Flucuating Turbo Pressure

Jeremy · 05-13-2004, 11:17 AM

I've notice some unstability of turbo pressure while under mid-to-3/4 throttle. My boost pressure varies by 2-4 psi, and is very noticable in power. Under WOT, the pressure hold firm and the car accelerates smoothly, but mostly around 3/4, it wavers. I've got a resonatorectomy and a gruppe-s up-pipe installed, but it was doing this well before the up-pipe. Any ideas?

Thanks, oh omnipotent subie pros!

Cosmo · 05-13-2004, 11:43 AM

Around 3/4 throttle that is not uncommon. Especially now. Your wastegate is working more at 3/4 throttle and can have a problem holding boost. With your catless uppipe the exhaust pressure is lower (but the velocity is higher). It takes less pressure to fill the pipe without the cat, so the pressure on the turbine wheel of the turbo isn't as high.

Basically, just learn to drive at WOT all the time and you'll be fine....

T WREX · 05-13-2004, 12:26 PM

What do you mean by "especially now" Cosmo?

REXronald · 05-13-2004, 12:36 PM

Think he means that this is not entirely uncommon to see a slight amount of variance in this midrange... and NOW that he has made the mods of catless uppipe, it would be a bit more likely and a bit more noticeable...... based on the explanation given...

Jeremy · 05-13-2004, 12:41 PM

I see... is there a fix? Granted, I have no problem running at WOT, but the state police seem to mind!

ALSO, I know you're a fan of the Gruppe-S pipe, Cosmo. I got a CEL three times, so I unplugged the sensor and replaced with a 2.2k resistor. Seems to be doing the trick.