Generation Vette

First impressions of the new generation Chevrolet Corvette can be deceiving. A casual glance at the familiar lines of the 2005 model might suggest the famous General Motors sports car has undergone only a modest redesign.

In fact deeper examination reveals that not only has the design been changed significantly, but the Corvette’s mechanicals have also been thoroughly re-engineered.

As Corvette Chief Engineer and Vehicle Line Executive Dave Hill puts it, the parts shared between this generation, the sixth in a line that dates back to 1953, and today’s car, would fit in a shopping basket. “It’s a comprehensive upgrade,” says Hill. “The goal was to create a Corvette that does more things well than any performance car. We’ve thoroughly improved performance and developed new features and capabilities in many areas, while at the same time systematically searching out and destroying every imperfection we could find.”

Production of the ’05 Vette coupe starts in the third quarter, followed by a convertible version in the fall.

Though it may be hard to gauge visually, the C6 Corvette is actually 5 in. shorter than the outgoing model and 1 in. narrower. In terms of length, 3 in. have been trimmed from the front overhang, 2 from the rear. At the same time the wheelbase has grown by 1.5 in. The changes, which have not compromised the Corvette’s usable interior space, give the Chevy the same basic dimensions as a Porsche 911. Wheel size is upped by 1 in. front and rear, to 18 and 19 in. rims respectively. Weight is on par with the current model, despite extra equipment.

Design

The interior keeps the wellknown wraparound theme.

Visteon-supplied fixed headlamps were made possible thanks to Xenon technology supplied by Osram Sylvania.

For Corvette Designer Tom Peters, the focus was on making the car look more dynamic. “I wanted to make the whole car leaner, more angular while keeping some of the soft round forms,” he says. To realize the full effect of Peters’ work it’s necessary to see the new and old versions of the Corvette side by side. Then the differences are striking. Aside from the obvious changes like fixed headlights instead of pop-ups, the whole front end is more aggressive, cleaner, sharper looking. The front and rear quarter panels arch more prominently over the wheels, a styling feature that links back to the classic Stingray Corvette.

The move to fixed headlamps for the first time on a Corvette since 1962 not surprisingly involved some controversy. “There was a lot of emotional discussion around that,” says Peters. “We finally settled on exposed headlamps because they fit the theme for the new Corvette — lean, purposeful, performance oriented.”

Key advantages of the Visteon-supplied lights are lower weight, less complexity and superior performance. The light assemblies use HID Xenon low-beam projectors and tungsten- halogen high-beam projectors. Also housed in the lights’ polycarbonate enclosures are the parking lights, side-turn markers and daytime running lights.

As well as cleaning up the front-end appearance of the Corvette, Peters spent much time on improving the rear view, which even the most devoted Corvette fans feel is its weakest aspect. The basic form is unchanged, but detailed touches like the integrated lip spoiler and exhaust tip surround panel help make the rear look less bulky. Two positive consequences of the ‘Vette’s distinctive rear shape remain unchanged; it has outstanding luggage space for a sports car and that sharp cut-off helps deliver a very slippery wind tunnel performance. The 0.28 coefficient of drag, achieved by 400 hours in the wind tunnel and know-how borrowed from the C5R racing team, makes the C6 the most aerodynamically efficient Corvette ever and has improved anti-lift characteristics for better high-speed stability.

In the opinion of Bob Lutz, GM’s ‘car-guy’ vice-president and a natural champion of the Corvette, radical design change was not the way to go. “It is very clearly an evolutionary design,” says Lutz. “That’s the right way to develop an icon; you tweak it, make it better but don’t violate the basic character of car. It’s the type of design approach that Ferrari or Porsche would use.”

Engine

The 400 hp LS2 is the most powerful engine offered in a Corvette.

In the engine department, the C6 is a development of the Gen IV small-block V-8, with displacement bumped up from 5.7 to 6.0L and a mass of other modifications. Dubbed the LS2, the new engine delivers peak output levels of 400 hp and 400 lb. ft. of torque, making it the largest, most powerful standard small-block engine ever offered in the Corvette. Compared to the Gen III-based LS1, the LS2 incorporates several significant changes:

• All-new aluminum block casting incorporates provisions for external knock sensors and revised oil galleries; external sensors improve serviceability.
  
• Cylinder bore diameter increased to 101.6 mm (4.00 in.), increasing displacement to 6.0L.
  
• Camshaft lift increased to take advantage of increased cylinder head flow.
  
• Camshaft sensor relocated from the rear of the block to the front of the block provides room for new oil galleries.
  
• Flat-top piston design with lower ring tension reduces friction.
  
• Piston floating wrist pins help quiet the engine.
  
• Redesigned, “wingless” oil pan with cast baffling has reduced mass and provides superior oil control under high-performance driving maneuvers.
  
• Revised exhaust manifolds are 33 percent lighter.
  
• More efficient ignition coils require less energy to provide a comparable spark.
  
• Compression raised to 10.9:1.
  
• Larger, 90-mm single-blade throttle body.
  
• Reduced-mass water pump design with improved sealing capability.
  
• Engine “redline” raised to 6500 rpm.
  
• Revised and more powerful engine controller incorporates all electronic throttle control functions.
  
• Mass has been reduced by 7 kg on the automatic version.

The cylinder heads for the LS2 are derived from designs used in previous Corvette Z06 models, including raised intake ports and an unshrouded-valve combustion chamber design that, when combined with the engine’s flat-top pistons, produces a more efficient swirl of the air/fuel mixture. This efficiency enables a higher 10.9:1 compression ratio, which increases fuel economy and horsepower. The LS2’s new oil pan was developed to provide better oil control under the extreme high-rpm/high g-force driving maneuvers. The elimination of the previous “gull wing” oil pan design reduces the engine’s oil capacity from 6.5 quarts to 5.5 quarts with a dry filter.

“We sweated the details to ensure the engine maintains a balance between performance and efficiency,” says Dave Muscaro, GM Powertrain’s assistant chief engineer of small-blocks for cars.

Vehicle	HP	Mpg	comb Index
C6 Corvette	400	22.6	9,040
Porsche 911 GT2	477	18.2	8,681
Porsche Turbo	444	18.2	8,081
Dodge Viper	500	15.5	7,750
Porsche 911	340	20.6	7,004
Ferrari 575 Maranello	515	12.7	6,541
Ferrari Modena	400	12.7	5,080

Advances in catalyst substrates made possible catalytic converters that are at the same time more effective and less restrictive for the LS2’s exhaust. The new converters are mounted closer to the exhaust manifold for quicker lightoff and reduced cold-start emissions. As a result, the more restrictive quad catalyst design of the LS1 — with its small, auxiliary “pup” converters — was not necessary to meet emissions requirements. An additional benefit of the exhaust system’s development was the elimination of the LS1’s air injection reaction system.

For the C6 there are major revisions to the manual and automatic transmissions. The Tremec 6-speed manual gearbox is available with two sets of ratios, one with more aggressive acceleration characteristics reserved for Corvette’s Z51 Performance Package that emulates the performance of the C5’s Z06 model. Shift characteristics are improved with new synchronizers that reduce travel by 10 percent, and a shifter knob that is an inch shorter and redesigned for better driver operation.

The Hydra-Matic 4L65-E automatic transmission is an upgraded version of the C5’s 4L60-E, strengthened and revised to accommodate the LS2’s 400 lb. ft. of torque. The transmission now shifts at higher revs to take advantage of the higher engine output.

As well as the increased output of the C6 engine, Chevrolet is trumpeting its fuel efficiency. When the LS2’s 400 horsepower is multiplied by its 22.6 mpg combined city/highway mileage estimates, it yields a total of 9,040. Here are Chevrolet-supplied figures of how the C6 compares with some of its key competitors: 

Chassis

The Corvette’s ‘performance architecture’ shared with the Cadillac XLR features hydroformed steel rails, cored composite floors, enclosed center tunnel, rear-mounted transmission and aluminum cockpit structure.

The C6 uses GM’s so-called performance car architecture which its shares with the Cadillac XLR roadster and which is essentially a development of the Corvette’s existing chassis. This means the familiar features of the chassis — the hydroformed steel frame rails, cored composite floors, enclosed center tunnel, rear-mounted transmission and aluminum cockpit structure — are carried over, but with important changes, notably the shortened frame rails. What’s more, while the design of the short-long arm and transverse leaf spring independent suspension is the same, the actual components are all new. The focus of the chassis development team was to deliver superior ride and handling, higher lateral acceleration, more body control, a more relaxing ride, less noise transmitted from the road and better traction and stability in corners. The specific tuning changes in the chassis and suspension include suspension and steering geometry optimized for better handling and ride, advanced compounds in the tires, new directional control arm bushings, and greater suspension travel achieved through more clearance in the hub knuckles and dampers. The progressive rates of the front and rear composite leaf springs have been tuned to take advantage of the greater travel of the suspension.
 
“It’s a much more pleasing ride,” says Mike Neal, ride and handling development engineer for the 2005 Corvette. “It’s less touchy, it’s less tuggy, it’s better isolated, it’s quieter for road noise. It’s all of those things and still a better handling car.”

A crucial part of the dynamic equation was the move to the latest generation Goodyear Extended Mobility Tires. These feature new compounds and sidewall design which permit the tire to absorb impacts yet resist heat generated by zero-pressure use. Despite its lower profile, the design of the new sidewall is more compliant over bumps and impacts, which improves ride comfort while reducing noise and isolating the car from road surface imperfections.

Goodyear is supplying two different tires, depending on the suspension package. For the standard and F55 magnetic selective ride control suspensions, a standard directional-tread tire is offered for a balance between handling and ride. The Z51 performance package features an asymmetrical-tread tire that offers maximum handling performance. The wheel and tire sizes are the same for the Z51 option, which will deliver handling abilities similar to the 2004 Z06, despite the slightly narrower width of the new tires.

To manage the Corvette’s greater performance, the C6 brake system has been re-engineered. Improvements have focused on heat dissipation and durability.

For the Standard and F55 Magnetic Ride configurations, the brake rotors remain the same diameter as the C5, at 12.8 in. in front and 12.0 in. in the rear. However, the rotors themselves have been thoroughly redesigned. The front rotors weigh 2 lb. more than the C5, aiding durability. They also generate less heat against the brake pads, which improves wear and reduces fade. In all brake applications, the front calipers utilize dual pistons and the rears use single pistons. The Z51 package comes with larger diameter rotors (13.4 in. in front and 13.0 in. in rear) that are cross-drilled.

Interior

Whether or not Peters’ exterior design reaches far enough will undoubtedly keep internet chat rooms buzzing, but there’s no question about the progress made inside the C6. The instrument panel layout, quality of materials, surface finishes, the seats — all are dramatically improved over the outgoing Corvette.

A convertible is due this fall.

According to Lead Interior Designer Eric Clough, the overall theme was inspired by Corvette’s dual-cockpit heritage, with a flowing, wraparound upper feature line and two-tone split between the instrument panel upper and lower. “We wanted the surfacing to echo the hightension character of the exterior to unify the whole car. The result lends spaciousness to the passenger and a nestled cluster pod for the driver. Switches and controls are located in modular groupings set into soft skin to reduce visual clutter.”

The interior materials are significantly upgraded for comfort and aesthetics. The instrument panel and doors are covered with castskin foam-in-place trim that is soft to the touch with low gloss to minimize glare. This advanced material has double the life of conventional automotive paneling materials, resists fading and sun damage, and minimizes interior fogging, which can occur as plasticizers migrate out of the material. Anodized aluminum accents the interior in key functional areas, such as the manual shift knob and door release buttons. This material includes a screen-printed appliqu? that minimizes sun glare, and is resistant to temperature changes and fingerprints. The new precision look is underscored by flush-fit radio and climate controls, surrounding trim plates and the instrument panel-to-door closure.

One benefit of the shared architecture with the XLR is that the C6 could be equipped with many of the Cadillac’s new electronic technologies. These include keyless access with push-button start, and optional features such as a reconfigurable head-up display (now including a cornering G meter), DVD-navigation system with voice activation, XM Satellite Radio and OnStar.

A major focus of attention for Hill’s team was eliminating many of the small but annoying flaws in the current Corvette. This included changes to the hood, which is still forward-hinged, but is 15 percent smaller, 35 percent lighter and 40 percent stiffer than the previous version. The rear hatch has a power-operated single-cinching latch for better fit and operation. Doors are stiffer and easier to close, doing so with a more refined sound. The removable-roof panel is 15 percent larger, yet offers the same structural stiffness as C5’s while weighing just one pound more. With new indexing side-window glass and redesigned seals, wind noise is reduced significantly.

Chevrolet expects the new Corvette’s enhanced performance attributes to lift it to a higher echelon among the world’s leading sports cars. “The difference in driving dynamics between the C6 and today’s car is as dramatic as was the progress from C4 to C5,” claims Hill. Couple that greater performance capability with newfound refinement and the future looks promising for the 2005 Corvette.