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Chevrolet’s eighth-generation C8 Corvette Stingray is a delightful mid-engine sports car that delivers exotic two-seat styling with an accessible price tag, but the car’s chassis is so immensely capable that the Stingray’s 495-hp 6.2-liter pushrod small block V8 (code named LT2) can seem like it doesn’t deliver enough power in race track driving.
That could be because Chevy engineers designed the C8’s mid-engine architecture to be even more capable than the performance we experienced driving the Stingray, and some of that potential has been revealed with the release of the Z06 high-performance version of the Corvette for 2023.
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The source of the Corvette’s transformation is the LT6, a 5.5-liter double-overhead cam V8 with a flat-plane crankshaft that churns out 670 horsepower without forced induction. The previous-generation C7 Z06 used a supercharger to produce 650 horsepower from an engine that weighed 31 lbs. more than the LT6.
This new engine doesn’t achieve this astonishing output just because of the specification of leading-edge technology. It was able to top the previous supercharged output because of attention to detail and input from the Chevrolet IndyCar engine program.
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The result is a quick-revving engine with prodigious power output and an exotic soundtrack that will never be mistaken for that of a lowly muscle car (unless you count the Ford Shelby Mustang GT350, which also employed a flat-plane crankshaft in its engine).
This dynamic response and the shrieking exhaust note that accompanies it are byproducts of the engine’s flat crank, but that crankshaft is only an enabling technology for the sky-high 8,600 rpm redline that contributes to the 670 horsepower. The timing of pressure waves in the intake and exhaust systems are equally spaced in engines with flat cranks, making it possible to optimize the intake and exhaust systems to exploit this pressure waves rather than suffer from their interference, as happens with traditional, smoother-running cross-plane crankshaft V8s.
The LT6 exploits this with an incredible intake tract employing downdraft intake trumpets that are each individualized for their specific cylinder in the engine and with their inside surface polished to maximize airflow. Those trumpets sprout inside an intake plenum chamber that is divided into halves for each side of the engine.
It has a trio of large butterfly valves in the bulkhead dividing the halves of the plenum so that communication between the sides is adjusted to maximize the benefit of pressure waves. These valves change position five times during the run to redline, opening and closing to prevent the peaks and valleys in the torque curve that would otherwise occur naturally.
Intake air rushes into combustion chambers that are CNC machined and laser-scanned to assure accuracy. As soon as it arrives, the air gets blasted from the side by a direct fuel injector mounted on the edge of the combustion chamber, beyond the exhaust valves, that imparts turbulence to the mixture to aid homogeneity before the spark plug sets off ignition. Chevy’s powertrain engineers got this idea from the company’s IndyCar engine team.
A couple little red Corvettes, but they look a lot like something from Italy. The lead car features the high-downforce Z07 bodywork, while the trailing car is a base Z06.
A couple little red Corvettes, but they look a lot like something from Italy. The lead car features the high-downforce Z07 bodywork, while the trailing car is a base Z06.
When the air rushed out of the cylinder is travels to a new muffler that carries variable bypass valves. The C7 Corvette used bypass valves that were either fully open or fully closed, but these new variable valves give the C8 Z06 driver a variety of options for sound. This is probably more important for this car considering the sharp edges of flat-crank engine sound in comparison to the mellow bellow of cross-plane V8s.
Engineers even tailored the fit of the exhaust pipes into the bezels passing through the rear bumper fascia. They looked at having the tips stop short of the bezels, stop even with them, or slide part way inside them, and found that the last option produced the best reflected sound to the driver, with an emphasis on more pleasing low frequencies than the other choices, according to vehicle performance engineer Cindy Molnar, who worked on the system.
The 8-speed dual clutch transmission (DCT) carries over fundamentally intact from the Stingray, but with a stronger case and bellhousing, stronger six-plate clutch, and larger output shafts, all with withstand the LT6’s greater power output.
The Z06’s suspension includes springs that are 35 percent stiffer than those in the Stingray, unless the driver selects the Z07 high-performance option upgrade, which boosts that another 10 percent. The upgrade also includes enlarged Brembo carbon ceramic brakes and reprogrammed magnetically adjustable shock absorbers. These shocks feature an increased range of authority for the Z06 versus the Stingray and a faster response time for changes, making the car even more adaptable for conditions. As has previously been the case with the Stingray, the comfort of street driving and the precise control in track driving is impressive for the Z06, only now with stupendous power and speed. The stiffer spring rates are not adjustable like the shocks are, but their added stiffness does not compromise the car’s ride in street driving.
The Z06 rolls on Michelin Pilot Sport 4S tires similar to the ones used on the Stingray. These are excellent street tires, but we found them inadequate for track driving in the Stingray and they prove to be even more overmatched in the Z06. Only a couple laps in to driving around Pittsburgh International Raceway with the 4S tires saw them turn greasy, leading the car to squirm around in corners.
However, the Z07 upgrade package also includes a switch to Michelin Pilot Sport Cup 2R tires, which have proved miraculous when tested on the Porsche 911 GT3 RS and Ferrari Pista. I drove those cars on warmer days, and the tires felt invincible, seemingly letting the car drive anywhere on the track without a change in grip.
In the 55-degree weather at Pittsburgh, the Pilot Sport Cup 2Rs were excellent, but seemed more mortal, I think because of the cooler temperatures. They are by far the best street-legal track tires in any case.
Another upgrade that is a stand-alone option for still more on-track speed are the carbon fiber wheels from Carbon Revolution. We’ve seen these before on Ford Shelby Mustang GT350 and GT500 models, and their benefit in this case is even more amazing. According to executive chief engineer Tadge Juechter, the wheels trim 41 pounds of unsprung rotational mass from the car.
This not only makes it feel more lively, it saves an astonished 1.5 seconds per lap when driving on a track with two-minute laps. That 1.25 percent difference probably sounds small to non-racers, but racing drivers would give nearly anything to gain such a large advantage over their rivals with aluminum wheels. They cost $10,000 in black paint and $12,000 in clear coat that showcases the carbon fiber weave.
These wheels contribute to the test car’s $167,205 MSRP, which is also padded by the $3,000 EPA gas guzzler tax. That fee is the consequence of the Z06’s 12 mpg city and 19 mpg highway fuel economy rating. Even with that, the price is half that of the Z06’s Italian supercar peers and about $50,000 less than a Porsche 911 GT3. It is undeniably a lot of money, but it is money well-spent when considering the unapologetically supercar-level performance the Z06 delivers.
And for those of us who still appreciate the virtues of a small block V8, along with its relative fuel efficiency, who knows, maybe Chevy will revive the Grand Sport version of the Corvette, which in the C7-generation cars married the Z06’s chassis goodies with the regular small block V8.
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