The muscle car era was full of legendary big-block engines. Chevy had the L88 and LS6, Pontiac had the Ram Air and Super Duty motors, while Ford countered with Clevelands and Cobra Jets. All of these nostalgia motors have earned a place in history but none have garnered the notoriety of the Chrysler Hemi. The name Hemi has become synonymous with performance, from its original inception right through to the age of electronics. This fact obviously did not escape the marketing department over at Chrysler, as the Hemi namesake was given to the most recent version of Chrysler's performance offerings. Though it can be argued whether the modern, injected Hemi is actually a true Hemi, there is no denying the impressive performance offered by the current combinations, especially those sporting the SRT8 insignia. Time and technology have marched on since the original Hemi, but the modern 6.1L SRT8 motor is every bit as powerful as the legendary (and much larger) 426 Hemi. That same technology has allowed the modern Hemi to offer not only exceptional acceleration, but a combination of performance, mileage, and emissions unheard of during the days of the original Hemis.
We all know blown Hemis are bad. This month we prove it by bolting Kenne Bell superchargers on not one but two Challenger SRT8s. Follow along to see the impressive results.
Despite the performance potential of the factory 5.7L and 6.1L offerings, enthusiasts being enthusiasts, they always want more. Lucky for us, more is almost always available, even for Chrysler's latest bit of nostalgia, the impressive Hemi-powered Challenger. As with the original, the injected Hemi responds very well to the usual assortment of bolt-ons, including ported heads, cams, and even stroker-based displacement changes. Heck, it is even possible to bore and stroke a modern motor out to equal the displacement of the original 426. While bolt-ons offer plenty of potential, many run afoul of current emissions regulations. Those that have received compliance usually offer only minor performance gains, air intake and cat-back exhaust systems being the most popular. For those Hemi owners looking for some serious power gains without fear of local law enforcement discovering their "off-road only" components, look no further than a Kenne Bell supercharger. Unlike some of the other available supercharger kits that offer just 5 psi, the Kenne Bell supercharger kits for 5.7L and 6.1L Hemi-powered vehicles will be certified at a full 8 psi.
Impressive even in stock trim, the 6.1L SRT8 offered in the '09 Challenger was just begging for some boost. While some scoff at the notoriously weak pistons, Kenne Bell has managed to coax 765 wheel hp out of an internally stock Hemi without hurting a stock piston. The key is obviously tuning and some good ole fashioned race fuel.
We followed along while the guys at Kenne Bell installed one of their Hemi supercharger kits on a new Challenger. In fact, they installed kits on a pair of Challengers, one automatic and one stick, making a comparison between the two all but mandatory. The photos cover some of the installation shots, but know that with an installation manual that spans 158 pages, it would be impossible to cover every detail. The highlights obviously include the Kenne Bell twin-screw supercharger. Offered in both standard and high-boost H-series, the twin screw supercharger displaced 2.8 liters. It is important to point out that the 2.8L H-series blower is capable of supporting over 1,000 hp (with dyno results to back up the claim), so it will have no trouble feeding a stock or modified Hemi motor. In fact, it is reassuring to know that if you install the blower on your stock motor, it has the capacity to grow with your power needs should you upgrade to ported heads, cam or even a 426 stroker motor at a later date. Compared to some of the smaller blowers on the market, the Kenne Bell twin-screw 2.8L offers an impressive combination of efficiency and airflow, making it equally effective on both stock and modified motors.
Installation of the new Challenger kit started with removal of some major components. We can't detail every aspect of the installation procedure (supplied KB instruction manual is 157 pages), it was necessary to remove the dual fan assembly.
When it comes to producing an effective supercharger kit, there are a number of details that make or break the kit. Supercharged Hemi performance is not simply a matter of installing a blower and calling it good. For the blower to perform optimally, both the air and fuel flow must be optimized. While some may argue that the blower adds all the air the motor can use, the reality is that superchargers, especially positive displacement superchargers, are ultra sensitive to inlet restriction. Restricting the air going into the supercharger will result in a drop in airflow (and boost) going out. Potential restrictions include everything positioned in front of the supercharger, including the blower inlet manifold, the throttle body, air intake tube, and filter assembly. It goes without saying that every effort should be made to provide a cold air source for the system, but the airflow rate of these other components must also be optimized. The blower experts at Kenne Bell are well aware of this problem and have made every effort to maximize the flow rate of the inlet system. Their changes include a dedicated Mammoth blower intake manifold that flows a whopping 1,500 cfm and a 4.5-inch air intake tube and an open-element filter that exceeds 2,000 cfm. The limiting factor in the air intake system in terms of flow is actually the stock 81mm throttle body that flows only 924 cfm.
Since the supercharger runs with a dedicated blower manifold, that meant the stock intake had to go.
In addition to the airflow, the supercharged motor obviously requires additional fuel. For the modern EFI Hemi, this should be as simple as reprogramming the ECU, right? Unfortunately, reprogramming the factory ECU has become more and more difficult, especially with the advent of drive-by-wire throttle activation. Naturally, the Chrysler engineers programmed all manner of safety devices to prevent the electronic throttle body from sticking in the WOT position and allowing the car to accelerate away under full throttle. Changing the fuel (and timing) values is not terribly difficult, but getting around the throttle and torque-limiting strategies is considerably more so. Lucky for enthusiasts, the guys at Kenne Bell are one of the few companies that have successfully conquered the Chrysler Hemi (drive-by-wire) programming. Changing the fuel and timing parameters was only part of the equation, as the stock fuel pump and injectors were not designed with the elevated power levels offered by the supercharger in mind. The Kenne Bell kit included a 17V Boost-a-Pump (BAP) to enhance the flow rate of the stock fuel pump, while the factory injectors were replaced by a set flowing 50 lbs/hr. According to Kenne Bell, the fuel system upgrades to the Hemi will support up to 650 rwhp. Additional power can be had with a 20V Competition BAP and 75-80 lbs/hr injectors.
The adapter plate used for the blower was bolted in place according to the supplied torque specs.
These air and fuel upgrades applied to the Hemi are actually pretty universal in terms of application, but Kenne Bell also applied a few other Hemi-specific tricks to their supercharger kit. First off was a cure to the PCV system. Stock Hemis rely on an elaborate oil control system to eliminate oil from pooling in the intake tract and winding up being burned in the combustion chamber. Since the Kenne Bell supercharger kit replaced the factory intake manifold and attending PCV system, it was necessary to come up with a suitable replacement. The cure was to design a dedicated oil control valve that increases horsepower while reducing detonation and oil consumption. Oil vapor is easily ignited (even more so than gas vapor) and as such can be the source for harmful detonation. Kenne Bell also had to solve the common surge and runaway throttle commonly associated with supercharged Hemis. Their cure was to design a new bypass valve, a design so revolutionary that they decided to patent it. The patent-pending Boost-Vac design reduces supercharger heat, improves mileage, and even works well with non-stock cams (where erratic idle and cruise vacuum reading play havoc with typical bypass valves). Combine these tricks with a set of detailed instructions, extensive R&D, and first-rate tech support and you have an impressive upgrade for any Hemi.
An adapter plate is used to mount the stock Hemi throttle body, though Kenne Bell also offers a throttle body upgrade. Remember, restrictions are the enemy of supercharged performance.
To illustrate the gains offered by the installation of the Kenne Bell kit on an '09 Challenger, we followed along during the installation and subsequent dyno testing. Naturally the first order of business was to baseline the Challenger in normally aspirated trim prior to the installation of the supercharger. In bone stock trim, the automatic 6.1L Challenger produced 342 hp and 337 lbs/ft of torque. The manual version did slightly better, as the stock six-speed Challenger produced 376 hp and 375 lbs/ft of torque. After adding the Kenne Bell supercharger kit, these numbers jumped to 515 hp and 472 lbs/ft of torque for the auto and 537 hp and 510 lbs/ft for the stick. All this glorious horsepower came at just 8 psi of boost, but we understand that replacing the 3.5-inch blower pulley with a smaller 3-inch version will increase the boost pressure to 12 psi and the peak power numbers to an even 600 hp. Every bit as impressive is the fact that this requires no revised tuning, only the use of higher octane fuel. Know that Kenne Bell has taken an otherwise stock 6.1L Hemi to the maximum with the installation of an 8-inch crank pulley (replacing the stock 6.25-inch) and a 2.75-inch blower pulley. Additional upgrades included the Kenne Bell throttle body upgrade (flows 1880 cfm), a 20V BAP, and 80 lbs/hr injectors. Equipped as such, the blown Hemi Challenger from ST Motorsports produced 765 rwhp (near 900 engine horsepower) and ripped through the quarter-mile in a blazing 10.25 at 131 mph (equipped with slicks). Much has been written about the weak factory Hemi pistons, but these results demonstrate that it is obviously possible to produce exceptional power with proper tuning and Big Bell Boost.
After proper preparation of the various sub systems, it was time to install the supercharger onto the awaiting lower intake.
