C8 Corvette Dyno Controversy Revisited by Motor Trend

Corvette was tested with incorrect dyno settings causing the insane numbers.

Motor Trend rocked the automotive world in October when they published C8 Corvette dyno numbers that were incredibly high. The outlet was testing a car with 495 horsepower at the engine, yet they saw dyno numbers as high as 561 horsepower at the wheels. Something had to be wrong with these dyno runs, obviously. It was. And now Motor Trend has explained what went wrong with their initial dyno testing, along with offering up some new numbers to consider.

First C8 Corvette Dyno Numbers

When Motor Trend first tested the 2020 Chevrolet Corvette last month, they did so as a spur-of-the-moment thing. A dyno shop squeezed the outlet into an open spot, but there was a problem. When dyno testing vehicles, there is more to it than just strapping down the car and spinning the rollers. Certain input parameters are required for each vehicle. In the case of the C8, the dyno operator didn’t know some of those inputs, so he guessed based on C7 numbers.

Some of those guesses were wrong, leading to incorrect dyno numbers for the C8’s LT2. Adjustments were made and some of the issues were fixed with each run. However, there were still some factors which were incorrect during the dyno runs, leading to more inaccurate dyno numbers.

In the end, the lowest wheel horsepower number shared by Motor Trend was 478 wheel horsepower. Using a 15% drivetrain loss factor, the LT2 would actually be making around 562 horsepower at the end to make that much power at the wheels.

Some people insist that the Corvette is grossly underrated. Others knew that something about the dyno test was wrong. Motor Trend has published a new piece explaining exactly how the dyno test went awry.

Dyno Errors

Motor Trend explains that during the C8 Corvette dyno testing, there were two main factors that contributed to the miscalculation.

First, the dyno was setup for an all-wheel-drive vehicle. The computer thought that the car was turning twice as much mass at the rollers. That is obviously a huge problem and testing a rear-drive vehicle with all-wheel-drive setting will always yield bad numbers.

Second, the dyno operator didn’t know the “road-load factor” of the C8 Corvette. The operator used 12.6, but the correct factor for the Z51 C8 is 15.4. When coupled with the all-wheel-drive setting, this explains the extremely high dyno numbers announced last month.

Calculating Power Numbers

The Motor Trend piece includes some calculated horsepower numbers for the C8 Corvette using data logs from drag strip testing. Using the acceleration rate at key points in third, fourth and fifth gear, along with the vehicle mass, they were able to come up with the amount of power needed. This calculation method with plenty of smoothing on the graph, Motor Trend got a number of around 425 horsepower and 6,300 rpm. A figure of 425 wheel horsepower with a 15% drivetrain loss would lead to roughly 500 horsepower at the crankshaft. That seems like a reasonable figure for a 495-horsepower car.

Finally, Motor Trend tested a different Corvette Z51 using a VBox and the numbers shifted to the other end of the scale. After posting very high numbers on a real dyno, the VBox numbers were very low. This second C8 only posted 395 horsepower at the wheels, which with a 15% loss factor–somewhere around 465 horsepower. This number can be thrown out along with the initial dyno numbers. The 2020 Corvette has been thoroughly tested by Chevrolet, and as such the horsepower numbers are not overrated.

We will have to wait for more dyno testing of the C8 Corvette to know how much power it really makes at the wheels. In the meantime, we know that it offers real world performance which exceeds any base car before it.

Photos:  Chevrolet

.