There are two models initially?
Ruedisueli: Yes, the base car and the GTS. The GTS has different wheels and two suspension settings—street and race. And it has a Harman/Kardon stereo, an ultrasuede headliner, red brake calipers, different-color brake ducts, optional interior colors. This is the first time for electronic stability control on Vipers. There are four positions, and you can turn it all the way off. We took a stand on that. The lawyers left us alone. [Ed.: Note that the “off” position is available on all SRT products.]
Gilles: The stability control on this car will make gods out of the drivers. In fact, it’s so subtle and effective that I don’t want to flash a warning light. Drivers don’t need to know how often it’s working. To turn it off completely, you hold the button for five seconds below 25 mph. We can’t even say that in the owner’s manual. We’ll leave it to you guys to spread the word.
You’ve replaced the Michelins with Pirellis?
Ruedisueli: Yes, P Zero Corsas. Very strong at the track—18 inches in front [by 295/30] and 19 inches at the rear [by 355/30]. Pirelli has really opened the envelope. In Arizona, we drove into the hills and hit snow. The old tires would get hard when they were cold. With the Pirellis, I couldn’t believe the traction still available.
Describe the suspension.
Ruedisueli: All independent, with aluminum control arms. The front geometry is pretty much the same, apart from some steering tuning. A half-inch-wider front track. We’ve got new Bilstein shocks; spring rates are up quite a bit; and at the back, there are geometry changes. We altered the toe link because we had so much grip that we were getting some compliance steer. That improved the way the car points, improved its behavior under braking and acceleration. The brakes are the same size, but optional equipment is a cast-iron rotor with an aluminum hub. Matched to lightweight wheels, it takes out about 50 pounds.
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You’ve driven the car on tracks?
Ruedisueli: All over the place but mostly in the U.S.—at Texas MotorSport Ranch, which has good elevation changes, at GingerMan, Willow Springs. All SRT products do a 24-hour run at Nelson Ledges. And at Nissan’s course in Arizona. The Nissan track offers two lanes. On one side, there are chatter bumps and potholes, and on the other side, it’s smooth. You can really hammer this car. I’ve been racing formula cars for a long time, and I was amazed how much traction it offers.
Was there a car—perhaps the Corvette—that was a performance target?
Ruedisueli: Well, sure. But remember that the Viper will never be a Corvette. We don’t ever want it to be. Our customers are very anxious about this becoming a Corvette. The Viper is more raucous. Of course, we looked at the ZR1 because it’s so capable. We looked at some Porsche 911s and at the Lexus LFA to make sure we were in the performance ballpark.
What’s new in the engine?
Dick Winkles (chief engineer, Viper Powertrain): We have an airbox that feeds directly off that big main hood scoop. Then it leads to our new composite intake manifold, replacing the aluminum version. The approach angle to the ports is improved, and the runners are longer for high-speed tuning. The plenums have better distribution front to back. It’s very smooth on those inner walls compared with the cast aluminum. We got about 20 more lb-ft and 10 hp from the new manifold, and it’s also seven pounds lighter—weight that was previously up high. It doesn’t transfer heat like the aluminum one did. It keeps the charge cooler in stop-and-go driving. The final figures are 640 hp at 6150 rpm, with fuel shut-off at 6400 rpm. And 600 lb-ft of torque at 4950 rpm. [Ed.: An increase of 40 horses and 40 lb-ft.]
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| Bit Parts: 1. New composite intake manifold10 hp gained, seven pounds lost. 2. Forged pistons will better handle turbocharging. 3. Overall, the V-10 is 25 pounds lighter, with 40 newfound horses. 4. Revisions to the block and head gaskets lowered rear cylinder temperatures. 5. Sodium-filled exhaust valves (the smaller ones) replace stainless versions. 6. Mahle “cam in cam” has new intake profile, good for 10 hp. 7. New aluminum flywheel was worth 0.1 second at the drag strip. |
You have the same cam-in-cam arrangement with variable valve timing?
Winkles: The same, although we altered the intake profile. It gave us 10 hp at the higher end. Mahle makes that cam. I don’t know of any issues in the field with it in the past three years of production. I don’t know anyone else using a cam like that.
Did you consider cylinder deactivation?
Winkles: Not really. On a V-8 with even firing, you can kind of skip a cylinder. But this is more like two five-cylinder engines paired, so what you end up doing is cutting one whole bank. That cools the cats, and when they relight, it’s dirty.
You took weight out of the engine?
Winkles: We got 25 pounds out, in total. The intake was big, but we’re also now using an aluminum flywheel. It’s quickened shift times and is 11 pounds lighter. Then we went to sodium-filled exhaust valves rather than stainless. Those valves are hollow, a 10th of a pound lighter apiece. That’s one pound right there.
You’re back to forged pistons?
Winkles: The cast pistons weren’t quite robust enough if an owner added a supercharger or a turbo or if he was pumping nitrous. Those pistons weren’t indestructible. Se we heard the owners’ cries, and we’re back to forged Mahles. Now we can protect the tuners from their own mistakes. We’ve also got a lower-tension ring pack with lower friction.
Ruedisueli: With the new flywheel, the motor spins up faster—it was worth a 10th of a second at the drag strip. And the engine is offset toward the passenger to help weight distribution when only the driver is onboard—like on the track. Overall, it’s 49 percent front, 51 percent rear [with the driver in the car]. The base car should come in at 3320 pounds. We’re looking at an optional track pack that will take out another 40 pounds.
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