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Thursday, September 11, 2008

Viper ACR is Dead Serious- what Chuck Yeager Would Drive

words: Bryan Joslin

It's not so much what you make that counts, but rather what you keep. That's what my rich friends tell me, anyway. And while that statement is certainly true of personal finance, it also holds up remarkably well as a mantra for the racetrack, where speed is the currency of choice. A great example of this philosophy is the 2008 Dodge Viper ACR, which makes not one single horsepower more than any other current Viper, but is virtually guaranteed to turn a faster lap.

The Viper ACR is the latest beast to roll out of Chrysler's SRT performance division, and the extra letters stand for American Club Racer. In other words, it's meant for track duty. Weight has been removed, critical chassis hardware has been upgraded, and some very serious aero bits have been applied. The ACR is dead serious — this one's not for lottery-rich poseurs.

To get a sense of how the ACR improves on the standard Viper SRT10, the Dodge folks sent a couple of SRT engineers to meet us at GingerMan Raceway in South Haven, Michigan. In fact, they insisted on bringing it to the track, because to drive it on the street alone would have been unfair to their efforts. That, and we may have ended up peeling off some of the carbon-fiber splitter.


The ACR gets its power from the same 600-horsepower, 560-lb-ft, naturally aspirated V-10 found in any other 2008 Viper, mated to the same six-speed Tremec gearbox. It's lighter on its feet partly because 40 pounds of total weight have been shed, but also because rotational mass has been removed from the clutch, the wheels, and the brakes. The standard single-plate clutch is gone in favor of a smaller-diameter dual-plate assembly that trims rotational inertia by 18 percent, sending more of the torque and power downstream. Forged alloy wheels reduce unsprung weight by 30 pounds, and StopTech two-piece brake rotors under each wheel result in the same pruning. For those who wish to put their ACR on a further diet, a "Hard Core" option exists, dropping another 40 pounds worth of stereo equipment, sound insulation, and trunk carpet. Air conditioning is still standard though, and it won't take long to appreciate that once you realize every lap in a Viper is a hot lap.


Controlling the 3400-pound coupe is a set of adjustable springs and dampers from KW Suspension. The coilover setup allows the ride height to be dialed in, and the shocks can be fine-tuned for both compression and rebound without removing wheels. Working with the race-tuned suspension is the most serious set of street rubber you can buy — Michelin Pilot Sport Cup tires are fitted as standard, delivering unmatched grip, especially once they have a little heat in them.

All of this special equipment is largely buried underneath the Viper's slippery skin. In plain view are all the aerodynamic pieces that endow the ACR with pavement-gripping downforce. The large adjustable carbon-fiber rear wing is most obvious, and it is aided by a carbon-fiber front splitter and a pair of carbon "dive planes" at each front corner. The result: At 150 mph, the ACR generates 1000 pounds of downforce, compared to the meager 150 pounds of a regular Viper coupe. That means serious stability at higher speeds, especially when braking hard, even if it shaves ten percent off the SRT10's 200 mph top speed.

At GingerMan, we're eager to see if the ACR would live up to its promises or if it is just a SEMA-show parts-bin project. Our concerns are quickly allayed, at least once the tires warm up. The cold tires are a quick reminder that the Viper is not for the timid, with its complete lack of traction or stability control. It takes about five laps before the Michelins start to play nice, doling out just a bit more bite with each successive lap up to that point. Once they're hot, they stick like a felony conviction.

acr3_center.jpg It takes several additional laps before we find our faith in the limits of the car, eventually trusting the brakes deeper and deeper into the corners. Perhaps the most exciting part was exploring the limits of trail braking, which, because of the aero effect, was simply mind-blowing. Even at speeds as low as 60 mph, the effect of the wind planting the car to the asphalt was hard for us to get our heads around. On the back straight, we reached 130 before crushing the brake pedal, a move that should have resulted in all kinds of tail dancing. Instead, the nose stayed straight and the rear end followed dutifully until we eased to the right at a speed that didn't seem possible. The suspension setup no doubt helps here as well. Because the dampers can be dialed in for specific conditions-and we had SRT engineers finessing the settings for us-the ACR transitions into corners more gracefully than the car on which it's based. Smooth, linear inputs, as opposed to quick jerks of the wheel, are rewarded with a response so natural it borders on telepathic.

Without driving the two back-to-back, it's hard to get a sense of how much quicker the ACR might accelerate, because even the "standard" Viper SRT10 is so damn fast. It's a brute, and a genuine challenge to drive fast, even with all the help from superior hardware. As one of our SRT friends so eloquently put it, "It's still a Viper; it'll fuckin' bite you if you don't respect it!" And therein lies the ACR's genuine appeal. Because it's such a pure, undiluted mechanical experience, you know at the end of a track day that you've not only shaved a couple tenths off of your lap time with each pass; you've actually come one step closer to mastering the machine.

At the track, the Viper ACR takes the focus off of the power and allows a committed driver to concentrate on getting faster by preserving as much speed as possible. If you need further proof of how serious the ACR is about going fast, consider that it now holds the production-car record at the Nurburgring, laying down an official time of 7:22.1. With a window sticker just shy of a hundred grand, you won't find another hard-edged, 600-horsepower sports car that lets you keep more of what you've already made.


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