Drop-top Supercar
Chevrolet has introduced one of the most capable drop-tops on the market: the 2015 Corvette Z06 Convertible. With at least 625 horsepower, and 635 pound-feet of torque, the Z06 is also the most powerful convertible ever produced by Chevrolet.
“The Z06 Convertible is a world-class supercar in every sense,” said Mark Reuss, executive vice president, Global Product Development. “Only a handful of convertibles in the world bring more than 600 horsepower and 600 pound-feet of torque. Even fewer can match the advanced technologies, aerodynamic design, and visceral driving experience of the Z06 Convertible.”
This is the first Z06 Convertible offered from the factory since 1963 when the Z06 option package was introduced for endurance racing. Records show only 199 Corvette orders with a Z06 package that year, including one convertible.
Recent technological advancements enable the building of a modern Z06 Convertible, said Corvette chief engineer Tadge Juechter.
“Until recently it was not possible to create a lightweight, open-roof structure strong enough to cope with the braking, cornering, and acceleration of Corvette’s top performance models,” Juechter said. “The frame for the Z06 convertible leverages advancements in computer-aided engineering, metallurgy, and manufacturing techniques – many of which were not available just five years ago.”
The aluminum structure is 20 percent stiffer than the previous, fixed-roof Z06. As there are no structural reinforcements needed for the Z06 Convertible, its curb weight is nearly identical to the Z06 Coupe. They also share the same chassis tuning, powertrain output, driver technologies and equipment options – including the Z07 Performance Package, which adds Brembo carbon-ceramic matrix brakes, Michelin Pilot Sport Cup tires and adjustable front- and rear-aerodynamic components.
“The most impressive aspect of the Z06 Convertible may be its performance bandwidth,” said Juechter. “Very few cars on the market can match its combination of extreme, supercar levels of performance; the flexibility for daily driving and long-distance commuting; and the 360-degree, open-air driving experience only true convertibles can offer.”
All-aluminum, high-tech foundation
The Corvette Z06 Convertible represents the culmination of more than four years developing an all-new, all-aluminum structure for the seventh generation Corvette. That structure, built at General Motors’ Bowling Green Assembly plant, was designed to the specifications of the Corvette Stingray, Corvette Z06 and the Corvette Racing C7.R.
“We wanted a frame that was lighter than the steel frame of the previous Corvette, yet strong enough for both a 600-horsepower convertible and a 24-hour endurance racer,” said Ed Moss, engineering group manager for Corvette structures. “That would not have been possible without improvements in computer-aided engineering software, which allowed us to model more than 17,000 frame iterations, with each iteration improving strength and stiffness, while reducing mass.”
The team used nearly 186,000 computational hours of modeling to develop the frame. It features main rails composed of five customized aluminum segments, including aluminum extrusions at each end, a center main rail section and hollow-cast nodes at the suspension interface points. The gauge of each segment varies in thickness from 2mm to 11mm, tailored – along with the shape – to meet the strength and stiffness requirements for each frame section with minimal weight.
The only structural differences between the Z06 Coupe and Convertible are provisions for mounting the power-folding top, and repositioned safety-belt mounts.
High-performance aerodynamics
Like the structure, only minor design changes distinguish the Z06 Coupe from the Convertible. The Z06 convertible features an electronic top that can be lowered remotely using the car’s key fob. The top can also open or close on the go, at speeds of up to 30 mph.
With the top up, the Z06 Convertible is designed for a refined driving experience. A thick fabric top, offered in four colors along with sound-absorbing padding and a glass rear window, contributes to a quiet cabin and premium appearance.
Behind the seat backs, dual accent panels – either Carbon Flash-painted or available with exposed carbon fiber – enhance the character lines of the tonneau cover. Corvette Stingray’s signature “waterfall” design originates in the valley between the nacelles, bringing the exterior color into the interior.
The power-operated tonneau cover necessitated moving the air intakes for the differential and transmission coolers from the rear quarter panels on the Z06 Coupe to the underbody of the Z06 Convertible.
Otherwise, both models share the same, performance-driven aesthetic.
“Practically every exterior panel serves a functional purpose to meet the performance goals of the Z06,” 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.”
Both Z06 models are fitted with Michelin tires (Pilot Super Sport tires for the Z06; Sport Cup 2 tires with the Z07 package): P285/30ZR19 front, and 335/25ZR20 rear.
Supercharged, efficient performance
The heart of the 2015 Corvette Z06 is the all-new LT4 6.2L supercharged V-8 engine, expected to deliver at least 625 horsepower and 635 lb-ft of torque. 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.”
The supercharged LT4 comes with a standard seven-speed manual transmission with Active Rev Match, or an all-new 8L90 eight-speed paddle-shift auto transmission designed to enhance performance and efficiency. The seven-speed manual incorporates rev-matching technology for upshifts and downshifts. A new dual-mass flywheel and dual-disc clutch deliver greater shift quality and feel through lower inertia.
The eight-speed automatic is tuned for world-class shift-response times. 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.
“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 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.
Track-proven technologies
The 2015 Corvette Z06 Coupe and Convertible leverage the technologies introduced on the Corvette Stingray, 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.”
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, adjustable for touring comfort or maximum track performance via the standard Driver Mode Selector, are standard on Z06.
The smart electronic limited-slip differential, or eLSD, is standard. It features a hydraulically actuated clutch capable of infinitely varying clutch engagement. The system enhances all aspects of performance by constantly tailoring the clutch-pack engagement based on a unique algorithm that factors in vehicle speed, steering input and throttle position to improve steering feel, handling balance and traction.
Founded in 1911 in Detroit, Chevrolet is now one of the world’s largest car brands, doing business in more than 140 countries and selling more than 4.9 million cars and trucks a year. Chevrolet provides customers with fuel-efficient vehicles that feature spirited performance, expressive design, and high quality. www.chevrolet.com