TPS vs MAP AE 7427 $0E

[CDeeZ]

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.

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.