Small Flat Spot On Boost Ramp Up And Fluctuating 2-3psi?

[RaZ_TuRbO]

Since getting my car tuned iv noticed i get a small flat spot immediatly after changin gears for only second, it mostly happens with big revs(7000rpm+) between 2nd and 3rd mostly. Also full boost in 4th gear and sometimes 3rd (18 psi) seems to fluctuate and the boost needle goes crazy from like 16 to 18 and it sounds like im slightly taking my foot off and on the gas making a chuffing flutter noise.

the car is a rb20det 306rwhp with safc management standard afm, but with everything else supporting. driving normal and below 15 psi its great and smooth.

Ideas? experiances?..

Cheers

[R34GTFOUR]

are you running a bov?

that chuffing/flutter noise is compressor surge, which slows the compressor speed quite alot during gear changes or when you back off on the accelerator, which can cause lag inbetween gear changes.

what boost gauge are you reading off? also what turbo setup are you running?

also that standard airfow meter would of been maxed out ages ago, my bet its at 5volts at 4500-5000rpm, so get a z32 and get it retuned

[RaZ_TuRbO]

I know what compressor surge is, its not when i back off the throttle its on throttle up hills, under load.. which it could be compressor surge, just different. So do you think its my afm causing the issues?..i think its compressor surge...as its fine when i give it enough revs.

Its a hiflow rb25 set-up by the way, im reading off the boost gauge i installed, its closest to the inlet i could get. Im running the std bov.

Edited March 17, 2008 by RaZ_TuRbO

[Elliot Wood]

Did you end up finding out what this was?

Iv got the same problem but My R34 GTT is stock (*except from new coils)