[King T]

(Hot Rod Magazine)



2015 C7 Z06: a Faster, Sexier, Less-Expensive ZR1

The 2015 C7 Z06 will be the fastest production Corvette that Chevrolet has ever built. It will have at least 625hp, and it will probably be a lot less expensive than the C6 ZR1 that was already one of the fastest cars $100,000 could buy. That in itself is no easy task for Corvette engineers, but not only does the C7 Z06 look to completely reset the bar on performance, it was also tasked with broadening the appeal of it’s track-focused machine.

The first real leap from previous Corvette Z06 models is the addition of forced induction. The new 6.2L LT4 direct-injected V8 in the C7 Z06 is expected to produce at least 625hp and 635lb-ft of torque thanks to a new, compact supercharger. Smaller than both the 2.3L supercharger from the ZL1′s LS9 and the 1.9L supercharger from the ZL1′s LSA, the 1.7L Eaton R1740 TVS supercharger in the 2015 LT4 spins up to 20,000rpm, a third faster than the 2.3L TVS used on the LS9. The new, smaller supercharger is able to build boost sooner by spinning faster, and is more efficient for cooler intake charges. The compact size of the rotors allowed powertrain engineers to mount the supercharger low in the lifter valley. The overall height of the LT4 is only one inch taller than the LT1 from the Stingray, keeping the center of gravity low and allowing for a flat hood.

The C7 Z06′s LT4 features several improvements to better deal with the increased cylinder pressure and heat:
-Rotocast A356T6 aluminum cylinder heads are stronger and handle heat better than conventional heads

-Lightweight titanium intake valves and machined connecting rods reduce reciprocating mass

-High 10.0:1 compression ratio – for a forced-induction engine – enhances performance and efficiency; enabled by direct injection

-Forged aluminum pistons with unique, stronger structure ensure strength under high cylinder pressures

-Stainless steel exhaust headers and aluminum balancer are lighter than their LT1 counterparts

The LT4 also marks GM’s first use of Active Fuel Management in a supercharged application. At cruise, the LT4 can run in 4-cylinder mode without boost. Chevrolet engineers told us that during development of the C7 Z06 they tested a tune that kept the LT4 in 4-cylinder mode longer, until the engine developed boost, but it was more efficient to switch back to V8 mode sooner.

Like the C6 Z06, the upcoming C7 Z06 features flared bodywork compared to the car it’s based on. Front fenders are wider by 2.2 inches and cover P285/30ZR19 tires that are 1.5 inches wider than the tires on the Stingray, while the rear fenders stretch 3.15 inches to fit 335/25ZR20 tires that are two inches wider. The new front fascia features front brake cooling ducts on either side of a wider opening that uses a carefully-designed grille that actually increased airflow compared to an empty opening. There’s no question; it looks like it belongs on the track.
To use the power and grip to its potential, Chevrolet engineered a tremendous amount of downforce into the car, with more available in increments depending on the car’s intended use.

-The standard C7 Z06 features a front splitter, spats around the front wheel openings, a unique carbon-fiber hood with a larger vent, and the rear spoiler from the Corvette Stingray’s Z51 Performance Package

-An available carbon-fiber aero package (in either black or a visible carbon-fiber finish) adds a carbon fiber front splitter with aviation-style winglets, carbon fiber rocker panels, and a larger rear spoiler with a fixed wickerbill or “Gurney flap” – a small, vertical tab at the edge of the spoiler that significantly increases downforce

-The available Z07 package adds a larger winglets to the front splitter, along with an adjustable, see-through center section on the rear spoiler for track use; with this package, the Corvette Z06 delivers the most amount of aerodynamic downforce of any production car that GM has tested.

Like the C6 Z06, the C7 Z06 will feature a Z07 option package that marks the pinnacle of track-focused Corvette performance. In addition to the aforementioned aero upgrades, the Z07 brings Michellin Pilot Sport Cup tires, and carbon-ceramic brakes from Brembo with 15.5-inch rotors in the front and 15.3-inch rotors for the rear. That’s up from the 14.6 and 14.4-inch Brembo two-piece steel rotors found on the standard Z06. While the track tuning was not yet complete at the time of our sneak peek, Corvette engineers told us that the C7 Z06 was setting lap records at GM’s Milford Proving Grounds; records previously held by the C6 ZR1.

The final major departure from past Z06 model, the C7 Z06 marks the first availability of an automatic transmission, making it the only 600+ horsepower car on the market with both a traditional manual transmission and an automatic. While the 7-speed Tremec transmission with Active Rev-Match is standard and will likely be popular, Chevrolet told us that the Z06 has to be able to turn a profit in order to earn its keep in the lineup, and a lot of potential Z06 buyers were turned away by the mandatory third pedal. To ensure the widespread appeal of the C7 Z06, Chevrolet engineered an all-new 8L90 eight-speed automatic that offers full manual control via steering-wheel-mounted paddle shifters. The transmission uses a torque converter for smoother shifts, but it’s fast as well, completing wide-open-throttle upshifts eight-hundredths of a second quicker than those of the dual-clutch transmission offered in the Porsche 911. The transmission was engineered to fit in the same space as the existing 6-speed auto, and thanks to creative packaging and the use of aluminum and magnesium, the 8L90 is more than eight pounds lighter than the six-speed it replaces.

The gear ratios for the 8L90 are:
1st: 4.56
2nd: 2.97
3rd: 2.08
4th: 1.69
5th: 1.27
6th: 1.00
7th: .85
8th: .65
Reverse 3.82

Chevrolet has not yet announced pricing, but after the presentation we saw, HOT ROD’s immediate thought was that this would be a $100,000 car like the C6 ZR1, at least. Tadge Juechter, the Corvette’s chief engineer, told us that they’re trying to get the C7 Z06 to undercut the base Porsche 911 that packs 350hp and starts at about $84,000. That’s not much more than a C6 Z06, which would make the C7 Z06 the performance bargain of the decade.