Viper SRT-10
For 2008, the Viper received a 90 hp (67 kW) bump up to 600 hp (450 kW), a 25 ft·lbf (34 N·m) torque bump up to 560 ft·lbf (759 N·m) and the engine displacement increased up to 8.4 liters (510 ci/8354 cc) from 8.3, also receiving better flowing heads with larger valves, variable valve timing on the exhaust cam, and dual throttle bodies. The development of the engine was done with help from McLaren Automotive and Ricardo Consulting Engineers. Changes outside of the powerplant are minimal, but still influential. The T56 transmission has been replaced with the new Tremec TR6060, and a revised shifter has been paired with the new gearbox. Shifts are claimed to be 18% quicker than Chevrolet's Corvette Z06. The Dana M44-4 rear axle from the 2003 model now has a GKN ViscoLok speed-sensing limited-slip differential that greatly helps the tires in getting grip under acceleration. One last performance upgrade was the removal of run-flat tires; the new tires have increased driver feedback as well as grip and, along with revised suspension, has made the Viper more nuetral in cornering. Another notable change is the reworking of the exhaust system, previous third generation Vipers had their exhaust crossover under the seats which resulted in a large amount of heat going into the cockpit, this was done initially to help improve the cars exhaust note, since the first 2 generations of Viper, which had no crossover, were criticised for their lackluster exhaust notes. For 2008, the Viper exhaust will utilize a new exhaust system with no crossover, reducing the heat that enters the cockpit, but still produces an exotic sound. Recently the car and got a 0-100 kph time of 3.5 seconds, and a Quarter Mile-time of 11.6 seconds at 203 km/h. Car and Driver also tested the Viper's track performance, and managed a fast sub 3 minute lap time around Virginia International Raceway. The Viper's time, despite hot weather, was faster than the Corvette Z06, Ford GT, Porsche 911 Turbo and 911 GT3, Audi R8, and other such cars. According to Car and Driver and Motortrend, the car's slightly adjusted suspension setup and new diff gave it cornering ability as sharp as before with even better control, feedback, and response.
The 2008 model also sees the return of the Viper ACR. The Viper SRT-10 ACR features track based upgrades, such as functional aerodynamic additions, adjustable suspension, racing brakes, and Michilin Pilot Sport Cup tires. Weight is also decreased by as much as 80 lb (36 kg) by way of the "Hardcore Package" which deletes radio, speakers, amplifier, trunk carpet, hood pad and tire inflater. The weight loss is not a lot considering the base Viper's 3460 lb (1569 kg) weight, but it is enough to make a difference in performance. The ACR should be one of the fastest street cars availble upon its 2008 release. Its aerodynamic upgrades produce 1000 lb (500 kg) of downforce at 150 mph (240 km/h) which will greatly effect cornering along with the new tires and modified suspension. Braking distance should be just as impressive thanks to slotted two piece StopTech rotors, for comparison the 03 Viper was capable of stopping from 100 mph (160 km/h) in 274 ft (84 m) on run flat tires. Although the ACR is street legal, it is clearly meant for track use. No upgrades were given to the interior except for a lap timer.
