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Old 08-28-2006, 09:32 PM   #3
Scooby Specialist
Member#: 56468
Join Date: Mar 2004
Chapter/Region: NWIC
Location: Seattle, WA
04 Improved STI
Dirty White


I'm sorry I missed the thread. Perhaps I should have bumped yours.

Yes detonation is at issue as well, but it always is. I'm assuming you saw detonation under boost. The combination of more advanced AVCS and less advanced timing could be very tricky to tune since they are working in opposite directions. Cylinder pressure increases with the AVCS advanced and "in boost", so you will have to retard timing to prevent detonation. From a tuning stand point, retarding your timing first and then adjusting the AVCS may be the way to go.

Another reason for an increase in detonation that I could also see is if your remained AVCS advanced up into high RPM and high boost, reversion might rear it's head as well, and more so because of the AVCS advance. That phenomena would only occur at a high boost threshold, and it would occure regardless of the AVCS, but it would be compounded by it.

Thanks for the post. I'll look for the thread.
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