To meet an ambitious 3000-pound weight target, C7 is constructed like an aircraft. The three-rail space frame GM patented for C5 continues with major improvements. The hydroformed-aluminum main members developed for Z06 and ZR1 are now standard across all C7s, an upgrade enabled by transferring frame manufacturing from an outside supplier to the Corvette’s Bowling Green assembly plant. Carbon-fiber (CF) floor and bulkhead panels adhesively bonded between the central backbone and the perimeter rails augment structural stiffness. We also expect CF to replace all the sheet-molded fiberglass exterior panels. A single-piece lift-off roof—a Corvette feature since 1984—remains standard on the coupe.
Bucking the global trend toward boosted small-displacement engines endowed with ample power and exemplary efficiency, the new, fifth-generation small-block—rechristened LT1—is a 6.2-liter naturally aspirated V-8 embodying a blend of traditional and advanced technologies. Though it is an all-new design, the bore, stroke, displacement, bore-center spacing, deck height, and camshaft location all carry over from the 2013 LS3 engine. The three new (for Corvette) technologies are direct injection, variable valve timing, and cylinder shutdown. Incorporating those features drove new shapes for the combustion chamber, piston crown, and intake and exhaust ports. Before settling on an 11.5:1 compression ratio (up from the LS3’s 10.7:1), GM powertrain engineers investigated more than 75 alternative *combustion-chamber configurations, consuming a staggering 6 million hours of computer-processing time. Contrast that with 60 years ago, when Chevy chief engineer Ed Cole and 14 draftsmen needed only 15 weeks to design the original small-block V-8 with pencils, paper, and slide rules.
The 450 or more horsepower (at 6000 rpm) expected from the new engine—only 14 more ponies than the LS3 equipped with bi-mode mufflers—isn’t that impressive. There is, however, roughly the same torque as the Z06’s 7.0-liter LS7 V-8 below 4000 rpm and what we predict will be spectacular fuel economy. Operating this engine as a 3.1-liter V-4 during cruising should boost EPA combined mileage from 17–18 mpg to the low- to mid-20s, comparable to six-cylinder sports cars (BMW Z4 sDrive35i, Lotus Evora, Mercedes SLK350, Nissan 370Z, and Porsche 911).
A five-degree splay angle between the 2.13-inch intake and 1.59-inch exhaust valves benefits volumetric efficiency. Cast-iron exhaust manifolds are heavier but smoother-flowing and better at retaining heat than the welded sheetmetal headers used before. A molded-plastic intake plenum containing eight tuned runners stifles the buzz of the new high-pressure fuel injectors. For the first time in a base Corvette engine, a dry-sump lubrication system is optional.
The new Corvette small-block V-8 adds direct injection, variable valve timing, and cylinder deactivation, and makes at least 450 horsepower.
The beauty of the new LT1 small-block is its compact size, low mass (approximately one pound per horsepower), and overall practicality. The phasing device that shifts intake- and exhaust-valve timing in lockstep and valve lifters that collapse on cue to disable cylinders will keep a Corvette V-8 kicking for some time. There will definitely be more-powerful versions—expect both supercharging and greater displacement—and quite likely that aforementioned 5.5-liter V-8. The much-maligned pushrod/two-valve system has limitations but not in its ability to stave off the Grim Reaper.
more gears
The addition of more transmission speeds is a sure thing. Because the eight-speed Hydra-Matic that GM has under development won’t be ready when C7 enters *production this summer, it’s Aisin AW to the rescue. The world’s largest automatic-transmission manufacturer’s TR-series ’box fits the space vacated by C6’s six-speed auto while providing ample torque capacity and the eight forward gears needed to achieve exemplary gas mileage. The dual-clutch automatic that GM has fiddled with for years appears to be dead, at least for Corvettes.
