I took my car to a shop today and they put a boost gauge on it. When getting on it for about 7-8 consecutive seconds, it only made a max boost of 7psi. Why is this? It has a 12 psi pulley, and is stock tpi. Could something be wrong with the supercharger? They also said the transmission was shifting soft and it felt like a stock transmission.

 

Is this the car with the ZZ4 like your title? and do you have an intercooler?

Both of these things would bring boost down the way you are saying.

 

yup thats me and yes, I have a 3 core intercooler. Should I put on my 15lb pulley to get more boost then?

 

what kind of blower is this? roots? procharger? vortech?

 

It is a procharger.

 

it could be the "surge" or "bypass" or whatever they call it. other than that The most common, even more common than that valve, is a leak. a leak like that is hard to find because it actually doesnt sound like it leaks until boost is pretty high. try loostening wiggling and then retightening all the hose connections.

 

They disconnected the bypass valve and it didn't seem to affect it at all. Could it possibly be that the supercharger is broken or something?

 

is your motor COMPLETELY STOCK? if you motor isn't completely stock you wont see a complete 12psi

you also wont see a full 12psi until 5500rpm in 3rd gear

are you testing that way?

is there black dust around the blower?

^^if so, belt is slipping

 

my motor is a completely stock zz4 if that counts. I also have completely stock tpi on it.

 

Boost is created ~linearly with engine rpm. Let's rule out one of the most common problem, belt slippage. As your rpm's increase, you should see boost increase. At any given point, do you see boost increase stop while engine rpm's still increase? Or do you see 7-psig at your shift point?

Also, what pulley diameters do you have? To say, "I have 12 pound pulleys" doesn't mean anything. It's a purely relative term and every engine will create different amounts of boost with the same pullies. With pulley diameters, I can do some number crunching to tell you whether 7-psig is realistic with your ratio. Which ProCharger do you have?