Max boost on square port blower.

StevenL72

Registered User
I am wondering the maximum overdrive on the square port (94-95) supercharger. I have a 10% od crank pulley and a 10% od supercharger pulley. I am wondering if that combination will be too much. I have ported the stock exhaust manifolds, upgraded the exhaust (true dual 2.5"), upgraded to a stage 1 camshaft, 76mm MAF and throttle body, 3" intake and also ported the heads. I have 42lb injectors and a 255lph fuel pump so exhaust, intake and fuel should be good. Any input would be appreciated.
 
20% is probably a bit much for that combination. You will wind up creating a lot of heat, and probably not make much if any more power. With what you have, I would use just the 10% crank pulley, and that should be good. If you want to step it up to 20%, I would want to have at least a MP inlet and a FMIC.
 
I had the 10% overdrive on the supercharger on the oval port supercharger. I thought the square port flowed much more? I don't think I have the original supercharger pulley. Could I go 5% on the blower and 10% on the crank? I do have the intercooler fan as well.
 
Yes, the square port does flow better, but the inlet is still a significant restriction. The more of a restriction you have on the inlet side, the more heat you will generate by spinning the blower faster. With a stock inlet, I wouldn’t go more than 10% total regardless of which blower. You can stick with the blower pulley and leave the crank pulley stock, I only suggested the other way around because that would be less likely to result in belt slip. I have a 10% blower pulley on the XR7, but in order to avoid belt slip I had to both swap to the heavy duty tensioner springs and also clock the tensioner for the supercharger belt. If you have stock tensioners in the stock positions, a 10% blower pulley usually results in belt slip.
 
20% is probably a bit much for that combination. You will wind up creating a lot of heat, and probably not make much if any more power. With what you have, I would use just the 10% crank pulley, and that should be good. If you want to step it up to 20%, I would want to have at least a MP inlet and a FMIC.
What exactly do you mean by the mp inlet? The square port blower has the matching inlet.
 
Magnum Powers makes (or made, not sure if they still make it) an inlet for the square-port blower that has a much larger opening from the throttle body to the back of the blower. The factory inlet is only about a 60mm opening. With porting, you can open up the throttle body side to 70mm, but it will still neck down where it curves into the blower. The Magnum Powers piece has an 85mm opening, and is pretty much that large all the way through. It is much less restrictive, which helps the blower breath much better at higher OD speeds.
 
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