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global vehicles global vehicles Viper Coupe nears competition When the Chrysler Group developed championship, rather than on its more the latest edition of its Viper sports car, a obscure—though popular with Viper tight budget meant that, while the owners—Viper sports car racing pro- previous generation was offered in both gram, an end to factory-backed Viper coupe and convertible configurations, racing seemed near. However, by the the new version arrived in roadster form time the decision to kill the racing only. Because convertibles are not as program came, the engineering team good for racing, and a lot of Viper was only five weeks away from con- enthusiasts like to race their cars, structing a prototype based on computer demand remained for a coupe, even if it designs. Stopping the program in its was for track use only. With its racing tracks was not an option. budget concentrated on winning With Viper enthusiasts—in the form NASCAR’s high-profile Winston Cup of Viper Owners of America president Tony Estes—clamoring for a coupe they could use for racing, Chrysler racing boss John Fernandez decided to use the designs and remaining funding to build a limited-production racing-only coupe for customers. The fixed-roof version of the car not only enjoys better aerodynamics for racing than the convertible, it is far stronger. Though based on the same frame as the convertible, the coupe’s additional bracing and roll cage increase torsional rigidity 200% and bending stiffness by 60%. The metal roof is also safer in a crash. The company has taken orders for 62 Viper Competition Coupes, at $100,000 each for the first 32, and $118,000 for A large X-brace over the engine contributes to the Viper Competition the second batch of 30 cars. All of the Coupe’s 200% torsional-stiffness and 60% bending-stiffness increases cars that have been ordered should be in compared to the street-going Viper. customer hands this summer. The fee may seem high, but the Viper Competi- tion Coupe is a bargain by racing standards because it is loaded with critical racing-grade equipment from a variety of suppliers and is the fruit of DaimlerChrysler’s considerable engineering capability. The car that media had the opportu- nity to test at Firebird International Raceway in Phoenix differs in significant details from the concept car highlighted in AEI previously. That is because the concept car was sketched by stylists, while the shape of the production Coupe was set by engineers using a moving- Considerable time in a moving-ground-plane wind tunnel ground-plane wind tunnel in Stuttgart, and with CFD modeling went into developing the Coupe’s splitter and front fascia for maximum downforce and Germany, and the company’s computa- brake/engine cooling. tional fluid dynamics (CFD) system. 8 JULY 2003 aei 307gvkja(0) 8 6/20/03, 3:05 PM global vehicles The rear diffuser under the tail of the the market,” Fernandez said. The switch from Michelin to Hoosier racing concept car has been significantly toned extremely rigid carbon-fiber Racetech slicks: 305/35ZR18 in front and 345/ down because air passing by it pulled seat is carefully designed to withstand 30ZR18 rear. away from the top surface, spoiling its the load of restraining the driver’s head The Coupe’s suspension is mounted effectiveness. The concept’s rear wing and upper body from moving to the side more directly to the chassis using was mounted by its outer edges, but in the event of a crash. “It is hard to spherical instead of rubber bushings. bent in the middle in use. The produc- build a seat that doesn’t bend away at Thicker antiroll bars replace the street tion version mounts the wing more the head and at the shoulders,” ob- car’s bars, and the ends are adjustable conventionally, with struts placed closer served Eric Peterson, Senior Motorsports on the Coupe so drivers can set them to together to better support the middle Development Engineer. The seat was match track conditions. Stiffer springs section. The production wing is also specifically designed to accommodate and double-adjustable (with settings for adjustable, so racers can trim it to suit the HANS neck-protection device. both compression and rebound damp- ing) Moton monotube gas shocks complete the suspension changes. The Coupe feels much stiffer and more responsive on the track. Brembo four-piston brake calipers are carried over from the production car, but significant development work went into finding the right compound for the The Motec data Mintex brake pads. The team wanted a acquisition system durable compound so owners would provides a critical not be saddled with constant mainte- tool for sorting nance. The trick was to find a compound both the car and the driver’s that maintains consistent friction technique in throughout its operating temperature competition for range, said Peterson. The problem was maximum performance. that many compounds lose friction as they heat up, giving the impression of conditions. CFD analysis showed that the Another component for restraining brake fade as additional pedal pressure concept wing was shrouded by the the driver’s lateral movement is the is needed to maintain braking force. Coupe’s greenhouse at racing speed, center net, which is simply a nylon net as Under maximum braking the Coupe’s reducing its effectiveness, so the new is commonly used to cover windows in pedal provides good feedback and wing juts out farther on each side. Vents racecars, running longitudinally through the ABS helps maintain stability by in the rear fascia draw air from under the cockpit to the driver’s right. In a automatically balancing front and rear the car, also improving downforce. right-side impact, it helps keep the driver braking power. At the other end of the car, the side in the protected area of the left side of The Motec electronic instrument gills curve deeper into the fender than the car. panel and data acquisition system lets on the concept car to evacuate more air Changes to the Coupe’s engine are the driver monitor the car’s condition from around the front tires. Front air minimal, with only a different camshaft and check on performance during each intakes have moved to higher velocity and engine management computer track session by downloading data into a zones on the front fascia, and hood programming, along with a smaller laptop computer. The system monitors vents are farther forward. accessory drive pulley to cut parasitic parameters such as throttle position, Most of the Coupe’s bodywork is losses. The engine carries a lightened engine and vehicle speed, lateral lightweight carbon fiber. Pre-impreg- flywheel for snappier throttle response, acceleration, and brake application. nated carbon fiber is autoclaved for use and the otherwise stock Tremec T-56 six- Additional features are built into the in any high-heat areas of the car, and the speed gearbox has a low-friction coating system and can be activated for a fee rest is laid up conventionally. applied to the shift forks to reduce shift with a phone call to the manufacturer Significant effort also went into effort. The improvement was noticeable for the access codes. maximizing the safety. “I have two while testing the Coupe. The corporate-backed development engineers, who, all they do is safety,” A larger oil cooler upgrades engine created a polished, well-executed said Fernandez. They work on racecars in cooling, and a cooler and an electric machine that would be difficult to all series in which the company com- pump are added to the transmission. A duplicate at anywhere near the Viper’s petes, and that has brought benefits to Ricardo speed-sensing viscous limited price. However, that does not mean that the Viper program. “A lot of what we’ve slip differential helps the driver put the project is an image-building money- done here has come out of our NASCAR power to the ground, and the car rides loser for the company. On the contrary, program,” he said. on 18-in BBS three-piece aluminum alloy Chrysler makes a profit on the Coupes. “We’ve designed a seat with better wheels. A change from the concept car Dan Carney lateral support than all of the seats on and most previous racing Vipers is a 10 JULY 2003 aei 307gvkja(0) 10 6/20/03, 3:05 PM Hundreds of Tests, One Test Driver The Automotive Test Platform National Instruments offers you a customizable test platform for your unique automotive test needs. 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Fax: (512) 683-9300 • [email protected] Circle 211 307gvkja(0) 11 6/20/03, 3:05 PM global vehicles Smart engineers two roadsters Production of Smart’s new two-seat roadster and roadster-coupe is now under way at its Hambach, France, factory in a separate building from that of the company’s city coupe and derivatives.