2008 CORVETTE: ICONIC SPORTS CAR RECIEVES LARGER, MORE POWERFUL LS3 6.2L V-8 AND HOST OF DRIVING, INTERIOR REFINEMENTS
Get comfortable. There’s so much new and exciting with the 2008 Corvette that you’ll want to grab a hot drink, sidle up to your computer screen and absorb all the details.
The changes involve everything from an all-new, larger and more powerful V-8 engine to refinements in driving characteristics that solidify the Corvette’s position as the preeminent American sports car – and further the argument that it is one of the world’s best. There are also a host of exterior and interior refinements that raise the Corvette’s luxury status and enhance the feeling of craftsmanship.
“Corvette is an uncompromising sports car that rewards its owners with impeccable performance and great comfort,” said Ed Peper, Chevrolet general manager. “The changes and enhancements to the 2008 Corvette reflect continual improvements that speak to Chevrolet’s unflagging commitment to building the best sports car – and with nearly 55 years of experience, the Corvette just keeps getting better and better.”
Also back again for ’08 is the 505-horsepower Corvette Z06, an American super car that has won over enthusiasts, journalists and racers around the world for its balance of racetrack-bred performance, daily-driving civility and value.
Here’s a look at the new and enhanced features for ’08 Corvette models:
Engine – A new, 6.2L LS3 small-block V-8 is the standard engine in Coupe and Convertible models. It is rated at 430 horsepower (321 kW)* and 424 lb.-ft. of torque (586 Nm)* with the standard exhaust system; with the new, optional two-mode exhaust system, power ratings increase to 436 horses / 325 kW and 428 lb.-ft. / 592 Nm. As a result, the standard Corvette is true supercar, capable of 190 mph. The LS3 with the six-speed paddle-shift automatic is the fastest automatic-equipped Corvette ever, with 0-60 mph capability of 4.3 seconds.
This new iteration of the storied small-block family features a revised, larger-bore cylinder block – 4.06-inch / 103.25 mm vs. the previous 6.0L’s 4.00-inch / 101.62 mm bores – high-flow, LS7/L92-style cylinder heads; larger-diameter pistons; revised camshaft and camshaft timing; revised valvetrain with offset intake rocker arms; high-flow intake manifold; high-flow fuel injectors from the Z06’s LS7 engine; and a new engine beauty cover.
The LS3 features an aluminum cylinder block with cast iron cylinder liners. In addition to its larger bores, which help create a 376-cubic-inch displacement, the block casting also features revisions and machining in the bulkheads that enhance its strength and improved bay to bay breathing. But while the bore of the 6.2L engine is increased when compared with the previous 6.0L engine, the engine’s stroke remains at 3.62 inches (92 mm). The pistons for the larger 6.2L engine also are new and are designed for its high-rpm performance capability.
Breathing for the new 6.2L engine is accomplished via new, high-flow cylinder heads. They’re based on the large port/large valve design found on the LS7 engine and other GM L92 engines, with larger-capacity, straighter intake ports. The design optimizes intake flow to the combustion chamber and the exhaust ports are also designed for better flow.
Complementing the larger-port design of the heads are commensurately sized valves. The intake valve size alone increases from 2.00 inches (50.8 mm) to 2.16 inches (55 mm) – an increase of nearly 9 percent. The intake valves feature lightweight hollow stems, which enable the engine’s 6,600-rpm capability. The exhaust valves also are large, measuring 1.60 inches (40.4 mm) in diameter.
To accommodate the engine’s large valves and enable more direct intake port flow, the intake-side rocker arms are offset 6 mm between the valve tip and the push rod. Actuating the valves is a new camshaft, with intake-side lobes providing more than a 5-percent percent in increase in lift, from 0.521-inch to 0.551-inch (13.25 mm to 14 mm). Exhaust-valve lift remains unchanged from the LS2. The camshaft timing was revised to optimize performance with the higher-lift intake cam profile.
Ensuring the cylinder heads receive all the air they can handles falls to a new, acoustically tuned intake manifold. The composite design is manufactured with a “lost core” process that improves runner to runner variation and reduces airflow losses. An acoustic foam material is used to reduce radiated engine noise; it is sandwiched between the outer top of the manifold and an additional “skull cap” acoustic shell. Also new beauty covers atop the engine shield the rocker covers and also feature a noise-reducing, acoustically tuned insert to provide a more refined engine sound.
Exhaust system – Optional on ’08 Coupe and Convertible models is a new, two-mode performance exhaust system. Similar in design and function to the system used on the Z06, the dual-mode exhaust uses vacuum-actuated outlet valves, which control engine noise during low-load operation, but open for maximum performance during high-load operation. It is not identical to the Z06 system; the Coupe/Convertible uses a 2.5-inch-diameter exhaust, while the Z06 uses a three-inch system.
With the new, dual-mode performance exhaust, power output for Coupe/Convertible rises from 430 horsepower (321 kW) and 424 lb.-ft. of torque (575 Nm) to 436 horses (325 kW) and 428 lb.-ft. (580 Nm). This system gives the Corvette a more aggressive exhaust sound character that will appeal to performance enthusiasts.
Transmissions and axle ratios – The shifting efforts for both the six-speed manual transmission and paddle-shift six-speed automatic transmissions have been improved in ’08 Corvette models. The manual transmission shifting improvements include a more positive and direct feel during gear changes, with better gate-to-gate location.
The six-speed paddle-shift automatic transmission on Coupe and Convertible is improved with new hardware and a new controller calibration that deliver quicker shifts. This change bolsters the feeling of performance and driver control when using the shifting paddles.
Also new for ’08 models is the availability of the 2.73 performance axle ratio with the automatic transmission. It is included with the Z51 package.
Steering system – The Corvette’s precise rack-and-pinion steering system is revised to provide improved feel at all speeds. The revisions are due to a new, premium machining process of the system’s internal components, a new, stiffer intermediate shaft and controller calibration changes.
Wheels – Corvette Coupe and Convertible models come with a new split-spoke wheel design for ’08. The design was introduced on the limited-edition ’07 Indianapolis 500 Pace Car replicas with a Sterling Silver finish. The standard 18-inch front wheels and 19-inch rear wheels feature a Sparkle Silver finish, with a Competition Gray version optional.
Also new is a distinctive, performance-oriented forged aluminum wheel for Coupe and Convertible. It comes in a polished finish.
Exterior colors – There are two new premium exterior colors available with 2008 Corvette models: Jetstream Blue Metallic Tintcoat and Crystal Red Metallic Tintcoat; they replace Le Mans Blue Metallic and Monterey Red Metallic Tintcoat.
Custom Leather-Wrapped Interior Package – Available on Coupe, Convertible and Z06 models, the new Custom Leather-Wrapped Interior Package offers a stylish, two-tone leather-appointed cabin with details that enhance the feeling of Corvette’s craftsmanship. Details include:
Two-tone, leather-wrapped upper and lower instrument panel, door pads and seats
Choice of new, exclusive colors: Linen or Sienna, with unique color breakup
Padded door panel armrests
“Corvette” embroidered on passenger-side dash pad
Embroidered crossed flags logo on headrests
Unique center trim plate with Bias pattern.
Interior enhancements – All models feature a new wrapped instrument panel center trim plate, with bright surrounds for the shifter and cupholder. There are also new metal-finish door sill plates that greet passengers as they step into the vehicle, as well as a new lighted control knob for the available Magnetic Selective Ride Control.
Feature changes and enhancements – All Corvette models now come standard with features that were previously optional or part of equipment packages. They include:
OnStar with available Turn-By-Turn Navigation
XM Satellite Radio
Auto-dimming rearview mirrors (with compass)
Audio input jack on all radio systems except navigation; Personal Audio Link is available as a dealer-installed item with the navigation system.
The ’08 Corvettes also come with a new Keyless Access fob, which features the key and remote-function controls integrated in a single unit.
Corvette design and interior details
Dramatic fender forms and exposed headlamps combine with the grille to create a strong visual identity for the Corvette, while the tapered rear deck and fascia improve high-speed performance. The lean rear design sports round taillamps and center-exit exhaust. The fixed Xenon high-intensity discharge headlamps provide superior lighting performance. With a 0.286 coefficient of drag, the Coupe models are the most aerodynamic Corvettes ever.
The 2008 Corvette Convertible features a power-operated soft top with the 3LT package; an easy-to-operate manual top is standard. Both configurations use a five-layer fabric that conceals the underlying structure for a good top-up appearance, plus it helps preserve the car’s excellent aerodynamics and reduces road noise.
Corvette’s interior is inspired by the car’s dual-cockpit heritage. High-quality materials, craftsmanship and functionality help deliver premium quality meant to enhance performance driving. The instrument panel and doors are covered with cast-skin foam-in-place trim that looks like a leather-wrapped, padded panel. It is warm and inviting and has double the life of conventional trim materials.
An AM/FM/XM radio with CD player and audio input jack is standard. An optional Bose audio system with an in-dash six-disc changer adds to the choices available to the audiophile owner. Steering-wheel mounted audio controls – introduced in ’07 – are included with the Bose premium system.
A full-function OnStar system is standard and an onboard navigation system with voice recognition is available. Using a 6.5-inch (165 mm) color touch-screen display, the DVD-based system contains all the map data for the 48 contiguous states and most of Canada on one disc.
Driving dynamics
Corvette Coupe and Convertible have a hydroformed steel rail backbone structure, which features cored composite floors, an enclosed center tunnel, rear-mounted transmission and aluminum cockpit structure. Suspension cradles, control arms, knuckles, springs, dampers, bushings, stabilizer bars and steering gear have all been redesigned. New Goodyear Extended Mobility Tires (EMT) take advantage of the latest sidewall design and compound technology for run-flat capabilities.
Three suspension choices allow drivers to choose the setup that best suits their driving style. The standard suspension is tuned for a balance of ride comfort and precise handling. Corvette is now more poised at even higher handling levels, yet easier to drive.
The optional Magnetic Selective Ride Control suspension features magneto-rheological dampers able to detect road surfaces and adjust the damping rates to those surfaces almost instantly for optimal ride control. Cross-dilled brake rotors are included when this feature is selected, allowing customers to combine the larger brakes from the Z51 performance package with the comfort of Magnetic Selective Ride Control.
The Z51 Performance Package brings Coupe and Convertible performance very close to the widely admired previous generation Z06. The Z51 offers more aggressive dampers and springs, larger stabilizer bars, Goodyear Eagle F1 Supercar EMT tires, enhanced cooling and larger cross-drilled brake rotors (13.4 inches / 340 mm in front and 13 inches / 330 mm in rear) for optimum track performance while still providing a comfortable ride.
With each suspension, three standard dynamic chassis control systems – anti-lock braking, traction control and Active Handling – operate in concert. In all, the dynamic chassis control systems are smarter, less intrusive and more adept at making the total driving experience precisely what drivers have come to expect from their Corvette.
Corvette Z06 details
As the fastest, most powerful and most technologically advanced production model in Corvette’s history, the Corvette Z06 offers an unprecedented level of capability and technology, making it one of the best performance values on the market.
Design – The Z06 has an unmistakable and aggressive appearance, with design cues that include:
A wide front fascia with a large, forward-facing grille opening, a splitter along the bottom and wheel opening extensions along the sides to provide aerodynamic downforce
A cold air scoop in front of the hood that integrates an air inlet system for the engine
The trailing edge of the front wheel opening is radiused to achieve improved drag, but protects the body finish with a tough molding, and a large air extractor is located behind the wheel
A fixed-roof body style optimizes body rigidity and mass
Wider rear fenders with flares cover the massive rear tires and a brake cooling scoop in front of the wheels visually balances the fender extractor
A tall rear spoiler houses the CHMSL on the top of the rear fascia
10-spoke wheels (18-inch, front; 19-inch, rear)
Four large stainless steel exhaust outlets
Z06 badging on the carbon fiber front fenders
The aerodynamics of the Z06’s exterior were shaped by the experiences of the Corvette racing program, where high-speed stability and cornering capability are paramount. And while the race cars use large rear wings, the Z06’s elevated spoiler provides sufficient downforce to balance the road-worthy front splitter without adversely affecting aerodynamic drag. The Z06’s Cd is 0.34.
For all its race-inspired functionality, the Z06 is designed to be a daily-driveable high-performance vehicle. To that end, comfort and convenience are held to a very high standard. High-Intensity Discharge lighting, fog lamps, leather seating, dual-zone air conditioning, cabin air filtration and head-up display (HUD) with track mode and g-meter are standard.
The Z06 gauge cluster displays the Z06 logo on the 7000-redline tachometer and has a readout on the oil pressure gauge to reflect the higher standard pressure of the dry-sump oiling system. The seats feature two-tone leather surfaces, with Z06-logo embroidery and contrasting stitching.
Z06 options include a Bose audio system with an in-dash six-CD changer, polished, Competition Gray or chrome wheels, a telescoping steering wheel, heated seats, side-impact air bags, a navigation system with GPS and universal home remote.
LS7 engine – The Z06’s LS7 7.0L engine delivers 505 horsepower (377 kW) in a 3,132-pound (1,421 kg) package – a combination that delivers 0-60 performance of 3.7 seconds in first gear, quarter-mile times of 11.7 seconds at 125 mph and a top speed of 198 mph (as recorded on Germany’s Autobahn). It also provides maximum lateral acceleration of 1.04 g and 60-0 braking in 111.3 feet; it also circuited Germany ’s famed N ü rburgring in a time of 7:43 .
The LS7 reintroduced the 427-cubic-inch engine to the Corvette lineup. It is easily identified under the hood by red engine covers with black lettering. The LS7 shares the same basic Gen IV V-8 architecture as the Corvette’s 6.0-liter LS2, but it uses a different cylinder block casting with pressed-in steel cylinder liners to accommodate the engine’s larger diameter, 4.125-inch (104.8 mm) cylinder bores.
Internally, the LS7’s reciprocating components make use of racing-derived lightweight technology, including titanium connecting rods and intake valves, to help boost horsepower and rpm capability. The rpm fuel shut-off limit is 7,100 rpm. The LS7’s details include:
Dry-sump oiling system
Unique cylinder block casting with large, 104.8-mm bores and pressed-in cylinder liners
Forged steel main bearing caps
Forged steel crankshaft
Titanium connecting rods with 101.6-mm stroke
Cast aluminum flat-top pistons
11.0:1 compression
High-lift camshaft
Racing-derived CNC-ported aluminum cylinder heads with titanium intake valves and sodium-filled exhaust valves
Low-restriction air intake system
Hydroformed exhaust headers with unique “quad flow” collector flanges.
One of the clearest examples of the LS7’s race-bred technology is its use of titanium connecting rods. They weigh just 464 grams apiece and besides being lightweight, which enhances high-rpm performance and rpm range, titanium makes the rods extremely durable.
The LS7’s CNC-ported aluminum cylinder heads are designed to meet the high airflow demands of the engine’s 7.0-liter displacement. A hydraulic roller camshaft with 0.588/0.593-inch valve lift is used to allow plenty of air to circulate in and out of the engine. To ensure optimal, uninterrupted airflow, the LS7’s heads have straight, tunnel-like intake runners. Very large by production-vehicle standards – even racing standards – they are designed to maintain fast airflow velocity, providing excellent torque at low rpm and exhilarating horsepower at high rpm. The heads feature 70-cc combustion chambers that are fed by huge, 56-mm-diameter titanium intake valves. They are complemented by 41-mm sodium-filled exhaust valves.
To accommodate the large valve face diameters, the heads’ valve seats are siamesed; and, taken from experience with the engines of C6.R racecars, the LS7’s valve angles are held at 12 degrees – vs. 15 degrees for the LS2 – to enhance airflow through the ports.
The LS7 has a dry-sump oiling system designed to keep the engine fully lubricated during the high cornering loads the Corvette Z06 is capable of producing. An engine compartment-mounted 8-quart reservoir delivers oil at a constant pressure to a conventional-style oil pump pick-up at the bottom of the engine. The pressurized oil feed keeps the oil pick-up continually immersed in oil at cornering loads exceeding 1 g.
Oil circulates through the engine and down to the oil pan, where it is sent back to the reservoir via a scavenge pump. The large-capacity reservoir, combined with a high efficiency air-to-oil cooler, provides necessary engine oil cooling under the demands of the engine’s power output. With the dry-sump system, oil is added to the engine via the reservoir tank – which includes the oil level dipstick.
Drivetrain – The Corvette Z06’s powertrain and drivetrain systems are matched to the LS7’s performance capability. The light, four-into-one headers discharge into close-coupled catalytic converters and through two-mode mufflers. The mufflers each feature a vacuum-actuated outlet valve, which controls exhaust noise during low-load operation but opens for maximum power.
At the rear of the LS7 engine, a single-mass flywheel and lightweight, high-capacity clutch channel torque to the rear transaxle. The six-speed manual transmission has been strengthened to handle the LS7’s increased torque load. The transmission includes a pump that sends transmission fluid to the front radiator for cooling. Upon its return, the fluid removes additional heat from the differential lube before returning to the transmission. The six-speed transmission connects to a limited-slip differential, with enlarged ring and pinion gears. Stronger axle half-shafts with tougher universal joints transmit power to the rear wheels.
Structure – The Z06 has a unique aluminum body structure for optimum stiffness and light weight for the fixed-roof bodystyle. Perimeter rails are one-piece hydroformed aluminum members featuring cast suspension nodes, which replace many welded steel components on other Corvette models. Other castings, stampings and extrusions are combined into the innovative structure with state-of-the-art manufacturing technologies.
Advanced structural composites featuring carbon fiber are bonded to the aluminum structure. The wider front wheelhouses, for example, are carbon composites and the passenger compartment floors combine carbon-fiber skins with an ultra-lightweight balsa wood core.
The Z06 has a new magnesium cradle that serves as the attachment point for the engine and some front suspension components. Magnesium is lighter than aluminum yet incredibly strong. The magnesium cradle helps improve the front-to-rear weight distribution, as do carbon-fiber front fenders and wheelhouses. Engineers also moved the battery from underhood to a position in the rear cargo area, behind one of the rear wheels.
The mass reductions are offset by some added performance enablers, including dry-sump lubrication, exhaust system with outlet valves, larger wheels and tires, larger brakes and larger roll stabilizers.
Suspension and brakes – The Z06 retains the 105.7-inch (2686-mm) wheelbase of other Corvette models, as well as the short-long arm suspension and transverse leaf spring design, but it rides on all-new wheels, tires, brakes, as well as its own rear spring and roll stabilizer.
The firmer suspension works harmoniously with large 18 x 9.5-inch cast-spun aluminum wheels and 275/35ZR18 tires in the front, and 19 x 12-inch cast-spun aluminum wheels with 325/30ZR19 tires in the rear – the largest wheel-and-tire combination ever offered on a Corvette. The tires use the latest extended-mobility technology from Goodyear to provide a satisfactory ride, but still allow the vehicle to achieve lateral acceleration of more than 1 g. The extended-mobility tires eliminate the need – and weight – for a spare tire and jack or inflator kit, while also reducing the chance of a sudden loss of handling capability.
Complementing the suspension system and large rolling stock is an equally capable four-wheel disc brake system, consisting of 14-inch (355 mm) vented and cross-drilled front rotors and 13.4-inch (340 mm) vented and cross-drilled rear rotors.
The front rotors are acted upon by large, red-painted six-piston calipers that use six individual brake pads. Individual brake pads are used because they deliver more equalized wear compared to what would otherwise be a pair of very long single-piece pads. For the rear brakes, four-piston calipers with four individual brake pads are used. A Delphi four-channel ABS system is standard, as is a very competent active handling system – complete with a Competitive Driving mode.
* Horsepower and torque are SAE certified.
SPECIFICATIONS
(See GM of Canada section for Canadian product differences)
Overview
Models:
Chevrolet Corvette Coupe, Convertible and Z06
Body styles / driveline:
2-door hatchback coupe with removable roof; rear-wheel drive (Coupe and Convertible)
2-door hatchback coupe with fixed roof; rear-wheel drive (Z06)
Construction:
composite body panels, hydroformed steel frame with aluminum and magnesium structural and chassis components (coupe); composite and carbon-fiber body panels, hydroformed aluminum frame with aluminum and magnesium structural and chassis components (Z06)
Manufacturing location:
Bowling Green, Ky.
Engines
6.2L V-8 LS3
7.0L V-8 LS7 (Z06)
Displacement (cu in / cc):
376 / 6162
427.6 / 7008
Bore & stroke (in / mm):
4.06 x 3.62 / 103.25 x 92
4.125 x 4 / 104.8 x 101.6
Block material:
cast aluminum
cast aluminum
Cylinder head material:
cast aluminum
cast aluminum
Valvetrain:
overhead valve, 2 valves per cylinder
overhead valve, 2 valves per cylinder
Fuel delivery:
SFI (sequential fuel injection)
SFI (sequential fuel injection)
Compression ratio:
10.7:1
11:1
Horsepower
(hp / kW @ rpm):
430 / 321 @ 5900* w/ std. exhaust
436 / 325 @ 5900* w/ opt. exhaust
505 / 377 @ 6300*
Torque (lb-ft / Nm @ rpm):
424 / 575 @ 4600* w/ std. exhaust
428 / 580 @ 4600* w/ opt. exhaust
470 / 637 @ 4800*
Recommended fuel:
premium recommended but not required
premium required
Estimated fuel economy :
TBD
TBD
Transmissions
6-speed manual
Base and Z06
6-speed manual, w/optional Z51 Performance Package
6-speed paddle-shift automatic
Application:
std
opt
opt
Gear ratios (:1):
First:
2.66
2.97
4.03
Second:
1.78
2.07
2.36
Third:
1.30
1.43
1.53
Fourth:
1.00
1.00
1.15
Fifth:
0.74
0.71
0.85
Sixth:
0.50
0.57
0.67
Reverse:
2.90
3.28
3.06
Final drive ratio:
3.42
3.42
2.56
Chassis / Suspension Coupe and Convertible
Z06
Front:
short/long arm ( SLA ) double wishbone, cast aluminum upper & lower control arms, transverse-mounted composite leaf spring, monotube shock absorber
short/long arm ( SLA ) double wishbone, cast aluminum upper & lower control arms, transverse-mounted composite leaf spring, monotube shock absorber
Rear:
short/long arm ( SLA ) double wishbone, cast aluminum upper & lower control arms, transverse-mounted composite leaf spring, monotube shock absorber
short/long arm ( SLA ) double wishbone, cast aluminum upper & lower control arms, transverse-mounted composite leaf spring, monotube shock absorber
Traction control:
electronic traction control; Active Handling
electronic traction control; Active Handling
Brakes
Coupe and Convertible
Z06
Type:
front and rear power-assisted disc with ABS; cross-drilled rotors with Z51 package and Magnetic Ride Control
front and rear power-assisted disc with ABS with 6-piston front and 4-piston rear calipers, cross-drilled rotors
Rotor diameter x thickness (in / mm): front: 12.8 x 1.26 / 325 x 32
rear: 12 x 1 / 305 x 26;
Z51 Performance Package:
front: 13.4 x 1.26 / 340 x 32
rear: 13 x 1 / 330 x 26
front: 14 x 1.3 / 355 x 32
rear: 13.4 x 1 / 340 x 26
Wheels & Tires
Wheel size:
front: 18 inch x 8.5 inch
rear: 19 inch x 10 inch
front: 18 inch x 9.5 inch
rear: 19 inch x 12 inch
Tires:
Goodyear Eagle F1 Supercar (w/Z51)
Extended Mobility
front: P245/40ZR18
rear: P285/35ZR19
Goodyear Eagle F1 Supercar Extended Mobility
front: P275/35ZR18
rear: P325/30ZR19
Dimensions
Coupe and Convertible
Z06
Wheelbase (in / mm):
105.7 / 2685
105.7 / 2685
Overall length (in / mm):
174.6 / 4435
175.6 / 4460
Overall width (in / mm): 72.6 / 1844
75.9 / 1928
Overall height (in / mm):
49 / 1244
49 / 1244
Curb weight (lb / kg):
Coupe: 3217 / 1459
Conv.: 3246 / 1473
3162 / 1434
Interior
Seating capacity
2
Interior volume (cu ft / L):
52 / 1475 (all models)
Headr oom (in / mm): 38 / 962 (all models)
Legroom (in / mm): 43 / 1092 (all models)
Shoulder room (in / mm):
55 / 1397 (all models)
Hip room (in / mm):
54 / 1371 (all models)
Capacities
Cargo volume
(cu ft / L):
Coupe and Z06: 22 / 634
Convertible: 11 / 295 (top up); 7.5 / 212 (top down)
Fuel tank (gal / L):
18 / 68.1
Engine oil (qt / L):
Coupe and Convertible: 5.5 / 5.2
Z06: 8 / 7.5
* Horsepower and torque are SAE certified. A new voluntary power and torque certification procedure developed by the SAE Engine Test Code committee was approved March 31, 2005 . This procedure (J2723) ensures fair, accurate ratings for horsepower and torque by allowing manufacturers to certify their engines through third-party witness testing. GM was the first auto manufacturer to begin using the procedure and expects to use it for all newly rated engines in the future.
