Review 2013 SRT VIPER GTS-R

INTRODUCING THE NEW  2013 SRT Viper GTS-R

Changes to the production 2013 Viper GTS enhance every part of the car. The chassis is the same in the GTS-R and the road-going Viper, in compliance with ALMS rules. The wheelbase of the GTS-R remains 99 inches as is it on the street-legal version of the Viper. The basic car looks the same for the most part, with changes to aerodynamics. Here are the major differences between the GTS and the GTS-R.

• Engine size is reduced to 8 Liters by changing cylinder bore and stroke
• Maximum engine size is 5.5 Liters, but the governing bodies allowed the 8-liter Viper V-10, requiring a restrictor in the engine’s intake tract
• A new intake manifold is created to work with the restrictor
• The engine will run on E-85 — 85% ethanol
• Transmission is moved to the rear of the car and will be sourced from Xtrac
• Dry weight of the car is reduced, with rules defining minimum weight as 1245 Kilos, 2740 lbs. dry
• A new roll cage is incorporated
• Bodywork is carbon fiber composite, with aerodynamic changes (body sides are lowered and front splitter/rear airfoil incorporated)
• New front and rear suspension systems designed to work with Michelin racing slicks
• Front and rear track increased
• Car has a climate-controlled cockpit, as required by the rules to keep the driver cool

STAYING IN SHAPE
Chrysler designer Alan Macey and other members of the SRT design group under Mark Trostle worked with Riley Technologies and SRT aerodynamicist Jeff Reece (a member of the original GTS-R team) to create the bodywork shapes that optimize performance while keeping the basic lines of the 2013 Viper.


"SRT wanted to keep the car looking as much as possible like the road car while incorporating the changes necessary for optimum performance on the track," said Bejnarowicz. "From my perspective it's probably the best integration I have ever seen - the sculpting design and the surfacing department interacting with the form and functionality of a race car. So it looks absolutely beautiful and the way everybody worked together was really pretty cool."
The engineering team started with the SRT Viper road car design and Riley morphed that shape to the Le Mans and ALMS rules for the permitted size of the car. By way of rules, GT cars can be slightly more than two meters wide. Thus the fenders were widened.


NEARLY IDENTICAL TWINS


There are also certain liberties allowed for the areas below the wheel centerline, and in front and behind the front and rear wheel centerlines. SRT and Riley engineers reshaped the car in those regions and gave it to the design office. The design team in turn surfaced everything, making sure all the design cues were correct. Last but not least, the race car was digitized and analyzed via Computational Fluid Dynamics (CFD).



"We've done a lot of CFD iterations to make sure that everything is working properly," said Bejnarowicz. "It's pretty important to Chrysler that the race car look as much like the street car as possible. We don't want a chopped-up street car look. But that's also important to the ACO - the Le Mans people - because the rules specifically say you can make all these changes, but they require that the car look as close to the street version as possible. I think the execution that has been done on this car is probably going to be one of the best out there on the race track."
"We had approval last December with our body shape and they commented how well we integrated everything - so far so good in that department," Bejnarowicz reported. "It is pretty cool to see Chrysler design go back and forth with a race car builders. The mentality in the design office is 'if it works well for a race car, it's cool from a design standpoint. The elegance is in the function. Every time they went through and cleaned up design surfaces, the aerodynamics also got better. The wind likes the same thing as the design office."


DESIGNED FOR ALMS AND LE MANS


On the engine side, SRT Chief Powertrain Engineer Richard Winkles will oversee the program with Roush Industries of Livonia, Michigan, SRT’s strategic partner. Le Mans and ALMS rules limit engine size to 5.5 liters, but SRT was not about to replace the vaunted Viper 8.4L V-10 with a smaller V8. The team approached rule makers and received permission to run an 8-liter version of the big overhead valve engine. To compensate for the size advantage, the engine is throttled back by means of an intake restrictor, just as GTS-R was in its previous life. The restrictor takes a big chunk out of Viper’s power curve, and it won’t let the engine run as fast. Nevertheless, Team Viper is confident that the car will be quite competitive.