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

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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.

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

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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..

https://www.AR15.Com/media/mediaFiles/59051/2020-Chevrolet-Corvette-C8-at-the-dyno-with-engine_jpg-1132665.JPG

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?
https://www.AR15.Com/media/mediaFiles/59051/2020-Chevrolet-Corvette-C8-RUN-1_jpg-1132662.JPG

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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There's no problem with the Dyno, as far as calibration/ functionality goes.. The operator is not a dummy either..

If your calling BS on the numbers (I'm ok with this) its some other factor.

Keep digging

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

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Ok, so what caused the erroneous readings?

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What kind of trouble did you get into OP? Just getting bitched at? Or worse?

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My guess is it has to do with the trans/slipper clutch...I remember hearing something years back about the top fuel slippers making for some funky shit until they got them figured out....

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

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

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there are ways around everything

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I only have experience with boat motors but the merc racing 1150/1350 are just a flip of the ECM switch and upgrade fuel so I don’t know why that couldn’t be programmed into the ecm if the motor were designed for it

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Basically because a boat engine runs a steady rpm, and has almost zero take off load as it comes up on the pipe...A car on the other hand has to move the weight of the vehicle thru a contact patch on a tire...with a clutch, its pretty easy, rev it up and get the motor in the powerband, then slip the clutch to get it rolling..On an auto with a stock converter it is much harder, same as not touching the gas on a stick and trying to crawl it up under full load...add a big enough stall converter and its back to acting like a revved up clutch....Different type of load across the board versus a boat engine, which makes it much harder to tune only a 150 hp jump on such a small engine..now make it a 900 cubic inch big block..yeah you might just be able to tune a 150 hp jump...Plus, to make more power you have to increase something..air/fuel getting into the chamber(better heads/cam) more cubes(bore/stroke) or rpm's(valve train/bottom end/ heads)...not as easy as just a tune...although the tune is going to have to work with the new mechanicals...

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Well someone might have got a ear full from the head of gm motorsports development

Lots of threats.. impending doom inbound.. the storm has passed, but there will still be damage to deal with, we'll see, but.. I was excited!

Being that there's no such thing as bad press, I defiantly caused some commotion with my OG post.. got people talking... .. its a good thing right...

Simple Car Guy

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Good post!

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Regardless, there is no free lunch. You can not have a transmission of energy without at least some loss in transmittance energy. The numbers can be skewed but there is no such thing as over unity in transmission of power.

Either way the numbers were skewed & something needs to change in reading the variable.

I agree from the get go MT’s idiots needed to stop touting a crank number of X amount of parasitic loss, because obviously it’s a BS assumption that GM tried to warn them of.

IMO they are hacks for even publishing that perspective of the article & couldn’t wrap their heads around what was going on & it shows.

What they should have done was take the trap times, as those are what is pertinent, cross referenced the Dyno numbers & threw up their hands. Instead they showed massive ignorance in how the real world works in terms of hypothetical & actual power figures.

Simply put, no logical person can look at those numbers, side by side, & think for a single second that engine was making 650HP. It’s complete idiocy.

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I'm still baffled by the C&D finding that front/rear visibility is less/more compared to the C7.

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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.

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Yet everyone else raves about the front/side views and all say the rear view is no worse than any of the other mid engine cars....

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Georgia has been cracking down on Montana registrations.

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I dont underestimate them, I just know enough about engines to know the new 6.2 C8 engine isnt putting out 150 more crank HP one tune alone.

Being NA It would have to be a much larger engine displacement wise or it would have to have a much larger bore than stroke and spin to the moon.

It is neither. Therefor that 6.2 engine would need more than a tune to see what you're effectively saying is an extra 120-130 wheel horsepower off of a tune alone.

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Regardless, there is no free lunch. You can not have a transmission of energy without at least some loss in transmittance energy. The numbers can be skewed but there is no such thing as over unity in transmission of power.

Either way the numbers were skewed & something needs to change in reading the variable.

I agree from the get go MT’s idiots needed to stop touting a crank number of X amount of parasitic loss, because obviously it’s a BS assumption that GM tried to warn them of.

IMO they are hacks for even publishing that perspective of the article & couldn’t wrap their heads around what was going on & it shows.

What they should have done was take the trap times, as those are what is pertinent, cross referenced the Dyno numbers & threw up their hands. Instead they showed massive ignorance in how the real world works in terms of hypothetical & actual power figures.

Simply put, no logical person can look at those numbers, side by side, & think for a single second that engine was making 650HP. It’s complete idiocy.

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Someone beat ya to it OP.

Linky

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I dont underestimate them, I just know enough about engines to know the new 6.2 C8 engine isnt putting out 150 more crank HP one tune alone.

Being NA It would have to be a much larger engine displacement wise or it would have to have a much larger bore than stroke and spin to the moon.

It is neither. Therefor that 6.2 engine would need more than a tune to see what you're effectively saying is an extra 120-130 wheel horsepower off of a tune alone.

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Again, would need more displacement and/or way high RPM (oversqaure bore at the sacrifice of torque)  to achieve this tune alone.

With mods like headwork/cam/FBO yes this NA V8 could easily achieve 150 more crank HP. But we're talking about a stock engine tune only.

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You guys are hilarious.
That's some damn wishful thinking right there.

Chevy isnt going to be giving these base C8 owners a high strung, high revving  essentially racecar V8 wolf engine hiding in sheeps clothing putting out just as much power as the C7Z's supercharged 6.2 and with a warranty.

Lmfao.
They would make you pay for that like any other manufacturer not give it away.

And BMW was one of the last big manufacturers to sell cars with near racecar engines (M cars) and look how that went. They all had some type of durability issue even though they were awesome engines.

Even the 7.0 litre LS7 in the C6Z had issues being a high revving large engine.

Again look no further then the Ferarri 6.2 V12 and see what it took them to get 650-700 crank HP out of a 6.2 NA engine.

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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...

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I dont doubt that.
Given all the things like you mentioned and just in general how the engine tech/parts/builds put more and more power as time goes on its definitely possible the new gen C8 engine could maybe get to that 100 crank hp mark increase tune alone. Prob be closer to 50-80 but I could entertain 100 crank hp.

The increase on this dyno and Chevy sandbagging it that much? Nope, definitely not believing that.