Corvette ZR1 Reaches Customers And The Dyno
The arrival of the C8 Corvette ZR1 signifies to the world that Chevy can kick it with the best of them, but even with a four-figure horsepower claim, aftermarket tuners will never be satisfied. Now that the ZR1 has begun to reach customers, some of whom represent tuning shops, the race is on to unleash the 5.5-liter twin-turbo V8’s full potential. Over the next few months, you’re going to see social media posts from one company then another claiming firsts and world records, be that on the quarter-mile or the horsepower leaderboard. But before tuners do battle, they need to understand what they’re really working with, and to do that, a dyno run provides some base numbers to build upon. Chevrolet claims 1,064 horsepower and 828 lb-ft of torque at the LT7’s crank, and Paragon Performance in Waukee, Iowa, has put that to the test on a rolling road. The video is embedded at the bottom of this article.
Math Suggests Chevy’s Claims Are Modest
According to Paragon’s dyno, the ZR1 produces only a little less horsepower at the wheels with a reading of 1,028 ponies. Automakers have traditionally quoted their figures at the crankshaft because of several reasons. Firstly, the transference of energy from that point through the flywheel and clutch, then through the differential, and then through the shafts that drive the wheels (which themselves must transfer energy to the tires and lose some to friction and noise) is never fully conserved through the system. Heat and sound are both forms of energy that exist as by-products of the process of delivering rotational force from the crankshaft to the tires, and because of these fundamental inefficiencies, and because those inefficiencies vary across applications (a 6.2-liter V8 will produce a different figure at the wheel of a truck architecture than that of a sports car, for example), it’s more cost-effective and consistent to quote the figures at the crank. But when it comes to performance cars, it seems that automakers prefer to tell a so-called white lie.
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Taking into account the losses described above, 1,028 hp at the wheels from 1,064 hp at the crank is astonishingly efficient, even in a package as compact as this one. Even more surprisingly, the torque figure is 11 units higher than claimed at 839 lb-ft. A mid-engine layout like this can be expected to have drivetrain losses of around 10%, and if that’s the case, this untouched ZR1 is actually producing somewhere in the region of 1,180 hp and 920 lb-ft of torque. So why are the claimed figures so far off?
GM Is Covering All Its Bases
We’ve seen this many times before. BMW, in particular, has a habit of underquoting its performance figures, including 0-60 mph times. IND Distribution usually tests every new M, and the latest M5 is no exception to the unspoken rules of overpowered German behemoths. We’ve also seen it on the Toyota GR Supra, with two independent dyno runs in 2019 and another in 2020 confirming that the BMW-supplied B58 engines under their hoods were overdelivering.
Back to the ZR1, and Car and Driver recently achieved a 2.2-second sprint from 0-60 mph, shaving a tenth off GM’s own claim, despite testing on an unprepped surface and omitting the 1-foot rollout that automakers often use to cut an extra 0.2 seconds or so from their timing.
Overdelivering on power and initial straight-line performance may be done to account for varying fuel grades, altitudes, and use cases, so the power figure announced by Chevy is likely an average figure, or one determined after extensive use, such as a track-day simulation. It also keeps the competition guessing. Another possibility is that this particular dynamometer is what people in the industry like to call a “happy dyno” that hasn’t been perfectly calibrated, or that the conditions in which the test was conducted were above average. Paragon Performance intends to find out with a lot more testing before fiddling with boost, fuel, and timing, so perhaps future dyno runs will result in a figure closer to the advertised. Thereafter, it’ll be open season in the rush to the record books.
