Prescription for Speed

A “doctor” and a pharmacist cook up a 700-horsepower performance panacea

May 7, 2015
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The practice of pumping Corvette engines full of compressed air to improve their performance dates all the way back to 1954, when a Paxton centrifugal supercharger briefly became a dealer-installed option on Chevy’s slow-selling—and slow-moving—sports car. Attempting to transform the sow’s-ear “Blue Flame” six engine into a silky screamer with bolt-on parts would prove a fool’s errand, however, and when the revolutionary small-block V-8 appeared on the Vette’s equipment list a year later, the ad hoc blower program was quietly discontinued. Only in recent years have superchargers found their way back into the Corvette’s engine bay, and even then only on low-volume flagship models.

That hasn’t stopped aftermarket performance-parts firms from developing their own Corvette huffer kits, a practice that seems likely to intensify as freshly minted C7 Stingray owners strive to endow their cars with the accelerative ferocity of the factory-blown Z06 edition. Consider the case of Ken Villani, a Long Island, New York, pharmacist with an insatiable jones for speed. While the 460-horsepower rated output of the stock 2015 Stingray furnished the desired quantum of euphoria for a time, Villani, like most addicts, soon found himself itching for a stronger dose.

The prescription came in the form of a ProCharger centrifugal supercharger system, installed by longtime Corvette tuner Vette Doctors Performance in nearby Amityville (yes, that Amityville). ProCharger, which has been hawking Corvette-specific blower kits since the company’s inception in the mid ’90s, was one of the first to market with a complete C7 package, which made Villani’s choice of forced-induction units an easy one.

At the risk of wading too deeply into the mire of engineering arcana, a few technical notes are in order. The term “centrifugal,” as applied to superchargers, refers to a type of compressor that is most often mounted on the front of an engine and operated via a belt- or gear-drive system. Benefits of the centrifugal layout typically include a higher maximum rotational speed—as compared with a top-mounted “Roots style” blower—along with superior thermal efficiency, since the compressor is physically separated from the hot intake manifold. ProCharger does the latter characteristic one better by an adding air-to-air intercooler (or two, in the case of some of its older Corvette kits) to lower intake-charge temps and enable the use of more power-building ignition timing. The downsides of the centrifugal approach include its relative complexity, which limits its use in OEM applications, and a softer low-rpm response than one would expect from a Roots-type unit such as the LT4’s Eaton TVS.

In the case of the Stingray’s direct-injected LT1, torque is both abundant and widely dispersed over the engine’s rpm range, a fact that militates strongly in favor of the centrifugal approach when maximum output is the goal. And since the amount of boost created by a centrifugal blower rises commensurately with engine rpm, heavy throttle application at low speed is less likely to induce a pulse-quickening power slide. (We’re looking at you, C7 Z06.)

The suitability of the pairing was borne out in the pre- and post-installation testing performed on VDP’s chassis dynamometer, where the rear-wheel output of Villani’s ‘ray jumped from an already healthy 427 hp and 437 lb-ft of torque in stock form to a Z06-quality 565/565 with the blower at full puff. Accounting for parasitic losses through the drivetrain, that calculates to right around 700 horses at the crank, which is nothing short of remarkable considering the modest amount of boost involved (8 psi) and the conservative, street-suitable PCM reprogramming performed by the shop.

Somewhat surprisingly for such a new engine design, the installation presented no unexpected challenges, according to VDP Manager Anthony Marianelli. “Supercharger installations on [C7s] are very straightforward,” he says. “Some steps a little more time consuming than others but overall they tend go in without a hitch.”

Also from Issue 98

  • Inside the Bondurant School
  • Buyer's Guide: C1/C2
  • History: Modern ME Prototypes
  • Racing: C7.Rs Shine at Sebring
  • Ultra-Rare '62 "Tanker"
  • Autocrossing Primer
  • '68 Owens Corning Racer
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