It takes a special car to get the attention of Darren Friedman, who’s no stranger to fast and exciting machines. His ears perked up, however, when in 2014 he read the basic specs for the soon-to-be available ’15 Corvette Z06. The heart of the beast was to be a 6.2-liter, direct-injected LT4 churning out 650 supercharged horsepower. Add in lightweight components, including carbon-fiber roof and hood panels, composite floors and an aluminum space frame; Magnetic Ride Control; electric power steering, the choice of a seven-speed manual or eight-speed automatic transmission; an electronically controlled differential; three different aero packages and a long list of other special features, and the new top Vette promised to combine true supercar performance with unmatched efficiency, civility and longevity. Even better, its starting price of $78,995 undercut the competition by tens of thousands of dollars.
Friedman’s approach to life in general, and cars in particular, is summed up by one of his favorite quotes, which holds that “It’s better to be a racer for a moment than a spectator for a lifetime.” This credo led him to establish Speed Limit Racing, a business that provides a safe and structured environment to promote driving skills through a variety of programs, including driver-education classes, autocrosses and track days. The C7 Z06 was thus tailor made for Friedman, and there was never any doubt about what he’d do with his when it arrived.
Not surprisingly, Friedman specified the Z07 Performance Package for his Z06. This option transforms an already ferocious car into the most track-capable Corvette Chevy has ever produced. The package includes larger end plates for the front splitter, an adjustable transparent “wickerbill” on the rear spoiler, unique suspension tuning, Brembo carbon-ceramic brake rotors (sized at 15.6 inches up front and 15.3 inches in the rear) and summer-only Michelin Pilot Sport Cup 2 ZP tires. Friedman patiently waited for his car to come in, and the moment the dealer called, he was ready to roll. “After receiving my Z06 in May of 2015,” he explains, “I immediately put on the required 500 break-in miles, changed the oil and then headed straight to the track.”
To paraphrase what the Hair Club for Men’s Sy Sperling used to say in his cheesy 1980s TV commercials, Friedman is not only the Speed Limit Racing president, he’s also a client. In fact, he may well be his own most active client, with more than 150 track events on his résumé. “And that number is growing,” he tells us, “because I’m doing at least three or four events per month, every month, all over California and in neighboring states.”
Friedman has done track days with a wide variety of vehicles over the years, and in addition to his Corvette, he currently competes in a Porsche Cayman GT4, a BMW M3, a Porsche 911 Turbo S and a Kirkham 427 Cobra. So how does the Z06 stack up? “My first impression was that [it offered] a great bang for the buck. Then the reality hit that it doesn’t like spirited driving in the heat. After I completed two or three fast laps, overheating issues set in and caused the dreaded ‘limp mode.’ I had to do something.”
The “something” that Friedman chose to do was neither minor nor cheap, but the results were practically guaranteed: He shipped the hot-running Corvette off to Callaway Cars’ West Coast facility in Temecula, California for a complete SC757 conversion. “The overheating problem was what got me thinking about Callaway to begin with,” he remembers, “but that was only part of it. From doing so much competition over time, my skill level had increased to the point where I wanted the car to be faster, and the SC757 package [would be] a huge help with that as well.”
The raw meat of the conversion consists of Callaway’s GenThree TVS2300 supercharger and TripleCooled intercooler system, along with a high-flow intake setup whose runners are designed to increase mid-range torque. The GenThree blower was designed in-house by Callaway’s own engineers, with a focus on reducing charge-air temperatures and increasing flow. With Callaway’s previous superchargers (and those of most other manufacturers as well), the compressed air is channeled through a single liquid-to-air intercooler and then downward into a log-style manifold shared by all cylinders. With the new design, engineers rotated the supercharger’s rotor-pack assembly 180 degrees to route the air up rather than down. It then goes through a primary intercooler and around the sides of the housing. The intercooler’s fluid circulates through a heat exchanger positioned in front of the car’s radiator.