The American Club Racing (ACR) model was introduced in 1999. This model had suspension and engine enhancements focused on maximizing performance in road racing and autocross environments. Horsepower was, by the use of K&N air filters and smooth intake tubes, bumped to 460 hp (370 kW) in these models, while torque increased to 500 lb·ft (678 N·m). Weight was reduced by over 50 pounds (23 kg) by stripping the interior and removing other non-essential items such as the fog lamps (replacing them with brake ducts). The new stiffer, adjustable suspension removed another 14 pounds (6.4 kg) These models, which also have engine and handling modifications, has an “ACR” badge and 20-spoke BBS wheels.
A new ACR was added to the Viper line-up after the 2008 model year. Its upgrades were more drastic than the original, including street-legal racing tires, two-piece brake rotors, adjustable suspension, and significant aerodynamic revision. No engine modifications were made, so power and torque remain at 600 hp (450 kW) and 560 lb·ft (760 N·m) as in the base car. The ACR is street-legal, and is similar to the MOPAR Viper that Dodge displayed at various auto shows. Weight was also decreased by 80 lb (36 kg) by using the “Hardcore Package”, without radio, speakers, amplifier, trunk carpet, hood pad or tire-inflator. Its aerodynamic upgrades produce 1000 lbf (4.4 kN) of down-force at 150 mph (240 km/h), or roughly 10 times the downforce the base Viper SRT-10 can produce at the same speed. The interior was upgraded only by the addition of a beacon-tripped lap timer.
The Viper ACR was built alongside the standard SRT-10 at the Conner Avenue plant in Detroit. The aerodynamic components were produced and assembled to the vehicle by Prefix Corporation located in Rochester Hills, Michigan. source:Wikipedia.org
Even with the end of production this year, the Viper will live on thru die-cast, video games, collectors and motor sports enthusiast around the world.