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.

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.

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

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!!

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.

* 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

"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

""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.

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.

""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.

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

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

"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

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

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.

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

""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.

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.

Sweet!

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