Corvette C8.R gets new 500-horsepower 5.5-liter DOHC flat-plane V-8
Our ears didn’t deceive us. When we finally got our chance to hear the C8.R fire up in person for the first time, we knew we heard a naturally aspirated V-8. We were thrown off by the lack of the typical thunderous exhaust note we’ve come to associate with Vettes, even those of the racing ilk. Even with some of the variables accounted for, there were still plenty of questions left unanswered, which is why we speculated on how the C8.R manages to sound like no other Corvette.
Chevrolet is confirming that its successful Corvette endurance racing team will continue to use a 5.5-liter naturally aspirated V-8 with direct-injection, but it’s moving to a flat-plane crankshaft and DOHC architecture. It’s the first Corvette without pushrods since the LT5-powered ZR1 left production in 1996 and likely previews future production C8 performance variants.
It’s a big deal that Chevy is leaving behind the pushrod, 16-valve small-block that’s powered Corvette Racing to class wins more than 100 times since the C5.R debuted in 1999. The new engine shares some parts with Cadillac’s twin-turbocharged Blackwing V-8, but rather than the Blackwing’s hot-V design that puts twin turbochargers in the valley between the cylinder heads, the Corvette’s DOHC powerplant utilizes unique heads that place the intake ports in the valley, just like every other Corvette V-8.
What’s decidedly new is the flat-plane crankshaft. A flat-plane crankshaft V-8 alternates the firing order from one cylinder bank to the other so that each exhaust collector gets a pulse every 180-degrees of engine rotation. The even spacing amplifies exhaust scavenging, therefore helping boost engine efficiency. It also gives a distinctive sound compared to a cross-plane V-8 that’s common with larger displacement engines. Speaking of displacement, at 5.5 liters, this V-8—as yet unnamed by Chevrolet—is larger than any other production flat-plane crank V-8 currently in existence. It’s solid-mounted in the C8.R’s chassis.
In race trim, Chevrolet says the engine makes 500 horsepower and 480 ft-lb. of torque, quite close to the production 6.2-liter LT2’s 495 horsepower and 470 ft-lb. output in the 2020 Stingray.
With no need for mild street manners or restrictive exhaust, the C8.R can go wild with the cam specs and push the torque curve up the RPM range. This powerband shift helps make up for the loss in displacement compared to the Stingray’s LT2 by spinning faster and maximizing the airflow the heads have to offer. There’s no doubt that an unrestricted race engine would have no problem making far more than 500 horsepower. However, Grand Touring Le Mans (GTLM) rules require the C8.R, like all competitors, to breathe through a restrictor that limits the airflow into the engine that’s determined by IMSA in an effort to balance performance between varying engine designs and displacements.
It wasn’t just engine details that Chevrolet released, though. We got some more tidbits about the rest of the C8.R’s development and specs. We learned that the C8.R will use a six-speed sequential transaxle from Xtrac. It’s more compact than the eight-speed dual-clutch in the production C8 and leaves more room for the huge rear diffuser that helps suck the race car down to the track.
Every C8.R begins with the same aluminum chassis that’s used in the production Stingray, and the race car is also built at the Bowling Green Assembly plant. Designed from its inception to be a targa or convertible, the C8’s chassis is both lighter and more rigid than the C7’s, giving the C8.R team a head start when turning the production chassis into an LM GTE racer. In fact, while there are some significant differences, the C8.R uses more production parts than any of its .R-spec racing predecessors.
The C8.R was designed simultaneously with the production C8 Stingray and thousands of parts used in the C8.R’s chassis and aerodynamics package were rapid prototyped and wind tunnel tested to make the most of the C8’s lower center of gravity and improved weight distribution. The racer’s new chassis also demanded new tires, so the Corvette team worked with Michelin to develop special Michelin Pilot Sport GT competition tires for the C8.R’s 18-inch wheels.
Corvette Racing first showed off the #4 car that uses a predominantly silver livery with yellow accents. It’s an homage to Corvette’s racing heritage and a nod to the 1973 Chevrolet Aerovette and 1959 Corvette Stingray Racer. The #3 car, which was first shown at Atlanta Motor Speedway during this week’s Petit Le Mans race keeps the traditional yellow livery we’ve come to know and love from team Corvette.
After its brief public appearance at Petit Le Mans, the C8.R will make its official race debut at the 24 Hours of Daytona on January 25-26, 2020 where it will compete on the world stage. Here’s to a good showing for Corvette Racing’s first production-based mid-engine cars as they make their way to Daytona and Le Mans. Viva la V-8!