Chevrolet today introduced the most track-capable Corvette in the brand’s history – the 2015 Corvette Z06. It stretches the performance envelope for Corvette with unprecedented levels of aerodynamic downforce, at least 625 horsepower from an all-new supercharged engine, and an all-new, high-performance eight-speed automatic transmission – all building on the advanced driver technologies introduced on the Corvette Stingray.
“The new Z06 delivers levels of performance, technology and design that rival the most exotic supercars in the world,” said Mark Reuss, president, General Motors North America. “And the Z06 leverages the engineering expertise of GM, offering the choice of two world-class transmissions, supercar performance without supercar fuel consumption and technologies that make it easier to fully enjoy the incredible experience of driving it.”
The 2015 model is the first Corvette Z06 to offer a supercharged engine, an automatic transmission and, thanks to a stronger aluminum frame, a removable roof panel. The new, supercharged 6.2L engine is expected to deliver at least 625 horsepower (466 kW), and can be matched with either a seven-speed manual or an all-new, high-performance eight-speed automatic transmission with paddle shifters for manual control. The aluminum frame carries over from the Corvette Stingray and will be used essentially unchanged for the Corvette Racing C7.R.
A track-focused Z07 Performance Package adds unique components for true aerodynamic downforce, Michelin Pilot Super Sport Cup tires for enhanced grip, and Brembo carbon ceramic-matrix brake rotors that improve braking performance and contribute to greater handling through reduced unsprung weight. Although development testing is ongoing, the Z07 package has already recorded some of the fastest lap times ever for a Corvette, surpassing even the ZR1.
“The Corvette Z06 is a great example of the technology transfer between racing and production Corvettes,” said Tadge Juechter, Corvette chief engineer. “First, we took what we learned on the Corvette Racing C6.R and applied that to the all-new Corvette Stingray. Then, using the Stingray as a foundation, the Z06 and C7.R were developed to push the envelope of performance on the street and the track.”
Supercharged, efficient performance
The heart of the 2015 Corvette Z06 is the all-new LT4 6.2L supercharged V-8 engine, expected to deliver an estimated 625 horsepower (466 kW) and 635 lb-ft of torque (861 Nm). To balance performance and efficiency, the LT4 leverages the same trio of advanced technologies introduced on the Corvette Stingray: Direct injection, Active Fuel Management, or cylinder deactivation, and continuously variable valve timing.
These technologies – combined with the fuel-efficient multi-speed transmissions, aerodynamic design and lightweight construction – help make the new Z06 surprisingly fuel efficient.
“The supercharged LT4 engine delivers the greatest balance of performance and efficiency ever in the Corvette,” said John Rydzewski, assistant chief engineer for Small-Block engines. “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 whenever the driver calls up its tremendous power reserve.”
To maintain the Z06’s mass and performance targets, the LT4 engine was designed with a more-efficient, more-compact supercharger. Even with its integrated supercharger/intercooler assembly mounted in the valley between the cylinder heads, the engine is only about one inch (25 mm) taller than the Corvette Stingray’s LT1 engine – while delivering nearly 37 percent more horsepower and 40 percent more torque.
The new 1.7L Eaton R1740 TVS supercharger spins at up to 20,000 rpm – 5,000 rpm more than the supercharger on the Corvette ZR1’s LS9. The rotors are shorter in length, too, which contributes to their higher-rpm capability – and enables them to get up to speed quicker, producing power-enhancing boost earlier in the rpm band. That boost is achieved more efficiently, thanks to a new, more direct discharge port that creates less turbulence, reducing heat and speeding airflow into the engine.
The LT4 engine also has several unique features designed to support its higher output and the greater cylinder pressures created by forced induction, including:
- Rotocast A356T6 aluminum cylinder heads that are stronger and handle heat better than conventional heads
- Lightweight titanium intake valves and machined connecting rods for reduced reciprocating mass
- High 10.0:1 compression ratio – for a forced-induction engine – enhances performance and efficiency and is enabled by direct injection
- Forged aluminum pistons with unique, stronger structure to ensure strength under high cylinder pressures
- Stainless steel exhaust headers and an aluminum balancer that are lighter than their LT1 counterparts
- Standard dry-sump oiling system with larger cooler capacity than Z51; used with dual-pressure-control oil pump.
The LT4 will be built in Tonawanda, N.Y., and at the new Performance Build Center in Bowling Green, Ky.
Eight speeds, no waiting
The supercharged LT4 is offered with a standard seven-speed manual transmission with Active Rev Match, or an all-new 8L90 eight-speed paddle-shift automatic transmission designed to enhance both performance and efficiency.
“Unlike most ultra-performance cars, the Corvette Z06 offers customers the choice between two transmissions to suit their driving styles,” said Juechter. “The seven-speed gives the driver the control of a true three-pedal manual transmission with perfect shifts enabled by Active Rev Matching. The new eight-speed automatic offers drivers the comfort and drivability of a true automatic transmission, as well as lightning-fast shifts and manual control for track driving.”
The seven-speed manual incorporates rev-matching technology for upshifts and downshifts. This driver-selectable feature can be easily engaged or disengaged via paddles on the steering wheel. The seven-speed is used with a new dual-mass flywheel and dual-disc clutch, which deliver greater shift quality and feel through lower inertia.
The eight-speed automatic is tuned for world-class shift-response times, and smaller steps between gears keep the LT4 within the sweet spot of the rpm band, making the most of the output of the supercharged engine for exhilarating performance and greater efficiency.
For performance driving, the transmission offers full manual control via steering wheel paddles, and unique algorithms to deliver shift performance that rivals the dual-clutch/semi-automatic transmissions found in many supercars – but with the smoothness and refinement that comes with a conventional automatic fitted with a torque converter.
In fact, the 8L90’s controller analyzes and executes commands 160 times per second, and wide-open throttle upshifts are executed up to eight-hundredths of a second quicker than those of the dual-clutch transmission offered in the Porsche 911.
“There’s no trade-off in drivability with the new 8L90 eight-speed automatic transmission – it was designed to deliver performance on par with dual-clutch designs, but without sacrificing refinement,” said Bill Goodrich, assistant chief engineer for eight-speed automatic transmissions. “It is also the highest-capacity automatic transmission ever offered in a Chevrolet car.”
Featuring four gearsets and five clutches, creative packaging enables the GM-developed eight-speed automatic to fit the same space as the six-speed automatic used in the Corvette Stingray. Extensive use of aluminum and magnesium make it more than eight pounds (4 kg) lighter than the six-speed. Along with design features that reduce friction, the 8L90 is expected to contribute up to 5-percent greater efficiency, when compared with a six-speed automatic.
The eight-speed automatic will be built at GM’s Toledo, Ohio, transmission facility.
Designed for downforce
The performance targets of the Z06 also posed a challenge for the design team, which had to create a striking design that also contributed to increased capabilities.
“Practically every exterior change served a functional purpose, as this beast needed more of everything,” said Tom Peters, Corvette design director, “The flared fenders accommodate larger, wider wheels and tires for more grip. 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.”
The design changes began not with the exterior panels, but the tires.
To deliver the levels of grip needed for the Z06’s performance targets, the Z06 was fitted with larger Michelin tires (Pilot Super Sport tires for the Z06; Sport Cup 2 tires with the Z07 package). The P285/30ZR19 front tires are 1.5 inches wider than the tires on the Stingray, while the 335/25ZR20 rear tires are two inches wider.
To cover the wider tire tread, the fenders of the Z06 were extended by 2.2 inches (56 mm) at the front, and 3.15 inches (80 mm) at the rear. These extensions give the Corvette Z06 a wider, lower appearance further emphasized by a unique rear fascia. It incorporates the same taillamp assemblies as the Stingray, but on the Z06 the taillamps are pushed approximately three inches farther apart, toward to edges of the body.
The tires are mounted on lightweight, spin-cast aluminum wheels that are also wider than the Stingray (19 x 10 inches in front and 20 x 12 inches in the rear). Their open, ultralight design showcases the massive Brembo brakes, which are part of the design aesthetic:
- The Z06 features two-piece steel rotors, measuring 14.6 x 1.3-inch (371 x 33 mm) front and 14.4 x 1-inch (365 x 25 mm) rear, with aluminum six-piston and four-piston fixed calipers, respectively
- The Z07 package adds larger, 15.5 x 1.4-inch (394 x 36 mm) front and 15.3 x 1.3-inch (388 x 33 mm) carbon ceramic-matrix brake rotors for consistent performance lap after lap, and collectively save 23 pounds over the standard Z06 rotors.
To harness the cornering and braking grip afforded by the larger tires and brakes, the exterior of the Corvette Z06 is tailored to produce aerodynamic downforce that presses the tires to the ground at high speeds.
The Z06 will offer three, increasing levels of aerodynamic downforce:
- The standard 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 – a small, vertical tab at the edge of the spoiler that significantly increases downforce
- The available Z07 package add 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 aerodynamic downforce of any production car that GM has tested.
The exterior design also reflects the increased cooling required for the new Corvette Z06. For example, the mesh pattern on the front fascia was painstakingly designed to deliver the most possible airflow to the supercharger’s intercooler heat exchanger, so much that the mesh grill directs more air into the engine bay than if the grille was removed.
The unique grille also features dedicated brake-cooling intakes and wider grille outlets on the bottom serve as air diffusers. The grille is complemented with a larger hood vent, which vents hot air from the engine compartment and contributes to downforce by allowing air driven through the grille to exit through the hood rather than being forced under the car, which could create lift.
Additional cooling elements include larger front fender vents and unique air blades over the inlets on the rear fenders, which force about 50 percent more air into the cooling ducts for the transmission and differential coolers than those on the Stingray. To cope with the additional airflow, the Z06 has also has larger rear-fascia openings than the Stingray.
Standard front and rear brake-cooling ducts, including Z06-signature rear ducts integrated in front of the rear fender openings, are also part of the functional design changes.
Inside, the Corvette Z06 is distinguished from the Corvette Stingray by unique color schemes that emphasize the driver-focused cockpit, and a unique, flat-bottomed steering wheel.
Like the Stingray, the Z06 will be offered with two seating choices: a GT seat, for all-around comfort, and a Competition Sport seat with more aggressive side bolstering, which provides greater support on the track. The frame structure for both seats is made of magnesium, for greater strength and less weight than comparable steel frames. They’re also more rigid, contributing to the enhanced feeling of support during performance driving.
The Z06 also benefits from interior details designed for high-performance driving, first introduced on the Stingray, including a steel-reinforced grab bar on the center console for the passenger and soft-touch materials on the edge of the console, where the driver naturally braces during high-load cornering.
The performance-supporting elements inside the new Corvette Z06 are complemented by unprecedented attention to detail and build quality. All models feature a fully wrapped interior, where every surface is covered with premium, soft-touch materials. Available materials, depending on the trim level, include Napa leather, aluminum, carbon fiber and micro-suede.
The 2015 Corvette Z06 leverages the technologies introduced on the Corvette Stingray, including the strategic use of lightweight materials and advanced driver technologies, with unique features and calibrations tailored for its capabilities.
“Our mission with the seventh-generation Corvette was to make the performance levels more accessible, enabling drivers to exploit every pound-foot of torque, every “g” of grip and every pound of downforce,” said Juechter. “It’s a philosophy we introduced with the 460-horsepower Corvette Stingray – and one that’s even more relevant with an estimated 625 horsepower at your beck and call.”
For the first time ever, the Corvette Z06’s aluminum frame will be produced in-house at General Motors’ Bowling Green assembly plant. It’s the same robust, lightweight frame used on the Corvette Stingray and it will be used essentially unchanged for the C7.R race cars.
The stiffer design of the aluminum frame allows the Corvette Z06 to be offered with a removable roof panel for the first time. With the lightweight, carbon fiber roof panel removed, the new Corvette Z06 offers 20 percent more structural rigidity than the previous model’s fixed-roof design. It is 60 percent stiffer than the previous model with the roof panel installed.
The new Z06 retains the SLA-type front and rear suspension design of the Corvette Stingray but uniquely calibrated for the higher performance threshold. The third-generation Magnetic Selective Ride Control dampers are standard on Z06. They can be adjusted for touring comfort or maximum track performance via the standard Driver Mode Selector.
Like the Stingray, the Driver Mode Selector tailors up to a dozen features of the Z06 to suit the driver’s environment, including:
- Launch control: Available in Track mode for manual and automatic transmissions, providing maximum off-the-line acceleration
- Active handling (StabiliTrak electronic stability control): A “competitive” setting is available in Track mode and is more suited for on-track conditions. It can also be disabled, giving the driver complete control
- Traction control: Weather mode tailors traction control and engine torque for driving in inclement conditions
- Performance Traction Management: Available in Track mode and offers five settings of torque reduction and brake intervention for track driving
- Electronic Limited Slip Differential: Adjusts the rate at which the limited slip engages, to balance between steering response and stability in different driving conditions with more aggressive performance in Sport and Track modes.
The smart electronic limited-slip differential, or eLSD, is standard on the Z06 to make the most of the torque split between the rear wheels. The system features a hydraulically actuated clutch that can infinitely vary clutch engagement and can respond from open to full engagement in tenths of a second. It shifts torque based on a unique algorithm that factors in vehicle speed, steering input and throttle position to improve steering feel, handling balance and traction.
The eLSD is fully integrated with Electronic Stability Control and Performance Traction Management systems. Its calibrations vary among three modes, based on the Drive Mode Selector setting:
- Mode 1 is the default setting for normal driving and emphasizes vehicle stability
- Mode 2 is engaged when electronic stability control is turned off in the Sport or Track modes. This calibration enables more nimble turn-in and traction while accelerating out of a corner
- Mode 3 is automatically selected when Performance Traction Management is engaged. This calibration has the same function as Mode 2, but is fine-tuned to work with Performance Traction Management.
The new Corvette Z06 will be available in early 2015. Performance data and pricing will be announced closer to the start of production.
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Published Dec 7th, 2015