of one.

I should aim for 14.7 and work my way from there but my current setup is:

~440 Dual Edelbrocks (500cfm each) set up in progressive formation, 10:1 compression.
~727 with GVO, 28" tall tire, 3.55s. At 80mph I am cruising at 2200rpm.
~480/280 Isky megaCam
~Recently installed Edelbrock RPM Heads
~HP manifolds (swapping out to shorty Hedman's in a few weeks
~26" Radiator, 4 core. 7-Blade fan with clutch
~I run 95 octane (Thats the standard here)

I have an Autometer O2 Wideband that I just rigged into a Pelican case and an cigarette lighter plug so it can move from car to car.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/29/12 11:05 PM

I think that the ideal number will be different due to octane, ethynol content, compression, and another factor that I found this year is vacuum advance.
Due to my car running on E10, vacuum advance and 9.7 compression, my current A/F is 13.8 to 14.2 cruise and WOT is 12.5-12.7. Last year w/o vacuum advance, I was able to run 14.8-15.2.

Posted By: Pyper70

Re: Tuning Results From An O2 Kit? - 09/30/12 12:03 AM

My dizzy is an MSD mechanical. IIRC I have 16� initial with a black bushing (18�) so its 34� total and with the spring combination I am all in at 2600.

There is no ethanol in the fuel here.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/30/12 12:20 AM

Stoich with gasoline is 14.7. Since you have a mild ignition curve and gasoline, you might be fine in the upper 14's to low 15's as a guess.

Posted By: Pyper70

Re: Tuning Results From An O2 Kit? - 09/30/12 09:10 PM

So I kicked her over today...she was 15.8 at startup...after revving a few minutes and then getting off high idle, she was 13.5 @ 7" Vacuum. I know I can improve this. When I was driving her and I opened her up she hit 9.9 @ 15". She is running a little fat.

Going to be fun adjusting because I have two carb's to adjust

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 10/01/12 01:36 PM

Some notes that I have run across:
12.5-13.5 cold startup and as the motor warms up, it should "lean out" to your idle A/F reading. If you start it up cold, leaner than your normal idle A/F, then it will be a bear to keep running during warm up.

Are you running an auto or a manual tranny?

Posted By: Pyper70

Re: Tuning Results From An O2 Kit? - 10/01/12 01:43 PM

so when cold...I need to bring the idle circuit up to 12.5 - 13.5...and then off high idle it should lean out to 14/15 when the chokes are fully open.....in gear I should be at 14.7 (ideally)

Auto trans

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 10/01/12 02:23 PM

It needs to be richer at cold idle. Then as the engine warms up, it needs to lean out to your N idle A/F reading. Once you come off of high idle, you should be in the 13's or so during warmup. Once you are at full running temp, then you should tune your in D (with brake applied) A/F number. This number is way more important than your N A/F number. Once you have the In D A/F number dialed in, (13.5-14.5 or so) then your N A/F will be what ever it is. You will need to test with your in D A/F number. Depending on your setup, your car may idle with a higher vacuum reading around 13.5 or it may idle in D with a higher vacuum reading at 14.5. The main goal is in D (with brake applied at full running temp), is the highest vacuum reading.
What I have found is that an auto car needs to be richer than a manual car due to the extra load at in D idle. It will also be different from car to car depending on timing at idle, air temp, sea level, etc.. No one will be able to give you THE correct A/F number for your setup. Let us know what works for you.

Note: Mine idles best in D at about 13.4-13.6. As it approaches 14.0, the idle gets choppy and the vacuum drops.

Posted By: radar

Re: Tuning Results From An O2 Kit? - 10/01/12 05:25 PM

I don't run a choke. My car idles in the 16+:1 range on cold startup but I keep it down with acc. pump shots for a minute until I can get going on the road. Hot is low/mid 13s. I can lean out the idle more but it makes it more prone to stall on braking after a blast.

I tune for good street manners and clean plugs more than economy or stoich

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 10/01/12 05:42 PM

""I can lean out the idle more but it makes it more prone to stall on braking.""

Radar,
I found this same problem when I tried leaning out my in D idle A/F into the mid/high 14's. I would slow down to a stop and my idle would start to fluctuate and I would have to kick the accel pedal to keep it going. After a few stops I richened it back up into the high 13's and it quit doing this.

Good point!

Posted By: radar

Re: Tuning Results From An O2 Kit? - 10/01/12 07:35 PM

I already run an electric fuel pump, maybe jet extensions would help? Haha breaking you quoted me before my edit to braking went thru.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 10/01/12 07:44 PM

I fixed it. No one but us will know.

I have jet extensions in the rear but I still had the issue when running lean.

Thanks

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 05/13/13 05:45 PM

2013: I just wanted to give a few updates for those who might be interested.

The first item is for WOT tuning. I have always thought that once you have the primary side tuned and then you have the secondary pump cam tuned, then you just change the secondary jets to tune your WOT a/f reading. On some carbs this is correct, but a cool thing that another member pointed out to me last year (and I did not believe him until I tried it) was if you have adjustable HSAB's, you can use them to tweak in your WOT A/F ratio without opening up the carb and changing the jets. For those who already know this, then this will be worthless info. For those like me who did not know this, I can tell you what I learned.
I have three sets of HSAB's (.033, .036, & .039). I started with the middle set (.036) and then I jetted the secondaries until I obtained a 12.5 WOT A/F reading (My WOT target reading year around). This allows me to just swap in the secondary HSAB's to lean out the carb apx .2-.4 or richen the carb by the same amount as the outside weather changes instead of opening up the carb and rejetting when the temps change. So in the Summer heat, I can swap in the .039's and in the Spring/Fall, I can swap in the .033's and depending on the outside temp, these two changes keep me right around the 12.5 A/F mark. I am still stagger jetting my secondaries to keep both A/F gauges close side to side. The passenger side is 2 jets leaner than the drivers side.

Another issues that I had last year was at cruising speeds (40-70mph) and then lightly giving more throttle (transition circuit, not mains), the A/F would lean out into the high 14's -15 until I pressed down enough to start the mains or until the seconds kicked in (DP carb). Since I was in the 15-17" vacuum reading range when this was happening, I was trying to cover this lean spot with the front pump cam/squirters. I made several cam/squirter changes with no real A/F changes. Keep in mind that my cruising A/F from 40-70mph was in the 13.8-14.0 range (E10 stoich = 14.1), so I did not want to change the cruising A/F, I just wanted to add more fuel during light accel at cruise. With this setup, I did not think that the main jetting was affecting this issue since I was seeing the 13.8-14.0 A/F readings from 60-70mph (I am on the mains at this highway speed.). I was using small IAB's (.054 to .060) to allow this to happen with 63 main jets. This combo cruised nice but I am now finding that this was my issue. Even though the cruising A/F looked good, it appears that when the carb was transitioning into the mains, that this was causing the lean readings at cruise to light accel.
This spring I am playing with the main jetting and the IAB's to once again obtain a 13.8-14.0 cruising A/F reading but with using 65 main jets. The first time out after swapping in the 65 main jets (no IAB changes), my cruising to light accel richened up to upper 12's to upper 13's which feels allot better. But my cruising A/F (40-70mph) dropped and my 60-70mph A/F readings are now 13.0-13.2 (mains) and my 40-60mph A/F readings (idle/transition) are now 13.6-13.2 which is richer than what I want to be. I will be able to lean out the cruising numbers with larger IAB's to get me back into the upper 13's but I need to see if that leans out the cruise to light accel numbers too much. Worse case if the 60-70mph A/F stays too rich but my 40-60mph leans out like it should, then I will swap out the primary HSAB's from .036 to .039 which should lean it out about .5 or so on the meters.

I test drove the .064 IAB's and the 40-60mph leaned out to 14.4-14.0 and the car just sounded off at that A/F reading in 60 degree weather. The mains only leaned out to 13.2 so the IAB's only helped out up to about 55mph or so.
The next move is to lean out the 60-70 (mains) into the mid 13's and leave them alone. I will also go back to the .060 IAB's to richen up the transition circuit back into the mid-high 13's and test drive it for a while.

Posted By: JS23U

Re: Tuning Results From An O2 Kit? - 06/19/13 03:48 PM

Y07_A66, this is a very interesting and comprehensive thread, I love it!
Now.... did anyone ever do all this on a Carter/Edelbrock carb?
I have a 493 stroker in my Challenger, stock intake, AVS Thunder 800 carb, quite big headers, 3:23 gears and automatic trans.
Idle vacuum is at 14" Hg in N. Cruising is at 20" starting at 35mph until I stopped logging at 70 mph.
I know that adjustment possibilities are not as vast as on the Holleys and derivates. After reading all this I am a bit concerned about the adjustments of the transfer circuit (or the lack of) which is needed up to 50mph on my car. My idle is at about Lambda 1.0 (AFR 14.7) and doesn't seem to change regardless of tuning the Idle mixture screws. Cruise up to 50mph is at about the same AFR, slightly richer, which is ok for me.
Any hints or links for a thread on a AVS carb, especially tuning the transfer and idle circuits?
Sorry for highjacking, though...
Thanks
Jens

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 06/21/13 04:14 AM

My recollection from the last time I looked at edlebrock instructions (helping a friend) there are two idle restrictions. Otherwise the idle transfer circuit is similar.

My guess is that the cause is the same as it would be on a Holley. If the idle mix screws are not getting any response, then most of the fuel is feeding through the transfer slot. See if you can close down the throttle plates a little. If the engine rpms drop to much to support idle in gear, then try increasing initial timing a 2 degrees.

Posted By: JS23U

Re: Tuning Results From An O2 Kit? - 06/21/13 10:21 AM

I checked the position of the throttle blades yesterday. The transfer slots are exposed in that they look just a tad taller than square. I think that should be ok, the blades are not too far open.
Maybe I should try more initial timing (is 15� now).
The rpm difference between N and D is not high. I'd say 100rpms or less.

Posted By: Mattax

Re: Tuning Results From An O2 Kit? - 06/21/13 12:40 PM

Its good that you looked at the transfer slot exposure. Next time take it one step further and write down how many turns to close them off completely. This way you'll know the relationship between turning the screw in and the slot exposure.

That said, at this point the question is why the mixture adjustment screws aren't having any effect. The fuel to idle is getting drawn from somewhere and the transfer slot is the only logical location.
On a Holley, the transfer slot itself is the restriction (and also picks up air from above the blade). However, my recollection is that on at least some Eddys, there is an additional restriction just for the transfer slot. Even so, assuming that internal restriction is not dominating, slightly reducing the transfer slot opening below the throttle should send more fuel past the idle mixture screws.

The shape of the transfer slot opening is based on a several assumptions which may not hold true in your engine or even your carb. As far as the latter goes, even amongst Holley 4150/60s, some slots were made wider, some are cut taller and so forth. As a result the 'square' can not be relied on for every version or list number. Its just a starting point that works for most. The engine's characteristics at idle and off idle will determine where it should be. With the strong vacuum your engine is producing at idle, it probably needs less than many hot rods.

Edit: After re-reading your first, is it just that the AFR doesn't change with the mix screws, or is it that the mixture screws have almost no effect on anything? In other words you can turn them to nearly closed and the engine rpms don't drop. If the screws don't effect rpm and manifold vacuum, then what I wrote above is relevant. If they do cause the rpm response, then adjustment to AFR is probably going to come from an internal restriction(s).

Posted By: JS23U

Re: Tuning Results From An O2 Kit? - 06/21/13 07:37 PM

The mixtue screws don't affect idle quality much and they don't affect AFR. AFR will always stay at about 14.7 (I measured Lambda 0.99-1.00).

The idle speed screw needs exactly one turn until the blades touch the venturi bores, or until the screw doesn't touch the throttle lever anymore.

Today I openend the MP distributor. I took out the heavy spring for a lighter one to get the mech. advance in earlier. Also I shortened the advance slots to raise initial timing by about 3 degrees and retain total mech at 34. Unfortunately time was running out and I couldn't start the engine for check. That'll be next.

Posted By: fuzzman

Re: Tuning Results From An O2 Kit? - 09/05/13 05:26 PM

yo7_a66
Do you have any updated results from your testing this summer since your last post? I have been following along and have used alot of your suggestions on my quick fuel 750ss carb. My motor is about the same set up as yours only on a 67 barracuda. I love this post it has been great information.Keep it coming
Pat Faley
East Peoria IL
67 Barracuda notch back
69 barracuda project covertible

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/15/13 04:02 PM

This Summer I was tuning with the different float levels. I started the Summer with both floats at the bottom of the sight glasses. I was able to achieve a real constant A/F range from In Gear Idle to about 65mph and I was happy with it. But I found a problem when I started testing my WOT A/F. 50mph to WOT was not bad, but idle to WOT sent my A/F gauges into the upper 14's and I had to let off.
I kept getting the carb leaning out on the top end so I started changing secondary jets with no real change. Then I started changing HSAB's with no real change. Then I decided to move the floats from the bottom to the mid line and my problem stopped. Now I could control the A/F better on the top end. So that problem was solved but my cruising A/F numbers went way rich on me so I had to start over again with my Idle In Drive to 65mph cruising A/F's. I knew that the float levels changed the curve of the entire carb range but this showed me exactly what that meant.
When I had the floats at the bottom, I used richer IAB's (.060's) to get the cruising A/F's where I was happy. Then when I raised the floats, I knew that I had to change the IAB's so I leaned them out a little at a time. I used (Front/Rear) .060/.060, .065/.060, .065/.065, .067/.065, .067/.067, .071/.067, then I ended up with the .071's front and back. After each change I wrote down my In D A/F plus 40/45/50/55/60/65mph readings. I also tested with different Main HSAB's to try to bring the numbers down doo. I tried to do these tests with the outside weather within reason to keep the tests accurate.

This morning I test drove with the latest changes with the best results. I now have the same results that I had back earlier in the year when the floats were at the bottom of the sight glasses, but with no leaning out issues at WOT.
I am once again happy with these cruising numbers (E10/9.7:1 comp/with Vacuum Advance):
Idle In D: 13.2-13.6
40mph: 14.0
45mph: 14.2
50mph: 14.2
55mph: 14.2
60mph: 13.8
65mph: 13.4
As you can see, my total A/F range goes from 13.4(ish) at idle in D to 13.4 at 65mph. You can see the gradual changes through out the range as the rpms go up. Going with these numbers, it appears that my mains are starting to kick in around the 60mph range. These numbers were obtained with the following carb setup:
64/78 jets, .071" IAB's, .039" HSAB's, .033" IFR's.
My 50mph to WOT A/F numbers are in the low to mid 12's (12.2-12.6 between both A/F gauges) at the shift point.

This shows the affect of the float levels. So when you move your floats around, it will affect the idle and all the way up the carb setup. (I know that allot of you already knew that, but this is for those of us still trying to get the hang of this.)

Once again, I started this thread to learn more about carb tuning and to try and learn why DP carbs were known to be difficult to tune on the street. What I have learned is that I can see why the older DP's got the reputation of being tuff to drive on the street, but these new DP's with adjustable circuits can be very efficient on the street too. Most of the above tests were done with the carb on the Idle/Transition circuit as it appears that my mains do not affect the curve until farther up the rpm range.

Posted By: Kern Dog

Re: Tuning Results From An O2 Kit? - 09/15/13 05:55 PM

Thank you for the update.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 09/15/13 05:59 PM

Cruise to Light/Medium Throttle A/F (No Secondaries):
When I first started I was cruising 40-55mph or and I was showing a lean reading when I went to light/medium throttle during a steady cruise. I found the A/F leaning out into the mid 14's. I started by testing Primary squirter size changes with no affect. Then I started testing larger Primary pump cam changes with little to no affect. Then I started on Primary HSAB changes and this showed a change. I then tested Primary jetting changes and this too showed some affect. I then tested Power Valve Channel Restrictor changes and this too helped. So I found that the PVCR's/Main Jets/Primary HSAB's all had an affect on the cruising to light throttle affect. (Note: I use a 10.5 High Flow (4 door) pv. which is the highest rated/highest flow pv)
After I had my cruising A/F under control (see previous response), I knew that I could not modify the Main Jets or the Primary HSAB's without affecting the cruising A/F. But since the Primary circtuit seemed to affect this issue, this left the PVCR's since they do not affect my cruising A/F readings.
My carb came with .059" PVCR's. I bought the remaining larger sizes from QF which were .065/.067/.069/ & .071's to test. I tested with each size and I found that the larger I used, the better the car felt and the richer my light accel felt. (Note: My current primary jets are four sizes smaller than the original jets in the carb from QF). Once I had the .071's in there I still wanted more fuel during this situation. I then drilled out my .059's to .078. (Note: I am not sure that a PVCR can go much larger than the .078" without worrying about the material cross section at the threads. I was very carefull when screwing in these bleeds not to break the threads since the hole is now larger.) The .078's really helped out the cruise to light/medium A/F rating.
I also tested some more after having the .078's in there. I tested with smaller and larger HSAB's to see what would happen. What I found was that the larger the HSAB, the leaner the light/medium throttle would get. Then the richer the HSAB, the richer the light/medium throttle would get. So I ended up with the .039 HSAB's since this was what gave me the cruising A/F that I wanted.
I am still finding out that I can get allot of things close, but other areas of the fuel curve will be affected. I am good with what I've got.

My next testing will be with the secondary linkage adjustment. My QF carb comes with different secondary linkages for 1:1, 40% and 60% delays. I have messed with this a little in the past but now since I have my cruising A/F reset, I am going to revisit this setup. What I have noticed in the past, since I have a short stroke motor, I have noticed that in the cooler weather the 40% worked great but not in the warmer temps. I found that the 60% worked better in the warmer temps but left some throttle response on the table in the cooler temps. This is basically like tuning a vacuum secondary carb. The springs can speed up or slow down the activation of the secondaries. The trick to the DP carb is to keep the secondary cam/squirter to a minimum and not flooding the engine when cruising at slower speeds and then going to WOT. I am currently using the smallest rear pump cam (black) with an 035 squirter with excellent throttle response both at slower speeds and at 50+mph to WOT. (Note: my 3800 converter helps this issue out too.)

Done for now.

Posted By: YO7_A66

Re: Tuning Results From An O2 Kit? - 07/12/14 04:18 PM

THREAD UPDATE:

I am updating this thread due to the request on the General Forum:

I have been tuning out the medium/heavy throttle A/F reading (once the PV is open but no secondary down shift). Since I have drilled out my PVCR's to the point of no material (.078") left before breaking in half, I have been messing with the primary HSAB's and the primary jetting. My carb came stock with 68's and I have been doing testing from the 68's down to 58's. I have also been doing testing on the stock .033 primary HSAB's up to .042" HSAB's. Since my problem was while cruising and I press down on the accel pedal until the PV opens (8.5), then my A/F readings were in the upper 14's. With the combination of the stock .033 HSAB's/.078 PVCR's, and 67 primary jets, I am now getting mid 13's under this same condition. The car is very responsive since sticking with this setup. It likes it a lot!!!

Another change for this year was swapping from 89 octane to 91/92. I have had to richen up my in D A/F (last year and this Spring it was at 13.8-14.0) and my cruising A/F and my WOT A/F. I am thinking that my local gas station must have changed gas again. It is UP TO E10 just like last year but I had to richen up the overall A/F by about .5 point. The car runs great at this level too!! Richening up the in D idle from 14.0ish down to 13.5ish helped a bunch on the cold start up and the hot startup. Both of these were a bear to keep the engine running but now since I am at 13.5ish, it is much easier to manage at both cold and hot start ups.
I have driven the car with the below setup now for a week or so in cooler outside temps and I am at the point where I can't change anything without compromising the A/F in other driving situations. I Now have a "middle of the road" setup. I always read where you can only tune a carb so much and that you have to pick your battles on what you want for readings. I have found my best setup since tuning with the two A/F sensors and on E10/91-92 octane.

This is my current setup:
In D idle timing: 32 (FBO "manifold vacuum" distrubitor, 18 initial, + 14 at idle = 32, then 34 total + vacuum advance) This makes starting the car and shutting the car off much cleaner. It has 32 degrees timing once the engine is started. Once the engine is cranking or shutting down, the timing drops to 18. I love this setup!
I have a idle stop solenoid wired into the NSS that allows me to separately adjust my D/2/1 idle rpms versus my P/N rpms. I can run 900rpms in P/N and then when in D I can run 1000rpms which allows the alternator to spin fast enough to keep the electrical gauge happy. I love this setup too.

You will see from the next numbers that I am currently charting my A/F numbers from in D to cruising at 65 mph and I get the A/F range from 13.4 to 14.0 to 13.4. The readings are nice and steady all the way up and down.
D: 13.4/13.6
40 mph: 13.8
45 mph: 13.8
50 mph: 14.0
55 mph: 13.8 (mains starting in:2700rpms)
60 mph: 13.6
65 mph: 13.4
NOTE: My engine starts to surge around 14.4 A/F.

I only test my WOT A/F by cruising at 50mph and going straight to WOT. This give me a good test procedure every time. Last year I was aiming for 12.6-12.8 but it was not as strong as I think it should have felt. This year I richened up this number to 12.2-12.4 and it feels great!

My current Quick Fuel carb is a SS-750-AN and this is my setup:
67/75 jets
IFR's at .033" (Metering Screws outward 1/2 turn)
.033/.036 HSAB's (I tune the secondary HSAB's to get me the WOT A/F desired after outside temps change year around.)
.050/.060 IAB's
Red/.037 both front and rear
Secondary linkage set on 40% delay
Bowls are set to 1/2 in the glass per QF
Idle fuel psi at 6-3/4"

This setup is a blast to drive. At a stop in D, I can mash the throttle and have instant tire spin. I might have to get some stickier tires next year. Any where in the cruising range I can mash the throttle and have instant acceleration.

I love this carb and my wideband sensors!!

Posted By: TJP

Re: Tuning Results From An O2 Kit? - 07/12/14 05:15 PM

This is an awesome thread that should not be lost. Add it to the archives ????

Tuning Results From An O2 Kit?