The Viper ACR (American Club Racing) model was introduced in 1999, three years into the second generation of the sports car. Available only as a coupe, the ACR received a host of aerodynamic and mechanical enhancements developed for the track. A revised front bumper, a vented hood and a fixed rear wing were the main body highlights, while a stiffer, adjustable suspension improved its handling. Likewise, the 8.0-liter V-10 of the second-gen Viper had its output increased by 10 ponies to 460 horsepower for the ACR. Curb weight was reduced by more than 50 pounds. The third-gen Viper didn’t offer an ACR version, but the track-ready sports car returned in 2008 with even more updates. But unlike its predecessor, the new ACR didn’t have any engine modifications as the 8.4-liter V-10 kept its stock 600 horsepower and 560 pound-feet of torque. In 2011, a 2010 Viper ACR lapped the Nurburgring track in 7 minutes, 12.13 seconds. The sports car remains the sixth fastest production car on the "Green Hell" as of 2014. The 2010 model year was the last year for the ACR, but as we approach 2015, Dodge is showcasing an ACR Concept based on the fifth-generation model at the SEMA Show.