 To properly illustrate the...  To properly illustrate the differences offered by each blower, the 5.4 was equipped with all manner of data-logging equipment. You can never have too much information. |  Shelby offers the 2.3-liter...  Shelby offers the 2.3-liter TVS supercharger, which utilizes an upgraded airbox but the stock throttle body, as an upgrade on its 600hp Super Snake. Unlike the 725hp Twin Screw version, the TVS option comes with a factory warranty. |  Compared to the stock M122,...  Compared to the stock M122, the TVS Roots blower is a significant step up the evolutionary ladder. It offers more displacement, efficiency, and ultimate power production than the stock supercharger. The Kenne Bell Twin Screw supercharger offers even more displacement and efficiency, and therefore even greater power potential. |
What do these improvements mean for a GT500 owner (and other Mustang applications as well)? Replacing the standard M122 supercharger on your GT500 with the more efficient TVS can be worth as much as 100 extra horsepower. Since the stock blower will already deliver 550 rwhp with bolt-ons and tuning (up from roughly 440 rwhp in stock trim), the TVS looks pretty enticing, and it's no wonder Shelby Automobiles chose to offer the TVS as on of the blower upgrades for its Super Snake program.
While the TVS is certainly a big step up from the standard M122 supercharger, Shelby knew that many Super Snake owners were going to want even more. To satisfy owners with a serious thirst for power, Shelby decided to make its Super Snake available with the Twin Screw design from Kenne Bell. Starting out where the TVS Roots blower left off, the 2.8-liter H-series blower from Kenne Bell is capable of supporting more than 1,000 flywheel horsepower and has already demonstrated that it's capable of producing 800 rwhp on an otherwise stock GT500 engine.
Officially, the Super Snake options from Shelby includes a 600hp version equipped with the TVS blower and a 725hp version using the Kenne Bell Twin Screw. These numbers are the rated flywheel power outputs just as the stock GT500 is rated by Ford at 500 flywheel horsepower. That the Kenne Bell Twin Screw is capable of producing 800 rwhp by simply cranking up the boost on a GT500 motor is truly impressive, and we'll likely see many Super Snake enthusiasts running the requisite race fuel and small blower pulley (2.5 inches) required to reach the 800hp mark.
Before beginning the official test, Kenne Bell tech tapped the 5.4-liter with all manner of data-logging equipment. The guys at Kenne Bell border on obsessive when it comes to information, and despite the time required, it's hard to complain about it. Our data logging included the air/fuel ratio, ambient air temperature, engine speed, boost pressure before and after the intercooler, inlet air temperature before and after the intercooler, water temperature through the intercooler core, mass air voltage, timing curve, and even inlet vacuum before the supercharger. The 5.4 looked like a cardiac patient with hordes of wires running out of every possible orifice.
In addition to the data-logging parameters, the Kenne Bell boys logged every ounce of data from the OBD-II port--coolant temps, ignition timing, throttle-position sensor values, and so on--to ensure accuracy between runs. In anticipation of the high-boost runs, the fuel tank was filled with 100-octane race unleaded fuel to eliminate any possibility of detonation. Naturally, backup runs were recorded to verify the power numbers generated by each pulley size. These runs help eliminate anomalies that can occur during testing. Knowing the intensity of GT500 owners (even more so, the Super Snake customers), every effort was made to ensure accurate, repeatable data.
Since it was already installed on the motor, the first series of tests was run with the stock Eaton M122. It should also be noted that the 5.4 was equipped with a standard 17V Boost-a-Pump, stock 52-lb/hr injectors, and a custom tune to maximize power production with an air/fuel ratio of 11.5:1 and 23 degrees of total timing (values used for all of the tests to ensure repeatability). The idea behind the fuel system upgrades was to ensure a stable air/fuel ratio at each boost level.
In stock configuration, the M122 blower provided a peak of 8.7 pounds of boost, but for our needs, we wanted to find out what was possible by running the smallest blower pulley possible. This meant the installation of a 2.59-inch blower pulley (using a smaller pulley requires machining of the blower snout).