Wednesday, June 29, 2011

2009 Dodge Viper

Dodge's answer to the Porsche 911 GT3 RS or Lotus Exige, a road car you can drive to the track, hot lap all day, and drive back home, tires, brakes, and ego intact. The Viper ACR is raw. It's wired. And it's probably the best weekend racer yet from Detroit.

The ACR has exactly the same power and torque as the regular Viper-600 horses and 560 pound-feet. The engine drives through a smaller dual plate clutch that reduces rotating inertia by 18 percent and the latest iteration of the Tremec T6060 six-speed that includes triple-cone synchros on first and second, and 10-percent-wider gears to manage the torque. The new GKN ViscoLok diff features its own sump to quicker generate the hydraulic pressure needed to actuate the limited-slip clutches faster, yet more progressively and with greater precision.

Most of the time, effort, and development dollars have been spent on stuff that makes the ACR go faster through the twisty bits-suspension, brakes, wheels and tires, and aerodynamics. Especially the aerodynamics. Just chew on this for a moment: At 150 mph, the regular Viper coupe generates 100 pounds of downforce; at the same speed, the Viper ACR generates 1000 pounds of downforce.

That giant carbon-fiber rear wing is the most obvious reason why. But there's also a new carbon-fiber front splitter that extends way back under the car and incorporates seven steps to diffuse the airflow. The new hood louvers unveiled with the 600-horsepower engine upgrade a year ago play a part, too. "We knew we were going to do a new ACR, so we moved the louvers forward to help change the aero balance of the car," says SRT boss Herb Helbig.

Suspension changes include race-style KW shocks all around that can be adjusted for stiffness and ride height, springs twice as stiff as those in a normal Viper, and a beefier front stabilizer bar. Forged "Sidewinder" alloy wheels save 30 pounds of unsprung weight, and new two-piece StopTech brake rotors save a further 30. Michelin Pilot Sport Cup tires-basically barely legal race rubber-are standard.

The standard ACR is 40 pounds lighter than the regular Viper coupe. An optional "Hard Core" pack saves an extra 40 pounds through the removal of the audio system, underhood silencer pad, trunk carpet, and tire inflator. The radio is replaced by a lightweight cover that can be configured to mount the lap timer that comes with the package. Hard-core, indeed.

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