Turbo acting up... Problem???

[AsILayDying]

I was just wondering if anyone knows what the problem can be....
Driving in 5th gear accelerating into the 2500 to 4500 rpm area I feel the power or boost fluctuate on and off. I can even hear it, like the boost is spooling for a second then off and back on and then off. Is this a symptom that my turbo is starting to fail?

I still hit target boost levels at 16.7 psi, and I only have this issue in 5th gear. All other gears seem to boost properly straight through until shift or lifting foot off. Any help would be appreciated. Thanks.

[Donkey]

Well are you saying you know the boost is fluctuating? I assume you have a boost gauge if you know your hitting target boost. You might just be getting boost osculations. Most maps target 3rd gear for max boost. Boost is load/gear dependent so you generally will overboost in 4th and 5th and the ECU tries to fix that. Are you still using the factory BCS?

[pzr2874]

^ What he said... mine did the same thing till I got a 3port and tuned. I have one 4sale BTW. PM me for details.

[Sarra]

Not sure on the 04+, or the STi, but the 2002/2003 has horrible mapping for boost, WGDC, and even timing is pretty bad. Example is, at part throttle, there's an actual dip in the boost target table, AND in the WGDC table, so boost would literally go from 6 PSI to 4 PSI and back up to 6 PSI.

At WOT, my stock tune was a little off as well. It would spool the turbo up to wastegate boost by about 2,250 RPM, and then the BCS wouldn't really do anytihng until higher in the RPM band. I've tuned this all out of my car now.

The one thing that came to mind would be a possibility of the wastegate arm being out of adjustment. I know mine was, I couldn't hit target boost, even if the boost target was 40 PSI and the WGDC was 96% solid everywhere, it would hit 12.3 PSI and stay there until I let off. Maybe talk to a local tuner about this, they might have specific knowledge on this issue and a fix for it.