Richard Holdener
January 5, 2010

Using a pressure relief system, the pressure is vented from the back of the seal to the inlet tube or air filter. Relieving the pressure eliminates the chance of seal failure thereby preventing rotor pressure from entering the gear box. According to Kenne Bell, the standard seal system works very well up to 20 psi of boost. It is in the 21- to 30-psi range where the SPE system comes into play, though the SPE does offer considerably less seal wear and friction under high-vacuum conditions. This helps eliminate the tendency to pull oil from the reservoir. The combination of the temperature reductions from the liquid cooling and the extended seal from the SPE has practically eliminated seal wear at high boost and vacuum conditions (not to mention adding a few extra hp).

All these ideas sound good on paper, but would all of the improvements equate to more power? To find out, we ran a series of back-to-back tests using a Shelby GT500 Super Snake comparing the 2.8L H and the new 3.6L. The first test was actually performed by Kenne Bell on its blower dyno. Running both blowers at identical boost (24 psi) levels demonstrated that the 3.6L require just 177 hp to spin compared to 217 hp for the 2.8L.

The 3.6L also reduced the all-important charge temperature by 31 degrees (at the same boost level). All of the results on the blower dyno were achieved by stabilizing the discharge temperature with a sustained run of 20 seconds. The differences would be slightly less in the real world unless you were running flat out for more than 20 seconds (think Silver State Classic open road race, Maxton Mile, or in a marine application).

The blower dyno results obviously indicated the power potential of the 3.6L over the smaller 2.8L, but how would these results translate on the chassis dyno? To illustrate the gains offered by the 3.6L, we ran the Shelby with both the 2.8L H and the new 3.6L. The first test was to turn the two blowers back to back at 15 psi. Naturally, both blowers were run with the same air/fuel and timing as well as the same air and coolant temperatures, the only difference being the blower swap.

Running both blowers at 15 psi, the 2.8L produced 643 hp while the 3.6L upped the ante to a peak of 674 hp, a difference of 31 hp. Remember this test was run at identical boost levels of 15 psi. Stepping things up to 23 psi resulted in 747 hp for the 2.8 and 832 hp for the 3.6L. The 3.6L offered an additional 76 hp over the 2.8L at 23 psi.

The final test was to illustrate what happens when you replace the 2.8L with the 3.6L using the same pulley size. Running both blowers with a 3.25-inch blower pulley resulted in 619 hp for the 2.8L at 13.5 psi and a whopping 774 hp for the 3.6L at 22.4 psi. Replacing the smaller blower with the larger one (run at the same blower speed) was worth an additional 155 hp.

With the capacity to support over 1,200 hp, these tests indicate that in the case of the 3.6L Kenne Bell, bigger is certainly better.

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