The folks at Motor Trend strapped the 2020 Chevrolet Corvette to a dynamometer to see if the 6.2-liter Small Block “LT2" V8 actually makes the stated 495 horsepower, 470 lb-ft. The websites findings?: “The 2020 Chevrolet Corvette C8 provided for all our testing produces more power than what Chevy claims.”
I’m always hesitant to write things like “Dyno proves that [insert automobile]’s horsepower numbers are underrated,” because there’s a lot that goes into horsepower certification, and there are quite a few factors that can cause results from one particular dynamometer to differ from those of another.
But Motor Trend, with input from its brilliant former Chrysler engineer and current technical director Frank Markus, discusses some of these concerns in the story.
Motor Trend conducted six dyno pulls on a production 2020 Chevrolet Corvette in fourth through sixth gears. Output ranged from 478 HP and 536 lb-ft at the wheels (that’s roughly 562 HP and 630 lb-ft at the crankshaft assuming a 15 percent drivetrain loss—note that Chevy engineers told Motor Trend that actual losses are lower) tested in sixth gear to 561 horsepower, 515 lb-ft of torque (or about 660 HP and 606 lb-ft at the crank assuming the same 15 percent loss figure) tested in fifth.
One possible explanation for the power discrepancy, Chevy apparently told Motor Trend, has to do with how the Corvette’s engine’s official power numbers were obtained. From the article:
The other explanation is that Chevrolet certifies most of its engines through the SAE, the Society of Automotive Engineers, which follows a strict set of rules and standards to determine the horsepower and torque ratings. In other words, the SAE acts as an independent party that’s present during the engine tests and is the one who determines the final output ratings. Their testing does not involve a simple pull from idle to redline, either. Rather, rpm are slowly ramped up and allowed to stabilize before accelerating further. This process results in significantly more heat generation than any single pull from our six dyno runs. For that reason, the engineers say, it’s not uncommon for single chassis dyno pulls to register higher output (and it is extremely unlikely any car will ever generate less than rated output).
The website even looked at the official SAE results:
A quick check of the SAE database reveals that the certification test of the 6.2-liter V-8 LT2 engine with the optional exhaust system took place at the Pontiac Engineering Center in Michigan on April 9, 2019. Jordan Lee, chief engineer of the Corvette’s engine, signed the certification on July 15—just three days before the reveal in Tustin. The engine was rated at 495 hp at 6,450 rpm and 470 lb-ft of torque at 5,150 rpm The vehicle code name 2020 Y2XX underwent three tests, and the power and torque graph looks similar to the one we had at the dyno.
Ultimately, Motor Trend isn’t sure why its numbers are so high, saying the dyno it used complied with the SAE procedure, and that this was the same dyno the team had used when testing a 2020 Ram 2500. The torque figure from that test, in case you are curious, wasn’t far from Ram’s claimed (but not SAE certified) peak figure. Still, despite a number of questions still unanswered, Motor Trend concludes that the Corvette tested does indeed produce more power than what Chevy claims.
This is all a bit odd, because if the Corvette’s engine is SAE certified to make 495 horsepower, then it’s supposed to make that much power—that’s a requirement.
As I’m not as well-versed in the area of power and torque certification as some, I called up Gary Pollak, a Program Manager at the Society of Automotive Engineers.
Pollak said when it comes to SAE certified horsepower, it’s “pretty tough to fudge the results,” and that “All production engines must be within 2 percent of the certification claim.”
He also said that automakers are allowed to claim an SAE certified horsepower number within 1 percent of the measured result—this might allow an automaker whose result was 499 horsepower to claim 500, for example.
“If somebody does run at that same kind of condition in 1349 and they see something that’s wider than that [2 percent] band,” Pollak told me, “they could make an appeal to SAE and we could actually re-test it and either revoke their certification or publish something...”
As for the numbers from the Motor Trend test, Pollak told me that this type of discrepancy is exactly what the SAE test procedure hopes to solve. “I’m not sure what conditions Motor Trend used, but the SAE standard basically tries to typify what the consumer would see” accounting for all relevant power draws, he told me, going on to say that while the dyno used in Motor Trend’s tests may have complied with the SAE procedure, “it’s all of the auxiliary conditions that they might not have accounted for.”
“There are so many conditions that are involved in the test...the numbers could be all over the map... It’s hard to compare from one dyno test to another,” he said. The SAE J1349 test, then, is meant to act as a sort of “datum” against which all engines can be measured so that they can be fairly compared. You can see the full list of SAE certified engines here. Among the engines on there is the supercharged 6.2-liter V8 found in the 2015 Dodge Hellcats.
That engine was rated at a peak power of 707 horsepower, and under the exact same conditions, the Corvette makes 495. Thus, it should be safe to assume that the Corvette’s motor is 70 percent as powerful.
But maybe it’s not safe to make that assumption? It’s easy enough to say simply “The test procedure was different,” but there’s always that chance that perhaps the test car really did have a more powerful engine. Motor Trend seems confident of this, though we may never actually know the truth.
Definitely check out their full story here.