'99 vette with lt's still getting KR at track (stock engine tune)

[anymanusa]

Hi all.

I've looked this over a bit, and can't quite figure out why I'm getting mild levels of KR. It was worse in the summer, now in the fall, I'm still seeing it.

93 octane, and I have a Bosche WB hooked up. To me, there doesn't seem to be a lot of rhyme or reason when the KR kicks in. Sometimes the A/F ratio will be 19 (in a deceleration scenario), and at other times it will be in the 10's.

Engine temp stays around 200*F the whole time too.

Any help would be appreciated.

BTW, this is under road course racing conditions at Barber in Leeds, Al.

--I've just now noticed that the inj B1 and B2 mV's are identical... what's with that? why would they be exactly the same? Would it have anything to do with my PO0160 code (a secondary bank sensor that has been replaced with an o2 simulator that has apparently gone bad)?

[EC_Tune]

10's are way too rich for a NA car. Try getting the WOT AFR in the high 12's to low 13's. You can actually get rich knock if it's too rich. Especially at lower RPMs. High RPMs not so much.

[anymanusa]

10's are way too rich for a NA car. Try getting the WOT AFR in the high 12's to low 13's. You can actually get rich knock if it's too rich. Especially at lower RPMs. High RPMs not so much.

are you trying to say that my a/f should NEVER in the course of it's operation be in the 10's? Not even for a spike? Because that is what I'm referring to. Almost all steady state and WOT operation is in the 12.5-13 range.

thanks

Have a lot at the KR at 7:27 in the attached log if you have a chance.

[EC_Tune]

Ok. Yeah I'm guessing that when you go into decel it spikes rich (that can be fixed with transient fueling but it's ok) and then when DFCO kicks in it goes to 19 AFR.

The way you phrased it made me think that the AFR was all over the place in all the wrong places.

[BBA]

The 1999 C5 I did had to have timing cells in multiple places reduced by 1 or 2 degrees in the high table to get rid of all KR.
Reduce the transient fueling milligrams, that will reduce the rich spike. Set the KR decay rate to 50 in all cells.

[anymanusa]

thanks BBA. You don't suppose that some of my problem might be injesting oil in the intake do you? Lot's of oil gets sucked into these LS motors, mine too.