About a month ago, this event happened at our shop, I was so excited I posted a play by play one ARF, and wound up getting in a heaping mess of trouble with GM, and The Magazine..

But, now the info is out, so we can chat about it.

https://www.motortrend.com/news/2020-chevrolet-corvette-c8-power-dyno/

From left to right is Famous Import drag racer Chris Rado, Eric "Grim" Kozeluh from Twins Turbo, and some magazine guy..

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How Much Power Does the 2020 Chevrolet Corvette Really Make? We Take it to the Dyno and Find Out
A lot more, it turns out

Miguel Cortina
Oct 21, 2019

I'm looking through a window, hands around my face, staring at a screen with all sorts of graphics and numbers that are too small to read. On the other side of the window, a red 2020 Chevrolet Corvette is strapped to the dyno with its rear wheels spinning very, very fast.

The double-paned windows are not enough to keep the engine note from reaching other parts of the facility. The speedometer on the screen reads 150 mph, but the front wheels are not moving at all. Once the engine noise winds down and the wheels stop spinning, the numbers we're looking for pop up on the screen—558 hp and 515 lb-ft of torque at the wheels. "We've got a hot rod!" says international bureau chief Angus MacKenzie, who has been standing next to me all this time.

We're in shock. A quick math check reveals that's an estimated 656 hp and 606 lb-ft of torque at the crank if we assume a 15-percent drivetrain loss—way over the 495 hp and 470 lb-ft that Chevy claims. (That 15 percent represents the power consumed by everything between the engine crankshaft and the drive wheels, including inertia of all the spinning parts, power to run the hydraulic pump in an automatic or twin-clutch transmission, the drag that occurs when gears spin through lubricating oil, friction between the gear teeth, etc. It's an educated guestimate frequently used across the industry for modern light-duty automatic transmissions—manuals experience slightly smaller losses; older or heavier-duty automatics slightly larger ones.)

But let's rewind. Earlier that morning, Chevrolet dropped the 2020 Corvette with VIN 10 at our headquarters in El Segundo, California, to perform a Real MPG test by our partners at EQUA. The early-built production car was shipped from the plant in Bowling Green, Kentucky, to Milford Proving Ground in Michigan for a check before it made it down to Southern California. The Corvette was tested by MotorTrend the week prior at Fontana and a few days later at the Hyundai-Kia proving ground for our Car of the Year competition. The 'Vette spent every night under the vigilance of the Chevrolet public relations team and was handed back to the editorial team in the mornings. The evening prior to the dyno run, the Corvette was driven by an editor from Tehachapi, California, to our headquarters, where it was taken by the Chevy team for the night.

That sunny September morning, the EQUA technician told us he didn't have the right equipment for the test—he needed a different set of tubes to seal around the exhaust outlets; the ones he had wouldn't resist the higher temperature from a mid-engine sports car. Our Plan B? Take it to the dyno before the Corvette got on a trailer to go back to Michigan that evening.

Which is how Angus and I ended up staring through the glass at those surprising numbers. We asked the dyno technician to run the test in fifth gear after a call Angus and I had with Chris Walton, our road test editor, who estimated that fifth gear could probably be the closest 1:1 ratio. (A call with Chevy would later confirm that, but more on that later.) We decided to run the test again.

The massive fan starts to blow air straight at the Corvette as the rear wheels start moving. Our attention shifts to the screen—558 hp and 512 lb-ft at the wheels, almost identical numbers as the first run. Assuming a 15-percent drivetrain loss, those numbers go up to about 656 hp and 602 lb-ft. Still too high. What is going on?
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Runs three and four are also done in fifth gear; the dynamometer reads 561 hp and 515 lb-ft, then 556 hp and 523 lb ft. That translates to 660 hp and 606 lb-ft and 654 hp and 615 lb-ft at the crank, respectively, assuming the same 15-percent drivetrain loss. We get Chris back on the phone.

The numbers are too similar. We don't have the gear ratios, so Chris suggests we try sixth gear to see if the numbers change. The engine starts revving, wheels start spinning, and once again everyone is staring at the screen.

The numbers are different. The dynamometer reads 478 hp and 536 lb-ft at the wheels. Per our calculations, that means the crank is outputting about 562 hp and 630 lb-ft of torque. Both numbers are still high, but why did the torque number rise instead of going down? The next run, our sixth, would be the last.

Our eyes are glued to the screen. The bright green numbers appear on the monitor, reading 478 hp and 544 lb-ft at the wheels. If we continue to assume a 15-percent drivetrain loss, this 'Vette would be producing about 562 hp and 640 lb-ft at the crank. We're all scratching our heads.

We couldn't come up with a conclusion other than the engine makes a lot more power than the advertised 495 hp and 470 lb-ft of torque. We call Chevy and ask them to set up a call with engineers and to provide the 'Vette's gear ratios.

A short time later, Chevy PR provides the following gear ratios:

2.905

1.759

1.22

0.878

0.653

0.508

0.397

0.329

"There has to be another transfer gear ratio between these and the axle ratio, I guarantee," MotorTrend technical director Frank Markus says. Using the rear wheel speed and tire size, Frank was able to estimate the output shaft ratios, but we waited until the call with engineers to confirm.

A couple of days later, engineers provide us two reasons for the discrepancy of power. The first one is that when the Corvette is cold, it actually produces more horsepower than when it's hot. But that doesn't make sense—we saw similar numbers after six runs, and the car was pretty hot by the end of the second run. 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). According to Chevy engineers, this is an expensive process, given that someone from the SAE has to be present, but the automaker has done this for years, and it's a procedure that it continues to follow with most of its engines in the U.S.

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.

Per the SAE website, only a few manufacturers certify their engines through them. General Motors dominates the list, and a few Ford and FCA engines have also been certified.

Chevy engineers also say that the drivetrain loss of a dual-clutch transmission, like the one in the Corvette, is less than 15 percent—but hesitated to give us an exact number (and even if it was zero loss, we still measured more wheel-horsepower than rated crank horsepower). They did provide the gears with the transfer ratio for the manual limited-slip differential and the electronic LSD. Our Z51 with an electronic LSD had a 3.454:1 axle ratio, and after applying the 1.459:1 transfer ratio the effective gear ratios are:

4.239

2.567

1.780

1.281

0.953

0.742

0.580

0.480

Turns out fifth gear is the closest 1:1. And the fact that the LT2 engine was certified by the SAE means that there could be more power getting to the wheels on our comparatively cool chassis dyno pulls.

Why the huge discrepancy with the numbers? We still don't know. The dyno we used complies with the SAE J1349 procedures, and we've used it multiple times in the past. To prove there wasn't a problem with the dyno, we ran a 2020 Ram 2500 Limited powered by the 6.7-liter turbodiesel Cummins engine, which produces 850 lb-ft of torque but is not SAE-certified. The dyno read 760 lb-ft at the wheels, which means there's about 890 lb-ft at the crank, much closer to the numbers Ram claims.

One thing we know for certain: the 2020 Chevrolet Corvette C8 provided for all our testing produces more power than what Chevy claims. The question is, will all subsequent production Corvettes match this one's output? You can be sure we'll be testing many C8 Corvettes to come, and we'll endeavor to test retail customer cars as well as press cars. Stay tuned.
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Neat

Someone beat ya to it OP.

Linky

Saw the last thread. I'm looking forward to more people dynoing them.

lol that first gear is nutso.  And holy shit..

I love calling dupe, but I think OP gets a pass for actually being involved.

Been talking about this since that first thread. No matter how you shake it out, the results are still wild.

2nd. All in favor....
Today Op was a cool dude.
1st time around he stuck his dick in an outlet....but as a car guy I can understand.  Hopefully he didn't get in too much trouble.

The burns have already healed

ARF gives me so much.. I wanted to give back something I kinda know a bit about..

As a car guy... you understand

Oh, I agree wholeheartedly

Other thread should be nuked, keep this one. (Conserves site resources)

They simply gave you a custom tuned car, different from production models.  No mystery there, and certainly not the first time a car maker did that.

Do it again in a few months with an actual customer car and I bet you won't get these results.

Theres no way any NA engine could make that much more power on tune alone.

except this thread is written by Someone Who Was There ™®©

Thank you for posting this again, turbo_infidel.

Good stuff.

Thank You OP.

https://www.ar15.com/forums/General/Remember-the-nuked-C8-dyno-thread-/5-2265301/

This..especially normally aspirated...

Even of that were true, ~150 HP from a tune? don't think so.

beat like a rented mule, so yeah, what they said.

I guess the ECM sends different fuel or spark-advance parameters for 5th and 6th gear? Or changes the valve timing or cylinder activation?

I wonder if the paddle shifters allow an actual instantaneous shift from 5th to 6th at full tach?

Maybe they discovered the car comes loose at 150mph when you do that, so they cut a little power?

Someone will eventually do runs in every gear. It will be interesting to see the power profile of all 8.

1 cent.

Dave

At least they are posting the same numbers I was, which I received a lot of flack for,

but I'm still impressed by what this car is/ will be.. this thing is going to be soo hot, were gonna be sick of seeing them everywhere.. you might turn your hed to check out a special model, but I really believe this car is a total

Gamechanga

Thanks for posting!

You're saying that a car maker couldn't detune a car from 640 hp to 495 hp.  Why do you think they couldn't do that?

Also consider that GM may have programmed in a dyno mode, so they get what you and I would call "full" power on the dyno, but for normal use it runs de-tuned for (a) safety, (b) reliability, and (c) so they can easily sell upgraded power a couple years from now. Of course they'd never admit that...

SAE certification bypasses all of that.

I wonder if perhaps there are insurance reasons for marketing 495hp, (vs 505) ie "499 and under"

Most likely.

I had a custom tuned GM Olds Aurora that I got from a GM Exec. Its was so much faster than a stock one it was amazing-for the time. The total HP of that car was nothing compared to the new Vette but on a % basis who knows how much they tweaked it...

I would love to see your guys numbers be right, but I've built to many engines and been down to many tracks to believe what my ears hear over what my eyes see....The track will tell it all...

This GM video on the autobahn backs up their numbers as well...actual 194 mph versus their claimed 193 top speed...

Even the MotorTrend guys say in the video that this car might be a ringer (special tuning), and they'll even give any customers a free dyno pull there to figure it out.  Very cool!

But that won't answer the question as to a dyno programming mode, so who knows if the cars will be making this power on the street.

There's no way chevy is going to get 640hp out of that 6.2 engine and be able to hide it.

It would have to spin to the moon, be way over square bore and would have less torque because of that.

Look at Ferrari had to do to get 700hp out of their NA V12.
NA engines have their physical limits.

So yes I'm saying chevy didnt build a 650hp NA engine and just detune it.

If this was a turbo engine then absolutely all bets are off. They could have easily sandbagged the official numbers and they could detune it 150hp but it's not a turbo engine. It's an NA with physical limitations.

California sure takes the fun out of everything, not just guns.  Try getting a modded car to pass inspection these days.

After your Supra build and the Mustang build...

Naw.  No evidence that you know what you are doing.

My question is what was the snafoo in Dyno testing parameters that led to the off numbers?

Track testing does not support the 550RWHP numbers, unless they were done at like 5k ft elevation.

If at, say, Carlsbad, well...

That said, was MT’s 123MPH 1/4 on their own “Stalker” type 1/4 mile #’s or an actual drag strip with timing lights? There is a difference.

Imagine when these hit the used market at $30-35k, just think of it bros! We about fixin' to have supercar eaters on the streets.

The struggle is real, I am sitting on pics/info about an engine I did a bunch of work on that was supposed to run at this years Engine Masters Challenge, it's neat from a engineering/machining perspective and should have been very competitive....however, it ate a ring pack/piston on the dyno during tuning and never made it...now I have to wait and see if the rules will allow it to run for next year! Fuuuuuuuuuuuuuuuuuck...lot of early mornings on that damn thing.

I'm proud of it and now I just look at the pics on occasion........so pretty....

Sounds bitchin'

Gapless top ring? I love a NA build.. congrats on the Engine masters Challenge is a really cool deal, and I always learn something...

BUT, I prefer adding a LB of boost when needed..

I need this fuckin car

I'm with you, its been ages since I lusted after a car that doesn't cost upwards of $200k

I hope I don't get sick of seeing these things in a few years..

I don't think its a stretch to assume it probably isn't a ringer but they underrated it a bit.  The 2019+ Mustang GTs are putting down 450 on Mustang Dynos (that typically read high), you talking about a car that you can buy for $28k and up new, not sure why it's a huge surprise the larger, more advanced, more expensive vette engine is a +100hp.

The problem is real world testing does not replicate the implied HP numbers. 123mph 1/4 in a 3600lb vehicle anywhere near sea level is about 500HP @ the crank.

Now lets say their parasitic loss is closer to say 8%, then that means about 460 to the wheels.

lol, oh wait you are serious?

Dayummmmmm

Someday...….

BMW was notorious for this also, reported numbers below actuals.

TXL

It's been built-in to the computers for a long time. There is a power-boost table in my 2000 Silverado that changes the fuel-air ration from 14.7 to whatever you want, max power usually happens around 13.8 - this table is disabled in the factory settings but is easily enabled and changed to whatever you want with the HPTuners or equivalent setup. Factory settings are prioritized first for minimum emissions, second for maximum mileage - maximum power doesn't happen under either of those priorities. But a press car, that won't ever be sold to the public, can easily get "tweaked". I think the most famous press car "tweak" were the GTO's that had the special built 428 engines installed instead of the stock 389's.

Yes I'll be buying one.

In before muh 84 Buick, etc...

I can't imagine GM and the Corvette team would take the risk on this car to send out ringer press cars for the mags and internet to report on, then production cars be down 50 to 100+hp. That kind of bait and switch is just asking, begging even, for biblical blow-back.

It would be the most ignorant thing imaginable with how much they have riding on this new model with such a shift from corvette history.

Dat ass tho...

Ouch, that sucks man, hopefully you can run it next year...

My '84 Buick Riviera became a rust bucket 3-4 years after purchase  GM made some real shit.

Well, they could, but it would be pretty obvious its not stock...I think the top builders now are able to wring 3hp per cubic inch but thats very very short term drag stuff, anything that would have to run on the street for any time would be down under 2 hp per inch..and still be noticeable on a dyne pull I would think..let alone on a drive...

So you're saying it's a problem with their dyno or their use of it?  That's a fair point.