Michael Galimi
December 10, 2009

Once the team decided to go all-out and utilize the 10-rib setup, the next step was moving the blower belt-drive in front of the engine accessories. A longer blower snout is used and Steeda designed a bracket support system for it. The support bracket also serves as the mount for the belt tensioner. On the bottom side of the engine, a new balancer is included in the kit. It's a Steeda SFI-certified unit that allows a blower pulley to be bolted on.

Steeda lists the 10-rib drive system as a three-hour installation, but we think it will take a little longer than that, even with an experienced technician on the job. We performed the swap at JPC with the car still strapped down to the chassis dyno; we wanted to do a true A-B comparison. Putting it on the lift would have made our lives easier, but we got the job completed, despite being a little longer than what Steeda estimates. The blower had to be unbolted in order for the snout to be replaced. The Steeda balancer was also a chore to bolt-on since we had to have someone crawl under the car to hold the torque converter in place as the balancer bolt was torqued down. Stock hoods need to have material cutaway in order for the 10-rib pulley to fit under it, which undoubtedly adds time to the installation. Our '07 is equipped with a Steeda cowl hood, so we didn't have to modify it.

"We currently offer three boost levels with a fourth on the way. The lineup will include 11-13, 13-15, 15-17, and 18-21. The final boost pressures are dependant on the engine combination and which generation of Whipple blower is being used," commented Pogel. Whipple has used two generations of rotors inside its blowers; our test vehicle has the Gen II rotors, which generally add 1 or so psi of boost over the Gen I version.

"The advertised boost range would be for a 4.6L displacement with stock internals and exhaust manifolds," said Pogel. "Larger displacements, cams, ported heads, and high flow exhaust all contribute to incrementally reduce boost. The 11-13 kit makes a pretty consistent 12.5 psi on a stock Mustang with a Gen II supercharger. We don't recommend the 15-17 psi kit or the 18-21 kit unless the bottom-end is built with forged components. The 13-15 psi kit is about the limit when using a stock bottom-end. It's mainly for the guys with additional mods looking for 12 psi." We decided to get the 11-13 psi kit due to the stock nature of our engine.

The stock balancer pulley checks in at 6.5-inches while the Whipple blower pulley is 3.5-inches. The Steeda pulleys feature a 2.5-inch upper and a 5-inch lower, which bolts on to the Steeda balancer. Using a calculator, the pulley ratios are different with the Steeda pulleys spinning the supercharger faster (Whipple's 1.85:1 versus Steeda's 2:1). That meant the more aggressive Steeda pulleys would turn the blower faster at a given rpm, resulting in more boost down low and upstairs.

We like the looks of the 10-rib setup and while it is pricey ($1,249 non-polished), the cost isn't bad when you start to break down the kit. We saw a few eight-rib conversions for centrifugal-style superchargers in the $800-$850 range. The Steeda 10-rib setup comes with an SFI-approved balancer, as well as a new snout for the Whipple blower, which other kits didn't include.

On the dyno, Pogel was dead-on with his prediction of 12.5 psi of boost being the consistent output in 100-percent stock applications. The extra 1 psi of boost (over our baseline) pushed power output from 458 to 479 rwhp, a gain of 21 rwhp. On track, the Mustang knocked off a best of 11.49 at 117 mph, while running on a pair of Mickey Thompson 275/40-17 ET Street Radials.

The power output at 479 rwhp is about as far as you'll want to go with the stock automatic transmission and stock Three-Valve modular engine. That level of horsepower has proven to be reliable in many other '05-newer Stangs so we aren't worried about breaking anything. While Steeda offers higher boost levels, we will just enjoy our mid-11-second ride for now.

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