Motor Trend Admits First C8 Corvette Dyno Test was Botched

During their initial testing of the 2020 Corvette Stingray, Motor Trend took an opportunity on their final day with the car to put it on a Mustang Dyno to see what kind of power the new LT2 V8 engine was making. The results were “out-of-this-world” as their first and subsequent tests found the car was making way more power than the 495-hp that GM advertises.

Here’s a quick recap of the flawed test and the results that it generated:

On Motor Trend’s first test, the dyno results showed 558 hp and 515 lb-ft of torque at the wheels, which means the engine was offering an estimated 656 hp and 606 lb-ft of torque at the crank. A far cry from the LT2’s SAE certified 495-hp and 470 lb-ft of torque. Multiple runs in 5th gear generated similar results so when they ran it again in 6th gear, the numbers came in at 478-hp and 536 lb-ft of torque, which translates to an estimated 562 hp and 630 lb-ft of torque. Their final dyno run would generate similar results.

While Corvette owners were appreciative for the extra horsepower, cooler heads prevailed and soon a number of journalists offered their opinions on why these dyno results were impossible. One of those was freelance writer Jason Cammisa who wrote the C8 Corvette review for Road & Track. In a follow-up piece posted on Motor1.com, Jason uses math and science to invalidate a scientific test.

This morning we got a heads up from a representative of the Corvette team who suggested we head over to Motor Trend this morning as they have posted a follow-up to their C8 Corvette dyno article.

In their investigation of the dyno test, Motor Trend admits their dyno operator had selected two dyno settings that were incorrect:

Now we’ve learned that our dyno operator selected two dyno settings that were incorrect. One is a key parameter that had yet to be released for the C8 and so was estimated from C7 data. That is road-load horsepower at 50 mph. This factor incorporates friction and aero drag, and it can be measured empirically by conducting coast-down tests, but because dyno-testing the C8 was a last-minute fill-in to our schedule when Real MPG testing proved impossible on our last day with the C8, we had no opportunity to measure it. The dyno operators used 12.6, when Chevrolet has informed us that the correct factor for our Z51 should have been 15.4. But the bigger boo-boo was that the dynamometer was also set to assume all-wheel drive.

These two factors conspired to make the dyno believe the Corvette’s powertrain was overcoming way more inertia than it really was, which led to the inflated results. Sadly, there’s apparently no way to virtually “rerun” the test in the computer with corrected parameters, so we simply must get another C8 back and run the test again.

Motor Trend goes on to say that the Torch Red Corvette road test results were so impressive that they wanted to find some proof of its actual horsepower and they attempt to do so utilizing “road-dyno” pulls from their drag strip runs. The magazine says they came up with the car producing 425-hp just past 6,300 rpms (and assuming for 15% loss, and you get 500 hp). A similar “road-dyno” test of a Sebring Orange C8 Corvette produces a result of 465-hp and 412 lb-feet of torque.

The magazine concludes that more dyno and track testing is required until we can get a base-line of what the car is actually making. While we are certainly not dyno experts in any degree, we hope the next dyno test of the 2020 Corvette Stingray takes place on a Dynojet dyno which is said to be more accurate than the Mustang-branded dynos.

Source:
MotorTrend.com

Related:
Motor Trend Dynos the 2020 Corvette Stingray and Finds It Produces More Power than Advertised
Why Motor Trend’s Dyno Results of the 2020 Corvette Stingray Were Impossibly Wrong
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