Chevrolet introduced us to its ZR1 super Corvette last January at the 2008 Detroit Auto Show, but didn’t have any concrete performance numbers at the time. We were promised at least 100 horsepower per liter — meaning a minimum of 620 horsepower — but were left to guess just how far over that magic equation the LS9 would be. But the hyper ‘Vette is back from testing and we now have a definitive answer.

According to the Corvette ZR1’s SAE Certification, the 6.2L supercharged LS9 motor pumps out 638 horsepower and 604 lb-ft of torque — proving Chevrolet officials were sandbagging back in January.

In addition to the LS9’s power ratings, GM also revealed that engineers have taken the Corvette ZR1 to 205 mph on a test track in Germany — putting the ZR1 is an elite class of supercars.

The ZR1’s fuel economy ratings aren’t in yet, but GM assures us that range-topping Corvette will be the most fuel efficient 600+ horsepower car in the world — a rather strange distinction.

With nearly 640 horsepower on tap and a 205 mph top speed, we can’t wait to see the ZR1 go head-to-head with some of the world’s best.

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