HP 101: Top Gear provides false info on GT500 horsepower rating

Someone help us understand what's going on here. In the latest episode of Top Gear, Richard Hammon revisits the Ford Shelby GT500 that the British motoring show tested late last year. For comparison's sake, Hammond brings along his own classic Shelby GT390. We're used to Top Gear bashing our U.S. ware at every opportunity, and the GT500 again takes a licking for having a suspension that can't handle the car's power. But when Hammond wheels out a portable chassis dyno to accurately measure the GT500's horsepower, he seems surprised to learn that the car produces 447 horsepower. Of course, that's 447 wheel horsepower, meaning the horsepower is being measured at the wheel where parasitic drivetrain losses are in effect and reduce the manufacturer's flywheel horsepower rating a good 10 to 20%. In fact, if you factor in a 10% drivetrain loss on Ford's flywheel horsepower rating of 500, you get 450 wheel horsepower, which is pretty darn close to the 447 achieved by Hammond's "rolling road". For some inexplicable reason, however, Hammond and his comparitavely giant co-host, Jeremy Clarkson, ding the GT500 for producing 53 less horsepower than advertised. Huh?

You can view the segment after the jump for the time being (until it gets yanked off YouTube) and make your own judgment, but from our perspective the segment appears highly misleading to viewers who don't know the difference between horsepower ratings at the wheel and the flywheel. What's up, Hamster?

[Source: Dubspeed Driven]

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