As long as there are engines, car folks will find ways to make them more powerful. Our unending quest for speed knows no bounds, or sanity, for if it did, well enough would have been left alone, years ago. The C7 Corvette Z06 powerplant dubbed LT4 is the very definition of “well enough.” With 650 hp and 650 lb-ft of torque off the showroom floor, street manners and fuel economy to boot, it would have legendary Corvette engineers absolutely astounded. And while there is plenty of power locked in the factory supercharged mill, its small-displacement, roots blower is limited. When power goals are sky-high it’s time to leave your roots (blower) behind. The folks at ProCharger specialize in the addition of boost, though it is usually relegated toward engines that didn’t have it in the first place. However, this Z06 specimen had already reached the limits of its factory equipped blower and the hunt for more required a more efficient supercharger. ProCharger utilizes a centrifugal supercharger that offers increased efficiency compared to a positive displacement design in both power consumption (the energy needed to spin it) and heat production, which results in a cooler, denser air charge and more power to the tires.
Adding a more powerful blower is, amazingly, a bolt-on affair. But due to the direct-injected nature of the LT4 engine, the problem becomes getting more fuel into the engine to pair with the newfound boost. Direct injection engines operate at extremely high fuel pressures and rely on highly specialized mechanical pumps to generate those pressures. Adding more fuel to the engine isn’t a simple, drop-in pump upgrade like most port injected cars. However, the aftermarket has remedies.
Before going under the knife for a supercharger swap, the Corvette first went into the welcoming arms of Supercharger Outlet and Performance (SOAP) to remedy the fuel shortage by performing a camshaft installation.
While that may sound strange, the camshaft is the key to bolster more fuel supply on LT-based engines. While the more aggressive grind will allow more air/fuel into the cylinders, the main benefit is increased fuel flow due to altered fuel pump lobes ground into the cam that allows about 32 percent more fuel capacity. For this car, a Brian Tooley Racing Stage 2 camshaft was selected along with matching valvesprings and an upgraded oil pump. Once SOAP was done with the internal upgrades, it was back to the supercharger installation.
“GM made a killer blower for size and packaging constraints, but the LT4 engine is dying for more airflow,” said ProCharger’s Erik Radzins. “At the same boost level, the engine picks up 118 hp due to the efficiency of a ProCharger. When boost goes up it gets even better.” And, that ProCharger efficiency is what has helped set all current LT1 and LT4 records at the dragstrip.
Looking ahead to four-digit power numbers, while under the knife a secondary fuel injection system from Holley EFI was also added. That way once the extra 32 percent of fuel from the camshaft has run out, there is an extra eight fuel injectors that spray into the runners, like a conventional port-injected engine. These aren’t used during normal operation, but when the tank is filled with race fuel and the boost is turned up they will provide additional hydrocarbons to take the engine over the 1,200hp mark!
A simple supercharger and cam swap brought an additional 246 more hp to a factory 650hp engine on pump gas, and a mind-bending 615 hp on race gas. We wonder what Zora Arkus-Duntov would have had to say about that one. Vette
Photography by Erik Radzins