2020 C8 Chevy Corvette spins up an eye-popping mystery on the dyno

The intrigue around the 2020 Chevrolet Corvette isn’t close to ending. Motor Trend secured a pre-production build of America’s sports car for two weeks of testing, including a trial at the Hyundai-Kia proving grounds for MT’s Car of the Year roundup. It was treated like a priceless museum exhibit on loan: MT staffers kept the Corvette throughout the day, then returned the coupe to Chevy’s PR team every night. The day before handing the car back to Chevy for good, the magazine wanted to run a real-mpg test, but the testing company didn’t have equipment to deal with square tailpipes. So MT took the red Z51 coupe to its local, oft-used dyno for what would turn out to be six confounding runs. The numbers after the first run in fifth gear run: 558 horsepower and 515 pound-feet of torque. At the wheels.

Assuming parasitic driveline losses of 15% would mean the Corvette was putting out around 656 hp and 606 lb-ft at the crank. If we assume a 10% loss, the crank figures come to about 620 hp and 570 lb-ft. Either set represents a shocking surplus over the Corvette’s official rating 495 hp and 470 lb-ft. And the official rating isn’t Chevy putting its best foot forward — GM pays to have the Society of Automotive Engineers (SAE) certify its output figures using the SAE’s strict protocols.

Having been thrown this stumper, MT personnel tried to sleuth it out. They called their road test editor. They called Chevrolet engineers. Their technical editor did some math. They put a 2020 Ram 2500 diesel on the dyno as a control vehicle. They spoke to Chevy engineers again and got revised gear ratios taking the limited-slip differential into account. They got explanations from those engineers about what might be happening. They performed five more runs, two of them in sixth gear even though fifth gear was the closest to a 1:1 ratio. The lowest figures came during run number five, posting 478 hp and 536 lb-ft at the wheels. Even at just 10% of parasitic losses, that’s 530 hp and a mongo 597 lb-ft of torque. 

At the moment, none of the numbers add up, and none of the explanations can explain them. Head to Motor Trend to read the whole story. All we know for now is that there’ll be a lot more Corvettes put on a lot more dynos before this is through. Whenever GM can start building C8 Corvettes, that is.