When it was introduced at the North American International Auto Show in Detroit earlier this year, the 2009 Corvette ZR1’s power was estimated at 100 horsepower for each of its 6.2 litres of displacement. GM Powertrain has completed SAE certification of the ZR1’s supercharged LS9 V8 and the results exceed the estimate: 647 horsepower (476 kW) and 819 Nm of torque.

The LS9’s output is nearly 103 horses per litre, or just about 1.7 horses for each of the engine’s 376 cubic inches. It is unquestionably the most powerful automotive production engine ever manufactured by General Motors and enables the Corvette ZR1 to achieve a top speed of 205 mph (330 km/h).

"One of the most amazing things about the Corvette ZR1 is the level of refinement that our designers and engineers have attained. Even with all that power, this car has road manners that will allow our customers to enjoy it on the streets as a daily driver, and on the track," said Chevrolet’s US General Manager, Ed Peper.

The Corvette ZR1 goes on sale in Europe at the end of 2008. Its 647-hp supercharged engine is complemented in the chassis by heavy-duty components not offered in any other model, including a six-speed manual transmission with race-hardened gears and dual-disc clutch technology that delivers exceptional clamping power and lower inertia, as well as strengthened axle components.

Fuel economy testing has not been completed, but engineers are confident the ZR1 will be the most fuel-efficient 600-plus-horsepower car on the market.

The LS9 engine is hand-built by specially trained technicians at GM’s Performance Build Center in Wixom, Michigan. It is a unique, small-volume engine production facility that also builds the Corvette Z06’s LS7 engine and other high-performance GM production engines.

“Developing the LS9 involved more than simply striving for a great horsepower number. Endurance and reliability testing have shown the engine to be robust and low-maintenance, just like other engines in the small-block family,” said Sam Winegarden, executive director, engine engineering for GM Powertrain. “That it is distinguished as the most powerful engine ever from General Motors is a source of immense pride among everyone involved with the LS9.”

Supercharged aspiration
The key enabler of the LS9’s performance is the industry’s first production application of a new, positive-displacement Roots-type supercharger that has a unique four-lobe rotor design. Its design promotes quieter and more efficient performance, while the large, 2.3-litre displacement ensures adequate air volume at high rpm. Maximum boost pressure is 0.72 bar. It is teamed with an integrated charge cooling system that reduces inlet air temperature for maximum performance.

“The combination of large displacement and the new, four-rotor design broadens the effective range of the supercharger, allowing the engine to make more power at lower rpm and sustain it throughout the power band,” said Winegarden. “The low-end torque is tremendous and the high-rpm charge from the supercharger is simply amazing.”

A raised bonnet provides adequate clearance for the LS9, while a polycarbonate window in the bonnet provides a view of the engine beneath it.