Corvette tuners have a long history of building low-production supercars. These come in a variety of levels of sophistication that range from the truly sublime to the just plain awful. While creating a Corvette with sociopathic power levels is not an ordeal, building one for reliable everyday use takes great skill. GM turned the tuning world on its head with the 638hp Corvette ZR1, a bona fide supercar with OEM fit-and-finish. The new King of the Hill challenged all comers, and STS Turbo accepted.
Rick Squires, the founder and VP of research and development at STS, had been considering building a limited-edition STS car for a few years, and the hype surrounding the introduction of the ZR1 finally motivated him to do so. The highly touted ZR1 offered an opportunity to demonstrate the benefits of his company's turbo kits as compared with a supercharged setup. The result is the STS ZR7 Corvette, a supercar of the highest order, boasting wild looks and extreme performance without sacrificing the daily driveability inherent to the stock C6.
The first ZR7 was assembled for Squires using his personal '08 Vette, after being conceived as a prototype to display on the car-show circuit. "Our quest was to build a 'green' supercar for the 2008 SEMA show that was capable of race-worthy performance yet mild-mannered enough for the street, with economy-car fuel mileage and ultra-low emissions," he explains. Crews at Kindigit Design and STS Turbo thrashed around the clock to have the ZR7 ready for SEMA in a mere seven days (see sidebar).
Rather than building a one-off show car just to prove a point, STS wanted to build a handful of ZR7 Corvettes to lure potential ZR1 buyers. A planned a production run of 50 cars will implement STS' proven rear-turbo technology to produce immense horsepower and torque and confer a top speed in excess of 200 mph. The ZR7 name is more than an arbitrary spin on the ZR1 moniker, as Squires explains: "'Z' is for the performance history of the many great 'Z-badged' GM vehicles. 'R' for the race-proven suspension setup and power delivery, and '7' is for the car's 700-plus hp."
Beneath the vented hood is an LS3 engine whose largely stock appearance belies the awesome power of the ZR7. Cometic head gaskets are used to lower the compression to 10.1:1 in order to reduce the risk of detonation and guarantee reliability. Factory cylinder heads have been bolstered with Comp Cams 918 valvesprings, titanium retainers, and pushrods. Most of the stock exhaust system is retained, including the catalytic converters, with the turbochargers filling in for the factory mufflers. A ceramic coating is applied to the exhaust manifolds to reduce underhood temperatures.
STS employs one of its remote-mount twin-turbo kits to produce the enormous power gains. A pair of 59mm ball-bearing STS turbochargers sit in the location of the factory mufflers. These are fed cold air by twin 9-inch conical air intakes mounted inside the rear fascia, just behind the taillights. Boost is held to a maximum of 8.5 psi using dual STS 38mm wastegates. An STS 50mm blow-off valve sounds off with each gear change, and four polished stainless tips allow exhaust to escape directly from the turbos' exhaust housings. Despite the relatively long distance from the engine, STS kits are painstakingly designed to deliver excellent boost response and maintain constant oil pressure to the turbos.
While the rear-mounted snails are the stars of the show, they're backed by an impressive supporting cast to achieve optimal performance. This includes a large dual-feed front-mount intercooler that reduces the intake-charge temperature to near ambient. The engine's increased fuelling demands are met with FAST 65-lb/hr injectors, and an Active aluminum radiator is implemented to enhance the cooling system.