Skies were overcast and conditions rainy at Daytona International Speedway early in February for the Rolex 24-hour endurance race, but the outlook for the Dodge Viper GTS-R -- Chrysler Corp.'s race-only version of the '96 Viper GTS Coupe -- is bright indeed.
Canaska/Southwind, the automaker's North American development team, put a new Viper GTS-R in the eighth position (out of 76) on the starting grid, finished seventh in the GTS1 class and 29th overall.
Viper GTS-R's appearance at Daytona is the start of an ongoing program putting the GTS-R up against the world's elite makes: global engineering on the racing circuit. At Daytona, Viper GTS-R shared the track and outperformed the likes of Callaway Corvette, Porsche 930 and Bugatti.
"I'm pretty enthusiastic about it," says Ken Nowak, GTS-R's senior product-development engineer. "There's a tremendous amount of potential in that car."
While the Viper GTS-R and its GTS Coupe relative look alike and share several components, that's where the similarities end. The GTS is restricted by federal highway safety and driver comfort requirements. The GTS-R is reined only by rules of the various race sanctioning organizations.
The GTS-R team -- a subset of the already small Team Viper -- engineered a lightweight body incorporating aerodynamic tweaks, while maintaining the Viper Coupe's unique shape. The team worked closely with Bicester, England-based Reynard Racing Cars, experts in composite technology, on the lightweight carbon-Kevlar fiber body.
"We specified the carbon for its stiffness and light weight," says Paul Owens, vice president of Reynard Composites and director of its race car-making group. "It's fairly easily formable compared to steel, and the modulus is high."
The weight saving is significant. The GTS-R's hood, for example, tips the scales at 28 lbs. (12.7 kg), compared with the production Viper's 65-lb. (29.4-kg) hood. Carbon fiber's strength allowed hood and rear fender inner panels to be eliminated.
A production Viper GTS Coupe's body is made of resin transfer molding (RTM) and the hood is sheet molded compound (SMC), Carbon fiber is molded in a high-pressure vacuum and is cured at 266[degrees]F (130[degrees]C).
Mr. Nowak says "very satisfactory" when asked how the GTS-R's body work held up during its first competition. "There was some scorching around the exhaust, but there were no failures of any kind."
Body molds were constructed using wind tunnel data taken from the most detailed 3/ 8-scale model ever made for Chrysler aerodynamic work. The model's underhood precision helped provide extremely accurate analysis of the crucial air flow through the engine compartment, says the automaker.
In addition to optimum air flow under the hood, wind-tunnel work helped shape an aerodynamically "cleaner" front end, side exhaust sill farings, various engine and brake inlet and cooling ducts, a large rear wing and undertray, which is designed to be easily adjusted for tuning the chassis for specific tracks.
Chrysler literature describes the Viper GTS-R's rear wing as a "carbon-fiber work of art." Although that sounds like a classic example of public relations puffery, Raynard's Mr. Owens says: "It was quite a sophisticated piece with some 3-D curvatures, which would have been difficult for anyone else to do."
The car's roof panel and windshield surround are integrated into a single carbon fiber/Kevlar-reinforced component, molded to allow clearance for the car's roll cage. Roll-cage tubes are recessed into the roof panel and A-pillars. Door inner panels, also of carbon-fiber, are molded to allow the side cage tubes to blend into the bodywork. This design gives the driver protection and interior space.
Carbon fiber isn't the only lightweight material used on the Viper GTS-R's exterior. Lexan, for example, replaces window glass throughout the car. And the side windows can be removed for sprint events.
By using these lightweight materials, GTS-R's total bodywork weight is 150 lbs. (68 kg) -- a 200-lb. (91-kg) reduction over stock. The complete vehicle weight is 2,750 lbs. (1,250 kg). A production Viper weighs in at 3,445 lbs. (1,563 kg). Couple that with 525 hp, 650+ hp and 700+ hp powerplants with aluminum cylinder block and heads, and you have a very fast machine.
Unlike carbon-fiber structures in aircraft and unlimited hydroplanes, the Viper GTS-R's body is not designed to absorb impact. It bolts onto the chassis, and if it contacts a racetrack wall, it'll break apart. The job of protecting the driver goes to the chassis/ roll cage.
The Viper GTS-R gets its next live test at the 12-hour race at Sebring March 16.
