Can't seem to get full boost

fivaxis

Registered User
I recently finished doing my HGs (167k miles). I have new plugs, new plug wires, and a new cam sensor. It runs good and feels fairly strong, but I am only getting about 8psi boost according to the stock gage.

My exhaust is stock, I did a little head porting around the valves though. I sealed the supercharger top plate/ back inlet with silicone, also I sealed the intake tubes with silicone and made sure they were nice and square when I assembled them. I have checked for vacuum leaks, I'm getting about 17hg. I have sprayed all around the tubes/vacuum lines/intercooler with carburetor cleaner to see if the idle changed, nothing.

I did a run on the G Tech (on a hot day) and only got 16.7 @87 and G Techs are usually a little fast.

What else can I do to check for boost leaks? My bypass valve seems to be working fine so i don't think it's that. I don't know what it could be other than the tubes, intercooler (maybe a hole in it or something), vacuum lines, or bypass valve.
 
It could just be that your supercharger is wearing out. Try taking the sc belt off and turning the sc pulley back and forth really fast and see how much play it has.

Also, the stock gauges are not the most accurate things either.

Shane
 
The car came with an additional supercharger that I put on, it looked newer than the one I took off. The coupler has some slack in it but I don't see how that would limit boost. The bearings are good and blades are tight.
 
fivaxis said:
The coupler has some slack in it but I don't see how that would limit boost.

Its not that its limiting your boost, its that it is leaking out your boost. The coupler needs to be completely tight inorder to create the proper seal.

Also, put hose clamps on the rubber lines on the back of the plenum too. Sometimes boost can leak out of there.

Shane
 
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