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Paxton's New Eight-Rib Belt-Drive System - The Driving Force
Testing for supercharged Coyote 5.0L Engines
The car made 843 rwhp with the six-rib serpentine belt, and boost peaked at 15 psi. It's an impressive number, but the boost data-logger on the chassis dyno showed the manifold pressure fluttering in the upper rpm range and power starting to fall off. The Paxton NOVI 2200 supercharger hits 15 psi by 6,200 rpm, and more or less remains around 15 psi through 6,600 rpm. After that point, the boost steadily decreases to just 13.5 psi by the 7,200-rpm redline. The power fell off as the boost dropped, as evidenced by the 6,600-rpm peak-rwhp rating. As mentioned before, we chose this car due to its extreme nature as Burcham has a 3.10-inch upper pulley on the supercharger. Its small size means less surface area and less belt traction.
We installed a 2.85-inch blower pulley after adding the eight-rib pulley kit. Astute readers will note that it isn't the same as the baseline six-rib supercharger pulley size. Our goal is to push the limits of the eight-rib drive system so spinning the blower harder would help reveal its effectiveness. The crank pulley remains the same as the out-of-the-box Paxton six-rib crank pulley--at 6.65 inches.
Once on the dyno, a few easy warm-up pulls were made and all systems were inspected. Once Burcham had the all-clear from his guys, he fired up the car, shifted his way into Fourth gear, and went wide open. The 7,200-rpm redline came quickly and all of us scrambled to get in front of the computer. Boost shot up to 19 psi and output increased to a staggering 996 rwhp! The boost curve was smooth from start to finish, showing the eight-rib drive certainly helped belt traction.
Naturally, we couldn't leave the car alone since the magical 1,000 rwhp was just a pulley change away. The lure of peer pressure is too great when you're in a room full of gearheads and only 4 rwhp shy of a significant accomplishment.
Paxton, however, cautioned Burcham that his supercharger is at its 60,000-rpm efficiency range with the 2.85-inch pulley. But if there is one thing we know, it's that the limit can be pushed a little more than advertised. Burcham grabbed a 2.75-inch, eight-rib pulley that was treated with Carbonite, which is a rough coating used to promote belt traction. If the belt held, then we knew the smaller-diameter pulley would be worth at least 1 psi of boost.
Burcham warmed the car up as he went through the gears in the Tremec Five-speed transmission. He got into Fourth and then went right to the floor. The car strained, screamed, and hummed its way to 7,200 rpm. We crowded around the computer monitor and to our enjoyment it read 1,032 rwhp and boost peaked at 20.5 psi.
At the time of the writing, the JPC Racing testbed recorded the highest rwhp of any Coyote 5.0L--street or strip--and it did so with stock camshafts, mildly ported heads, and a better rotating assembly. Most importantly, the eight-rib drive system performed nicely as the boost curve had a smooth ramp right up to its peak boost of 20.5 psi. A few backup pulls showed the 20.5-psi max was dead on. We spun the NOVI 2200 to 62,679 rpm and the boost held rock solid through 7,200 engine rpm. Putting an eight-rib pulley system through this extreme case is certainly proves its effectiveness for milder combinations.