With more displacement, it was time to increase airflow. The stock cam was ditched in favor of a more aggressive hydraulic roller from Crower Cams www.crower.com). The dual-pattern cam featured a .587/.597-inch lift, a 235/243-degree duration (at .050-inch), and a blower-friendly 114-degree lobe separation angle. The high lift cam
was designed to work with a set of high-flow heads supplied by Inertia Motorsports www.nertiamotorsports.com). The 6.1 heads featured full porting, increased valve sizes and a revised spring package to eliminate valve float. Providing the majority of the flow to the Hemi is a Kenne Bell www.kennebell.com) twin-screw supercharger. The stock 2.8 Kenne Bell kit adds 175 horsepower and 135 lb/ft of torque to
an auto-equipped 6.1. Looking for big power numbers, they opted to replace the smaller 2.8L with a massive 3.6L blower. The difference between the 2.8 and 3.6 is size (displacement). Both are offered with liquid cooling and Seal Pressure equalization. The 3.6 is longer and slightly taller than the 2.8 unit. A larger rotor pack means more airflow per revolution. This equates to an increase in maximized flow and boost potential. Capable of supporting 1,200 horsepower on the right application, the 3.6L also featured patented Liquid Cooling (not to be confused with intercooling). Liquid Cooling stabilized the temperature differential that exists between the cool inlet and heated discharge sides of the supercharger.
Liquid Cooling enhanced both longevity and performance of the supercharger, while an air-to-water intercooler system greatly reduces the inlet air temps. The Kenne Bell kit featured both Liquid Cooling (of the blower) and an air-towater intercooler. Liquid Cooling was used to cool the heated (discharge) side of the supercharger by circulating water though dedicated passages in the front of the blower. This helps control the difference in rotor growth between the hot (discharge) and cool (inlet) sides of the blower. It is desirable for the rotors to grow evenly front to back, in order to maintain proper tolerances. Intercooling is used to reduce the temperature of the boosted intake air. Heat is a natural byproduct of compression, so any boost provided to the motor will heat the air. The greater the boost pressure, the higher the charge temperature. Higher intake charge temperatures both reduce power and increase the likelihood of harmful detonation. Running the boosted air through a heat exchanger located under the blower dramatically reduces the intake charge temperature (by as much as 200 degrees), thus increasing power and reducing detonation. Using intercooling, makes it possible to run higher boost/power levels on any given octane rating (pump gas).
With the major components taken care of, it was time to address a few secondary systems, namely air intake and fuel flow. Air flow into the supercharger has a direct affect on the boost level coming out. Maximizing airflow to the blower is a 4.5-inch air intake system, a massive single-blade throttle body (flowing 2,150 cfm) and a Mammoth intake manifold all from Kenne Bell. Fuel was supplied by a pair of 255 ltr/hr fuel pumps augmented by a dual Kenne Bell 17V Boost-a-Pump, feeding eighty-pound injectors. Though boost was increased gradually after the break-in period, the Kenne Bell supercharger was eventually configured to produce 23 psi of boost using a 3.375-inch blower pulley and a 7.5-inch crank pulley. Running 23 psi, the supercharged street stroker pump out 989 horsepower at the wheels (well over 1,000 flywheel hp), and 907 lb/ft of torque. Track testing the Challenger with 18 psi of boost resulted in a best et of 9.96 seconds at nearly 139 mph. Future changes include a change to E85 fuel and testing with an even larger 4.2L blower. We are not sure what Webster or Wikipedia would say,
|61 Cylinder Head Flow Numbers
8. Looking to go beyond stock, ST Motorsports stepped up from the 2.8 to the larger 3.6 s
9. Knowing heat is a natural byproduct of boost (compression), the Kenne Bell supercharge
10. Knowing inlet restrictions severely limit supercharged performance, the supercharged
11. Assembled and installed in the Challenger, the supercharged stroker was equipped with
12. Elevated boost levels require precise tuning. Miss the ignition timing by a degree or
13. After a break-in period, the Challenger was strapped to the dyno for fullpower runs.