How to Upgrade Your Accessory Drive System for Maximum Boost

If you’re stepping into the world of superchargers – perhaps crossing over from the turbocharged side of the racing world – you already know that forced induction is the key to making massive horsepower. However, while a turbo relies on exhaust gases to spin its compressor, a supercharger is mechanically driven by the engine’s crankshaft via a belt.

This fundamental difference means that your supercharger is directly dependent on your Front Engine Accessory Drive (FEAD). The FEAD is the ecosystem of belts, brackets, tensioners, and pulleys on the front of your engine block that powers everything from your alternator and water pump to your supercharger.

When you start turning up the boost to chase the 900 to 1,200+ rear-wheel horsepower range, the factory belt drive system becomes a weak link. To help you navigate the upgrade path, let’s dive into all things FEAD, including the science of 8-rib and 10-rib belt systems, front cover idlers, tensioners, and the heavy-duty bracketry you need to keep your supercharger spinning flawlessly.

The Basics: Belt Slip, Ribs, Idlers, and Tensioners

Before we dive into the hardware, let’s quickly define a few critical mechanical concepts that dictate how a supercharged setup behaves on the track:

• Belt Slip: Because a supercharger requires mechanical force to spin, the belt can lose traction against the supercharger pulley under heavy load. When the belt slips, you lose boost, generate excess heat, and create a cloud of belt dust.
• Rib Count (6, 8, or 10-Rib): Belts have longitudinal V-shaped grooves called ribs. A factory Mustang Coyote typically uses a 6-rib belt. Upgrading to an 8-rib or 10-rib belt provides a wider surface area, which dramatically increases grip and eliminates belt slip.
• Idler Pulley: A free-spinning pulley that simply routes the belt and dictates its path, keeping it wrapped tightly around the other drive pulleys.
• Tensioner: A spring-loaded arm with a pulley on the end. As the engine revs and makes boost, the belt naturally stretches. The tensioner’s job is to swing outward, maintaining constant pressure on the belt so it doesn’t go slack.

Building the Foundation: VMP’s 8-Rib and 10-Rib FEAD Kits

If you are running a Street FEAD kit on a standard 6-rib belt, you are generally safe in the 600 to 800 HP range. But if you’re upgrading to one of our Odin, Loki, Gen 3R, or a Predator blower swap, you’re going to want to step up to one of our 8-Rib Race FEAD or 10-Rib Upgrade Kits.

When you widen the belt from 6 to 8 or 10 ribs, the idler pulleys and the belt itself become physically wider. Because these components take up more space on the front of the engine block, standard parts will no longer fit. To accommodate these wider belts, our kits include a low-profile water pump pulley. We machine the back lip off this specific pulley to ensure it safely clears the wider 8 or 10-rib front cover idlers.

Eliminating Flex: The VMP Bomber Bracket

As you push your engine harder, standard brackets can actually flex under the immense rotational stress of the supercharger. Flex leads to misalignment, which leads to belt shredding.

Enter the VMP Bomber Bracket. Replacing our older Boomerang bracket, the Bomber Bracket is a heavily reinforced, completely redesigned billet aluminum piece. It ties into five different mounting points across the front engine cover and lower intake. By locking everything perfectly parallel to the engine block, it guarantees that your idler pulleys and tensioners won’t deflect under the extreme loads generated by our 2650 and upcoming 3100 superchargers.

The Bomber kit also utilizes an adjustable idler pulley. Because different supercharger pulleys vary in size (smaller pulleys make more boost, larger ones make less), the adjustable idler allows you to dial in the perfect amount of belt wrap (how much of the belt is physically touching the supercharger pulley) regardless of your setup.

Taking up the Slack: The VMP Billet HD Tensioner

Having the right belt length is critical. If your belt is too long, your tensioner will max out its travel range as the belt stretches under wide-open throttle. Once the tensioner bottoms out, the belt goes slack, jumps out of its grooves, and snaps.

To combat this, we completely revamped our VMP Billet HD Tensioner for two of our most popular applications:

• Stiffer Internals: We upgraded the internal springs to provide more resistance through the entire range of travel, ensuring the supercharger pulley stays in contact with the belt under maximum boost.
• Laser-Etched Position Indicator: We anodized the body black and added a laser-etched indicator. This gives you a clear visual aid to confirm your tensioner is sitting in the optimal operating range and that your belt isn’t too long.
• Smaller Idler Integration: On older tensioners, a stretching belt could actually contact the lip of an oversized idler pulley, cutting the belt in half. We now include a smaller idler pulley and a custom standoff in the package to provide ample clearance when the tensioner swings through its travel path.

For the Hardcore Track Addict: The Adjustable AC Delete Bracket

If you are building a dedicated drag car, you likely want to shed the dead weight of the air conditioning compressor. However, deleting the AC compressor creates a headache when you are running a custom 8 or 10-rib belt system: belt availability. As belts get wider, auto parts manufacturers produce fewer length options, making it difficult to find a belt that perfectly fits your custom AC-deleted routing.

We solved this with our Adjustable AC Delete Bracket for 2020+ GT500 & 2011+ Coyote engines. We replaced the factory AC compressor location with a fully adjustable billet idler pulley. By sliding the idler up, you can accommodate a shorter belt; by sliding it down, you can take up the slack of a longer belt. This widens your range of available belt options. Tested on a 1,200 rear-wheel-horsepower 7-second race car, this bracket is built for war.

Ready to Upgrade?

A supercharger is only as reliable as the belt that drives it. If you’re tired of fighting belt slip, shredding belts on the dyno, or you’re simply prepping your engine for a massive jump in horsepower, VMP Performance has the front engine accessory drive components to lock it down.

Visit VMPPerformance.com today to find the perfect 8 or 10-rib belt drive, bracket, and tensioner combo for your build!

We are racers, engineers, and enthusiasts who are uniquely positioned to help you achieve your build goals. Whether you purchase from us online, or give us a call for advice on finding your perfect 8 or 10-rib belt drive, bracket, and tensioner combo, we’re ready to help every step of the way!