only 10psi from MPII sc and 5% pulley

super red91

Registered User
I have a 91 5spd , all bolt ons, MPII sc with 5% pulley, fmic, 42# injectors, 255lph fuel pump and full exhaust (no converters). When the car gets to about 3k im making 10psi and nothing more all the way to 5k. It seems as soon as it hits 10psi that theres just no more power there. Ive already changed plugs, have new wires, and my vaccum is normal. I also have the T-bolt clamps on all my ic connections so i know that there isnt any boost leaking there. I replaced the tensioner for the sc belt and the belt is tight and not slipping. The only thing i know of thats wrong with the car is that it needs a new iac. Anyone know why my car is acting like this?
 
You could be losing boost through the bypass valve. It might be a good idea to make sure thats closing right and not sticking open.
 
Sounds about right for a car with a good exhaust like you have. You're putting out more power than you think. Dont worry about that boost needle unless you drop below 8 psi.;) :cool:
 
Ryan what gauge are you reading this from? You should be getting more psi than that but your power is more or less where it should be. I had a boost leak on mine that dropped it from 13psi to 11psi and power went down only 10rwhp but torque was off by 20ft lbs. Maybe you just need to add a 10% jack pulley. ;) We could let you try my S-model one day if you want. It makes 13.5psi on my motor. :D
 
Mike:
The only reason im concerned about the boost is that last year i was gettin 13-14 with my belt slipping and the car pulled good all the way through redline. I just got a new tensioner and im using the shorter sc belt and now it wont make more than 10 and seems like above 3k its got nothing.

Dave:
I just put in new autometer guages so thats what im going off, my stock guage is also showing nothing more than 10-11. I might take you up on that offer of the S-model that way i could see if somethings up with the sc. I just got home from school and im on break all week so email me or post here so we can get something together.
 
Well if your experiancing a drop in boost from an old setup then yes you do have a problem. I misunderstood your post. :eek: Could be a vac leak or maybe belt slippage.
 
with my mp2 blower and all other components-my stock gauge reads only 10-11psi tops--but on the dyno they measured the the boost toping out at
14.8 psi
thats with a 5% pulley
maybe its fine?
g/l
 
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