1990 “Active Suspension” Prototype

This car sold for $66,000, including buyer’s premium, at Barrett-Jackson’s auction in Palm Beach, Florida, on April 11, 2009.

Defying the laws of physics—that was the promise of Active Suspension. Instead of using springs, dampers, and anti-roll bars to react to and manage a vehicle’s dynamics, Active Suspension systems used sensors, computers, and high-pressure hydraulics to totally control a vehicle’s behavior. An “active” automobile could actually lean into a curve while preventing any faults in the pavement from upsetting the steering and cornering dynamics of the car.

John Dinkel of Road & Track magazine wrote after driving one of the Active Corvette prototypes: “A stock Corvette has wonderfully quick, direct and precise steering. The effort and feedback are superb. But after jumping back into the standard ’Vette, I thought some engineer must have removed the car’s steering system and replaced it with mushy spaghetti while I was evaluating the active car. There was that big a difference. Incredible, simply incredible.” He experienced driving through a turn a full 15 mph faster with the Active car than with a standard Corvette.

Like many revolutions in auto racing, Team Lotus invented Active Suspension for Formula One. Development began in 1981, and by 1983, the system would see limited action with Nigel Mansell at the wheel. At around the same time, Lotus Engineering was beginning development of the engine and chassis of what would become the ZR-1 Corvette. In December 1985, Lotus was purchased by General Motors, and by 1987, GM had budgeted $27 million to develop Active Suspension for the ZR-1.

Built a fleet of 50 prototypes, only two remain

Ronald W. Cox, who was Manager of Advanced Body and Chassis Electronics for Delco Electronics in Kokomo, Indiana, wrote in the GM Next wiki: “Delco Electronics, a subsidiary of GM Hughes Electronics, provided CPC (Chevrolet-Pontiac-Canada) Engineering with prototype active suspension electronic control modules during 1986. In early 1987, CPC Engineering established a program to evaluate the technology by building a fleet of 50 active suspension Corvettes with the ZR-1 32-valve engine. Instrumentation for this program was initially proposed to be the vehicle qualified Buick Touchscreen CRT system developed for the 1986 model year Riviera and Reatta, but the vehicle engineers preferred to have the instrumentation on their new laptops. The required 50 units were delivered to the Bowling Green, Kentucky, assembly plant as required complete with software operating as specified.”

Over in F1, Lotus never fully came to grips with the technology, but the Williams team got it to work. By the 1993 season, the Williams cars were lapping nearly two seconds per lap faster than the non-Active competition. The advantage was so unfair, and the cost of developing the systems so high, that F1 banned Active Suspension for the ’94 season. Then a hydraulic failure on Alex Zanardi’s Lotus during the Belgian Grand Prix weekend caused such a horrific crash that the systems were gone by mid-1993.

3,000 psi system added weight, generated heat, sapped power

For all the benefits of Active Suspension, why didn’t it make it to the production ZR-1? During the media press preview for the 2009 ZR1 Corvette, one of the two remaining Active Corvette prototypes was on display. Harlan Charles, Corvette Product and Marketing Manager, explained that the system could consume over 25 horsepower in a hard turn, though only 3 hp was needed at rest. The hydraulic fluid, circulating at 3,000 psi, required extra heat exchangers and vents for cooling, while the added components brought the total weight of the Corvette to nearly 4,000 pounds. Those added components included aircraft-grade pumps and actuators, along with cutting-edge electronics, and the cost of Active Suspension on the ZR-1 was estimated at $35k–$40k. Service in the field would have been difficult, and the high-pressure hydraulics allowed no room for a mechanic’s error.

As is often the case with pioneering technology, lessons learned in the Active Corvette program were used a few years later. The F45 “Selective Real Time Damping” option introduced on the 1996 Corvette, while not a true active system, used sensor and digital signal processor technology developed on the Active Corvettes. And the F55 Magnetic Selective Ride Control option available since 2003 is an active suspension that uses a “smart” magneto-rheological fluid instead of high-pressure hydraulics to accomplish what the 1990 Active Corvettes attempted to do.

It seems Chevrolet built 50 or more Active Corvette prototypes, but only two remain. One car, EX5878, was displayed at Corvettes at Carlisle in 2007. CM reported on the sale of the other prototype, EX5881, in CM6, when it sold at Barrett-Jackson Scottsdale for $150,700 (p. 44). Yet here was EX5881 on the block again, just three months later. I’m not sure why it was auctioned a second time, but if the Active Corvette prototype was “a good buy on an important and unique engineering study” at $150k, at $66k it was an absolute bargain, at least for the buyer. And a major loss for the seller