The 2014 Stingray is a radically new Corvette. With its sharply creased lines, race-inspired vents and reconfigured greenhouse, the C7 has a boldly different appearance—edgier, less nostalgic. Under the skin, the new machine is just as much of a departure. It features an aluminum frame, a direct-injection V8 engine and a completely revamped cockpit. Whereas the move from C5 to C6 was a small step, the progression from C6 to C7 constitutes a giant leap.
The styling change is a brave move on Chevrolet’s part, as it runs the risk of alienating the Corvette’s traditional customer base, but in some ways the carmaker didn’t have a choice. With Corvette sales having fallen to alarmingly low levels in recent years, it had to do something drastic in to order reach more customers. “We wanted a clean departure,” says Corvette Product Manager Harlan Charles of the Stingray’s styling. “We wanted to evoke the Corvette, but every surface of the car had to be different. We wanted it to get noticed by a new group of people who may not have been paying attention to Corvette for a long time.”
More than simply being attention grabbing, the new Corvette’s styling needed to be purposeful. “The goal was a bold design statement that embraced the advanced technology of the car, while enhancing its overall performance in everything from the wind tunnel to the track,” explains Ken Parkinson, Executive Director of GM Global Design.
Executive Chief Engineer Tadge Juechter says he knew from the outset the Corvette needed a major redesign. Fortunately, he and his team had the full support of GM. “We had a blank sheet of paper,” says Juechter. By leveraging knowledge gained from Corvette Racing, incorporating new technology and refining existing designs, Chevrolet has created what Juechter describes as “the most capable standard Corvette that we’ve ever built.”
The 2014 Stingray looks striking. It has the head-turning wow factor of an exotic supercar, something that cannot be said about the sixth-generation Corvette, even in ZR1 trim. “It’s a hard car to ignore,” says Product Manager Charles, which is exactly the point. Yet the C7’s skin also needed to move the game forward in terms of airflow management, lighting technology and material usage. “Developing a new Corvette, while every designer’s dream, is not an easy task,” says Global Design boss Parkinson. That difficult assignment was given to Exterior Design Manager Kirk Bennion.
“For the exterior, the first goal was that we needed a new upper,” says Bennion of the Corvette coupe’s greenhouse. “Basically since 1978, the Corvette upper in its layout hasn’t really changed all that much. In ’78 we went to a bubble backlight, single basket handle and single removable roof panel. We said we need a different solution.” What he and his team came up with was the incorporation of C-pillars and rear quarter windows, something never before seen on a Corvette coupe. The single removable roof panel remains, now constructed of lightweight carbon fiber, as does the “basket handle” roll-over hoop, yet both are now more seamlessly integrated into the car’s greenhouse.
The new “upper” significantly alters the appearance of the car. “For us in exterior design, the DLO, the daylight opening, that’s a big design element,” says Bennion. “You do a nice shape there and from 50 yards away, you’ll see that as a different car.”
But the move to three rear glass panels instead of one also has functional benefits. The amount of glass has been reduced, thus lowering weight. The rear hatch itself is smaller and its struts are now buried inside the C-pillar, making for a cleaner-looking storage area. There is price to be paid, however, as the quarter-glass design eats into cargo space somewhat. But according to Bennion, “It was a negligible loss.” He also maintains that rearward vision was not seriously compromised.
Changing the Corvette’s rear end was another design goal, as Bennion and his team felt that it had hardly changed between fourth, fifth and sixth-generation models. The distinction between upholding tradition and stagnation can be a narrow one, but Bennion felt the latter had occurred. “We had to be critical of ourselves,” he says. The design they came up with is arguably the most controversial aspect of the car—certainly based on the reader feedback we’ve received thus far—but then creating a “bolder, more expressive” Corvette was yet another goal.
Far more sculpted than its predecessors, the C7’s tail features trapezoidal taillights with indirect LEDs and lit reflectors—real cutting-edge technology. The vents that flank the taillights are not styling cues; they work in conjunction with fender-mounted heat exchangers. Now set four in a row, the exhaust tips (4.25 inches in diameter with the optional dual-mode exhaust) are surrounded by the integrated diffuser. The rear end now looks much more complete, with no exposed mechanical bits to be seen under the car. The aftermarket is going to have a lot less to work with when it comes to the C7’s rear end.
Bennion and his design team also wanted to re-do the Corvette’s front end, but the impetus for this was driven more by aerodynamics than styling and was directly influenced by lessons learned on the racetrack. Since the C3, the Corvette has used a rearward-tilted radiator fed by cooling air from beneath the car. This arrangement was ditched with the C7. “The first thing we did when we started this car was we changed the front-end architecture to adopt the forward-tilt radiator,” says Bennion. “We’ve learned through Corvette Racing that a front-breather with the exit out the top of the hood is really the most efficient way to go. You benefit your cooling, you benefit your downforce and there is a drag reduction.”
The new Stingray’s coefficient of drag has yet to be released—small details are still being fine-tuned—but Bennion says it will be roughly comparable to the C6’s figure. If that seems like a disappointing result, consider the fact that the designers had much more on their plates. “It used to be we only concentrated on just getting a low Cd, a slippery shape,” says Bennion. “Now it’s gotta be a slippery shape, low lift and, by the way, you have to pull in enough air to cool the engine, cool the front brakes, cool the rear brakes and cool the trans and diff, all off the exterior surface. There’s a lot more responsibility put on the exterior design than what we’ve done in the past.”
One of those responsibilities was ensuring that enough air flowed through the rear fender-mounted inlets. The one on the driver’s side feeds the transmission cooler on automatic-equipped Stingrays, while the one on the passenger side directs air to the differential cooler on Z51 Performance Package-equipped cars. At the Corvette team’s weekly development meetings, Juechter would slip Bennion a subtle reminder: “If we don’t get enough airflow to that transmission, we don’t have a car.” After running computational flow analysis on 16 different iterations and testing the finalists in the wind tunnel, Bennion’s team hit its mark. Thanks in part to the ramped-up quarter lines along the Stingray’s sides, the small inlets flow an incredible 8 cubic meters of air per minute.
Though the protruding triangles at the leading edge of the car are primarily aimed at improving the Corvette’s pedestrian safety test results, Bennion and his team made sure that they were of aerodynamic benefit as well, both in terms of lowing the Cd and reducing lift. “Every element of the Corvette has to earn its way onto the car,” he says.
As far as aerodynamic lift is concerned, the C7 has made progress over the C6. With the Z51 package, which includes a full-width rear spoiler and an altered air dam, the Stingray generates less lift than a ZR1; a base car has less lift than a Z06. The 700+ hours of wind-tunnel time were put to good use. Still, given the number of lift-reducing elements in the design—especially the vented hood—we were surprised to learn that the Stingray doesn’t actually generate downforce. “It’s not that we didn’t want a downforce car,” explains Bennion. “We could have put more downforce in the car, but that would have raised the Cd. We’re trying to achieve that optimal balance. We felt that if we’re better than a ZR1 for the Corvette Stingray’s starting point, that’s awfully good. A zero-lift, downforce car—that’s something we want to get to.”
The Stingray’s body panels are fabricated using a new Sheet Molded Compound material that is both lighter and constructed to tighter tolerances. One of the drivers for this change was the C7’s carbon-fiber top and hood. Because carbon fiber has less thermal expansion than traditional fiberglass, it maintains its shape better and yields tighter tolerances. Essentially, the decision to use carbon fiber on the base car—a Corvette first—raised the bar on the rest of the body structure, forcing Chevy to come up with improved SMC. As a result, the Stingray’s body is 37 pounds lighter than its predecessor’s—despite the fact that the car is one inch wider and 2.4 inches longer—and will be assembled with body gaps of 3 mm or less, making for much-improved fit and finish.
When the C6 Z06 debuted as a 2006 model, its aluminum frame was a big breakthrough. Lighter and stiffer than its steel counterpart, the structure paid immediate dividends in term of performance. However, the frame’s design was compromised by the fact that it had to fit in exactly the same space as the steel version and use all the same pick-up points during the assembly process. Because of this, the material’s usage could not be optimized. With the 2014 Stingray, no such design limitations existed; the car’s aluminum chassis is all-new and takes advantage of the latest in alloy construction techniques.
Instead of using hydroformed frame rails with a continuous 4-mm wall thickness from front to rear, the C7’s rails are composed of five different segments of varying compositions. Referred to as “crash cans,” the outermost segments are 2.4-mm aluminum extrusions. These are attached to ultra-strong cast nodes to which the suspension is directly mounted. The hydroformed middle rail is 3.8-mm thick. Combined with a larger tunnel section and additional bracing, these new rails result in a frame that is 22-percent stiffer than its alloy forerunner. That might not sound like much, but the Z06 chassis is a closed-roof design, unlike the Stingray’s open-top layout. The two frames weigh about the same, but the C7’s structure is 99 pounds lighter than a steel C6 frame and a whopping 57-percent stiffer.
Whereas the C6’s aluminum frames were provided by an outside supplier, the new ones will be constructed in-house at the Bowling Green Assembly Plant. A $52-million investment in the facility converted the former Cadillac XLR production line into the new frame shop.
Though the C7’s basic suspension design is carried over—short/long double wishbones with transverse-mounted composite springs—individual parts have been upgraded. New hollow-cast aluminum front and rear cradles are approximately 25-percent lighter and 20-percent stiffer than the solid cradles used previously. Similarly, hollow lower control arms shed about nine pounds per vehicle and new aluminum rear toe links save 2.4 pounds over the previous steel links.
The standard Stingray features 35mm-piston Bilstein monotube shocks, while Z51-equipped cars feature 45mm-piston units. The Z51 can be coupled with an upgraded, third-generation version of Magnetic Selective Ride Control, which features a new twin-wire/dual-coil damper system that reacts 40-percent faster than before, providing both improved ride comfort and superior body control.
The C7 uses electric power steering. Juechter says the industry has switched over to this technology so completely that Chevy could no longer source a hydraulic unit for the Stingray, so it really didn’t have a choice in the matter. However, the Corvette team did want to do the most it could to preserve steering feel, something that electric systems usually lack. “We were super worried about it,” says Juechter of the desire to keep the driving experience as tactile as possible. To that end, Chevy engineers went about creating an incredibly rigid steering system. They increased steering-column stiffness by 150 percent and intermediate shaft torsional stiffness by 600 percent. Overall, the steering system is five times stiffer than the previous hydraulic setup.
According to Juechter, the C7 benefits from being somewhat late to the electric-steering party, as the latest systems are now much improved compared to earlier generations. The Stingray’s advanced unit offers variable ratios and variable effort, both of which can be tailored via the Driver Mode Selector control located in the center console. Capitalizing on the system’s increased speed and directness, the diameter of the steering wheel has been reduced to a diminutive 14.1 inches. Juechter says customers are going to find the Stingray’s steering a revelation in terms of precision, adding that his team rendered the steering feel problem a “non-issue.”
Wheels and Tires
In standard trim, the C7 rolls on 8.5 × 18-inch front and 10 × 19-inch rear cast-alloy wheels; Z51 cars get larger-diameter 8.5 × 19 front and 10 × 20-inch rear forged aluminum wheels. While these wheel sizes are unchanged compared to the C6, the choice of rubber is new. Having beat Goodyear in a shoot-out, Michelin is now the Corvette’s sole tire supplier. It will deliver Pilot Super Sport run-flats (245/40ZR18 front, 285/35ZR19 rear), with Z51 cars getting a higher-performing version (245/35ZR19 front, 285/30ZR20 rear) good for 1 g of lateral acceleration—a figure that bests that of the C6 Grand Sport, a model that features significantly wider wheels and tires.
With input from Corvette Racing, the 2014 Stingray features new Brembo braking systems with fixed front and rear calipers. The base car gets 12.6-inch front rotors and 13.3-inch rear rotors, which add up to a 35-percent increase in swept area. With curved slots just like those found on the C6.R racer, Z51 rotors measure 13.6 inches in front and 13.3 inches in the rear—a 6-percent increase in swept area compared to a C6 Grand Sport. In addition, the Z51 package includes brake-cooling ducts, with the fronts being fed from the grille and the rears from beneath the car.
We’ve already discussed the Stingray’s LT1 engine at length in a previous issue so we’ll keep it brief here, but suffice it to say that the 6.2-liter V8 is a technological tour de force. It incorporates direct injection, continuously variable valve timing and cylinder deactivation in the pursuit of lower fuel consumption, higher output and better torque delivery. The Active Fuel Management system automatically alters the exhaust note for a seamless transition between V8 and V4 modes.
These sophisticated technologies do come at a price, however, as the LT1 is both longer and heavier than the current LS3 engine. The C7’s one-inch wheelbase increase was made to accommodate the longer engine while still maintaining optimal weight distribution (the cockpit is no larger). Actually, weight distribution has been improved, with Z51 models now benefiting from a slight rear bias of 51 percent. Still, thanks to the Chevy small-block V8’s time-honored cam-in-block layout, the LT1 is lighter and more compact than a comparable overhead-cam V8.
Though GM has yet to provide the Stingray’s final engine-output figures (the 450 hp and 450 lbs-ft of torque numbers are estimates) or curb weight, it does claim that the car has a better power-to-weight ratio than a Porsche 911 Carrera S, the car it benchmarked for much of the C7’s development. It also claims that the Stingray will accelerate from zero to 60 mph in less than four seconds.
The LT1 is paired with either a 7-speed manual or an updated version of the existing 6-speed automatic. The manual’s extra cog was added in the interest of increasing fuel efficiency, but the new gearbox also features Active Rev Matching, which is aimed at improving both downshifts and upshifts. It is defeatable via steering-wheel paddles (the same ones are used on the paddle-shift automatic) for those who prefer to perform their own rev matching, though Juechter says that even the most accomplished track drivers will find themselves impressed with the system.
The Z51 package includes an electronic limited-slip differential. Using a unique algorithm which factors in vehicle speed, steering input and throttle position, it continuously varies the torque split between the rear wheels, going from completely open to full engagement in tenths of a second. As a result, the electric unit offers of the benefits of a traditional mechanical LSD without any of its drawbacks. According to Vehicle Systems Engineer Mike Bailey, “The eLSD can improve traction accelerating out of corners, improve stability on the highway and enhance steering turn-in and responsiveness.” Says Juechter, “I was stunned by the difference the electronic diff makes.”
While the Stingray will no doubt post some impressive performance and fuel-economy figures when it undergoes independent testing near the time of its late-summer release, Juechter claims that was not the point of Stingray development. “This car is not just about the numbers,” he says, “it’s about the way it drives. We transformed the driving experience in every way. The first time you get behind the wheel, you’re going to know that Corvettes have changed forever.”
Considering that the interior is the most-maligned aspect of the current Corvette, it comes as no surprise that Chevy set lofty goals when it came to designing the Stingray’s cockpit. “We set out to transform and reinvent this interior,” says Interior Design Manager Ryan Vaughn. “The Corvette is all about the driving experience, so we wanted to make this interior ergnomically designed for the driver. Everything is very cockpit-like and driver-oriented. We also set out to bring a new level of materials and craftsmanship to the interior. It’s got premium materials throughout: hand-stitched, leather-wrapped trim, soft-touch points—even where the driver’s leg touches the center tunnel. Authenticity was important, too: Everything has a function, everything’s there for a reason. If something looks like carbon fiber, it’s real carbon fiber. It if looks like aluminum, it’s really aluminum.”
“The seats were a huge push for this car,” says Vaughn. To better serve the varying needs of Corvette customers, he and his team came up with two designs—a standard GT seat and an optional Competition seat: “The GT seat is the great all-around sports-car seat; the Competition sport seats are very aggressive.” Both are more supportive than the current seat, but increasing stiffness was also a big priority, as recent Corvette chairs have been widely criticized for their general floppiness. Stouter magnesium frames work in conjunction with a hard back panel to prevent flexing and bending under load.
One of the challenges of making stiffer, more supportive seats was that they had to fit in ostensibly the same space as found in the current Corvette. One of the ways the designers accomplished this was to re-engineer the placement of the airbag. Instead of it being integrated into the seat, it is now housed in its own separate module so that the seat itself could be slimmed down as much as possible. “It allowed us to squeeze more into the space that we got,” explains Vaughn.
When Juechter and his engineering team put in the request for a smaller steering wheel, the interior-design group was handed a huge challenge. That’s because in order to reduce the wheel’s size while still maintaining its multi-button functionality, they had to completely redesign the airbag module. What they came up with was the smallest such module in GM history. “That was the enabler,” says Vaughn.
When it came to the wheel’s shape, thickness, stitching and button placement, the interior team really sweated the details. “A lot of working went into the six and nine positions, making sure they feel right, that the seam lays nice and flat, so you don’t feel it when you grip the wheel,” explains Vaughn. “We let the arc of your thumb determine where the switches are placed.”
A similar driver-focused approach was taken in the design of the Stingray’s instrument panel; it wraps around the driver to make sure every control is close at hand. At the center of the instrument cluster is a reconfigurable 8-inch hi-def video screen with Tour, Sport and Track modes, all of which display a a central tachometer. An analog speedometer is always off to the left.
The infotainment screen is within the “reach curve” of the driver. Though the system offers a number of functions such as navigation, a conscious decision was made to retain plenty of dedicated buttons, knobs and switches. “It was all about achieving the right balance between the touch functionality and hard buttons,” says Vaughn. “There are things that are more intuitive and natural to control with the screen, and there are things you want to just be able to do a blind poke, without looking, and hit the right button or find the right knob. Simple is better.”