Wes Duenkel
May 22, 2019
Contributers: Wes Duenkel, Damon Rivetti Photos By: Damon Rivetti

Belt-driven superchargers are a great way to make power, but they require a lot of horsepower to turn—sometimes hundreds of horsepower! That's asking a lot from a lowly serpentine belt originally meant to spin some accessories.

By nature, serpentine belts slip a little when spinning smooth metal pulleys, and the slip increases with RPM. If the belt is spinning an alternator or a water pump, a little slip isn't a big deal. (In fact, some high-end applications slip the belts on purpose to reduce parasitic losses, but that's a whole other story.)

While belt slip for accessories isn't a problem, a slipping supercharger belt not only costs boost (and therefore, power), but slip initiates a vicious circle of friction, heat, and more belt slip. Pretty soon the boost needle drops and the belt is destroyed.

Engineers reduce belt slip by increasing belt surface area or friction between the belt and the pulley. You'll notice higher-boost supercharger systems use wider (more ribs) belt and pulley setups. Aftermarket idler pullies (such as those available for 2003-2004 Cobras) increase the belt wrap around the supercharger pulley, which also increases surface area.

If packaging constraints prevent a wider belt or more belt wrap, increasing the tension on the belt can help. However, increased tension also increases heat (remember the vicious circle?)

Now there's another option: GripTec has developed a pulley surface finish that increases belt friction without adding ribs or belt tension. The secret lies in their "micro ablation" process that adds microscopic "teeth" to the pulley's surface which greatly increases the belt's hold of the pulley. The result is less belt slip, more boost, and more power.

To test this for ourselves, we installed GripTec's pulley and hub system on a 2018 Mustang GT equipped with a Vortech supercharger. Over time, our supercharged S550 abused the belt to where it shredded a rib (oops). The reduced surface area and worn belt slipped so much that we noticed peak boost fell from 9.5 PSI to 8 PSI. That certainly was costing us power.

As an experiment, we first combined the GripTec pulley with the damaged belt. Even with the shredded "five-rib" belt, the GripTec pulley returned our maximum boost to 9.5 PSI! With a fresh six-rib belt installed, our max boost remained 9.5 PSI—meaning the GripTec pulley eliminated our belt slip even with the shredded belt.

We can't wait to try a GripTec pulley on higher-boost applications and see how a little friendly friction makes more horsepower.

In order to swap the supercharger pulley, we first relieved the tension on the serpentine belt.
With the belt loose, we pulled it away from the supercharger pulley.
Then, we removed the bolts securing the supercharger to its bracket.
Next, we loosened the clamps securing the inlet and discharge couplers to the blower.
Finally, we removed the blower from the 2018 Mustang's engine compartment.
After removing the pulley bolt, we used a three-jaw puller to separate the supercharger pulley from the blower's shaft.
With the original pulley removed (left) we compared it to the GripTec pulley (right). Even though the GripTec pulley appears larger, both pulleys are 3.60" to make sure we're comparing "apples to apples."
The GripTec pulley's advantage (right) is where the "rubber meets the road," so to speak. Note the rough surface microscopic "teeth" that are machined into the surface of the GripTec pulley's ribs. This surface increases the pulley's bite on the belt, and greatly reduces belt slip.
Before installing the GripTec pulley's hub, we made sure to reinstall the key on the blower shaft.
The GripTec pulley system converts the Vortech's press-fit pulley setup to a bolt-on style by using this aluminum conversion hub.
We lined up the keyway on the shaft to the hub and slid the hub over the blower shaft.
Then, we installed the blower shaft's washer.
Then, we installed the bolt that we coated with a bit of thread locker for security.
With the bolt tightened on the blower shaft, we were ready to install the GripTec pulley
The pulley's six-bolt pattern makes swapping blower pulleys later much easier.
We installed the supplied socket head cap screws to secure the GripTec pulley to the hub.
The bolt-on design of the GripTech pulley hub allows future pulley swaps without completely removing the blower!
Before reinstalling the blower, we torqued the hub bolts to spec.
With the Vortech blower reinstalled, the GripTech hub allows clearance to swap the pulley without completely removing the blower.
After testing the blower with the shredded belt, we installed a fresh belt.
The GripTec pulley exceeded our expectations. With a shredded belt and the original (smooth) pulley our Vortech-supercharged 2018 Mustang was down to 8 PSI (from 9.5 PSI) due to belt slip. Even with the shredded belt, The GripTec pulley eliminated slip and got our boost back up to 9.5 PSI. We then installed a fresh belt, which should last longer now that our belt slip is history.

Source:
ZPE/GripTec
31200 Santiago Road
Temecula, CA 92592
www.z-industries.com
(951) 303 6857

Photography by Damon Rivetti