My turn for a wideband O2 tuning thread

My turn for a wideband O2 tuning thread - 04/29/12 07:17 PM

So, I finally got my wideband O2 hooked up, and leaned it way down to where it is now. I also made an intake vacuum sensor that hooks up to the LMA-2 RPM thingy, so I have that logged as well.

'72 W200. Edelbrock 1406. Currently jetted with 0.095 mains, I think the secondaries are also 95s, 73/52 rods, stiffest step up springs. IMSs are ~1.75 turns out. Idles with 18"hg. New plugs. Initial timing is ~15ish, total ~35ish @2500. With vac advance it's hitting ~60* (

). With vac advance unhooked it actually seemed to make my stumble worse.

At cruise it's running ~16:1.
Part throttle acceleration ~12-12.5ish
WOT 13.5ish (why it's higher than part throttle, I'm not sure?)

At very light acceleration it dips into the 11's, and has a pretty annoying stumble/hesitation, which is currently my main frustration that I've been chasing for a while now. It seems to clear up once the RPMs get a little higher, and with more throttle.

I think the stumble is a rich stumble, but I'm not sure how to lean that bit out any more. I had the Orange step up springs in and it made the light accel stumble horrendous. I saw it dipping into the 10s off idle

Any thoughts how I can get rid of that stumble before I have to pull a horse trailer next week?

FYI, attached is 'tunabrock.xls'. It's an excel file where someone entered every jet and rod combination showing the resulting areas for economy and power. Makes it easy to go richer/leaner in one mode or the other and know exactly what rod/jet to use. It has been VERY handy.

edit: ok, maybe I can't attach it. If anyone wants it, PM me and I can email it.

Posted By: YO7_A66

Re: My turn for a wideband O2 tuning thread - 04/30/12 06:43 PM

""At cruise it's running ~16:1.
Part throttle acceleration ~12-12.5ish
WOT 13.5ish (why it's higher than part throttle, I'm not sure?)""

I will say that your cruise number is lean, your part throttle accel is rich, and the WOT is a little lean. Try aiming for the 14's at cruise (maybe low 15's), the high 12's to the mid 13's for part throttle accel, and the mid 12's for your WOT and see how it acts.

Can any of the Edy/Carter guys help him out?

BUMP

Posted By: Dunnuck Racing

Re: My turn for a wideband O2 tuning thread - 04/30/12 07:06 PM

Looks like you need to try a different metering rod size. The bigger the number,the leaner it gets. I would go for something around 68/52 if you have something close to that. Not sure what is in the kit,my sheets are out in the shop.
I like to get the metering rods sorted out as far as getting the A/F numbers I want, then work with the step up springs to get them working in the right rpm/throttle position range.
Keith

Posted By: hooziewhatsit

Re: My turn for a wideband O2 tuning thread - 04/30/12 07:52 PM

Quote:

Looks like you need to try a different metering rod size. The bigger the number,the leaner it gets. I would go for something around 68/52 if you have something close to that. Not sure what is in the kit,my sheets are out in the shop.
I like to get the metering rods sorted out as far as getting the A/F numbers I want, then work with the step up springs to get them working in the right rpm/throttle position range.
Keith

Yea, I have a 68/52 I can swap in. Think I should go back to the middle Orange step up spring for now?

The truck is mainly a pavement pounder, so I'm looking for whatever mileage I can get, but want it with good driveability most of all.

Attached is a portion of that file I was talking about. Columns to look at are the 'Area Economy', and 'Area Power', and the corresponding big/small rod sizes. Highlighted row is where I am now.

Thanks

Posted By: ThermoQuad

Re: My turn for a wideband O2 tuning thread - 04/30/12 08:31 PM

Do you have a 195 degree hi flow thermostat??
Today's gasoline requires it.

Typically too much gasoline collects inside the intake when using the lower operating temperature thermostat which makes it difficult to get consistent a-f numbers.

Posted By: hooziewhatsit

Re: My turn for a wideband O2 tuning thread - 04/30/12 08:51 PM

Yep, it has a 195 thermostat in it. I forgot to mention it also has a 1" 4 hole spacer

It does tend to run warm, but I think that's another issue entirely. I just need it to work until I can build the new engine and fuel inject it

Posted By: herkamer

Re: My turn for a wideband O2 tuning thread - 04/30/12 09:01 PM

Is the stumble off-idle or part throttle? Could be the accel pump nozzle having the wrong size. Sounds like it's dumping fuel if it goes rich, but it also could be too small of a pump shot if it goes rich then lean. You may need to move the linkage to the top hole for more shot and a smaller nozzle to allow that shot over a longer period of time. I'll brush up in the Carter tuning manual...

Posted By: hooziewhatsit

Re: My turn for a wideband O2 tuning thread - 04/30/12 09:11 PM

Quote:

Is the stumble off-idle or part throttle? Could be the accel pump nozzle having the wrong size. Sounds like it's dumping fuel if it goes rich, but it also could be too small of a pump shot if it goes rich then lean. You may need to move the linkage to the top hole for more shot and a smaller nozzle to allow that shot over a longer period of time. I'll brush up in the Carter tuning manual...

The discharge nozzle has a 28 stamped on top of it. I haven't measured to see if anyone has messed around with it. I see the pack they sell comes with a 24

Accelerator pump Linkage is in the top most hole already.

I think the stumble is more light acceleration than off idle, though it shows up just off idle while lightly accelerating (lolwut).

Think of the throttle necessary to slowly accelerate from 25 mph up. Just a little throttle at lower speeds, and it doesn't like it.

Posted By: herkamer

Re: My turn for a wideband O2 tuning thread - 04/30/12 09:21 PM

Float level becomes really important when using the top hole, because if the accel pump is above fuel level you will get air mixed in with the pump shot leaning it out. The nozzle only controls timing via length of shot, not pump volume which is controlled by which hole you are using.

If you are using the stiffest step up springs it will go into power mode faster which may be why it's going rich. I always use the orange springs but I'm also at 5000' so I get about 14" of vacuum here. You may want to try the pink springs first for your application.

There's a couple good pages in the Carter book. Let me see if I can scan them.

Posted By: hooziewhatsit

Re: My turn for a wideband O2 tuning thread - 04/30/12 09:35 PM

Quote:

Float level becomes really important when using the top hole, because if the accel pump is above fuel level you will get air mixed in with the pump shot leaning it out. The nozzle only controls timing via length of shot, not pump volume which is controlled by which hole you are using.

If you are using the stiffest step up springs it will go into power mode faster which may be why it's going rich. I always use the orange springs but I'm also at 5000' so I get about 14" of vacuum here. You may want to try the pink springs first for your application.

There's a couple good pages in the Carter book. Let me see if I can scan them.

Hmm, did I get my thinking for the step up springs backwards

I'm at ~4000' elevation here (and am getting ~18" at idle).

I'm not sure why I put the accel pump in the closest hole. I may move it to the middle and see what it does.

Thanks for the help thus far,
-Dave

Posted By: herkamer

Re: My turn for a wideband O2 tuning thread - 04/30/12 09:36 PM

Page 1 of 3.

Sorry for the camera phone pics, scanner is more trouble than it's worth but these should be readable.

Attached picture 7186279-IMAG0233.jpg

Posted By: herkamer

Re: My turn for a wideband O2 tuning thread - 04/30/12 09:37 PM

2 of 3

Posted By: herkamer

Re: My turn for a wideband O2 tuning thread - 04/30/12 09:38 PM

3 of 3

Posted By: hooziewhatsit

Re: My turn for a wideband O2 tuning thread - 04/30/12 09:51 PM

Wow, that was actually a good read and explained the stuff well.

Looks like I should probably back off 1 or 2 steps on the springs, and move the accel pump back to the middle hole (and maybe even the farthest hole).

I need to go get some stuff later today, so I'll test it then and report back.

Posted By: herkamer

Re: My turn for a wideband O2 tuning thread - 04/30/12 09:54 PM

Quote:

Hmm, did I get my thinking for the step up springs backwards

Stronger spring pushes the metering rod up to the enrichment stage faster. The weaker springs need less manifold vacuum to overcome. You are going to power mode at about 9.5" Hg right now.

Quote:

I'm not sure why I put the accel pump in the closest hole.

3rd hole is the stock setup, but there is also a measurement of how far the pump is supposed to be above the air horn. The book shows 13/32" but this is also for the Carter AFB. Should be pretty close for a Eddy, but might want to double check their manual.

Posted By: MileHighDart

Re: My turn for a wideband O2 tuning thread - 04/30/12 10:32 PM

1st, thanks for the file.

2nd, is there any chance you could explain the "area economy" and "area power" numbers and what they mean, or how to use those numbers to tune your carb ? I'm lost with that chart.

I understand using the o2 sensor and changing jets, metering rods, etc to get the mixture within a certain range so its not rich, not lean. But I dont get what this chart does or what I'm suppost to do with it.
Sorry, I dont have much experience with this.

Posted By: herkamer

Re: My turn for a wideband O2 tuning thread - 04/30/12 10:40 PM

The "area" is the amount of area left open after being filled with the metering rod. Let's just say .100 jet with a .070 rod would leave you a .030 area. It gives you a comparative chart of what rod and jet combination may best for your setup. Economy is the fatter part of the rod, and power is the skinny part which is when the step up springs push the rods up. The chart is in thousandsth of an inch.

Posted By: MileHighDart

Re: My turn for a wideband O2 tuning thread - 04/30/12 10:50 PM

Ok, I think I got it.

Thanks

Posted By: hooziewhatsit

Re: My turn for a wideband O2 tuning thread - 04/30/12 11:48 PM

Yep. Typically you would start with whatever jet/rod combo is 'stock', and looking at the chart, you can see the effective areas of each. More area = more fuel = richer.

Then to go leaner on say economy, you find another rod with the same area for Power, but smaller for economy. Or vice-versa to richer. Or, if you can't go leaner with a new jet, you can go to a smaller jet and know which rod to use to lean the economy side and keep the power side the same or similar.

Just got back from a drive. Before hand I moved the accel pump to the 3rd hole (farthest from body), and it got much much better. Then I moved to (what I think) is the pink spring. The springs are old and the paint isn't really there anymore

Still under very light throttle it's running in the high 11s:1 for AFR and popping lightly. Get into it more and it goes to mid 12s. So, I think I'm still hitting the enrichment circuit at light throttle, so I think I need to go to the orange springs and test again.

I've fought and messed with this carb for 5 years. Now a week and half after getting the O2 sensor installed it's almost perfect. Should've done this years ago

Posted By: herkamer

Re: My turn for a wideband O2 tuning thread - 05/01/12 12:37 AM

Going in the right direction!

Since you have a way to datalog manifold vacuum, check to see where the problem is. That will let you know where the enrichment is coming in, and where the springs needs to be.

Posted By: hooziewhatsit

Re: My turn for a wideband O2 tuning thread - 05/01/12 02:12 AM

Quote:

Going in the right direction!

Since you have a way to datalog manifold vacuum, check to see where the problem is. That will let you know where the enrichment is coming in, and where the springs needs to be.

Alrighty, looking at the log, assUme-ing I got my voltage-to-vacuum conversion correct (pretty sure it is), at 'light' throttle, it drops to ~5"hg with high 11s for AFRs. As speed increases and I pass through ~7"hg, AFRs shoot up to high 15s & low 16s. Which makes sense with the 7" springs in.

Just went for another drive with the Orange springs in. At light accel the AFRs stay high. I do think my pump shot either needs to be bigger, or longer, as it's spiking to 18ish just off idle, right when I feel a hesitation now

Looking at another light acceleration; vacuum is 5.5ish with AFRs in the 15s. Right when I give just a little more throttle and it drops below 5" vacuum, AFRs drop to the 14s.

I've been debating whipping out a circuit board for this manifold vacuum sensor and selling it. Not sure if anyone else would find it handy though, as it requires the LMA-2 RPM adapter to work

Attached is a light acceleration pass with the Orange springs, and accelerator pump in the 3rd hole. (For some reason it logs the tach as being really jumpy. Probably the points bouncing

)

Attached picture 7186693-LightAccelPass.png

Posted By: hooziewhatsit

Re: My turn for a wideband O2 tuning thread - 05/01/12 02:13 AM

And here's a WOT pass, right after the previous light acceleration pass.

Attached picture 7186695-WOTPass.png

Posted By: herkamer

Re: My turn for a wideband O2 tuning thread - 05/01/12 02:57 AM

Try the middle hole for pump shot, and double check the measurement from top of stem to air horn. Definitely going lean on the tip in. It would really be sweet to see throttle position, that definitely shows a bit of information. You might need to increase the size of the nozzle (and amount of pump shot accordingly) to keep it from leaning out. As the book says, go for the minimum pump shot to get you accelerating correctly.

Posted By: hooziewhatsit

Re: My turn for a wideband O2 tuning thread - 05/01/12 03:45 PM

For the accelerator pump, if the middle hole doesn't get rid of the lean spot, I may need to go to a smaller squirter to lengthen the duration of the shot, right?

The only thing I've seen in regards to measuring the accel pump (on an Edelbrock vs Carter) is someone mentioning to make sure at full throttle the pump is all the way down, and to bend the arm to make that adjustment. Which I guess does make sense to me; make sure you have maximum travel and that it doesn't pump air at the top of the stroke.

I had thought about how nice it would be to have throttle position, but have yet to find a good way to connect a potentiometer to the throttle shaft. Instead I came up with the vacuum idea, which has actually been quite useful as well.

As for the cruise AFR; am I ok as long as I don't feel any surging or bucking? I can richen that up a little, but figure if it's running fine and I won't burn a hole in the pistons... might as well stay where it is and enjoy the (mild) mileage gains.

Posted By: herkamer

Re: My turn for a wideband O2 tuning thread - 05/01/12 04:17 PM

If moving to the middle or even back to the top hole doesn't correct the lean spot, you might need to increase the nozzle size so it discharges fuel faster. It really depends where the lean spot is and how long it lasts. If it feels like a 2 second hesitation, then a smaller nozzle would cure it by lengthening the shot. Full throttle bog would probably require more fuel faster, so bigger nozzle and higher up on the hole. To start, I would put it in the middle hole, and check to see if the pump shaft top is 13/32 above the air horn so you know you are starting at factory spec and continue from there.

Cruise AFR looks ok. I run 15-15.5 and it doesn't surge in my W350 with TBI. I notice about 17 or so is when it feels like it's going to fall on it's face and starts bucking a bit.

Posted By: Dunnuck Racing

Re: My turn for a wideband O2 tuning thread - 05/01/12 05:02 PM

If you are goig to be pulling that trailer,I would richen up the part throttle mixture. You will lose torque a lot faster on the lean side of stoich. Add in the fact that you are tuning without a load right now,you will have more throttle opening(less vacuum) while pulling your trailer. Just hate to see you go too lean and hurt something.
Keith

Posted By: hooziewhatsit

Re: My turn for a wideband O2 tuning thread - 05/01/12 06:11 PM

Quote:

If you are goig to be pulling that trailer,I would richen up the part throttle mixture. You will lose torque a lot faster on the lean side of stoich. Add in the fact that you are tuning without a load right now,you will have more throttle opening(less vacuum) while pulling your trailer. Just hate to see you go too lean and hurt something.
Keith

That makes sense. I also (think I) got some light surging at 35mph through town earlier. So, I'll go another step or two richer on the cruise side and see what happens. The trailer itself is ~3500#, and add a couple 1k# horses...

After looking at todays logs, I may need a longer pump shot as well. WOT seems to be fine, but at slow acceleration AFRs tend to jump to 18ish for ~1s, then go back to normal.

Thanks again for all the help

Posted By: hooziewhatsit

Re: My turn for a wideband O2 tuning thread - 05/06/12 02:58 AM

Earlier today I put 70-52 rods in (one step richer on cruise).

Much much better overall. I still have a lean spike off idle at low acceleration that I can barely feel. I'm thinking a smaller nozzle will extend the duration of the shot, and should probably cover that?

I've also noticed at part throttle in enrichment (under 5"hg), the AFRs are mid to high 12s. At WOT, the AFRs are in the mid 13s. I think this is saying it could use one step richer jets on the secondary side, right?

I think I'm nearly to the point where it will 'just drive'

Posted By: Dunnuck Racing

Re: My turn for a wideband O2 tuning thread - 05/06/12 03:17 AM

Sure sounds like you are getting it dialed in! I should also mention that with oxygenated fuels that are at most places at least in this area,I have found that just about everything likes to be a little bit richer than what you would think.
The stoich numbers are different for different fuels so you have to adjust accordingly. I know some guys are trying to lean everything down for mileage these days but fuel qualities vary and it can be frustrating when you fill up out of town and get some fuel that makes you get lean surging and pinging all the way home pulling a trailer.
I would fatten it up a tad more.

Keith

Posted By: hooziewhatsit

Re: My turn for a wideband O2 tuning thread - 06/10/12 08:50 PM

So that stumble I've been chasing

Finally got time to hook up with Jeremiah yesterday and take him for a ride to see what he thought. The off idle stumble I thought was fuel related, he thought was ignition related. He had the electronic distributor and a spare box & harness, so a few hours later, the points distributor was out, and it was running.
Wow, it's never run this well before

All of the off-idle hesitation/stumbles are gone.

So NOW I can finally get to tuning it

Currently running:
mid to high 13s at cruise (55mph, ~12"hg)
mid-high 11s at part throttle enrichment (I think this is still a little rich?)
mid 12s at WOT

If I floor it from a stop, I can see the AFRs go to mid 11s, then to 14ish (over the course of a second), then it evens out in the mid 12s. I think I still need a smaller squirter to lengthen the pump shot. Otherwise I don't feel any stumbles off the line. I can only see it in the log.

So, big thanks to Jeremiah for giving me the electronic disty & Orange box and fixing the issues I've been chasing for a few years now

Posted By: dart1962_440

Re: My turn for a wideband O2 tuning thread - 06/10/12 09:07 PM

Excellent info!

Posted By: YO7_A66

Re: My turn for a wideband O2 tuning thread - 06/11/12 01:03 AM

Your cruising a/f might be a tad rich but you won't know until you try. I would suggest low to mid 14's for cruise.
Your mid 12's sound good for WOT and this should be your richest a/f reading. Your 11 readings for enrichment are too rich. I would suggest making your part throttle enrichment a/f numbers be in between your mid 12's for WOT and 14's for cruise. The enrichment numbers may vary pending on the seat of the pants feel of the driver.
My cruise numbers from 30-70 are currently at 13.6 to 14.6. My enrichment for light throttle is 13.8 to 14.2 and my WOT is 12.8 to 13.0.
Each motor combo will be different, but over the last year of driving with an a/f sensor, the above numbers are what my current combo and my butt-ometer feel are good driving numbers for my car. Hope this helps.

Posted By: hooziewhatsit

Re: My turn for a wideband O2 tuning thread - 06/21/12 01:03 AM

Got some more testing done. Current set up is:
95 mains
101 secondaries
68/52 rods
orange springs

Cruise is mid 14s
Part throttle enrichment is low to mid 12s
WOT is 14ish

(Remember, I'm at 4000' here)

Other than the weird WOT numbers, I'm pretty happy with the driveability and overall tune. I guess part throttle enrichment could probably be a little leaner.

I think once I get everything dialed in, I'll keep a second set of rods that are a tad bit richer for the rare times I do have to tow something. 98% of my driving is highway just moving things around.

Posted By: YO7_A66

Re: My turn for a wideband O2 tuning thread - 06/21/12 08:51 PM

Your definitely making the correct changes. Your numbers are falling right into place.
I would suggest that you tune the part throttle until it "feels good". I played with mine from low 14's to low 13's and it felt better/crisper in the upper 13's to 14.0. Your low to mid 12's (part throttle) is where you might end up for a WOT reading, so once you lean the part throttle out your WOT will go even leaner, so be carefull.