long story made short. 1996 chevy tahoe. intercooled Procharger kit. only making 5lbs of boost ( supposed to be 8lbs) . and running stock speed. it picked up nothing from the install. The FMU (fuel management unit) is working right because if we crank it up it runs rich. So basically a supercharger made it slower. Am i missing something? anybody know what might be a cause?

 

Is there supposed to be a pcm calibration that goes with this?

 

Nope, procharger says the only tune you "NEED" is to turn the needle on the FMU. im sure a tune would be smart tho.

 

You might get better response to your question if you post in the FI forum.

 

Maybe belt slip, or a boost leak someplace.

 

Sounds like you need to check the piping from the supercharger for leaks.It could also be a problem with the blowoff valve bleeding your boost.Be sure you check for vaccum leaks too.

 

I would agree on the belt slip also, as far as boost. But even 5 psi should make some difference. Check for belt dust under/behind the upper blower pulley. And a tune is pretty much mandatory when adding a blower, at least in my opinion.

Jody

 

probably not belt slip on that kit... I'd say you have a pipe leaking bad, or your bypass valve is stuck. Check those out first. Then you might want to think about a real tune. FMU's are a joke. Call Ed Wright in Tulsa.

 

I ran the same kit on a 99 tahoe. My buddy also had one on his 99 he put down 400 to the ground with 12 psi.

The FMU does work its just a p.o.s. to tune.

You most defintely need a PCM calibration no matter who you get it from. There are several places that offer it on the forum as well as several private members. This defintely is a big part of making power. Also.. if you are running the old style bypass valve check for boost leaks. They are prone to leakage.

If you are anywhere near pitts I might be out there mid next week so I possibly could shed light on it.

 

5 psi is kinda low to be running on a centrifugal. When I was running 5psi on my car(procharged camaro) it was a dog down low until it started building some boost and felt a "little" better up top.

IMHO, you need to run more boost than 5psi on a centrifugal to really feel a nice difference. Not sure what those engines can take boost wise though.

I also agree with everyone else that a tune would be a smart move.