There's been some question as to the accuracy of the 505 HP rating for the Corvette Z06, considering that magazine tests have resulted in quarter-mile performance that would usually point to a somewhat higher rating. LG Motorsports put a brand-new car (right down to the paper floormats and plastic around the steering wheel) on their chassis dyno and obtained rear-wheel measurements of 442 HP and 413 lb-ft of torque. One can calculate an almost-believable drivetrain loss of about 12.5% if the car actually makes 505 at the crank, keeping in mind that assigning drivetrain loss as a strict multiplier isn't a good practice (especially when using an inertial-type dyno). The bottom line is that the car likely isn't underrated by more than 10-15 HP, lending some credibility to the new SAE J2723 rating procedure. Then why is the car so fast? There's more to acceleration than just peak power, and the dyno graphs of the Z06 are damn near perfect. That flat-and-wide torque curve (and the mathematically corresponding smoothly ramped horsepower curve) mean great acceleration anywhere in the rev range.