7. The big power adder was obviously the Kenne Bell supercharger kit. Even on a stock 6.1, the Kenne Bell twin-screw supercharger offered exceptional performance, to the tune of 175 horsepower.
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,...
8. Looking to go beyond stock, ST Motorsports stepped up from the 2.8 to the larger 3.6 supercharger. When it comes to maximum supercharged performance, bigger really is better.
9. Knowing heat is a natural...
9. Knowing heat is a natural byproduct of boost (compression), the Kenne Bell supercharger kit also featured an efficient air-to-water intercooling system. The only thing better than big boost is big intercooled boost. Unlike some centrifugal super charger kits that come with an intercooler that mounts in front of the radiator. The Kenne Bell kits places it under the supercharger, and forces the boosted air through it.
10. Knowing inlet restrictions...
10. Knowing inlet restrictions severely limit supercharged performance, the supercharged stroker was equipped with a massive oval throttle body. The oval throttle body flows more air as compared to a conventional round blade, because it eliminates the restrictive central bridge section inherent in a dual-blade throttle body. Every portion of the internal section of the throttle body is used to flow air. The oval throttle body employed on this motor flowed 2,150 cfm (2,350 cfm with a radiused inlet), as compared to less than 1,000 cfm for a stock throttle body.
11. Assembled and installed...
11. Assembled and installed in the Challenger, the supercharged stroker was equipped with a set of 80-pound injectors, dual 255 ltrs/hr fuel pumps augmented Kenne Bell 17V Boost-a-Pumps and a 3.375/7.5-inch pulley set up. The fuel system upgrade included 80-pound injectors (spacers were used to mount the rails with these taller injectors), and a pair of 255 ltr/hr in-tank fuel pumps. The flow rate of the pumps was further augmented by increasing the supply voltage to them from 12-13 volts to 17 volts. Pump flow is a function of pump size, speed, and head pressure. Increasing the supply voltage to the pump increases the pump speed, which in turn increases the flow rate. The stock injectors flows 35 lb/hr at 58 psi, and will not support the power level of the supercharged stroker. The fuel lines were also replaced with -6 lines and AN fittings to ensure adequate flow.
12. Elevated boost levels...
12. Elevated boost levels require precise tuning. Miss the ignition timing by a degree or two and you can say goodbye to that expensive supercharged stroker. Adam Montague from ST Motorsports was on hand to dial in the air/fuel and timing using Diablosport software. The tune for a stock install is supplied using a hand held tuner (flash device), but the combination of boost, increased displacement, wilder cam timing, and ported heads required extra time on the street and chassis dyno for our application, to ensure ideal air/fuel mixture and timing under all conditions is accurate. It was not possible to use an off-the-shelf tuner.
13. After a break-in period,...
13. After a break-in period, the Challenger was strapped to the dyno for fullpower runs. Blower pulley changes eventually increased the boost pressure to 23 psi, where the supercharged Hemi eventually pumped out 989 Hp and 907 lb-ft of torque. Run at 18 psi (900 whp), the Challenger has run a best of 9.96 At 138.9 mph on slicks.