Chevrolet's Corvette ZR1 made its debut at the North American International Auto Show back in January, but at the time the published output for the supercharged LS9 engine powering it was an approximation only.
As part of our coverage of the Detroit show, we reported the Corvette ZR1's "estimated" power was 462kW (more here), but the power is actually slightly better than that, although the certified torque figure is about 4Nm down on the original figure published -- albeit still 819Nm.
Now, the division responsible for development of new GM engines, GM Powertrain, has officially declared the LS9 engine good for 638hp (476kW) and 604lb.-ft of torque (819Nm). The figures were released following certification in accordance with the testing procedures laid down by the Society of Automotive Engineers.
In the relatively light weight Corvette, the LS9 achieves a power-to-weight-ratio unparalleled in any previous General Motors design. The car can reach a top speed of 322km/h, with the hand-built V8 driving through a six-speed manual transmission and heavy-duty twin-plate clutch.
As if displacing 6.2 litres isn't enough in itself, the all-alloy LS9 engine draws much of its muscle from the positive-displacement Roots-type supercharger with four-lobe rotor design. Maximum boost attainable is 0.72bar (10.5PSI) and the unit features an integrated charge-cooling system.
"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."
Watch the Corvette Development Engineering team with the new ZR1 at the test track in Papenburg, Germany topping 205mph.
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