Slipping or loose belt?

[PonyExpress]

I have a Billetflow 2.93" S/C pulley & 4 Idler pulleys (1 - 100mm / 3 - 92mm).

Just had Ford replace the S/C belt with the same Gates belt I've had for 10 years (although the new Gates belt is 1mm longer than the previous even though Gates stock # is identical).

When I hit the gas hard in 3rd or higher, the boost gauge climbs but RPM's climb as well. Not sure if the new belt is slipping? Tensioner issue?
(This was happening before the new belt was replaced.)

Any help would be appreciated!

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[nytebyte]

You need to clarify what exactly is happening. The boost should climb and so should the RPM's. Do you not accelerate?

If not, it could be a slipping clutch instead.

If you suspect a slipping belt, check for excessive belt dust around the SC. Since you have a new belt, you might have a bit of dust which is normal.

 

[Jokerzl]

The best way you will know if belt is slipping is when the blower is spinning at its fastest under wot. If you watch the gauge and as your rpms increase and your boost gauge goes down you have belt slip.