If you're an engineer, a buildup project typically has a precise timeline from start to finish, with performance benchmarks pacing a tight schedule. Miss any milestones, and you might be out of a job. But when you're talking about a high-velocity Vette, it's not whether you complete it on time, but how fast you can pass by those road markers once it's done.
Rob Rose knows both sides of these equations. Since he's handled all sorts of complex computer projects in his professional life, he's accustomed to staying on schedule. After all, he waited three years to the day for his '03 Z06's warranty to expire before calling a number of turbo companies to improve the car's power output. Even so, his buildup project's timeline stretched out much longer than expected until he reached an 800-plus-horsepower benchmark of performance. (Punctuality wasn't the issue, and really, if you're running a bit late, you can always stomp harder on the go-pedal, right?)
After shopping around a bit, Rose settled on the STS Turbo Systems kit, which mounts a pair of puffers remotely near the tailpipe, replacing the stock mufflers. He chose the STS unit for two key reasons: space and temperature. "There's not a lot of room under the hood," he points out, "and I didn't want to try to cram a turbo in there. Not only that, it can generate a lot of heat. I've seen turbo housings glow cherry red from running hard on the track, and I didn't want that in the engine bay, melting wires, hoses, or other components."
STS claims a reduction in heat by as much as 500 degrees at the turbos themselves, eliminating the need for a turbo timer to prevent coking on the bearings. In being mounted farther downstream in the exhaust system, the STS unit has a few other advantages as well, such as ease of installation (about a day for a moderately experienced wrench, using standard shop tools). In addition, the rear-mounted turbo acts as a muffler, creating a special sound that is completely different from the typical huffing and rattling of a blow-off valve.
Other benefits include a cooler intake charge for the engine, due to the inherent intercooling effect of the longer tubing, and the fact that no special headers or other exhaust components are required. (Rose nevertheless added Kooks ceramic-coated 1 7/8-inch headers and a 3-inch midsection.) In addition, the system improves on the front/rear balance by putting more weight near the back end. (Factoring in the poundage removed by the elimination of the factory mufflers, the total increase in weight of an STS system is about 125-150 pounds.)
But Rose's selection of the STS system was contingent on one thing: The kit had to be street legal. While some Corvette tuners might sneer at that requirement, Rose had good reasons for doing so, and STS principal Rick Squires agreed with them. Getting a CARB E.O. number for an aftermarket power-adder can be a daunting task, but the process was vital to the company's marketing plans for the C5 system.
The first turbo that went on Rose's ride was an air-cooled unit with a conventional journal-bearing setup. The results were impressive. With a dual boost controller, he could dial in anywhere from 5 to 8 psi, good for as much as 558 hp at the wheels (around 657 hp at the flywheel, assuming a 15 -17 percent loss from the driveline).