Corvette ZR1 makes 638hp

DETROIT — The 2009 Chevrolet Corvette ZR1, which will go on sale this fall for around $100,000, will pack 638 horsepower.

That makes the ZR1 easily the most powerful vehicle General Motors has ever produced and puts the king of Corvettes into a mighty exclusive club. The ZR1 essentially matches the output of the Lamborghini Murcielago LP640 and trails the extra-extreme limited-edition Ferrari Enzo by only a smidge. Perhaps, just as important to Chevrolet, is that the ZR1 brings 38 hp more to the American-car smackdown than the new Dodge Viper.

And at an estimated weight of 3,350 pounds, each of the ZR1's horses will have only 5.25 pounds of Vette to carry around. That weight-to-power ratio is closer to the Enzo (5 pounds) than the Viper (5.75 pounds). The Murcielago LP640 saddles each of its horses with almost 6.5 pounds. The ZR1's hp peak comes at 6,500 rpm. Its torque peak of 604 pound-feet comes at a low 3,800 rpm. Passing should not present a problem in the ZR1.

When it was unveiled at the 2008 Detroit Auto Show, General Motors estimated that the supercharged, 6.2-liter LS9 V8 would make at least 620 hp. The company has learned a thing or two about under-promising and over-delivering. The LS9 is a strengthened version of the tried-and-true small-block pushrod design, with an Eaton TVS (four-lobe) Roots-type supercharger and twin intercooler unit crammed in the V. Maximum boost is set at 10.5 psi and all of the engine's internals have been upgraded to more robust and/or lightweight parts, including a forged steel crank, titanium connecting rods and forged aluminum pistons. It's fitted with a dry sump oil system and is mated to a stout six-speed manual through a twin-disc clutch.

In the most curious press release line we've read in some time, Chevrolet claims the ZR1 will be the most fuel-efficient 600-plus-hp car on the market today. Um, OK. Guess those upcoming CAFE standards have GM really spooked. In related news: My great grandmother won the national nursing home ultimate fighting championship.

Notably absent from the press release was any boasting about the ZR1 being able to take the production-car lap record at the Nürburgring — something GM had earlier claimed.

What this means to you: With the Viper on the chopping block and the Ford GT but a memory, the Corvette ZR1 will be the undisputed king of American sports cars. — Daniel Pund, Senior Editor, Detroit