Corvette STS C5 Turbo Kit - After-Burner

Think of Rick Squires as a modern incarnation of the late Alfred Buchi. Dedicated students of automotive arcana may know Buchi as the Swiss engineer who in 1905, between fixing Rolexes or designing fondue fountains or whatever it is that Swiss engineers do, pieced together the world's first exhaust-driven forced-induction device. Later dubbed the turbocharger, Buchi's bauble has spent the last 100-plus years engorging the output of everything from race cars and fighter planes to tugboats and industrial machinery. More recently, bolt-on turbo setups have enjoyed a well-earned reputation as the ne plus ultra of aftermarket performance hardware.

While Squires' contributions to the realm of automotive engineering are rather more modest than Buchi's in a macro sense, their effect on how we think about some of the most basic precepts of turbocharger science has been nothing short of epochal. Since 2003, Squires' company, STS (for "Squires Turbo Systems"), has garnered popular and critical raves for its innovative line of bolt-on turbo kits for late-model cars and trucks. What makes these packages exceptional is not their horsepower potential or cost, but, rather, their orientation.

Specifically, they mount in the back.

While you're trying to get your brain around the concept, consider the claimed benefits of the rear-mount configuration. The most obvious is a simplified installation process. Liberated from the tight confines of a modern engine bay, the turbos and most of their supporting hardware can, according to STS, be bolted into place in 8 to 15 hours (depending on vehicle application) by any competent mechanic.

Remote mounting also reduces underhood temperatures, potentially increasing both engine performance and component longevity. As a side benefit, relocating the turbo and related componentry to the rear should even have a salutary effect on weight transfer.

Given all this theoretical goodness, our editorial radar went into full squawk mode when STS announced late last year that its long-rumored C5 twin-turbo system was finally nearing production status. But before we coordinated an installation and dyno test, we wanted to clear up a few lingering concerns about the rear-mount layout.

Chiefly, we were worried about the pressure drop that might result from routing the boosted air from the rear of the car several feet forward to the engine compartment. According to Squires, extending the intake tract actually has the opposite effect, inasmuch as it allows heat to dissipate through the exposed tubing as the air makes its way from the turbos to the engine. This "passive cooling" is so effective at chilling the intake charge, says Squires, that STS is able to sell most of its kits in non-intercooled form, cutting costs and further reducing installation time.

In the case of the STS C5 kit, where most of the plumbing is routed inside the car's bodywork, the passive-cooling effect is less pronounced. The company's solution was to include with the system a large, front-mounted intercooler with a 29-inch-wide core. Squires says the unit cools the boosted air to within 10 degrees (F) of ambient temperature before it enters the engine, with a total pressure drop of around 3 psi from turbos to intake.

Fair enough, but we're Luddites at heart, and typically skeptical of purported technological breakthroughs until we've seen their merits demonstrated for ourselves. To find out how the STS C5 system worked in the real world, we contacted Greg Lovell at Anti-Venom Performance, a Seffner, Florida-based performance tuner specializing in LS-engined Corvettes and F-bodies. Lovell is an approved STS dealer and installer, and he was among the first in the United States to get his hands on a production C5 kit. Our test subject was an Electron Blue '02 drop-top, fully modified to Z06 specifications by owner David Thomas.

You'll have to read on for the details, but suffice it to say that, aside from an unhealthy appetite for air bridges (more on that anon), the kit easily met STS's claims for both performance and packaging efficiency.
Somewhere, Alfred Buchi is smiling.

Editor's note: Given the necessarily conservative nature of the provided ECM tuning, Lovell elected to perform a slightly more aggressive (though still safe) dyno-based custom tune on the car in both low- and high-boost configurations. The output figures shown here reflect that custom tuning. Given the tuning variances that exist between individual vehicles, and the cost and complexity of the modifications involved, we strongly recommend that a vehicle-specific, dyno-based custom tune be performed in any forced-induction application where maximum output is desired.