For fifth- and sixth-generation-Corvette buyers, ticking off the order-sheet box marked “Z06” always represented something of a tradeoff, since certain potentially desirable equipment—most notably an automatic transmission and a removable roof panel—was unavailable with that august model designation. The ostensible reason was that such comfort-and-convenience items had no place in a narrowly targeted track car, but the truth was that the C5/C6 platform was never intended to accommodate those features in the first place.
Those days are officially over. When the ’15 Z06 hits streets and road courses early next year (an exact on-sale date was not available as we went to press) it will do so as a wholly uncompromised ultra-high-performance vehicle, in the tradition of such six-figure exotics as the Porsche 911 Turbo and the Ferrari F12 Berlinetta. That means a self-shifting trans and a pop-off top are finally on the menu, right alongside all the performance-enhancing hardware you’d expect from the line-topping version of America’s Only True Sports Car.
While we’ll have to reserve final judgment until we’ve had a chance to drive one, the details on the spec sheet make one thing clear: the C7 supercar has arrived. Let’s take a look at what separates this speed-tuned Corvette from a standard Stingray.
The heart of any performance car is, of course, its engine, and the new Z06’s ticker is appropriately leonine. Dubbed the LT4, a name first deployed on a limited run of performance-tuned LT1 engines offered in 1996, the 6.2-liter, 625-horsepower (estimated) mill brings both historical fidelity and vastly improved performance to the C7 Z’s résumé.
Unlike its immediate predecessor, the 7-liter LS7, the LT4 relies on artificial aspiration, rather than a bump in displacement, to achieve its stratospheric output numbers. Using a lightly annealed LT1 as a foundation, Chevy engineers added an all-new Eaton R1740 supercharger that spins at up to 20,000 rpm, some 5,000 rpm more than the one employed on the C6 ZR1’s LS9. Those extra revolutions are critical, since the R1740 is considerably smaller in size—1.7 vs. 2.3 liters—than the LS9-spec TVS2300. According to Chevy, benefits of the downsized compressor include improved low-rpm response and an overall engine height just one inch taller than the naturally aspirated LT1. Torque is expected to crest at 635 lb-ft or more.
Beneath the supercharger, forged pistons, titanium intake valves, machined connecting rods, stronger aluminum heads, and standard dry-sump oiling fortify the basic LT1 architecture to withstand the rigors of forced induction. Compression drops only a hair—to 10.0:1, down from 11.5:1 in the LT1—a benefit of retaining the base motor’s direct-injection technology. Also making the transition from LT1 to LT4 is Chevy’s Active Fuel Management technology, which shuts down four of the engine’s eight cylinders under light loads to improve fuel economy.
“The supercharged LT4 engine delivers the greatest balance of performance and efficiency ever in the Corvette,” notes Assistant Chief Engineer for Small-Block Engines John Rydzewski. “It is one of the world’s only supercharged engines to incorporate cylinder-deactivation technology, enabling it to cruise efficiently on the highway with reduced fuel consumption, but offer more than 600 horsepower when the driver calls up its tremendous power reserve.”
We’ve long pined for a dual-clutch or sequential-manual Corvette, but cost and durability hurdles have heretofore conspired to keep such a car beyond reach. While the ’15 Z06’s 8L90 eight-speed automatic is a conventional self-shifter with a torque converter, Chevy engineers promise that there will be no compromises with the new trans.
“There’s no trade-off in drivability with the 8L90—it was designed to deliver performance on par with dual-clutch designs, but without sacrificing refinement,” says John Goodrich, Assistant Chief Engineer for Eight-Speed Automatic Transmissions. “It is also the highest-capacity automatic transmission ever offered in a Chevrolet car.”
As you’d expect, the 8L90’s shifts may be directed either automatically, by the powertrain computer, or manually, via the steering-wheel-mounted paddles. In either case, the trans is said to execute full-throttle upshifts as much as eight hundredths of a second quicker than the Porsche 911’s dual-clutch gearbox.
Manual Z06s, meanwhile, will receive a version of the Tremec TR6070 seven-speed box used to great effect in the base Stingray. The manual’s ingenious Active Rev Matching feature carries over, making it possible for even novice drivers to practice their Oliver Gavin impersonations behind the wheel.
Uplevel Corvette offerings have long been distinguishable by their tumescent wheel arches and aerodynamic add-ons, and this latest version is no exception. Still, as Team Corvette is keen to note, all such exterior modifications were born out of functional necessity in the case of the seventh-gen Z06.
“The flared fenders accommodate larger, wider wheels and tires for more grip,” explains Corvette Design Director Tom Peters. “The larger vents provide more cooling air to the engine, brakes, transmission, and differential for increased track capability. The more aggressive aerodynamic package generates true downforce for more cornering grip and high-speed stability.”
At first glance the most striking deviations from stock include wider fenders (by 2.2 inches in the front, 3.15 inches in the rear), along with the aforementioned larger vent openings and a pair of rear brake-cooling ducts added just aft of the doors. Less noticeable are the dual front brake-cooling ducts mounted in the Z06-specific grille.
For the first time in Corvette history, three different levels of downforce-enhancing bodywork will be available. The standard Z06 treatment combines a front splitter and wheel-opening spats with a vented carbon hood and a rear spoiler shared with the Z51 Stingray. Moving up the aero ladder, optional carbon-fiber and Z07 (shown) packages bring increasingly aggressive body mods, with the latter said to offer more downforce than any previous GM car.
Wheels, Tires, and Brakes
While the C7 Z06 is sure to be a world-class performer in any guise, RPO Z07 is clearly intended to transform the car into a track-day warrior nonpareil. In addition to the previously noted aero tweaks, Z07-optioned cars will be shod in gummy Michelin Pilot Sport Cup tires (sized 285/30ZR19 front and 335/25ZR20 rear) and fitted with ginormous carbon-ceramic brakes similar in size (15.5/15.3 inches, front/rear) and configuration to the C6 ZR1’s binders. The result is a car that is reportedly capable of outpacing even the “King of the Hill” C6 ZR1 on a track.
Standard Z06s will receive slightly less sticky Pilot Sport rubber in identical sizes, along with two-piece steel brake rotors in 14.6- and 14.4-inch diameters. Gone are the novel eight-puck calipers from the previous car, replaced by conventional aluminum clampers in a six-/four-piston layout.
Both flavors of Z06 will ride on ultra-lightweight, spin-cast aluminum wheels measuring 19x10 inches up front and 20x12 inches in the rear.
Built to Win
It’s a testament to the fundamental goodness of the C7 platform that much of the base Stingray hardware—including the aluminum frame, the two available seat designs, the Magnetic Selective Ride suspension, and the eLSD electronic limited-slip differential—carries over directly to the Z06 (though the Z’s suspension is “uniquely calibrated for the higher performance threshold,” according to Chevy.) And with staggering performance increases like these arriving just over a year into the seventh-generation model run, we can hardly to wait to see what Team Corvette has planned for the future.