Boost leak?

Bumpity Bump.


I have a new ported 94 blower on running 13%OD. I am getting only 11psi up top, I'm pretty sure it should be making a lot more than that. Still has the GTP rotors in it, coating has a couple knicks in it but is in good condition. I swapped intercoolers yesterday (stockies, I know don't yell at me for running that much OD on a stock IC, front mount stuff is coming soon.)
Anyway, car pulls well, but only 11psi is discouraging and makes me think something is wrong somewhere. All vacuum lines are brand new, and I have MP springs in the tensioners (not clocked, stock pulley).


Anyone have any insight to what's going on?
 
What gasket or gasket maker is being used on the IC lines?
Is there one behind the nut?
Does the SC have a raised top?
Vac lines can be brand new, but are they routed correctly?
Gauge as mentioned would be the first look.
Inlet and return plenums ever been removed?
If they have been removed what gasket was used?
Same with the hat which gasket was used?

Had bad gasket leaks with the poly gaskets. Tighten the bolts to spec and could hear the air going past those gaskets especiallly with the hat.
 
What gasket or gasket maker is being used on the IC lines?
Is there one behind the nut?
Does the SC have a raised top?
Vac lines can be brand new, but are they routed correctly?
Gauge as mentioned would be the first look.
Inlet and return plenums ever been removed?
If they have been removed what gasket was used?
Same with the hat which gasket was used?

Had bad gasket leaks with the poly gaskets. Tighten the bolts to spec and could hear the air going past those gaskets especiallly with the hat.

Everything has a fat bead of gasket maker on it. I know the vac lines are routed correctly, it has a stock top, return plenum was removed when I put in the new motor 1400 miles ago, inlet plenum on the new blower has gasket maker on it too.

Should I get an aftermarket boost gauge or replace the stock one? I don't really have a place to put an aftermarket because I already have a dual gauge pod in the A-Pillar. And how do I know if the stock one is junk?
 
I am thinking that the stock guage is shot. My stock guage only shows 11-12 PSI but my car makes almost 18 PSI when measured on a dyno....If you really have to know what boost your really making get an aftermarket guage and stay away from a stock replacement.
 
Belt slip.....

Frit, you really think I have belt slip occurring?
When I floor it from a lower RPM when I'm making a pull I can smell it slipping and burning a little, so I don't do that anymore. I always make gradual pulls now and haven't smelled it slipping in a while.

If I am slipping, how do I stop it? I have the MP springs already but I was thinking about buying a bigger idler pulley for the SC tensioner.

Could my belt have stretched to the point where it won't grab as well?
 
With that much OD on that blower I would say the belt is slipping. Its not an MPII, III or X so it hasn't been modified to run at that much OD so its taking more HP to turn it than the belt can hang on to it.

I also think that once a belt starts slipping it pooched... but not sure.

Try dropping 5% and see what you get with a new belt.

Frit
 
Bumpity Bump.


I have a new ported 94 blower on running 13%OD. I am getting only 11psi up top, I'm pretty sure it should be making a lot more than that. Still has the GTP rotors in it, coating has a couple knicks in it but is in good condition. I swapped intercoolers yesterday (stockies, I know don't yell at me for running that much OD on a stock IC, front mount stuff is coming soon.)
Anyway, car pulls well, but only 11psi is discouraging and makes me think something is wrong somewhere. All vacuum lines are brand new, and I have MP springs in the tensioners (not clocked, stock pulley).


Anyone have any insight to what's going on?

If you are overdriving all 13% from the supercharger pulley, then it probably is belt slip. The pully can become very slick and won't grip very well...sandblasting the belt contact surface helps. Sometimes machining the tips of the ribs down a little will provide better fit for the belt into the grooves/ribs of the pulley.

Overdriving 10% from the jackshaft and only 3% from the supercharger pulley will work much better.

David
 
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If you are overdriving all 13% from the supercharger pulley, then it probably is belt slip. The pully can become very slick and won't grip very well...sandblasting the belt contact surface helps. Sometimes machining the tips of the ribs down a little will provide better fit for the belt into the grooves/ribs of the pulley.

Overdriving 10% from the jackshaft and only 3% from the supercharger pulley will work much better.

David

I went racing last night, and now I think you and Frit are right. When I parked the car I could clearly smell rubber and instantly what Frit said popped into my head.

Should I get a new belt and one of those bigger Dayco idler pullies, or save up and get a 10% JS pulley?

Would 15% OD be too much on my blower? All internals are new, and I ported the case as much as possible without welding it.
 
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