The Viper SRT-10 ACR X is a more powerful, track only, limited edition variant of the Viper ACR produced at the end of the Generation IV Viper’s production run. The ACR X is powered by the same 8.4L V10 engine as all the generation IV Vipers but receives a power increase to 640 bhp (480 kW) and 605 lb⋅ft (820 N⋅m) of torque. The suspension is fully adjustable and sports higher spring rates that allow the chassis to maximize grip from the special 18-inch-front and 19-inch-rear Michelin racing slicks. Various aerodynamic enhancements, such as additional dive planes on the front fascia, provide up to 1100 pounds of downforce at 150 mph, or about 100 more than on the regular ACR. The X’s curb weight is claimed to be reduced by 120 lb (54 kg) compared with the standard ACR’s weight. The new total—about 3,200 lb (1,451 kg)—was mostly realized by thoroughly stripping out the interior. The dash board and the center console remain and an eight-point, SCCA-certified roll cage and fuel cell have been fitted, but the cabin is definitely sparse, with no side windows to roll down, a single racing seat and harness, and a removable Momo steering wheel. Other racing add-ons include a fire-suppression system, transmission and differential coolers, and larger front brake rotors fed by ducting that is more efficient than the street car’s. The X’s improved power-to-weight ratio improves acceleration by 1/10th of a second as compared to the ACR’s 3.4-second 0-to-60-mph time and enables the car to complete the quarter-mile in 11.8-seconds at 126 mph (203 km/h). The racing slicks help the car obliterate the street car’s 1.08 g of skidpad grip, but courtesy to the extreme drag generated by all the downforce-generating aero components, the top speed is reduced to 185 mph (298 km/h)

Brandon, Mississippi, United States