Timing retard without knock count inrease? Wtf...? ($0d)

[helo]

I'd like to understand what causes the PCM to induce spark retard when no knock count is registered. No matter what I do, the PCM occasionally decides to retard the timing sometimes even though the knock count isn't increasing. WHY ?!?

I've been struggling with SA in high map low rpm, and I finally figured out my motor just needs more timing during low vacuum. A LOT more timing than stock $0d bins, or else I get a lot of intake backfiring and it runs like crap accelerating.

I do get occasional knock count increments, but it doesn't seem like anything outrageous, could just be exhaust noise. No pinging [anymore] now that I'm making use of PE. PE threshold of 30% tps yields awesome torque for going uphill in OD, I didn't know what I was missing until I tried it (after reading some posts by fast355).

7427/$0d, l31 vortec 350tbi.

[Pauly]

Burst knock?

peace
PAuly

[1.721afr]

PE retard?...Not a likely issue @ low rpm. TCC lock retard...not likely to occur @ high MAP. Strange entry in your coolant comp advance table?..I think that table is limited to lower (below 40?) kpa.

Try to get IT (the retard) in a log to see what causes it.

[helo]

aha, burst knock, indeed. Never heard of it before today.

The common theme is it only happens during increasing MAP.

I do generally get a knock increment after the burst retard, but I strongly suspect that's just exhaust noise; I have a few leaks to weld up. I keep procrastinating because it's been muddy as hell (welder is outside in a shed =).

[Fast305]

I do get occasional knock count increments, but it doesn't seem like anything outrageous, could just be exhaust noise. No pinging [anymore] now that I'm making use of PE. PE threshold of 30% tps yields awesome torque for going uphill in OD, I didn't know what I was missing until I tried it (after reading some posts by fast355).


It certainly does, I generally set the TPS% vs RPM table for PE to enter PE right about the same time the intake manifold reaches its lowest. This has the same effect as the power valve of a carburetor. The way it should have worked from the factory.

[HaulnA$$]

If you look at where knock counts come from, there are two 8 bit words that are put together to form a LSB (least significant byte) and an MSB (most significant byte) that make up the knock counter as a 16 bit word in the code. The knock counter will not increment until the LSB has reached its maximum count of $FF (255). Once this happens. the knock counter shows "1" knock count although the LSB of the knock counter has recorded 255 events which can result in knock retard. This is universal within all GM OBDI BCC's.

Burst knock is when these counts run away at throttle tip in. HTH

[Rally Smith]

So how would one fix the burst knock problem? I just realized I have that going on too. I seen that when my knock counts go up, I see no knock retard, if that means anything....