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Thread: TPS vs MAP AE 7427 $0E

  1. #16
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    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.

  2. #17
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    Quote Originally Posted by Fast355 View Post
    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.
    Quote Originally Posted by Fast355 View Post
    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.
    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.

  3. #18
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    Quote Originally Posted by CDeeZ View Post
    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.
    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
    Last edited by Fast355; 03-06-2019 at 06:40 PM.

  4. #19
    Fuel Injected! brian617's Avatar
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    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?
    89 K1500 Scottsdale 5.7L 5spd 3:42

    Build specs: 97 4 bolt main block 350ci, Eagle rotating assembly with flat tops and 4 valve reliefs, Dart 165cc/67cc Iron Eagle heads, Manely SS valves and springs 110lbs seat @1.7, GM Ram Jet cam 196/206 @.50 .431/.451, stock intake and throttle body, heads and intake gasket matched, Delco EP377 fuel pump @ 22 psi, 427 PCM.

  5. #20
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    Quote Originally Posted by Fast355 View Post
    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
    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....

    Quote Originally Posted by brian617 View Post
    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?
    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..

  6. #21
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    Well, more efficient heads require less timing. Or so I've read anyways.
    They do. Max timing on the older Bowtie race heads was around 36-38 degrees. Vortec are generally run with 32 degrees.

    Trick Flow aluminum heads
    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.

    I can now see the potential benefit from adjusting the curve rather than moving the whole table up..
    Correct. The shape of the curves needs to be adjusted to match the engine's needs.

  7. #22
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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.
    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?

    Trick Flow Chamber.JPG

  8. #23
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    Here is the design I run.


    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.

  9. #24
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    Nice, are you going to put your new marine intake on this setup?

  10. #25
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    Quote Originally Posted by PlayingWithTBI View Post
    Nice, are you going to put your new marine intake on this setup?


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

  11. #26
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    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.

  12. #27
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    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.

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    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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    Quote Originally Posted by PlayingWithTBI View Post
    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?

    Trick Flow Chamber.JPG
    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.

  15. #30
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    Quote Originally Posted by 1project2many View Post
    I can't remember... did you increase the max asynch PW yet? This value limits maximum AE even if the tables command more.
    It is at the stock value of 12 msec. Think it should be changed? If so, to what?

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