I've posted this thread to the Astra chat forum but I guess this is the most appropriate place to do so...
I have a Zaffy GSI with phase 3, downpipe, standard exhaust, 9lt side mounted intercooler, vxr turbo with standard vxr wastgate, powerpipe, KN pannel filter, iridium spark plugs.
The car has made 280BHP on the rollers, and I am about to fit camshafts and exhaust
I experience the following problem: When in full throtle under load (say 4th the car overboosts at 1,7bar and the holds steady 1,3-1,35 untill 5500rpm then drops to 1,1-1,2Bar until 6200 rpm.
The overall performance is great but I experience the following problem during the 1,7 overboost: Sometimes (not all times) when peaking at 1,7 (3200 RPM) the engine makes small drawbacks, like it is cutting fuel, and when the boost comes down to 1,5 it is normal again.
Tech2 does not raise any error (no missfires or anything else) whatsoever and no engine lights come on when that happens.
Let me note again that the problem sometimes does not happen.
Has any of you experienced something like that?
Many told me about getting new spark plugs, mine are Denso IK24 with 40Kmeters already....
any other opininons?