Chevrolet gives enthusiasts what they want, a Z06 convertible
Andy Bolig - April 11, 2014 08:53 PM
Chevrolet introduces the most powerful convertible they've ever produced.
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. The only structural differences between the Z06 Coupe and Convertible are provisions for mounting the power-folding top, and repositioned safety-belt mounts.
“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 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.
These components are assembled using many advanced manufacturing processes:
- 439 spot-welds
- 188 Flowdrill-machined fasteners installed by a high-speed drill
- 113 feet of adhesives used in conjunction with welding and fasteners
- 37 feet of laser welds
High-performance Design: 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 (50 km/h).
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.
The tires are mounted on lightweight, spin-cast aluminum wheels (19 x 10 inches in front and 20 x 12 inches in the rear). Their open, ultralight design showcases the massive Brembo brakes, which contribute to the design. 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. They collectively save 23 pounds over the standard Z06 rotors.
Both Z06 coupe and convertible will be available with one of 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 rear spoiler. An available carbon-fiber aero package delivers aerodynamic downforce four times greater than the standard Z06. It 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 package is available in black or a visible carbon-fiber finish
The available Z07 package adds larger winglets to the front splitter, along with an adjustable, see-through center section on the rear spoiler enabling customers to tailor the aerodynamics to their preference.
Compared to the Corvette Stingray, the Corvette Z06 fenders are 2.2 inches (56 mm) wider at the front, and 3.15 inches (80 mm) at the rear. Those 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 exterior design also reflects the increased cooling required for the new Corvette Z06. For example, the mesh pattern on the front fascia was 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. A larger hood vent allows air driven through the grille to exit through the hood rather than being forced under the car, which could create lift. 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.
The Z06 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.
Like the Stingray, the Z06 comes 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. A magnesium frame structure for both seats provides greater rigidity and strength compared with steel frames.
Unprecedented attention to detail and build quality complements the Corvette Z06’s performance. All models feature a fully wrapped interior, with every surface covered by premium, soft-touch materials. Available materials, depending on the trim level, include Napa leather, aluminum, carbon fiber and micro-suede. The interior also features a flat-bottom steering wheel with a carbon fiber center spoke. The Z06 comes in five interior colors, including two that are unique to Z06 – blue and dark gray.
Supercharged 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 (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.”
The supercharged LT4 comes 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 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 (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.
Track-proven Tech: The 2015 Corvette Z06 Coupe and Convertible leverage the technologies introduced on the Corvette Stingray, with unique features and calibrations tailored for its capabilities.
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.
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
•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, balancing 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. 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.