Loss of power, low boost pressure

MTTod

Registered User
I finally got to drive my 90 this weekend and it seems to be lacking power big time.

It's only running about 8 pounds boost at WOT and vac at idle is around 15-17. Suggestions on where to start tracking it down? Will leaks in the system cause low boost pressure?

It runs fine but mash the pedal to the floor from a stop and no wheelspin at all. No smoke from the pipes or any bad noises, just no power. It's got stock size Potenza RE730s on it.
 
check the exhaust on the car. If you have an exhaust system that is opened up, you won't see much more than 8lbs at WOT. I'm not too sure about the idle vacuum as I haven't done anything to my exhaust yet. But I do know that freeing up the exhaust will cause lower boost and lower low end torque, but will reward you in more top end. If you're still running the stock exhaust, the first places I would look is the IC tubes. The top nut will tend to come loose very fast if not properly torqued down. I've had trouble with my lower IC tube where it mates with the inlet to the lower manifold. Easiest way is to take a can of propane or starter fluid and spray around the joints. If the rpm changes, you found your leak.
 
Well just changed the SC belts and got a little improvement. Only about 1 psi though.

Is the bypass valve the one on top just behing the SC? The lever moves when the vac drops? Opening the throttle slowly it didn't do anything.
 
Its a vacaum leak, check all the lines running off the sc, check the pcv lines to the intake tube,and check your intercooler tubes. And if you find something or even just in case get those small plastic zip ties and tie the lines at the ends. If your exhuasts was modified you would light the tires up even more than if it was stock exhuasts.
 
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