Although traditional belt-drive systems can work great in supercharged applications up to 2,000 hp, as engine output quickly eclipsed that mark, racers demanded an improved means of spinning up their superchargers. The aftermarket responded with gear drive systems that allow driving a supercharger directly off the crank through a series of gears instead of a belt. "At extremely high power levels, gear drives are more reliable. Having a backfire at the track can throw off a belt, but that's not an issue with a gear drive," says Ken. Likewise, gear drives eliminate side loads off of the crank snout, and reduce parasitic power loss as well. Mounting the supercharger directly in front of the engine also allows fabricating a ram air system that feeds cool ambient air into the supercharger inlet. Through necessity, ProCharger has developed its own gear drive system called the RaceDrive. "While developing the F-4 supercharger, we overshot our power goals and developed a supercharger unit capable of 3,500 hp. This exceeded the limitations of the gear case, which led to the development of the RaceDrive. The gears in the RaceDrive are very easy to swap out if you want to change the blower speed, and it had additional drives for a fuel pump or a vacuum pump. It also offers great ground clearance for superchargers with large volutes."
Low-End Torque And Top-End Power
Despite the all-out power and efficiency that centrifugal superchargers offer, the long-standing knock against them is that they don't build boost until high rpm. Since centrifugal superchargers rely on fixed internal step-up ratios and engine rpm to determine boost, it has long been accepted that it's impossible for centrifugals to produce lots of boost at low rpm, but ProCharger has transcended the impossible with its ingenious new i-1 supercharger unit. "The i-1 supercharger utilizes a continuously variable transmission coupled to a standard gear case. The CVT multiplies the supercharger's internal 8:1 step-up ratio by as much as 2:1 at low rpm, and as little as .5:1 at high rpm," Ken explains. "The result is an incredibly flat boost curve that offers the high-rpm horsepower that centrifugal superchargers are known for as well as immediate boost at low rpm. The CVT employs a remarkably durable dry hybrid drive system, and the CVT's ratio is controlled by a sophisticated electric motor. With the i-1 supercharger, now you don't have to worry about the shape of the boost curve anymore, which allows us to design the supercharger for peak efficiency. On a 2010 Camaro SS, the i-1 supercharger system produces 425 lb-ft of rear-wheel torque at just 2,400 rpm on a Mustang chassis dyno. The peak figures check in at 568 hp and 538 lb-ft of torque at the rear wheels on just 7.5 psi of boost. The shape of boost curve isn't as important on a race car, but in street applications it's very important to maximize the area under the curve."
Granted that integrating a CVT into a supercharger is earth shattering in its own right; that only tells half the story of the i-1. Since the CVT ratio is controlled by an electric motor, hot rodders can also dial in the exact amount of boost they want at the touch of a button. The i-1 supercharger system includes an in-car touchscreen that can load programs for three boost modes into the i-1's electronic brain: Touring (low boost), Sport (medium boost), and Competition (high boost). "Touring mode locks the supercharger at 1 psi, so it gives you peace of mind when you hand the keys over to your wife, or if you have to drive in bad weather. Changing between modes also changes the amount of blower whine, so it's fun to surprise people at stop lights," says Ken. "The i-1 also has a Custom mode that allows users to program a custom boost curve in 250-rpm increments. You can also change the rate of boost gain, and dial in throttle response by customizing the amount of boost that's produced at part throttle. You can even have custom boost curves for drag racing and road racing. In addition to performance and customizability, we have some customers that are reporting a 2- to 3-mpg improvement in gas mileage on the freeway."
Some people think that all intercoolers are created equal, and these days, there are lots of cheap knock-off intercoolers on eBay. As the saying goes, you often get what you pay for, and high-quality intercoolers offer several advantages that an untrained eye might not notice. "First and foremost, ProCharger is proud to design and manufacture all of our products in America, including our intercoolers. The performance of an intercooler comes down to its design, testing, and manufacturing quality," Ken explains. "You can't easily see what's going on inside an intercooler, but the use of turbulators inside the cores, the ratio of crossflow air to charge air, and the location and design of the end tanks all play a very important role in intercooler performance. The leak rate of cheap intercoolers is fairly high, and many users will never know how severely they're leaking. Furthermore, parts like intercoolers can't be designed in a vacuum. They have to be designed within the context of how they're going to fit in a car. In some of our supercharger kits, upgrading from one of our Stage 2 intercoolers to one of our race level intercoolers can increase quarter-mile trap speed by four mph. Improvements like that aren't simply the product of increasing the core size. The entire intercooler system must be refined from top to bottom.