A funny thing happened before my last drive of the day at Virginia International Raceway, site of the first drive of the fantastically focused and commendably rapid Viper ACR: the SRT team decided to make some quick aerodynamic adjustments to my test car. The idea was to give me a little more grip in the nose and a little more slide in the tail.It took about three minutes to reduce the angle of the monstrous semi-biplane rear wing and fuss with the carbon-fiber-and-aluminum front splitter.

Then, just for the hell of it, someone completely removed the bolt-in vents over the front wheels, allowing bystanders to view the 295-width Kumho V720 tires, engineered specifically for this car and this car only, through massive rectangular holes in each front fender.

"Be careful," one of the SRT honchos said as I nosed out onto VIR's main straight, "the car's going to behave differently now." And it truly did. There was less "push" in the nose, enough so that I turned in too far and chomped the inside of a curb heading for the track's famous Climbing Esses. And when I cranked hard right for the Oak Tree turn, the rear end stepped out in a way that had been previously prevented by the rear wing. The changes were worth about two seconds to me over the distance of VIR's challenging Grand Course layout.

Jack Baruth

It wasn't until I was packing to leave for the day that the full significance of those final laps hit me. After a decade racing and testing everything from Mazda Miatas to World Challenge McLarens, I don't find the idea of making a few aero changes in search of a faster lap terribly shocking.

In a purpose-built race car, that is.

This Viper ACR is not a purpose-built race car. but it behaves just like one in many ways. Let's see: there's the Extreme Aero Package, what SRT President Tim Kuniskis confidently calls "the most aggressive aerodynamic package ever put on a production vehicle." That includes a massive LeMans-style rear diffuser with rub strips to protect the carbon-fiber tunnels beneath the body.

Dodge

There's the fully-adjustable Bilstein suspension package that offers the same adjustments you'd get in a World Challenge car, all the way down to the ability to "corner balance" the Viper for differently-sized drivers. There's a new brake system with 390mm carbon-ceramic front rotors and six-piston front calipers. And there's a far-reaching program of interior weight savings that ditches everything from interior soundproofing to some of the cargo-compartment interior panels to nine of the Viper's standard twelve loudspeakers.

Dodge

All of that screams "race car." Yet my time behind the wheel of the ACR revealed this Maximum Viper to be far more than a quick-and-dirty chop job of the already outstanding Viper TA 2.0 that some of us (raises hand) thought should have been our 2014 Performance Car Of The Year. No privately-developed trackday special ever inspired this much confidence at speed. Start with the running gear. Erich Heuschele, a longtime SRT engineer and club racer, told me that his jaw dropped the day he got the call from the designers at Kumho. "Knowing how much grip we were getting from this tire, we thought it might be a 60 or 100 treadwear. It's 200 -- and unlike the tires on some competitive cars, it doesn't lose two seconds a lap after you heat it up a few times."

Just putting these tires on the current TA 2.0 would have made a big difference, but the ACR has been re-engineered to work them to their limits. The spring rates are more than double those found in the TA, there's additional camber available from the Bilsteins, and, of course, there's nearly one ton of real-world downforce at the aero-limited top speed of 177 miles per hour.

All of this has been engineered to work as a cohesive whole over the course of nearly two years worth of clandestine testing on multiple racetracks. "I can't believe we didn't get caught by someone," Heuschele laughed, "we were hiding in various race trailers and garages but sometimes we had to 'hide' in plain sight." Released into the sunlight at Virginia International Raceway, the ACR is unapologetically bold and brash, sporting double "dive planes" on each front corner and squatting at the just-over-four-inch minimum possible ride height. There's a subtle waving-checkered-flag pattern woven into the doorliners. The familiar 645-horsepower V-10 awakens with a roar through low-restriction exhaust tips, producing just a twinge of anxiety in anyone who has to operate it at full throttle down VIR's kinked front straight.

Jack Baruth

As always, the acceleration is shocking, a thrilling naturally-aspirated push that shrinks the gaps between corners just as reliably on the third hot lap as the first. No surprise; that's what Vipers have always done. The magic of the ACR is that finally someone has managed to come up with a chassis that feels equal to the demands of an 8.4-liter engine. All the balance between power and poise that makes a Miata or old BMW E30 such grand fun is replicated here on a grander, far more terrifying scale. The brakes are capable of pulling your tongue forward in your mouth every time you step on them. The tires stay sticky and the aerodynamic grip is evident at all speeds. You can trail-brake the ACR with abandon, slide the tail under power, make last-minute corrections as your mind recalibrates again and again to the car's seemingly unapproachable limits. It's impossible not to laugh, or at least smile, every minute you're on track.

Over and over, SRT's engineers emphasized the adjustability of the ACR, the ability to customize the ride height, corner weighting, suspension behavior, and aerodynamic load for each track. They explained to me that a trained driver can usually detect downforce changes once the changes result in the addition or subtraction of 20 "points" of downforce. "Points" are a racing-engineer term that translate, in a car the size, shape and speed of the Viper, to around one pound per point. Sure enough, I could easily tell the difference in the ACR's behavior after I lost some points in back and gained them in front. In the longer, faster turns, the nose bit harder on turn-in and there was more rotation from the back of the car.

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In the "Patriot" section of the course, with its low-speed blind turns, the Viper seemed more alive, more responsive. But when I got on the brakes hard from triple digits, there was some instability around the rear tires that wasn't present before. Nothing too worrisome, but it certainly had my attention the first time it happened. But the beauty of the ACR is that you can tune it to behave the way you want. If you're capable of driving a tail-happy drift machine, you can make it happen. If you want it to understeer with the security and consistency of a Volkswagen GTI, it's just a few minutes' worth of adjustment away.

Jack Baruth

Think of this as SRT's take on a Ferrari 458 Speciale. All

the virtues of the base car, plus a refined, casually vicious focus on laptime.

It's so good that it threatens to render every Viper ever built a mere

footnote. And the best part? If you want all the on-track capability with none

of the hardcore aesthetic, you can use the "1 of 1" program to load it back up

with everything from the Harmon-Kardon stereo to a quilted-leather console cover. Think of the

resulting Viper as the finest double-barrel African hunting gun ever built:

immensely powerful, thoroughly elegant, utterly personal, and requiring no

excuses or explanations whatsoever, to anyone.

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