Supercharger questions
 

Hi, I have a '95 GT with a 9 psi Powerdyne BD-11a installed. I am not getting anywhere near 9psi at my WOT of 5,800 rpms (previous owner set that).

This car has ported/polished heads and high flow intake etc, (no flow rates provided to me), and very free flowing exhaust. Would the lower psi be normal, or should a 9psi charger always make 9psi?

Thanks. BTW, I am measuring the boost by the pillar mounted Auto Meter boost gauge.

RE: Supercharger questions
 

Where is the 9 psi being read from?

RE: Supercharger questions
 

You might measure the pullie and confirm with Powerdyne
you have a 9psi pulley and go from there.

Also, if you're getting up close to 8psi or so that might be
all it gets. S/C psi ratings usually dont meet what they're rated
at but should come pretty close.

RE: Supercharger questions
 

This is the stock 9 psi unit from Powerdyne. I will measure the pulley to make sure it's the right one, but I'm guessing it is. Also, the supercharger squeals upon start up, but then runs silent from then on. The external belt seems tight enough, I'm now wondering if the internal belt is starting to slip a little. That would account for the lower than normal boost... right?

I checked my boost gauge again, I'm getting 5 psi tops.

And, if everything checks out, and it's a 9 psi pulley set, can I run a smaller pulley to bring my boost back up to 9 psi? Like if I run an aftermarked pulley designed to give say 13 psi, would it then actually give me 9 psi?

Thanks.

RE: Supercharger questions
 

running a smaller pulley on the sc will increase boost. maybe your belt is slipping. sc belts need to be on pretty tight to make full boost. the more boost you try to make, the harder time the belt will have trying to grip the pulley. when i first put on my 12psi pulley i didnt put the belt on tight enough and all i could get was 4psi of boost because the belt slipped really bad

RE: Supercharger questions
 

Thanks for the reply, wow, what all mods do you have to be making the rwhp that you're making?

I'll check the belt tension, but it seemed pretty tight. The previous owner of the car said the supercharger was 2 years + in age. I'm guessing the internal belt and bearings could use some going over.

RE: Supercharger questions
 

i was told that if you can twist the belt in the midle more then 90* with your fingertips, the belt is too loose. could also just be a worn out belt if its been on there for 2 years. a worn belt, even if tight can slip.

http://koolpages.com/potatohell/trucks.html this page has a list of my mods at the bottom and a pic of just about every mod ive done to the car

RE: Supercharger questions
 

Yep, that's what I was thinking. If the internal belt is worn, it'll probably slip... I definitely can't turn the crank belt 90 degrees, but it may be worn too. I may just bite the bullet and send the whole unit to 928 motorsports and let them look it over. They supposedly check the boost output and that's what I want anyways, since mine is only making like 5 psi. Do you guys think the shim/ venting deal they offer is worth the extra money? It sounds like a good deal if it actually works...

RE: Supercharger questions
 

Maybe its a 6lbs kit and the previous owner bull ****ed u....

RE: Supercharger questions
 

i would definetly look into this. you dont want to spend a bunch of money on a sc thats working fine just cause some guy lied to you