YOU’RE looking at 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.
While many modern supercars rely on sophisticated electronics to optimize their setups, like the Bugatti Veyron’s active aerodynamics or the Ferrari F430′s manettino, the ACR does it the way Carroll Shelby used to. Ride height, damper rates, aerodynamics are all fixed, but adjustable by hand. Our tester had been tweaked for the fast, sweeping big track at Willow Springs-the ride height had been dropped 28 mm (the shocks can be tweaked without removing the wheels) and the four-inch-deep removable center for the front splitter (so the car passes standard bumper offset laws and doesn’t headbutt every bump in the road) fitted to improve front-end downforce by a third.
The first thing you’ll notice about the ACR on the track is just how deceptively fast it is. It’s like a Le Mans racer that’s been to charm school: direct and precise, but without the clanging suspension, clonking brakes, and ear-splitting drivetrain whine. The big V-10 has so much torque, and such a linear delivery, that it barely seems to be raising a sweat. Yet on a flying lap you’ll easily see 150 mph on Willow’s relatively short front chute.
Nail the brakes, and the speed washes off rapidly. Pedal feel is terrific: firm, consistent, and easily modulated. Pull the steering wheel off center, and the nose dives for the apex. Just like that. No waiting, no delay. It’s like you’re hard-wired into the thing.
Squeeze on the power and feel the forces build. Feel, too, the aerodynamics squeezing the car down onto the track, keeping everything eerily calm. Helbig claims the wings ‘n’ things work from as low as 50 mph, and on fast sweepers the Viper engineers have seen a sustained 1.5g lateral grip. At 120 mph through Willow’s long Turn 8 the downforce was like a giant hand, settling the car over a mid-corner bump that has machinery like 911s and M3 CSLs feeling a bit squirrelly.
At $98,110, the Viper ACR is priced neatly between two of the best track-rats in the business, the new $65,815 Lotus Exige S 240 and the $124,060 Porsche 911 GT3 RS. It’s bigger and heavier than both, but it shares their utter commitment to steering and braking, corning grip and driver involvement. Bring on Sunday!