Let's face it. When it comes to performance, American drivers are looking for immediate gratification. Sure, a high-winding small-block is a joy to behold, but there's nothing quite like the feel of a torque-heavy big-block. And that's exactly what a C5 equipped with Kenne Bell's new LS supercharger kit feels like. Even in Second gear, this motor has more than enough power to make the car swap ends.
It's not so much the impressive peak power number that's responsible for the tremendous shove in your backside. Rather, it's the massive swell of torque that accompanies a twin-screw blower. Check out the accompanying dyno graphs and see for yourself. Even down at just 1,500 rpm, the KB unit boosts the LS1's already healthy torque output by a solid 50 lb-ft. By 2,000 rpm, the gain has increased to over 100 lb-ft. Even better, these improvements carry all the way to redline. Let's see...strong on the bottom, with huge midrange power and a strong pull all the way to the fuel cut. Where do we sign up?
Making all this boost and power possible is one of Kenne Bell's 2.4-liter twin-screw superchargers. For Corvette applications, the assembly is available in either black satin or polished to a show-quality finish. We like the fact that the blower, intercooler, and dedicated lower intake manifold come pre-assembled for ease of installation. The assembly includes a compressor-bypass valve and a powdercoated bypass tube.
One cool trick incorporated into the bypass system is a manual "valet" mode. By physically locking the bypass valve open with a simple screw, you can greatly reduce the amount of boost supplied to the motor and make your car a less tempting target for the parking-lot hot-lappers down at the dealership.
The blower assembly (including drive, pulleys, and even fuel rails) also boasts billet construction to maximize strength and minimize distortion of the blower case. The high-flow, cast-aluminum inlet system features a 93mm opening designed to accept either the factory 78mm throttle body or any of the factory or aftermarket 90mm units. (The inlet is also compatible with both the manual and electronically operated "drive-by-wire" versions.)
The Kenne Bell supercharger kit includes a set of 42-pound injectors capable of supporting 560 rear-wheel horsepower. Available as an option is a set of injectors that flow 62 pounds per hour, allowing Vette owners to step up to 750 rwhp. The new injectors were not the only changes to the factory fuel system, as the blower kit included a billet-aluminum fuel rail and a dedicated housing for the relocated fuel-pressure regulator.
The stock Corvette's in-tank pump could not supply sufficient fuel to feed the needs of the blown beast, so Kenne Bell augmented it with one of its Boost-a-Pump units. The Boost-a-Pump improved the flow capacity of the stock pump by increasing the supply voltage. The flow rate of a fuel pump is dependent on both supply voltage and head pressure. Higher fuel pressure means less flow, while higher voltage equals more flow. Using the Boost-a-Pump, Kenne Bell was able to supply enough fuel to the blower motor without replacing the factory pump.
Knowing the 2.4L supercharger was capable of supporting well over 850 hp, the gang at Kenne Bell realized they'd have to keep inlet restrictions to a minimum. With the ability to accept a 90mm throttle body, the free-flowing inlet into the blower was up to the task, but they worried about what was in front of the throttle body-namely, the air-inlet system. Accordingly, the factory airbox assembly and filter were ditched in favor of a custom filter and inlet tube. The 93mm inlet tube was designed to maximize flow yet still fit within the C5's cramped engine compartment.
Even with boost pressure at a very reasonable 7.5 psi, the Kenne Bell blower kit required an air-to-water intercooler. This unit features a bar-and-plate design to maximize thermal efficiency. Before being forced into the cylinders, the heated inlet air must pass through the air-to-water intercooler core. The heated inlet air is cooled as it comes in contact with the much cooler transfer medium (in this case, water).
To rid the air-to-water core of the unwanted heat, an electric pump is used to circulate the water through a second heat exchanger mounted in front of the radiator. This basic system is used successfully on many OEM supercharger systems, including the 550hp Ford GT. The combination of the efficient twin-screw design and effective air-to-water intercooler allows the Kenne Bell supercharger system to provide huge power gains at a relatively low boost level. The intercooler should also allow the boost to be safely cranked up on a dedicated blower motor.
Given the tight constraints of the Corvette engine bay, installing the supercharger and intercooler does require the use of a new hood. The KB design looks a bit like a factory hood that took a short but beneficial trip to a Beverly Hills plastic surgeon. Nothing outlandish mind you-just enough to make bystanders take a second look. Each Corvette blower kit comes with an unpainted hood, ready for color-matching.
With the hardware completed, the Kenne Bell folks spent considerable time tuning the supercharged combination. Supercharged motors require a slightly richer mixture and significantly less total ignition timing than do stock, normally aspirated ones.
Accordingly, the programming KB supplies with its Corvette kits provides safe-but still powerful-air/fuel and timing curves. Remember: When it comes to successfully running a supercharged motor on the street or strip, tuning is the key.
While the components and tuning all seemed to be first-rate, we were most interested in the power gains. As luck would have it, Kenne Bell had two LS-powered Corvettes available for us to test. One, an '02 C5, was equipped with a modified LS1. The other was a stone-stock '04 Z06.
The '02 was powered by a stock short-block that had been augmented by LS6-spec heads and exhaust, along with a mild Lingenfelter cam. In normally aspirated trim, this Vette produced 360 hp and 359 lb-ft of torque. With the Kenne Bell unit installed, peak numbers jumped to 550 hp and 501 lb-ft of torque. While the peak gains of 190 hp and 140 lb-ft were certainly impressive, the graphs show huge gains throughout the rev range.
We initially had misgivings about installing the blower kit on the higher-compression LS6 motor, but the dyno results and a follow-up testdrive quickly put our fears to rest. In stock trim, the LS6 produced 372 hp and 364 lb-ft of torque. Once Kenne Bell applied 7.5 psi of boost, the peak numbers jumped to 547 hp and 522 lb-ft. The power delivery from this supercharged LS6 was seamless, offering near-stock driveability and all the instant gratification you could ever ask for.
While we can't imagine ever wanting or needing more power than this base kit provided, there will always be those who feel that if 550 hp is enough, then 600 hp or even 650 wheel horsepower is just right. Fear not, as the Kenne Bell supercharger system has another few hundred horsepower left in reserve. Of course, reaching much beyond the 550-rwhp level will require a dedicated engine with forged internals and even larger injectors, but it's good to know the power is available-just in case you should ever go looking for ludicrous speed.
Modified '02 Corvette: NA vs. Kenne Bell Blower
This particular C5 Corvette was equipped with a lightly upgraded LS1. The stock-displacement motor was augmented with a full complement of LS6 hardware, including heads and exhaust system. The stock cam was also ditched in favor of a mild LPE grind. In normally aspirated trim, the modified C5 motor produced 360 hp (the peak number shown is a spike that occurred at the end of the run) and 359 lb-ft of torque. After the installation of the Kenne Bell supercharger kit, the peak numbers jumped to 550 hp and 501 lb-ft of torque. Check out the huge torque gains throughout the rev range-all from just 7.5 psi of boost.
Stock '04 Z06 Corvette: NA vs. Kenne Bell Blower
The power gains on our stock LS6 were every bit as impressive as those of the modified LS1. This engine produced 372 hp and 364 lb-ft of torque in normally aspirated trim. Running 7.5 psi, these numbers jumped to 547 hp (again, ignore the spike number) and 522 lb-ft. What is most impressive about this supercharged LS6 is the immediate gratification that accompanies stepping on the throttle. Traction is scarce, and you'd better be pointing in the right direction when you finally put the spurs to it...well into third gear.