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What's new? Chevrolet Corvette
Chevrolet’s latest C7 Corvette has had a thorough dynamic makeover
by Marc Noordeloos
“The Corvette has always been such great value,” notes Josh Holder, its program engineering manager. “We want this new car to be aspirational. We want people to want to own the car, to wish to own the car.”
In the USA, the average Corvette buyer is getting older. Nearly 50% of owners are over 55 (20% are 65 or older) – compared with around 20% for the Audi R8 and 30% for the Porsche 911. Clearly, Chevrolet needs to attract younger people to the US icon and this new, seventh-generation (C7) model is looking to do just that. Still, we’d forgive you if scanning the data panel made you think there isn’t much technical progress hidden behind the new design. Don’t let the pushrod V8 and seemingly familiar architecture fool you; this is a very advanced Corvette.
The outgoing C6 Corvette featured a steel frame and later introduced an aluminum frame for the higher-performance Z06 and ZR1 models. An all-new aluminum structure graces the C7 from the start and is 45kg and 57% stiffer than the outgoing steel frame. It’s stiff enough that the convertible version of the C7 needs no additional structure. The laser-welded chassis is built at the Corvette assembly plant in Bowling Green, Kentucky, and uses aluminum extrusions and high-pressure die-castings. Additionally, the front and rear cradles are hollow cast, compared with solid on the C6.
This new chassis gains structural reinforcements in the pedal box, making a right-hand-drive Corvette difficult. Holder adds, “Right now, it’s a business decision, but we are also trying to expand our market globally, and we’d like to do that with this car. So, who’s to say that there wouldn’t be one (a RHD version) down the road?” Final testing and tuning for export models will be done around Europe and at the Nürburgring. Also, all Corvettes bound for Europe and the Middle East use the cooling setup from the higher-performance Z51.
The 6.2-liter LT1 V8 powering the C7 is all-new. It continues with a pushrod valvetrain, but the engine uses new fuel-saving technology, including cylinder-deactivation. The packaging constraints of these systems forced engineers to extend the wheelbase by 25mm. An added bonus of this stretch is rear-biased weight distribution – likely to be 51% for final production cars.
The basic suspension design is the same as the C6, including double-wishbones and transverse leaf springs. “We prefer to call it a transverse composite spring!” clarifies Holder. “The technology involved to manufacture the spring enables a low mass, low center-of-gravity spring choice versus a conventional coil-over. It packages very well in the car. There is a lot of science in it. It helps reduce roll without giant anti-sway bars.” Holder also notes the excellent durability of this setup and the fact that many popular, aftermarket coil-over setups work well, but don’t pass GM’s strict durability tests. The C7 is further enhanced and lightened through the use of hollow lower control arms and new aluminum rear toe links.
The Corvette will be offered in both base form and the more focused Z51 at launch. “The biggest difference is roll stiffness,” says Holder. “The base car has no rear anti-sway bar and a smaller front bar. This improves the ride. The base car also comes with a taller (aspect-ratio) tire.” Both cars feature standard Bilstein dampers. The 45mm piston setup on the Z51 – versus 35mm – is very track-oriented; therefore it sacrifices some on-road comfort.
Buyers can also specify magnetorheological (MR) dampers on the Z51. Supplied by BWI Group, they now use a twin-wire/dual-coil setup, reacting 40% faster. Holder elaborates, “When you go to the MR damper, the extreme setting is just a touch stiffer than the passive Z51 damper. Where you really notice is on the softest setting. It is much, much softer so the ride frequencies are going to be lower. We look at the Z51 with MR as the no-compromises car.”
Further technical advancement is shown in the steering system. Supplied by ZF, it is now electrically assisted – a first for Corvette. Chevy claims increased steering feel, helped by a 150% stiffer steering column and 600% increase in intermediate shaft torsional stiffness. The end result is five-times stiffer overall compared with the C6. Holder notes, “We’ve toyed with it (EPS) for some time. Our biggest concern, as with everyone, is that EPS compromises on-road sensitivity or road feel. Our experience in integrating it into the C7 has shown us no compromises.”
Steering is just one of the systems integrated into the new Driver Mode Selector. This new feature uses a rotary knob near the shifter. It offers five settings – Weather, Eco, Tour, Sport and Track. Within each mode, up to 12 performance parameters are adjusted. This includes the steering and the active exhaust system, as well as the stability/traction control and available six-speed automatic transmission. An added benefit of cars equipped with the MR dampers is the utilization of ride-height sensors. Holder adds, “The data from these sensors allows the chassis systems to act progressively and work more quickly in a track environment. This is for things like weight transfer and how much power we can apply.”
Another system integrated into the Driver Mode Selector is the new hydraulically actuated, electronic limited slip differential (eLSD). “The eLSD can basically go from nearly an open differential to a fully locked differential,” says Holder. “When you’re in a yaw rate change, it can lock and unlock accordingly to maintain control. Where you’ll really see it is in slalom runs. In a conventional differential, you get some body-roll upon transitions – head toss. With the eLSD, the car feels planted.” The eLSD is included in the Z51 package and has three calibrations, depending on the Drive Selector Mode. The system improves stability on the highway, enhances steering turn-in as well as responsiveness, and improves traction out of corners. Holder adds, “With the traction-control features active, you can mat the throttle with the wheel at full-lock, and power out of a corner. It’s a pretty amazing setup [the eLSD].”
The Corvette’s wheel, tire, and brake package rounds out the dynamic advancements. Both models come equipped with Michelin Pilot Super Sport ZP runflat tires. The Z51 adds larger, 19in front and 20in rear forged alloys. We talked to Holder about the decision to continue with runflat tires on the Corvette: “We’re at a point where the structure of the sidewall that used to be required for runflat technology has evolved so that you can now get a quiet, compliant tire. The Corvette is a grand touring car. We felt the little bit of mass savings [of going with a non runflat] was not worth the package space and mass of a fill (fix-a-flat) system.”