Turbocharged Corvette Prototypes - Early Aspirations

A notable innovation was the method used to reduce turbo lag. In contrast to a blow-through (carbureted) system, the TBI engine's throttle blade, which controlled incoming air, was upstream of the turbo. This meant that when the throttle was shut off, the turbo effectively ran in a vacuum, creating a backlog of pressure. When the throttle was again opened, the vacuum created a ram effect, speeding up response time.

All other mechanicals were stock Corvette, including the Turbo 350 transmission and 3.55 axle ratio with Posi-traction. The suspension was Chevrolet's FE7 Gymkhana option, and the tires were 255/15s mounted on 8.5-inch rims.

An updated look accompanied the new car. The base body color was rich metallic silver and was embellished with a striping scheme combining claret (reddish maroon), deep red, and flaming orange. A similar color scheme adorned the seats and door panels.

The last of the turbocharged C3 prototypes, the white-and-blue Phase III Turbo car was unquestionably the most advanced and sophisticated of the series. Piggins' group had continued to refine the existing turbo design, adding aluminum heads and other trick parts to pare weight and enhance performance. But the package's high cost, combined with tightening federal emissions regulations and advances in naturally aspirated engine technology, spelled doom for the project.

Obviously, these cars were not the last of the artificially aspirated Corvettes. Turbo work was reactivated with the C4 and the Callaway-produced RPO B2K. But there was to be one more twist for the turbo C3s.

At the time, the National Council of Corvette Clubs (NCCC) was deeply involved in fund-raising initiatives in support of the Spina Bifida and Hydrocephalus Association. From 1980 through 1982, the council contracted some very accurate replicas of GM's Phase II, Phase III, and '82 Collector Edition cars for the annual raffle.

The 1980 raffle featured the Phase II car. John Gibson, of Corvette News, provided the contacts at Piggins' group, and NCCC president Tom Henry challenged his many organizers to finance the deal. By the time the whole package was approved, it included not just the car, but matched Mid America Designs apparel and a full set of leather luggage as well.

The job of preparing the car was contracted to several partners. Cars & Concepts, in Brighton, Michigan, installed the gas-strut hatch system. The car was then sent to American Custom Industries, in Sylvania, Ohio, for paint, interior, and turbo installation.

The replica car was different from the original Phase II in a few important ways. Instead of the prototype's developmental engine, the replica featured a regular L48 fitted with an off-the-shelf Martin turbocharger kit. This system provided a reasonable power increase and was easy to maintain.

In addition to the extensive leather work performed on its interior, the replica's console-mounted instruments were swapped out for a set of Javelina Digitron II digital gauges. By the time the whole car had been assembled, it made for quite an attractive package. The Phase III replica, which was raffled in 1981, was not quite as sophisticated but followed essentially the same pattern.

As suggested at the start of the story, few viable technologies ever really disappear. Turbocharging work continued with the C4, as customers clamored for more power to keep pace with the Vette's international competition. Corvette chief Dave McLellan continued developmental work on the turbocharger option even as the ZR-1 was being developed. This work led to the Callaway-designed RPO B2K package.

Separately, the IMSA GTP race car, based on a Lola chassis, was being used as a live test bed for both the turbocharger and a pair of newer-generation engine-management systems. Many of the lessons learned here were applied to the twin-turbo LT5 developed for the 1990 CERV III engineering concept.