OVERBOOST

I am getting detonation as my revs hit 2700-2800 rpm's under full load in 3/4/5 gear. This is the point at which i reach full boost, 15 psi. I don't get detonation after that load range. Before my rebuild I would get full boost at 3000rpm's and NO detonation. The question: Is the fact that I am building boost earlier causing the Detonation? Is the timing fixed by the chip program vs rpm or does it figure in boost? Should I move up to a 3 bar FPR? My current FPR is OK! I have stock 26/6 turbo, test pipe 3.0 exhaust, APE stage 2 chips(Switching to GURU's), Tial 35mm WG w/Hallman MBC, NGK copper's #7 heat range.

Thanks in advance. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

Russ Murphy

I experienced a similar detonation problem in that rpm range when WOT with the stock turbo and after I installed The SDS. I was getting detonation at a much lower boost level (7-9psi) due to the very aggressive timing. The solution after talking to Ross the SDS guru/founder was to remove a little advance at that specific rpm range and not a boost specific retard. The problem comes from the overlap of high (in your case, peak) boost and your (probable) torque peak which result in the greatest BMEP's your motor ever gets, hence the detonation. So yes, fix it with timing vs. rpm. Or just buy yourself some 104 octane unleaded.

OVERBOOST

BUMP!

Thanks Russ.....anyone else?

dand86951

You might be able to cure it by using the setting on the DME for retarded ignition. I know there was a recent thread on it and Danno had a great explanation complete with pics. It would probably retard through the rev range however.