Spark Retard Question

New to the tuning game. Got a question about spark retard. I ran a log on a pass I made at the track. (used datamaster) I noticed a 9 deg spark retard at launch with a increase in knock count. (think it might be my new exhaust setup baging on the bottom of the car) As the run progressed the spark retard decreased to 4 deg. but I had no increase in knock count for the rest of the run. My question is why would I get spark retard without an increase in knock count? 93 octane gas. KPA at 98 with 34 deg. of timing above 4K rpm. O2 mv 890s on both sides. 94 Z28. Any guesses?

Mec

It went into "low octane" mode which retards the spark under WOT regardless of knock count. Resets after you turn the car off.

Knock count increasing does not necessarily cause knock retard, and it is possible to have knock retard without the knock count increasing.

Knock count increasing does not necessarily cause knock retard, and it is possible to have knock retard without the knock count increasing.


What situations would cause the spark retard but no increase in knock count? Car is running well otherwise. Just want to get things cleaned up a little to see if 11.90s are in my future.

Mec

I have no idea how the knock "count" is generated, or how its used. I just know from helping people out by reviewing hundreds of data logs, that what I said is correct. Knock "count" appears that it may be some number calculated internally by the PCM, based on engine operating conditions. Knock retard without increasing knock count APPEARS to be a response to a knock sensor signal.

I remember reading a post by Loyd Elliot. He was having the same issue. I will drop him a PM to see what he did with it and I'll post it.

Mec