I have a P1-1 and it seems no matter what size pulley I run I could never make more than 8 PSI. I've tried a 6 rib 3.4, 3.2, and a 3.00 and all results were about the same. So, I chalked it up to belt slip and recently upgraded to an 8 rib setup with 7.65 crank and a 3.85 blower pulley and still at 8 PSI. I was expecting around 10-12. I believe the belt slip is no longer an issue so do any of you have this size pulley with a P1 and how much boost are you seeing? I've done a leak down test and have no leaks, I also recently installed a FMIC set up and I know its all good. I know there are many different factors that will determine boost such as cam, exhaust, etc. but I feel like something else is wrong and I really want to run about 10 psi. Could not enough fuel restrict the amount of boost or would it just run lean. my AFR is about 11.5. Should I just pulley down again? I'm running out of ideas. Any help is appreciated, thanks!

 

Talk to bob @ brute speed . He is the procharger guru

 

 

Bob is who I’ve bought all my parts from and I’ve been annoying the crap out of him with questions lately so I figured I’d make a post to see any other opinions. Also, I had the mondo bypass valve and recently changed to the Big red race valve when I did the FMIC. I thought these were set from factory and didn’t need adjusting?

 

Air inlet/filter restriction. What air inlet hat and air filter are you using? I've had good luck with the truck inlet hat and a HUGE air filter.

 

 

My 7.65 crank and DP438I-08D (4.38) I am at 6-7psi.

I am running a D1x with FMIC and Red Race Valve. I was supposed to be at 8psi with a 4.63 and was only around 5psi. Tried two sizes smaller pulley and only gained roughly 1-1.5