Now that I have some time to post after being away for the past few days I noticed that Bill pretty much gave you all the update. I basically got my tune dialed in with myself in the car, running 11.7 AFR and 19-19.5 degrees of timing, zero knock. I then piled three other friends into the car and went WOT from 30-65 mph, just a quick pull. Compared to the day I was dialing in AFR and timing (about 45 degrees out) we had a cold spell come through and outside it was maybe 15 degrees outside. Between the change in temperature and added weight in the car, I assumed my AFR was a little leaner than 11.7 (probably more like 12.0-12.1) and with the 19.5 degrees of timing on 93, cylinder #3 got pissed and chipped the piston.

Now that I have put a little over 50 miles on the L36 bottom end (was the stock bottom end out of the car) and running a 3.5 pulley, I'm keeping things conservative on both boost and timing until I dial in the tune. So far the car runs great, trims are already spot on within -2 LTFT to 0 LTFT. Next is dial in AFR and this time I'll shoot for 11.4-11.5. Timing right now is about 14 degrees, may increase to 16 degrees (max).

I'm just glad I finally got the car back on the road and can enjoy it again. If any of you either have tuned top-swapped cars or are running a similar set-up, please chime in if you have any knowledge on what to tune differently, what to watch for, etc.

Quote Originally Posted by darkhorizon View Post
is there any data to back up the failure? Chipping pistons is EXTREMELY hard to do... it takes alot of things going wrong to get those sort of piston temperatures.
As Bill said, no data to back up the failure. I was watching my Aeroforces, saw maybe 1-3 degrees of knock. The refresh rate of the gauge may have prevented me from seeing 10+ degrees of KR for all i know at a given second. AFR on my wideband was high 11's, low 12's (leaner that day compared to when I was tuning the AFR/timing in 45 degree weather).