Since the introduction of the Sixth-Gen Camaro in 2015, Chevrolet has steadily rolled out a number of special model designations. At the moment, the most potent offering in the Camaro arsenal is the recently announced ZL1 1LE, powered by the supercharged 6.2 LT4 V8 rated at 650 hp and 650 lb-ft of torque. With enhanced aerodynamics and handling the ZL1 1LE has bragging rights as the most track-capable production Camaro ever. Hot on the heels of that announcement, Chevy unveiled the purpose-built Camaro GT4.R racer, which has been homologated to global GT4 regulations. Developed by the SRO Motorsports group and sanctioned by the FIA, this class is structured around factory-built racecars that are available to the public, though not street legal.
GM has decided to take a page out of the Porsche Racing handbook and offer the Camaro GT4.R as a fully backed customer car program, which will allow them to compete with the likes of Porsche, McLaren, Aston Martin, BMW, Mercedes Benz, Audi, and the recently unveiled Shelby Mustang GT350-based GT4 racecar. Built on the Alpha platform. The GT4.R is about 200 lb lighter than the previous generation Camaro, and in race trim sheds another 700 lb. It requires only a few deviations for performance and safety, some of which are mandated by class rules. Pratt & Miller Engineering (P&M) was once again chosen as the development partner in this project. They were responsible for the fabrication of the Fifth-Gen Camaro Z/28.R racecar.
Rules require that body dimensions, shapes, and materials must remain original, so the stock hood and trunk lid, along with the front and rear bumpers, doors, fenders, and engine have to be used. A closer look at the rules shows that there is actually some wiggle room in the form of waivers for certain areas. Each manufacturer can request these waivers from the SRO Technical Department for changes they want to incorporate in their cars as part of the homologation process. The engineers at GM took advantage of these waivers and requested a number of material and mechanical alterations for the construction of the GT4.R. On the exterior, they were granted permission to replace the production doors with a set of quick-change carbon fiber units, and swap the factory front fascia with a carbon fiber piece. Beyond those changes, P&M starts with a production body-in-white and adds a FIA-approved roll cage, internally mounted pneumatic jacks, a fire suppression system, safety nets, a racing seat, a quick release steering wheel, and polycarbonate rear and side windows. The interior is textbook racecar with only the bare essentials fitted. As allowed by the rules, the driver will have within reach controls for ABS, traction control, and brake bias. The fuel filler location has also been moved from the right quarter panel to the rear trunk lid where it dumps into an FIA-approved fuel cell secured in the original tank location. Aerodynamic devices for the GT.4R consist of larger dive planes and a front splitter similar to what is found on the 1LE, along with a larger carbon fiber rear wing that pushes the rules to the limit.
Under the skin lies the biggest deviation from the road-going car. Instead of using the supercharged LT4 V8 from the ZL1, GM requested, and was given a waiver to use the naturally aspirated LT1 found in the Camaro SS. Shawn Meghar, Chevrolet’s Program Manager for the Camaro GT4.R explains, “We start with what is essentially a crate LT1. It’s an incredibly robust engine, so for us we really don’t have to do much to make this thing ready to go.” This engine choice serves two purposes, it reduces the additional complexity and weight that comes with the LT4 supercharger and also simplifies the reduction in power needed to achieve the mandated SRO Balance of Performance (BoP). The engines start life at GM’s Powertrain Performance and Racing Center, where engineers have cooked up a recipe that deletes the Active Fuel Management system (cylinder deactivation), and Cam Phasing. They also install a different camshaft that has been spec’d for road racing applications, and at the bottom end swap out the stock bearings with a set of Clevite H-Series rod and main bearings. This version of the LT1 also uses the dry sump oiling system found in the Corvette. Without a restrictor, The LT1 makes 480 hp, but we’ve been told that the adjusted power number will change depending on the track, so it isn’t a very accurate representation of the engine’s capabilities. Before each engine is shipped to P&M for installation, it gets broken-in and power-checked at the GM Global Propulsion Center.
Backing up the race-prepped LT1 is an Xtrac sequential six-speed transmission with pneumatic paddle shifters. As with the LT1, the use of a sequential transmission also required a waiver from the SRO Technical Department. At the rear, a limited-slip differential is also sourced from Xtrac. In terms of braking, the engineers went with a combination of the existing ZL1 four-piston fixed calipers at the rear, and larger Brembo six-piston units up front.
One of the biggest challenges when building a racecar to run on a global stage is to predict how it will handle with a variety of different tire brands. Having raced the previous generation Camaro in both the Pirelli World Challenge GTS class, and IMSA’s Continental Tire SportsCar Challenge GS Class, there was plenty of suspension data available to create a baseline for the GT4.R; however, the engineers were limited in what they could do because of the restrictions outlined in the rules. Items like the position of the suspension and the steering box anchoring points on the chassis must remain in their original location. Most of the components used are also required to be off-the-shelf OEM pieces. In terms of adjustability, the road car features lightweight dampers at all four corners. Mounted on adjustable camber plates, the front dampers also allow for front-end ride adjustments. These features were all eliminated on the racecar. Ride height is set in the homologation process as well as the use of springs. There are only three different sets of springs (front and rear) that are homologated. As part of that approval process GM was allowed to install two-way adjustable Öhlins Racing coil-overs. The other part of the handling equation comes down to the wheels. While the road car comes with 19×11-inch forged aluminum fronts, and 19×12-inch rears, the GT4.R includes Forgeline 18×10-inch fronts, and 18×11-inch rears.
All these different components make up the homologation packet that GM delivered to SRO for approval. Once approved, the technical aspects were locked in, and going forward teams are not allowed to make any modifications. The manufacturer can make small adjustments, which need to be approved by SRO, but then have to be implemented on every vehicle they’ve sold that is actively being used in competition.
At the moment a price hasn’t been established. Mark Kent, Chevrolet’s Director of Motorsports Competition, recently alluded that you might be able to walk into a dealership and place and order for a GT4.R, just like you can with a COPO Camaro. They’ve had plenty of tire kickers that have expressed an interest in buying a car, both for competition and as a collector item, but it is difficult to determine how many of those are actually serious inquiries at this point in time.
GM has stated that 2017 will be a development year for the Camaro with two teams doing the work. In Pirelli World Challenge, the Lincolnshire, IL based Blackdog Speedshop Racing team will compete with two cars in the GTS class. Team owner Tony Gaples will drive one car, while Lawson Aschenbach will pilot the other. In the IMSA Continental Tire SportsCar Challenge, the Jacksonville, NC based Stevenson Motorsports team will field one Camaro GT4.R in the GS class for drivers Matt Bell and Robin Liddell. Since the previous generation ran in both series, GM used both brands of tires in the development of the GT4.R. Also worth noting is that Aschenbach did the bulk of the development driving on this new car. Having driven the previous car in both series, we asked him about this new car. He states that, “From a driver’s perspective, the new GT4.R is a big step up in performance and drivability compared to the previous generation Camaro. It is much more refined, which allows the driver to focus all of his attention on racing. You’ll also become more precise because of the paddle shift function. The Camaro GT4.R has more stability due to the setup and aero development. That gives the driver more confidence when attacking brake zones and entering high speed corners. The setup development also improved the tire longevity – an issue we had with the Fifth-Gen car. Lastly, the power and tune of the LT1 gives you better response and feel. It has similar acceleration to the previous car, but now we’ve got the top speed necessary to create passing opportunities.”
The true test of any racecar ultimately depends on how it performs in competition, and how successful it is at the drop of the checkered flag. In early March, the crew at Blackdog Speedshop took delivery of their cars a few days prior to the opening round of the Pirelli World Challenge season in St. Petersburg, FL. Aschenbach validated the effort with a pole position and a pair of second-place finishes in both races. That success was followed up at Virginia International Raceway with a pair of third-place finishes, and the points lead in the driver’s championship. In the IMSA series, the Stevenson GT4.R also saw its first outing at the Continental Tire SportsCar Challenge race at the Circuit of the America’s. Matt Bell qualified the Camaro in the fifth spot, and Robin Liddell brought it to the checkered flag, also finishing fifth.
This performance straight out of the box indicates that Chevrolet has built a car that is both fast and reliable, which will be a key selling point once the cash register is set up for business.
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