Richard Holdener
October 16, 2013

Drinking and driving is one of the worst decisions people make, but we are here to tell you that the combination of booze and boost might just be one of the best. What's the difference, you ask? It's all about who takes the drink. Getting behind the wheel of a supercharged Shelby after having a few shots, especially one with a Kenne Bell blower upgrade, is just plain dumb. But feeding that alcohol directly to the supercharged Shelby is another matter.

While alcohol and seat time don't mix, alcohol—E85, to be precise—and superchargers go together like gin and tonic. The elevated octane and cooling effect of the E85 fuel is the rocks to Shelby's supercharged scotch.

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To illustrate the merits of this form of drinking and driving, we combined boost and booze on a '13 Shelby GT500. Given the power output, it is amazing that the modifications only included E85 and the Twin Screw supercharger upgrade.

Despite more than 100 extra horsepower over the previous Shelby, 5.8L owners are always looking for more. Though the Super Snake and GT1000 vehicles (also powered by a twin-screw from Kenne Bell) are certainly options, it is possible to jack up the power of your Shelby with nothing more than a blower upgrade. Toss in a little E85 and you can safely run the required boost to make one serious animal. We chronicled the Kenne Bell blower upgrade previously in MM&FF, but this test had a couple of updates, including running the combination on E85 and the introduction of the larger 4.2L supercharger.

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When it comes to making power from a twin-screw, bigger doesn't always mean better. A 5.4L Two-Valve motor is bigger than a 5.0L Coyote, but which one makes more power?

The obvious answer is the killer Coyote, and the reason isn't displacement, but rather design and efficiency. The inlet and discharge design of a Twin-Screw supercharger are critical elements in power production. If they are inadequate for a given displacement, increasing said displacement will only make matters worse.

Using its Superflow flow bench, Dynojet chassis dyno, and dedicated blower dyno, the design team at KB has spent endless hours increasing efficiency before stepping up in displacement. The extra effort ensured that (in this case) bigger really was better, but the larger 4.2L Twin Screw also required a revised intake design. Given the space limitations of the GT500 engine bay, the longer (by 1.5 inches) 4.2L supercharger required a shorter (Mammoth) intake manifold. Not wanting to limit flow into the larger blower, the team at Kenne Bell burned the midnight oil on a new intake design that maximized flow, despite the limited available space.

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For GT500 owners, Kenne Bell offeres three blowers, starting with the 2.8L. Capable of supporting over 1,000 hp, the 2.8L is already a serious step up from the factory 2.3L. Next up the line is the 3.6L. Having exceeded 1,500 hp now with the 3.6L, it is safe to say it is a serious player in the field of forced induction.

The final step up the liquid-cooled ladder is the 4.2L. Offering a 16.6 percent increase in displacement over the 3.6L, one may ask: Why is such a blower even be necessary for anything but a dedicated race motor? The reason? Shelby owners want the biggest, baddest blower on the block.

The benefit of the bigger blower is, of course, more flow and boost potential at any given blower speed. This also allows the user to run more boost at a lower blower speed. The increased boost can come with a larger blower pulley, which in turn minimizes the chance of belt slippage. If you're planning on running the blower at stock boost levels, you might be better served by the 2.8L or 3.6L, but if you have big boost on the brain, the 4.2L is the way to go.

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Loyal readers should recall that the Kenne Bell blower upgrade for the Shelby GT500 retained the factory air-to-water intercooler. Intercooling is another critical element in the success of running elevated boost levels on the street or super elevated boost levels at the track.

Combining the efficient air-to-water system with the cooling effects of E85 took performance to the next level. In addition to the 4.2L blower, the upgrade includes a massive 5-inch (true) cold-air intake system; high-flow, single-blade throttle body capable of flowing 2,350 cfm; and 225cc injectors from Injector Dynamics suitable for use with the E85.

Also included in the blower kit is a 20V Kenne Bell Boost-A-Pump, used to increase the flow capacity of the stock GT500 dual-pump assembly. After the installation of the blower upgrade, the only thing left to do was choose the desired boost level. Though we obviously started at a lower level, the big boost (29 psi) and power eventually came with a 3.00-inch blower pulley and 7.1-inch crank pulley.

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What did this Shelby make with the Kenne Bell blower upgrade and E85? It spit out an amazing 985 rwhp!

It is important to remember that this came with no other modifications other than a Centerforce clutch upgrade (which is required at 900 rwhp). That means all stock engine internals and a stock exhaust. Noticeably missing were long-tube headers and an after-cat exhaust, ported heads, or even cams. Fill the tank with E85, add the Kenne Bell 4.2L blower upgrade and your Shelby can pump out nearly 1,000 wheel horsepower. What could be easier?

Just imagine what's possible with long-tubes, increased head flow, wilder cam timing, and more compression? The modular experts at Accufab recently exceeded 1,600 hp using the new 4.2L, so there is plenty of power left in the blower if you have the right combination.