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I have a 1996 mustang gt with a Vortech V1 supercharger. The idler pulley went out so i replaced it with the larger one and the new belt supplied by vortech. it was running rough after that and there was a loud chirp when i let off the throttle. i replaced the tensioner, and it runs better, but it still feels bogged down when accelerating and there is still the chirp when i let off the throttle. i think its is belt slip, but a smaller belt wont fit. how can i stop the belt slip?
 

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Can you adjust the idler pulley?
 

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Discussion Starter #3
There is no way to adjust the idler pulley. the new one is composite and the old one was metal. i don't think that would affect anything because it is the replacement straight from vortech
 

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Can you push on the belt and deflect it? In the old days with V belts if we could twist them more than 1/2 way there wasn't enough tension. With a serpentine you should get yourself a tension tester. Maybe your local parts store can test it for free.

Gates 91132 Belt Tension Tester

I have to believe that the store would also have, or be able to order, a belt of the correct length.

You might also try some belt dressing which might get you some temporary grip while you're waiting for a new belt.
 

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With the new tensioner and new belt. it has enough tension, but still sounds like it slips when i let off at high RPMs. The supercharger also doesn't quite have that same whine as it should at idle sometimes.
 

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The Vortech application guide shows the 98GT should have the V-2Si or V-3Si. I suppose it doesn't matter, except that particular model may have a higher pressure rating, therefore requires more torque to spin.

There's no belt diagrams on their website but the more "wrap" the belt has on the pulley then the more friction it can develop. And of course you can always go to an 8-rib belt, but then you'd have to buy all new accessory pulleys.

You should check for adequate tension with the tool, as well as adequate movement of the tensioner pulley beyond its static point. Other than that the only other advice I can offer is to discuss the problem with the factory. There may be an issue with the unit itself, such as a pressure release, lubrication or wear.
 

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No the system is not inter cooled. How can you tell if it is compressor surge? It's weird because it ran perfect the past 2 years that i've owned it and the supercharger has been on for 5 years. It didn't start running like this until i replace the idler pulley.
 

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It doesn't sound like that. It's hard to describe but it's kind of like one quick high pitched chirp. The impeller spins free also. The guys at Vortech said maybe a bearing but they said that wouldn't affect performance at all. I think if it was a bearing it would make the noise all the time.
 

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The bearing could be making it harder to turn, so the belt slips.
 

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Discussion Starter #12
I only hear the noise when i let off the throttle. If the bearing was making it harder to turn, it would slip when i accelerate. The impeller also spins freely by hand.
 
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