I have noticed that power drops off up top. I wasn't really sure what caused it, but when I looked back it appears to have started showing up sometime around when Fuji from NF and I advanced the cam timing by one tooth last summer. Prior to that the plots mostly showed power holding pretty flat out past 7k. This was on smaller turbos and lower power levels, so not a perfect comparison to now, but it seemed like something to look into. A little more info on the cam setup here:
Quote:
Originally Posted by xluben
My car has single AVCS cams. The intake side has AVCS cam gears and AVCS cams (but are not functioning). The exhaust has NON AVCS cam gears and NON AVCS cams. To address the cam timing issue on the intake side we advanced the timing by one tooth. This will put the AVCS cams/gears approx where the NON AVCS would end up.
http://forums.nasioc.com/forums/show...8&postcount=30
If I went back a tooth and was fully retarded I could probably get some more top end back (this is how the car originally was running), but as-is it should be similar to if I had NON AVCS cams.
Last night Fuji and I re-timed it to be back to "normal". We moved it 1 tooth back more retarded. I did a quick pull before and after. Same location, same tune, etc, just the cam gear change and a couple hours of time. It looks like it did shift the power slightly to the right (maybe 400rpm or so). This caused the peak power to bump up despite slightly lower peak torque. It does still drop off up top, but it's holding a little better.