TPS vs MAP AE 7427 $0E

I'm still working on getting the AE acceleration enrichment to play nicely on my TBI. I'm still getting a lean pop when the throttle is planted open quickly.

I have copied over every AE parameter from BMHK 454 bin into my bin. I did this because I figure these AE parameters ought to be a closer start for me since I also have a large throttle body and even more plenum volume from the single plane intake. Additionally, This bin was setup for the higher pressure 454 TBI, which also ought to be closer for me since I'm running about 28 PSI..

I have been increasing the Delta TPS and Delta MAP AE tables by 20% or 30% at a time, and also reducing the filter tables ($4B3A and $4B62) values by 10%... RBob mentioned this.
These changes have helped with the lean pop, some, but the issue is still there. Also, this has made the engine bog down way rich (10 AFR on WB02) when just tipping into the throttle from a start.

I'm thinking that I need LESS TPS AE at this point as indicated potentially from the rich bog on tip in. AND, that I need MORE MAP AE to cure the lean pop..... Sometimes It will even lean pop when climbing a hill at interstate speeds as the load and MAP increase....

Thoughts?

In the beginning of my tune learning I chased what I thought was a lean pop. After install WB realized it was not lean pop but anticipated spark retard. I lowered the amount of spark retard allowed and increased advance in the 60-85 map area and haven't had a pop in years. I had a friend with mod 454 that had similar results. Your mileage might be different.

I've run into the same problem. Popping is not rich, it's lean. IIRC there is a max PW size that needs to be increased. Then you'll probably end up reducing values in the other two tables.

You'd think the high pressure cal would be closer but the high pressure 454 had a TBI specific manifold which had a smaller volume than the old carby manifold plus adapter.

Increasing spark advance or changing the spark retard limit can increase how quickly the engine accelerates which in turn draws the fuel/air mix out of the manifold before it can ignite.

Edit: Yes, the maximum Async pulsewidth value will limit total AE.

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Originally Posted by 1project2many

I've run into the same problem. Popping is not rich, it's lean. IIRC there is a max PW size that needs to be increased. Then you'll probably end up reducing values in the other two tables.

You'd think the high pressure cal would be closer but the high pressure 454 had a TBI specific manifold which had a smaller volume than the old carby manifold plus adapter.

Increasing spark advance or changing the spark retard limit can increase how quickly the engine accelerates which in turn draws the fuel/air mix out of the manifold before it can ignite.

Edit: Yes, the maximum Async pulsewidth value will limit total AE.

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Lack of timing advance can also cause popping.

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Originally Posted by myburb

In the beginning of my tune learning I chased what I thought was a lean pop. After install WB realized it was not lean pop but anticipated spark retard. I lowered the amount of spark retard allowed and increased advance in the 60-85 map area and haven't had a pop in years. I had a friend with mod 454 that had similar results. Your mileage might be different.

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Interesting. I know this is a lean pop because I can see it on the WB02 gauge itself, as well as the logs. I have wondered if I don't have enough timing now though.

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Originally Posted by 1project2many

I've run into the same problem. Popping is not rich, it's lean. IIRC there is a max PW size that needs to be increased. Then you'll probably end up reducing values in the other two tables.

You'd think the high pressure cal would be closer but the high pressure 454 had a TBI specific manifold which had a smaller volume than the old carby manifold plus adapter.

Increasing spark advance or changing the spark retard limit can increase how quickly the engine accelerates which in turn draws the fuel/air mix out of the manifold before it can ignite.

Edit: Yes, the maximum Async pulsewidth value will limit total AE.

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Well what I was saying is that increasing the Delta TPS and MAP AE seems to help lessen the lean pop when you smash the throttle open quickly, however, those same changes appear to have made it overly rich on very light throttle tip in pulling away from a stop. It literally pegs my WB on 10 AFR for a second or two. I've read several threads on TGO where Dewey talked about having a similar/same issue... Here's one I stumbled on
https://www.thirdgen.org/forums/tbi/...ifold-big.html

Where is this max PW you speak of? Do you think the 350 AE parameters would be closer??? I thought with the big throttle body and single plane carb intake it would be closer, but now that you mention the 454 manifold was smaller.......

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Originally Posted by Fast355

Lack of timing advance can also cause popping.

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I was running the stock L05 timing table from the $0E bin I started with. I then copied over the timing table from Brian, (sturgillbd on here). His timing table IIRC has a little more advance in it. It seemed to help mine with the lean pop when you smash the throttle open....

I'm running TrickFlow aluminum heads https://www.summitracing.com/parts/SUM-162108

Maybe with these new heads and the single plane, flat top pistons and everything else I don't have near enough timing advance for this combo? Anyone have a timing table for such a combo that might be closer in the ball park vs what I've tried?

Initial spark advance is 3*

I have the same heads and a 46mm TB with 18LB spring on a 3704 intake (bored out to 48mm).

Attachment 13880

How's yours running? My TB measures nearly 52 MM... One of the reasons I suspect AE is what is causing this lean pop.

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How's yours running? My TB measures nearly 52 MM... One of the reasons I suspect AE is what is causing this lean pop.

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It's getting better, Dave helped me get the Main Fuel table dialed in so my BLM is ~127 ave. Now i'm adjusting VE and PE with data logging. Of course mine's an '88 with 7747 and I'm guessing my cam (207/213 @.050, .466/.484 with 1.6 rockers) is milder than yours. Here's where I am so far;

Attachment 13881

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Well what I was saying is that increasing the Delta TPS and MAP AE seems to help lessen the lean pop when you smash the throttle open quickly, however, those same changes appear to have made it overly rich on very light throttle tip in pulling away from a stop.

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The first 25% of throttle angle change makes a greater difference in air density than the next 50%. I tend to ramp MAP AE in faster than TPS on a larger plenum. Then I'll increase the MAP difference to enable AE as a limit to MAP contribution at low throttle angles. This helps prevent rich surges when load changes without much change in throttle.

Are those heads a fast burn style? They might require a fair amount more timing.

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The first 25% of throttle angle change makes a greater difference in air density than the next 50%. I tend to ramp MAP AE in faster than TPS on a larger plenum. Then I'll increase the MAP difference to enable AE as a limit to MAP contribution at low throttle angles. This helps prevent rich surges when load changes without much change in throttle.

Are those heads a fast burn style? They might require a fair amount more timing.

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Thanks 1p2m, Good info! These heads (SUM-106108) have 170cc intake runners, from what I understand "fast burn" heads are 210cc which come into power at higher revs. Although these heads have bigger valves (2.02/1.60 compared to ~2.00/1.55) I'm wondering if they are a good match for a single plane manifold with a 7.4 TB on a SBC???

CDeeZ: do you have a 5.7 or is it stroked? A 350 @ 6,000RPM only needs a little over 600CFM (check out the "Carburetor Sizing" at the bottom")

http://www.tciauto.com/tc/racing-calculators

I thought fast burn was just another name for the OEM vortec castings? Yeah the heads are linked in post #5.


It's a 355, (.030" over) The Holley TB is probably a tad overkill, but I found it for $5 at a swap meet... It measures a tad larger than a BBC TB. Stock unmodified 4.3/5.0/5.7 TB probably wasn't quite enough for this engine?

Shannen , sounds like you're saying more MAP AE might be the answer..... But you're also saying that you increase the filter table values? This is in contrast to what I had read RBob post about? He was saying to decrease the filter tables. More than one way to skin a cat I suppose?

Chamber design has come a long way since the days of the first smallblock. The size, shape, depth of the chamber all play a part in efficiency. Today engineers are looking for faster and more complete combustion and heads with a well designed chamber need less spark advance. Look at some of the old and new designs in this link: https://www.chevydiy.com/chevy-small...-fundamentals/ If the Summit heads are a copy of an old design head, you may need to add a bunch of spark timing. If they are a newer fast burn type chamber the increased efficiency may work to balance the heat loss through the head in a way that lets the stock L05 timing work. My comment wasn't necessarily about curing popping with timing changes, but more of a comment on how close the stock L05 tables will be to correct.

For AE in a wet manifold you need to increase fuel delivery with an increase in air density. The amount of increase has to be greater at low rpm when the manifold air charge has more time to be exposed to the intake valves, the primary heat source responsible for popping. As rpm increases the fuel/air charge spends less time in the manifold so there's less chance for popping. And when throttle angle is greater there's less change in density with a given change in throttle angle so less fuel needs to be delivered.

The AE tables don't care what RPM or throttle angle the engine is at. They deliver fuel based on change. So you could go from 0% to 20% TPS or 60% to 80% and both changes get the same amount of fuel from the delta TPS table, even though the 0-20% change should get more fuel.

Decreasing the filter values makes AE respond faster. For most engines I don't feel this is the first step. For a larger plenum engine I try to shift AE fuel delivery so MAP is responsible for more of the job at low rpm. At higher rpm or lighter loads, too much AE shows up as a rich reading on O2 and possibly as soggy performance. If AE is correct when you stomp on it, but it's showing as rich with a small throttle change, then you might try increasing the MAP difference to enable AE and/or the TPS difference to enable AE. The 7.4 cal I'm looking at now (BHDC) shows a 2% difference in TPS to enable AE, an 18% difference in MAP, and a 14% difference in MAP to enable idle AE. I might try increasing the TPS difference to 4% and increasing the MAP at idle to 18%.

If you opt to lower the filter values then you may end up redoing the AE tables. With a faster response time on AE there may be noticeable differences "all over." The filters delay AE reaction time so it may be easier to increase AE on a 0 to WOT transition, but I would expect the rich surge at light load, small throttle changes to get worse.

Then again, I'm only on my first coffee so who knows...

Just finished my 2nd cup and starting to understand some of this great info, LOL

It seems like I'm getting somewhere with wrastlin' this AE into submission. I'm starting to get a better understanding of the what/how/why. AE is just to compensate for the drop in manifold vacuum when the throttle is opened quickly. Much like pump shot in a carburetor since TBI is also a wet manifold... AE is just to get you into PE then PE is in play from then on out.

My throttle only opens 60%, I need to adjust the throttle cable or something, possibly move the home-made bracket that mounts it. Most of the time, when I slam the pedal down to 60% it is no longer lean popping. I'm still getting some lean pop occasionally.

Once I got rid of most of the lean pops, I was also seeing the WB02 pegged on full rich 10 AFR. It was sluggish going off the line, especially when lightly stepping into the throttle. I have reduced some of the TPS AE and that seems to have helped.

Does it stand to reason that with a large throttle body, and all the open plenum space of a carbed single plane, that MAP AE is going to probably be the main requirement to get AE in line? It seems that way in my case. I have read about other people having similar experiences with needing more MAP AE than TPS AE in similar setups.

Really makes me appreciate my LS truck.... A dry manifold that comes off in 5 minutes, No distributor to hassle with, no AE to have to tune. Just slug the PE right into the 11.5 AFR range, turn up the boost and let it eat.

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Originally Posted by CDeeZ

It seems like I'm getting somewhere with wrastlin' this AE into submission. I'm starting to get a better understanding of the what/how/why. AE is just to compensate for the drop in manifold vacuum when the throttle is opened quickly. Much like pump shot in a carburetor since TBI is also a wet manifold... AE is just to get you into PE then PE is in play from then on out.

My throttle only opens 60%, I need to adjust the throttle cable or something, possibly move the home-made bracket that mounts it. Most of the time, when I slam the pedal down to 60% it is no longer lean popping. I'm still getting some lean pop occasionally.

Once I got rid of most of the lean pops, I was also seeing the WB02 pegged on full rich 10 AFR. It was sluggish going off the line, especially when lightly stepping into the throttle. I have reduced some of the TPS AE and that seems to have helped.

Does it stand to reason that with a large throttle body, and all the open plenum space of a carbed single plane, that MAP AE is going to probably be the main requirement to get AE in line? It seems that way in my case. I have read about other people having similar experiences with needing more MAP AE than TPS AE in similar setups.

Really makes me appreciate my LS truck.... A dry manifold that comes off in 5 minutes, No distributor to hassle with, no AE to have to tune. Just slug the PE right into the 11.5 AFR range, turn up the boost and let it eat.

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AE is still in effect in a LS truck and there are substantial throttle response gains to dialing them in as well. All the Wall Wet/Evaporation tables in the PCM are how they do it. I got it all dialed in the way I wanted on my L31 too.

I found my old setup liked more bias toward the MAP AE. You can run into driving conditions were the manifold vacuum will suddenly drop from fairly high to almost non-existing with zero movement of the throttle pedal and need to have the MAP AE to keep the engine from experiencing a lean spike. Watch your part-throttle upshifts effect on the 02 sensor voltage and short term fuel trim. If the 02 voltage and narrow bands spike lean on a part throttle upshift at say 25% throttle you need to add more MAP AE. My old 350 Vortec Single Plane setup on the G20 van had 3x the MAP AE of a stock 454.

If you are at 10:1 and it is still popping you have issues that are not AE related. Retarded spark timing as well as overly tight valves can cause popping and even fireballs out of the TBI unit.

In my experience the L03/L05 spark maps only work well on the swirl port heads. They do not have enough timing in them to work well with other heads. Most other heads want more timing in the low rpm/high map area than the TBI heads work OK with in factory form. Most L05 timing maps actually have negative timing values off-idle at WOT. I have tuned cammed LS engines with 3,000+ rpm stall converters that like 20* of timing at 1,200 rpm @ full load and only run 26-28* of total timing at high rpm.

With a loose converter you can typically advance the timing substantially under the stall speed. I usually use the PE spark added to ensure the extra timing is only there at WOT. I use 4-8* in my PE adder. When you are cruising around with a locked converter, out of PE the same timing values that help spool the engine up at WOT from a stop would cause spark knock.

Will also give this tid bit. Almost none of my engines are under 12* of timing anywhere in the timing map and some have as much as 20* as the LEAST amount of timing in the whole graph. Even stock cam engines often have zero issues with what I will call initial timing at 16* aka the lowest value in the MAP. I cannot tell you how many of those old 260 HP GM Crate 350s that I woke up drastically by recurving the distributor and welding up the slots to limit the total advance with the new advanced timing. I would shoot for 18* initial, 18* centrifical (36* total) and 10* vacuum advance on those engines. I am confident enough in it that I will say any value less than 12* in the timing map, make 12* and see what happens. If it likes it go 14*, if it still responds without tip-in knock, go 16*, etc.

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Originally Posted by Fast355

AE is still in effect in a LS truck and there are substantial throttle response gains to dialing them in as well. All the Wall Wet/Evaporation tables in the PCM are how they do it. I got it all dialed in the way I wanted on my L31 too.

I found my old setup liked more bias toward the MAP AE. You can run into driving conditions were the manifold vacuum will suddenly drop from fairly high to almost non-existing with zero movement of the throttle pedal and need to have the MAP AE to keep the engine from experiencing a lean spike. Watch your part-throttle upshifts effect on the 02 sensor voltage and short term fuel trim. If the 02 voltage and narrow bands spike lean on a part throttle upshift at say 25% throttle you need to add more MAP AE. My old 350 Vortec Single Plane setup on the G20 van had 3x the MAP AE of a stock 454.

If you are at 10:1 and it is still popping you have issues that are not AE related. Retarded spark timing as well as overly tight valves can cause popping and even fireballs out of the TBI unit.

In my experience the L03/L05 spark maps only work well on the swirl port heads. They do not have enough timing in them to work well with other heads. Most other heads want more timing in the low rpm/high map area than the TBI heads work OK with in factory form. Most L05 timing maps actually have negative timing values off-idle at WOT. I have tuned cammed LS engines with 3,000+ rpm stall converters that like 20* of timing at 1,200 rpm @ full load and only run 26-28* of total timing at high rpm.

With a loose converter you can typically advance the timing substantially under the stall speed. I usually use the PE spark added to ensure the extra timing is only there at WOT. I use 4-8* in my PE adder. When you are cruising around with a locked converter, out of PE the same timing values that help spool the engine up at WOT from a stop would cause spark knock.

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Originally Posted by Fast355

Will also give this tid bit. Almost none of my engines are under 12* of timing anywhere in the timing map and some have as much as 20* as the LEAST amount of timing in the whole graph. Even stock cam engines often have zero issues with what I will call initial timing at 16* aka the lowest value in the MAP. I cannot tell you how many of those old 260 HP GM Crate 350s that I woke up drastically by recurving the distributor and welding up the slots to limit the total advance with the new advanced timing. I would shoot for 18* initial, 18* centrifical (36* total) and 10* vacuum advance on those engines. I am confident enough in it that I will say any value less than 12* in the timing map, make 12* and see what happens. If it likes it go 14*, if it still responds without tip-in knock, go 16*, etc.

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I never had to mess with those settings in my 3 bar SD '411 running my 75MM LQ4... 8 PSI boost. I decapped the stock truck injectors and slapped 75 in the entire IFR table. The only other thing I really had to change was the Min Injector Pulse and Short Pulse Adder. Ended up dropping these considerably in order to allow the decapped injectors to idle without being stupid rich. Throttle response has always been good on this one. The farther you press the skinny pedal, the more likely you are to break loose and start drifting towards the ditch. It's always the ditch on the RIGHT hand side. Maybe with decapped injectors and a compressor the LS AE isn't as sensitive as compared to a wet manifold system like TBI? The decaps turn the finely atomized mist into a stream like a faucet... People warned me that because of this, idle and low speed drive ability would not be good. Of course, this turned out to be bullshit.

Yes, that seems to be the same thing my TBI is experiencing. It seems to like more MAP AE like you said. Climbing hills is when this is most noticeable on this TBI truck.

No, when it was 10:1 is when you just lightly tip into the throttle pulling away from a stop sign. When it was lean popping I could see on the WB gauge itself that it was in fact a lean spike. Two different issues. Confirmed the lean spike by looking at logs. I remember Dewey posting on TGO about having the same issue here, he added TPS and MAP AE incrementally in order to cure a lean pop when jamming the throttle open. Only to find that he ended up with too much TPS AE which caused a similar issue to mine where it would go way rich on light throttle.

Do you think the heads linked above would respond well to more timing? I was thinking if anything it would be the other way around since I would assume these Trick Flow aluminum heads would be more efficient than the old swirlports? Either way, you got me thinkin'. Maybe some more timing is in order here.

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Originally Posted by CDeeZ

I never had to mess with those settings in my 3 bar SD '411 running my 75MM LQ4... 8 PSI boost. I decapped the stock truck injectors and slapped 75 in the entire IFR table. The only other thing I really had to change was the Min Injector Pulse and Short Pulse Adder. Ended up dropping these considerably in order to allow the decapped injectors to idle without being stupid rich. Throttle response has always been good on this one. The farther you press the skinny pedal, the more likely you are to break loose and start drifting towards the ditch. It's always the ditch on the RIGHT hand side. Maybe with decapped injectors and a compressor the LS AE isn't as sensitive as compared to a wet manifold system like TBI? The decaps turn the finely atomized mist into a stream like a faucet... People warned me that because of this, idle and low speed drive ability would not be good. Of course, this turned out to be bullshit.

Yes, that seems to be the same thing my TBI is experiencing. It seems to like more MAP AE like you said. Climbing hills is when this is most noticeable on this TBI truck.

No, when it was 10:1 is when you just lightly tip into the throttle pulling away from a stop sign. When it was lean popping I could see on the WB gauge itself that it was in fact a lean spike. Two different issues. Confirmed the lean spike by looking at logs. I remember Dewey posting on TGO about having the same issue here, he added TPS and MAP AE incrementally in order to cure a lean pop when jamming the throttle open. Only to find that he ended up with too much TPS AE which caused a similar issue to mine where it would go way rich on light throttle.

Do you think the heads linked above would respond well to more timing? I was thinking if anything it would be the other way around since I would assume these Trick Flow aluminum heads would be more efficient than the old swirlports? Either way, you got me thinkin'. Maybe some more timing is in order here.

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My Assault racing heads have a nice fast burn style chamber and like timing. The Vortecs I have tuned like about 12° at the minimum.

You are thinking wrong. The old swirl ports like less timing than Vortecs. About 26-28° is all they need.

Also you likely need to change the shape of your AE tables. Progressively higher values with bigger TPS/MAP delta's. Ease off on the lower values if it is getting rich at slight throttle changes.

Must have gotten really lucky on the LS. I had the Express van with the 0411 run 5.7 dialed in very well. I went from the factory converter to a looser converter. All of a sudden it started lean popping if you smacked it to the floor. I ended up adding both timing and AE to fix it. After it rapped up much quicker.

Even port fuel setups can lean pop. Its not a TBI or Carb only thing.

https://youtu.be/gNyr_Z6Q_ck

When you change your AE tables both MAP and TPS, are you moving the whole table up and down or are you playing with the curve?

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Originally Posted by Fast355

My Assault racing heads have a nice fast burn style chamber and like timing. The Vortecs I have tuned like about 12° at the minimum.

You are thinking wrong. The old swirl ports like less timing than Vortecs. About 26-28° is all they need.

Also you likely need to change the shape of your AE tables. Progressively higher values with bigger TPS/MAP delta's. Ease off on the lower values if it is getting rich at slight throttle changes.

Must have gotten really lucky on the LS. I had the Express van with the 0411 run 5.7 dialed in very well. I went from the factory converter to a looser converter. All of a sudden it started lean popping if you smacked it to the floor. I ended up adding both timing and AE to fix it. After it rapped up much quicker.

Even port fuel setups can lean pop. Its not a TBI or Carb only thing.

https://youtu.be/gNyr_Z6Q_ck

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Well, more efficient heads require less timing. Or so I've read anyways. That's what got me to thinking that. But, I believe you. It really seems like based upon what you're saying, that with these Trick Flow aluminum heads, that this setup can really benefit from some more timing. I will sprinkle some in today or tomorrow and see what happens. I built this 355 with forged pistons. Since it has forged pistons, I might just slug the entire spark table up 5 degrees and see what happens in the knock retard.

What exactly would be a good proportion for "progressively" higher values in the Delta MAP and TPS AE tables? Thinking maybe something like bump the first 1/3 of the tables up 25%, the middle 1/3 of the tables up 50% and the last 1/3 of the tables up 75% or something similar?

The S475 LS has a frankensteined 32 spline T56 built by yours truly. Might have been an issue if it was an auto with a loose converter.

Oh yeah I'm sure. TBI or carbs seem most susceptible to it, to me anyways. LS has the injectors nearly right behind the intake valves. TBI or carb being all the way upstream of the incoming air, seems like either system would be more prone to lean popping as the fuel would be more likely to fall out of suspension and wet the intake walls....

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Originally Posted by brian617

When you change your AE tables both MAP and TPS, are you moving the whole table up and down or are you playing with the curve?

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Well so far, I have usually been slamming the entire tables up by a percentage. RBob and several others on TGO have posted about multiplying the entire tables by 10% to 30%... I can now see the potential benefit from adjusting the curve rather than moving the whole table up..

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Well, more efficient heads require less timing. Or so I've read anyways.

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They do. Max timing on the older Bowtie race heads was around 36-38 degrees. Vortec are generally run with 32 degrees.

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Trick Flow aluminum heads

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Aluminum is the key. Aluminum heads transfer heat out of the combustion chamber more quickly and it takes longer for the reaction to occur. So you have to start spark sooner.

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I can now see the potential benefit from adjusting the curve rather than moving the whole table up..

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Correct. The shape of the curves needs to be adjusted to match the engine's needs.

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Chamber design has come a long way since the days of the first smallblock. The size, shape, depth of the chamber all play a part in efficiency. Today engineers are looking for faster and more complete combustion and heads with a well designed chamber need less spark advance. Look at some of the old and new designs in this link: https://www.chevydiy.com/chevy-small...-fundamentals/ If the Summit heads are a copy of an old design head, you may need to add a bunch of spark timing. If they are a newer fast burn type chamber the increased efficiency may work to balance the heat loss through the head in a way that lets the stock L05 timing work. My comment wasn't necessarily about curing popping with timing changes, but more of a comment on how close the stock L05 tables will be to correct.

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Here's a picture of the chambers in the Summit 162108 heads CDeeZ and I are using. From what I can tell, based on your link these are the newer "fast burn" style?

Attachment 13917

Here is the design I run.
http://www.gearhead-efi.com/Fuel-Inj...7&d=1549316251

9.6:1 350
271/284 @ .006
215/224 @ .050
.578/.578" w/1.7 rocker
110 LSA
106 ICL

Idle = 24* BTDC @ 750 rpm

WOT
12* @ 800
16* @ 1,200
20* @ 2,000
24* @ 2,400
28* @ 3,000
32* @ 3,600-6,500

Cruise timing is up to 48* BTDC @ 3,000 rpm and 40 KPA MAP.

WOT air/fuel ratio is 12.5:1 near peak torque and leans out to 13.2:1 at higher rpm

Cruise air/fuel ratio is stoichiometric or up to 16.5:1 in highway lean cruise.

Nice, are you going to put your new marine intake on this setup?

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Originally Posted by PlayingWithTBI

Nice, are you going to put your new marine intake on this setup?

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That is my plan. Will have the intake ported first.

Will also say I was working on an 0411 running a stock long block LQ4 6.0L with an Edelbrock Proflow intake, stock manifolds and 3" dual exhaust in a 1971 Chevelle last night. Cruising around with the stock timing map it was running 48-50* of advance at 2,500 rpm @ 70 mph and that car gets about 25 mpg highway. Pretty impressive for a big car with a 4L80E and 4.10s. That was closed loop with the VE and MAF tables calibrated to a point the fuel trims were staying within +1 and -2%. It had been running a bit rich in the -10 to -15% range. After tuning it smoothed out and just flat ran great.

I have been increasing the Delta TPS and MAP AE tables by 10, 20 or 30%. No matter what I do, it still lean pops. Increasing the AE seems to help. But, by the time it's enough AE to reduce some of the lean popping, then this seems to cause it to be very rich on throttle tip in....

The VE map does need work, but every cell logged with the wideband shows an AFR of 12.5 or less. Nothing leaner than that. So if anything the VE table should be on the rich side and not causing this lean pop when you smack the throttle open?

I have thought that maybe I should return to stock AE settings and go do some logs, trying to make note of what TPS or MAP the lean pop is occuring. Just progressively smacking the throttle down more and more until it lean pops. Then from that point in TPS or MAP onwards is where the most AE needs to be added???? Raising the whole talbes is causing it to be rich on tip in.

What to do at this point?

I also wondered about lowering the flow rate a tad, making it more rich everywhere? Then just reshape the VE as necessary once that point arrives.

I can't remember... did you increase the max asynch PW yet? This value limits maximum AE even if the tables command more.

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Originally Posted by PlayingWithTBI

Here's a picture of the chambers in the Summit 162108 heads CDeeZ and I are using. From what I can tell, based on your link these are the newer "fast burn" style?

Attachment 13917

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They're a much better chamber design than many of the earlier heads. The spark plug is angled toward the exhaust port to reduce intake shrouding, the chamber walls appear to be slightly tapered at the intake valve to improve flow, and the shape of the chamber appears to encourage swirl during combustion. I would expect these heads to require less spark advance than most of the pre-80's heads.

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Originally Posted by 1project2many

I can't remember... did you increase the max asynch PW yet? This value limits maximum AE even if the tables command more.

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It is at the stock value of 12 msec. Think it should be changed? If so, to what?

I usually end up increasing this value. The amount will depend on injector size, plenum size, fuel pressure, and engine responsiveness. Maybe try 14 ms? Back down if the engine is too sluggish.

It would be helpful to know what your pulsewidth is during AE now.

IIRC 12.5 msec is all the time you have between injector pulses in Asynch. 12.5 msec would be 100% duty cycle. I doubt you are coming close to 12.5 msec during AE. MAP and TPS AE added together would have to have a value of 12,000 usec to max that out.

Screen shot your TPS/MAP AE and multiplier tables and post it up.

I tried 14 MS in Max Asynch BPW, Makes it sluggish on throttle tip in, and still lean pops when you smack the throttle open.

Chris, here are the AE paramters, I returned them to stock. Also here is the pulse width in AE from the last time I drove it. This was with the Max Aynch BPW raised from 12 to 14 Msec.

Here are my AE settings. This is an $E6 bin and ,I think, a BDJY mask.

It's been over a year since I set it up this way so I don't remember all of the symptoms that led me to this set-up. I could make the engine happy in warm weather, then when it would get below 40 degrees, AE would be way off. Rich in some places and lean in others. Thank God for WB02.:rockon:
The one thing that really helped me was tweaking the coefficients.
Now the engine runs really well with the exception of a slight lean spot at tip in when it gets down in the 20's, but only until the engine is heat soaked, so I haven't bothered fixing it yet.

These settings probably won't work for you, but you can get an idea of what I did to get mine running right. It'll light the tires without effort from a stop light in any weather now.:thumbsup:

My engine is a stock rebuilt 93 TBI block with vortec heads and RamJet "395" roller cam. Also a 46mm throttle body, shorty headers and Edelbrock 7116 intake manifold.

I'm also running a mildly tweaked LT1 timing table from a station wagon, I think.

The $42 TBI big blocks used a carburetor manifold with a heated spacer. The power level was low on these engines but plenum volume is still large and needs to get enough fuel so it doesn't pop. $42 doesn't have as many AE variables as $0D but you can still develop an idea of the way fuel was delivered.

Quote:

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Originally Posted by CDeeZ

I tried 14 MS in Max Asynch BPW, Makes it sluggish on throttle tip in, and still lean pops when you smack the throttle open.

Chris, here are the AE paramters, I returned them to stock. Also here is the pulse width in AE from the last time I drove it. This was with the Max Aynch BPW raised from 12 to 14 Msec.

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I see a lot of your problem from that screen shot as well as the BPW during AE. Even if you could reach the highest values you are only giving it 3.6msec of injector pulse.

This is a WAG based off what I ran with the single plane victor jr 2bbl intake as well as the Weiand 177 blower.

MAP AE
0 122
20 1000
40 2250
60 3500
80 5000


TPS AE
0 122
3.1 500
6.3 1000
9.4 1500
12.5 2000
15.6 2500
18.8 3000
21.9 3250
25 3500
28.1 3700
31.3 3900
34.4 4100
37.5 4300
40.6 4500
43.8 4700
46.9 4900
50 5100

Quote:

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Originally Posted by dud

Here are my AE settings. This is an $E6 bin and ,I think, a BDJY mask.

It's been over a year since I set it up this way so I don't remember all of the symptoms that led me to this set-up. I could make the engine happy in warm weather, then when it would get below 40 degrees, AE would be way off. Rich in some places and lean in others. Thank God for WB02.:rockon:
The one thing that really helped me was tweaking the coefficients.
Now the engine runs really well with the exception of a slight lean spot at tip in when it gets down in the 20's, but only until the engine is heat soaked, so I haven't bothered fixing it yet.

These settings probably won't work for you, but you can get an idea of what I did to get mine running right. It'll light the tires without effort from a stop light in any weather now.:thumbsup:

My engine is a stock rebuilt 93 TBI block with vortec heads and RamJet "395" roller cam. Also a 46mm throttle body, shorty headers and Edelbrock 7116 intake manifold.

I'm also running a mildly tweaked LT1 timing table from a station wagon, I think.

---

Quote:

---

Originally Posted by 1project2many

The $42 TBI big blocks used a carburetor manifold with a heated spacer. The power level was low on these engines but plenum volume is still large and needs to get enough fuel so it doesn't pop. $42 doesn't have as many AE variables as $0D but you can still develop an idea of the way fuel was delivered.

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Thank you both for offering this insight!! I have been busy with other things past few days, going to get back to studying this now.

Quote:

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Originally Posted by Fast355

I see a lot of your problem from that screen shot as well as the BPW during AE. Even if you could reach the highest values you are only giving it 3.6msec of injector pulse.

This is a WAG based off what I ran with the single plane victor jr 2bbl intake as well as the Weiand 177 blower.

MAP AE
0 122
20 1000
40 2250
60 3500
80 5000


TPS AE
0 122
3.1 500
6.3 1000
9.4 1500
12.5 2000
15.6 2500
18.8 3000
21.9 3250
25 3500
28.1 3700
31.3 3900
34.4 4100
37.5 4300
40.6 4500
43.8 4700
46.9 4900
50 5100

---

Chris,

Please elaborate. I'm trying to understand what you're telling me. Also, are you suggesting those values from your single plane Weiand TBI for my two Delta AE tables on this one I'm working on? Thanks.