Viper ACR vs. Trans-Am Challenger: Hunt Race Cars With Your Street Car – Hot Rod Network

Day broke over Lake Michigan’s eastern shore, the late-winter March morning was all blues and grays. Clouds scurried reasonable from the Wonderful Lake, and merely a handful of miles inland at Gingerman Raceway, two snarling Mopar monitor monsters posed for glamour shots on the asphalt, still damp from early morning rain showers.

The shrill winds off the lake tested the Stevens-Miller Racing Trans-Am Collection group and HOT ROD testdriver Kevin Wesley. The Stevens-Miller crew toweled down their TA2-class Dodge Challenger sitting tail-to-tail along with our 2016 Dodge Viper ACR, the exact auto that set 13 production-auto monitor records and that Wesley will certainly pilot up the 2016 Pikes Peak Worldwide Hill Climb in the TA2 class this June.

Both cars cost in the reasonable 6 figures and their performance envelopes are fairly similar. The top speeds for both are about 180 mph and, as we discovered, they lay down comparable lap times at Gingerman. That aside, the differences are striking.
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The Race auto That Looks Like a Street Car
The TA2 Challenger uses a fiberglass physique atop a Howe Racing GT2 chassis, which is one of a handful of approved chassis in the SCCA’s TA2 class. Under the physique (the Trans-Am Collection outlaws carbon fiber as one of several cost-saving measures in TA2), the Challenger is mostly empty space along with merely the bare minimum to make it go, stop, and turn. At the end of a race, the auto ought to weigh 2,830 pounds along with driver.
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The Arrow Racing–built, fuel-injected, 385ci Hemi—which includes a dry-sump oil system and a C&R Racing water-to-oil heat exchanger—churns out concerning 500 hp. The engine channels its power through a Jerico four-speed dogbox and in to a Tiger quick-adjustment rearend along with 4.11 gears and a Torsen-style limited-slip differential. The Stevens-Miller crew has actually chased gear-ratio changes as small as 150 rpm at previous races to grab an advantage, which takes maybe 10 minutes, so that’s a relatively easy adjustment to make.
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StopTech four-piston calipers and iron rotors halt the Trans-Am cars along with the driver able to adjust front-to-rear brake bias from the cockpit. Ohlin dampers are the centerpiece of a suspension fully adjustable for camber, spring rates, damping, and roll-focus and rear-link adjustment on the rear durable axle. The auto sits on enormous Hoosier 27×10-15 bias-ply slicks, which will certainly be familiar if you’ve been about asphalt stock-auto racing. The aero setup is relatively simple along with a large ankle-chopping front splitter and an adjustable rear wing.

The brand-new SCCA TA2-spec engine control unit will certainly be utilized by the season’s third round at Watkins Glen Worldwide in could 2016, and while Trans-Am allows data logging and a digital dash—Stevens-Miller uses AIM for that—no real-time telemetry can easily be monitored from the pit wall. The cars are relatively easy to job on, and the Stevens-Miller crew can easily disassemble one of the Challengers to a bare chassis in a single 10-hour day. Numerous of the items on the auto are subject to cost-capping, and the group estimates the auto holds a price tag between $100,000 and $110,000 as raced.
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Howe will certainly deliver the chassis in various stages of assembly from a bare tubeframe ($41,415) to a turnkey race auto that can easily be optioned out north of $112,000. Stevens-Miller has actually opted for a middle ground in terms of assembly, which allows it to pick and go for the elements that make the auto most effective for them, and it’s worked as Cameron Lawrence won back-to-spine TA2 championships in 2013 and 2014 along with the auto and came a bad qualifying session away from a three-peat last season.
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The Street auto That’s Race-auto Fast
For the 2016 Dodge Viper ACR, the customization is considerably much more limited. This is a production road auto that has actually been artfully converted to a pavement-ripping monitor monster through three years of testing by Chrysler SRT engineer/testdriver Chris Winkler and veteran Chrysler SRT race-auto builder/developer Tom O’Dell. The pair worked out the kinks through at least four test mules prior to coming up along with a dynamite package based almost entirely on aerodynamic, brake, tire, and suspension upgrades.
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The most striking features of the ACR are undoubtedly the aero elements. The massive rear wing generates tremendous downforce that keeps the Viper’s rearend planted and allows the driver to grab on the power early devoid of having to fight the car. Dive planes adorn the front corners, generating front downforce from air channeled about the car’s nose via a huge front splitter. The extended splitter is section of the Extreme Aero package, a factory option intended for monitor use that you bolt on as quickly as you arrive at the track. The various other end of the package includes extended scimitar-shaped strakes for the rear diffuser that, you guessed it, likewise generate much more downforce.
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The suspension is double A-arm all around, however the big upgrade for the ACR are the two-way-adjustable Bilstein shocks on all four corners. The shocks can easily be adjusted for bump (blue knob) and rebound (red knob) travel and, owing to the gaping holes in the front fender to evacuate high-stress air neatly, the front Bilsteins are easily accessed and adjusted in mere seconds. The rears require a bit much more finagling, however a four-corner shock adjustment takes, at most, 5 minutes.
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Braking comes from massive Brembo calipers—six-piston units in the front and four-piston pieces in the rear—however the actual trick to the ACR’s stopping power comes from enormous carbon-ceramic brake rotors. Not only do the carbon rotors stop the auto rapidly, they likewise dissipate heat rapidly. Unfortunately, this means much more brake heat sinks in to the calipers, which calls for a special brake ducting to route cooling air directly to them.
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All of these items would certainly be moot devoid of good rubber contacting the ground, so Kumho specially designed massive versions of its Ecsta V720 for use along with the ACR. The big rubber—and we do mean big, along with 295/20R19 doing the turning and 355/30R19 placing down the power—fits over 19-inch wheels and were HOT ROD’s primary reason for this initial day of Viper testing ahead of Kevin Wesley’s entry at the 100th anniversary operating of the Pikes Peak Hill Climb. We required to know just what these tires would certainly do at the temperatures we’d see on the mountain.
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For all intents and purposes, the rest of the ACR, paint aside, remains the same as you’d locate on the rest of the Viper lineup: the same 645hp, 8.4L V10 and Tremec six-speed manual. The ACR even has actually the back-up camera and a USB port.
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Viper ACR vs. Trans-Am Challenger
After a couple idling laps to finish the photo shoot, both cars retired to the paddock. This wasn’t merely a senior-portrait session, though—these cars came to test in the blustery 45-degree conditions. For Wesley, it was a possibility to make acquaintance along with his 645hp chariot. prior to this, he has actually never turned a wheel in the ACR.
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For the assembled crew, which included the ACR’s technical caretaker O’Dell, the car’s transformation from street auto to monitor beast was minimal: bolt on the bigger monitor splitter and scimitar-shaped diffuser strakes, check tire pressures, and adjust the dampers as needed. That took concerning 30 minutes along with handtools, even though there was no hurry along with the damp monitor on the various other adverse of the Armco barrier.
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Across the pit wall, Stevens-Miller unloaded the final two of their three tubeframe Challengers, all of which wear classic Mopar colors: Sublime, Plum Crazy, and Bright Red. We’re only going to prove to you the Plum Crazy auto and point out that we only brought one ACR to the shootout.

The crew set to job on assembling the cars, switching out dampers, bleeding brakes, checking tires, and double-checking all of the suspension settings. The setup on all the cars takes some time due to the cars’ infinitely adjustable components, however purpose-built race cars make results, as this auto is capable of 1.76 lateral g.
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Louis-Phillippe Montour, fresh off a Fifth Place complete at Sebring in his first-ever Trans-Am race, turned over the Arrow Racing–built Hemi in the Challenger. The engine bellowed, and the sudden roar startled the unwary nearby. After a few seconds of throaty idle, the TA2 auto loped away up Gingerman’s pit road and onto the wet track, tearing the calm, misty air as Montour’s right foot met the firewall.
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Meanwhile, Wesley got a short talk-through of the auto and the monitor from the passenger seat along with Winkler—the Viper ACR’s chief testdriver and the holder of the aforementioned monitor records—in the driver seat. The soggy monitor offered little in the means of actual beneficial instruction, however a few minutes of feedback and chatting gave Wesley a durable foundation. Soon, he was attempting to manage the broad Kumho Ecsta tires on Gingerman’s damp surface, managing a 1:52 lap on a water-logged monitor and finding it endlessly entertaining to see the sticky Ecstas pick up everything—especially loafing worms—and fling them up through the wheel vents. After O’Dell softened up the rear shocks, Wesley knocked 4 seconds off his pace and then an additional 5 throughout the next 15 minutes as the monitor began drying out.
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Stevens-Miller run their own program and Chris Orr, a club racer that usually races BMWs, was testing out the Plum Crazy Challenger for the initial time on this day. The wet monitor caught your man off guard, and a run over the curb put your man off in to the wet grass, where the 2,800-pound muscle auto slid. Orr returned the auto to pit road along with a damaged splitter and—to the crew’s chagrin—tire-tossed worm guts plastering the engine bay. Race-auto crew life is hardly glamorous, even much less so on a rainy, 45-degree day along with worm-gut cleaning suddenly added to the maintenance list.

Lunch paused the testing for a short time, and while the small cadre of individuals at Gingerman ate, the sun finally poked through the clouds and the monitor dried out. The wind, however, did not abate.
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100th Pikes Peak Pre-Run
The whole purpose for Wesley operating in March was to test most likely tire conditions at Pikes Peak, where the racing starts at 9,000 feet, so 45 degrees along with some dampness and stiff winds is exactly just what he was looking for. Winkler’s lap tape-record for Gingerman stands at 1:31.9, which was set on a warmer, drier, sunnier day. Wesley reckoned there was a 1:33.9 in the auto on this blustery day.
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On the dry track, the ACR looked absolutely composed. The car’s attitude constantly perfectly steady entering the corner and in its middle prior to it exploded toward the starter stand halfway down the front straight. Testdriver and veteran racer Winkler compared it to a much different racing animal.

“along with the power-to-weight ratio and the aero, it drives much more like a Formula Ford compared to an actual Viper,” Winkler said. “It’s incredible driving the same lines as I did in Formula Ford 14 years ago.”

From the same vantage point, Montour’s Challenger skated about on corner exits as he gave it throttle. The bias-ply Hoosier tires took a moment to settle and locate the grip, letting the tail end hang out luridly until the slicks grabbed. as quickly as they did, the beastly TA2 auto settled onto its haunches and reared spine like a drag car.
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The Challenger braked long prior to Wesley even had to think of the Viper’s middle pedal—that’s exactly how good the Viper’s carbon-ceramic brakes are. Like Numerous various other sections of the TA2 car, the Challenger’s cost-controlled iron rotors maintain the formula affordable. Wesley only triggered the Viper’s ABS system—which the Challenger does not have actually at all—a couple times and didn’t locate it a nuisance. He drove devoid of traction or stability controls “on”—points the Challenger doesn’t have—and found the auto perfectly compliant.
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The straight-line speeds of the two cars seemed comparable, even though the sensation of speed differed greatly as quickly as accompanied by the engines’ respective sounds. The Viper’s V10 may as well have actually been silent compared to the Challenger’s V8 roar. Rapid Hemi downshifts seemed to drown out the shrieking winds momentarily, and while the ACR noise was audible as Wesley throttled it, the distinctive V10 was probably not collapsing any groundhog tunnels two counties away like the Challengers seem to be.

Interestingly, Stevens-Miller driver Montour had his own Viper ACR delivered to his local Dodge dealership in Quebec while he was at our Gingerman test. throughout a lull, he got a walkaround from O’Dell and a possibility to turn a few laps. He’s no stranger to Vipers: Montour is the 2013 NARRA Viper Mug Champion and has actually raced in the V10 beasts since 2011, including the strange hot lap in one of Riley Motorsports’ Le Mans–spec Vipers.

“[The ACR] drives much more like a GT3-spec car,” Montour said. “The aero is actually amazing. It’s easy to drive and forgiving.”

And the TA2 Challenger?

“This is actually pure driving: No ABS, no traction control, no stability control,” Montour said. “It’s a lot of fun.”

Lap Times: that Wins?
So exactly how did lap times actually compare? As it was a test day, outright lap times weren’t actually a cause of concern for either the Stevens-Miller group or Wesley and O’Dell. That said, Montour still clocked a 1:31.9 in a Challenger, which is thoroughly quick for contending along with sturdy crosswinds on the longest straight. The group said that two-time TA2 champion Cameron Lawrence—that is signed up to coach Montour at a handful of Trans-Am rounds—ran a 1:30.0 at Gingerman last year, so that’s a minimal time delta, offered the conditions.

For Wesley, he worked hard and learned fast to grab the Viper ACR to a 1:34.1 after a number of incremental shock adjustments, a tire change, and then much more shock adjustments. For a day along with challenging weather conditions, operating merely 2.2 seconds off the Viper ACR’s outright lap tape-record at Gingerman isn’t too bad.

Especially considering the previous lap tape-record for a production auto here was 1:35.3.
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Spec For Spec: ACR vs. Trans-Am
 Dodge Viper ACRDodge Challenger TA2
ChassisSteel and aluminum unibodyHowe GT-2 tubeframe
BodyAluminum and carbon fiberFiberglass
Engine8.4L (513ci) Dodge V10
(4.055-inch bore, 3.96-inch stroke)
Arrow Racing 385ci (6.3L) Hemi V8 (4.055-inch bore, 3.720-inch stroke), along with SCCA-spec crank. Fuel-injection and spec ECU.
Engine output645 hp, 600 lb-ft torque500 hp, 450 lb-ft of torque (restricted)
TransmissionTremec six-speedJerico four-speed
ClutchTwin-discTilton twin-disc
Curb weight3,374 pounds2,830 pounds (minimum competition weight along with driver)
Weight distribution50/5052/48
RearendDana Super 44, 3.55 gears, GKN ViscoLok limited-slip differentialTiger quick-change, 4.11 gears, Torsen limited-slip differential
0-60 time3.5 secondsQuicker compared to 4.0 seconds (estimated)
Top speed177 mph181 mph at Daytona
Lateral acceleration1.5 G1.76 G
Best ever lap time at Gingerman Raceway1:31.91:30.0
Best time throughout cold-weather testing1:34.11:31.9
Front suspensionDouble A-arm along with two-way-adjustable Bilstein dampers.Double A-arm along with adjustable Ohlin dampers and Hyperco Springs. Geometry fully adjustable for camber, spring rates, damping, roll-center.
Rear suspenionDouble A-arm along with two-way-adjustable Bilstein dampersLive-axle along with three-link suspension
BrakesBrembo 15.4×1.3-inch (front) and 14.2×1.25-inch (rear) carbon-ceramic rotors. Brembo six-piston (front) and four-piston (rear) calipers. Brembo CCM-compound brake pads.StopTech 13-3/16-inch (front) and 11-11/16-inch (rear) iron rotors. StopTech four-piston calipers on all corners. Pagid RS brake pads.
Tires295/20R19 (front) and (355/30R19) Kumho Ecsta V720Hoosier 27×10-15 bias-ply slicks
AerodynamicsFront splitter and rear diffuser extensions. Front dive planes, adjustable rear wing.Front splitter, adjustable rear wing.
SafetyFour-point rollbar (to be upgraded to PPIHC safety requirements). Fire-suppression system.Full rollcage, containment seat, adverse nets, fire-suppression system, 24-gallon fuel cell.
Other AIM digital dash and data logging system.
Base price$118,795Howe chassis deliverable from $41,415 for an unassembled chassis kit to $112,000 for an assembled, optioned-out race car
As-tested price$135,190$100,000-$110,000 (estimated)