No KR, but timing pulled on launch

[efizjb]

On launch, in between ramp up from 0% to 100% TPS, I go from 26 degrees to (950 RPM idle) 12 degrees at 87% throttle with no KR, then at 100% TPS it then goes to 21.5 showing 4 degrees knock retard.

Why does the timing drop while throttle is intially opening? Is it truly KR but not indicating it?

I can figure out the KR while running down track (lean fuel, too much timing,etc), but is there something in the factory tune that pulls timing on launch or during initial acceleration/throttle opening? I'm guessing this probably hurts my 60 ft....

I'm new to this so hopefully I'm posting in correct forum...

[5.7ute]

Burst Knock retard (B6212) will pull timing as will torque limiting. The best way to find what the culprit is is to log the spark pids.

[efizjb]

Thanks for that reply, I'm used to a FAST EFI, but new to Efilive factory ECM tuning, the factory ECM has so many more factors to learn...

Burst Knock is something I'll have to look into now.

What defines burst knock, huge change in TPS? any other factors, MAP, MAF that play into the equation?

[5.7ute]

Burst knock is governed by B6210 delta airmass. Basically an increase in cylinder airmass exceeding these values will cause timing to be pulled to prevent knock from occuring. When tuning I always zero B6212 until the fuelling side is sorted as the airmass calculations will be incorrect. Then burst knock can be tuned back in if necessary.

[efizjb]

Thanks again, I'm going to zero in on this according to the log, looks like if I zero it out under 2000 RPM (as it approaches 100% TPS on launch) I should be able to work this out.

Only thing I don't understand, is it appears as all my tables are only set for max timing pull of 4 degrees, but burst knock is pulling timing from 26 to 12, much more than 4...

[5.7ute]

Can you post your logs as well?

[efizjb]

Sure can, I'm off to work for now, but here it is!


Thanks for the support!

[5.7ute]

At launch your g/cyl is spiking at 0.96 at 1000rpm. Since the spark table only calls for 9.7 deg in this cell this will be the reason for lower spark timing.

[dc_justin]

Thanks again, I'm going to zero in on this according to the log, looks like if I zero it out under 2000 RPM (as it approaches 100% TPS on launch) I should be able to work this out.

Only thing I don't understand, is it appears as all my tables are only set for max timing pull of 4 degrees, but burst knock is pulling timing from 26 to 12, much more than 4...

There are various 'factor' tables as well that will apply a multiplier to that 4*.

[efizjb]

Thanks guys, I've got to find some time to make some adjustments, your input is greatly appreciated.