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Paxton's New Eight-Rib Belt-Drive System - The Driving Force
Testing for supercharged Coyote 5.0L Engines
Belt-driven boost-makers, better known as superchargers, go with Mustang performance like hot dogs and baseball. The popularity of supercharging is evident by the sheer numbers of systems and configurations, especially those for the '11-present Mustang GT and Boss 302. Last we counted, there was no less than eight manufacturers offering varying levels of superchargers for that genre of Mustang. And there are even more kits for the Three-Valve.
The Coyote 5.0L responds well to boost, as we've documented on these pages and in the virtual world on the magazine's website. We've watched the Paxton kit help a Coyote produce over 600 rwhp with minimal aftermarket upgrades. Turning up the boost has also become a time-honored tradition when out-of-the-box boost just doesn't quite cut it. And a simple swap in blower pulley is usually all that's required to accomplish such a task.
A supercharger is driven by the crankshaft and for most applications a serpentine belt connects the crank to the supercharger. There are exceptions like race-only, cog-belt-drive systems and gear-drive setups, but those are rare for street machines. For those who purchased a Paxton supercharger system for the Coyote, the supercharger is driven with a six-rib belt system that is run inline with the factory serpentine-belt-drive setup.
A series of idlers and tensioners keep tension on the belt, thus providing traction on the pulley. The six-rib configuration works well for the average installation, and also in cases where a slightly smaller (than stock) supercharger pulley has been added. The smaller supercharger pulley increases supercharger impeller speed, which creates more manifold boost, but it also provides less area for the belt to grip and drive the blower. The byproduct of more boost is increased output--provided your fuel system and drivetrain are up to snuff. Moving past the higher boost concerns of tuning and durability, there is one issue that can rear its ugly head: belt-slippage.
As the impeller speeds up, there is more load placed on the drive system, and that can lead to slip. Paxton recently released an upgrade kit to convert the six-rib pulley system on the front of the Coyote engine to an eight-rib combination, which offers more area for the belt to grip. The kit retails for around $650 and has all the necessary pulleys, idlers, spacers, bolts, and washers. The installation is rather easy, and the two biggest steps are removing the supercharger head unit and brackets, along with installing a new crank pulley. It sounds complicated, but the swap is relatively simple--especially if you installed the system yourself.
The extra two ribs of surface area might sound like a small increase, but it's a significant one as the width goes from 0.82 inches to 1.10 inches, making the eight-rib belt 34-percent wider than the six-rib. We had one car in mind to properly test the eight-rib belt upgrade and it was the in-house mule at JPC Racing, which belongs to the shop's owner Justin Burcham.
We figured if we were going to torture test a belt-drive system then this car--and owner--was our candidate. It represents the highest rwhp rating of any Paxton-equipped Coyote 5.0L and is one of the more prolific Coyote performers, with a best of 9.34 at 150 mph on the drag strip.
The 2011 Mustang features a stronger RGR bottom-end with mildly ported heads (stock valves and valvesprings), valvespring shims for more seat pressure, OEM camshafts, and a stock intake manifold. A JPC Racing return-style fuel system ensures the engine is fed plenty of Shell URT fuel while the final touch for fuel involves a set of Injector Dynamics ID1000 fuel injectors. The exhaust system is all JPC Racing from the headers to the mufflers. A Paxton NOVI 2200 head unit is included in the company's High Output tuner kit. JPC Racing converted the kit to a blow-through MAF sensor setup.