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Saturday, March 29, 2008

GTR is no joke- Godzilla is coming

Dyno Test: 2009 Nissan GT-R Makes 507 Horsepower... at least!

We reveal Nissan's little white lie...

By Frank Markus
Photography by Evan Klein Art By Mike Royer

Godzilla is coming!

The hysteria surrounding the impending launch of Nissan's GT-R has prompted a mad rush to judge its performance. Various media outlets have attempted to test well-worn engineering mule cars and Japanese-spec vehicles with 112-mph speed limiters. Some have run acceleration tests on sloped track surfaces. Many an unsuspecting GT-R has powered the tire rollers and hub mounts of various dynamometers, registering widely varying power ratings. Most of the numbers generated and quoted have been heroic, which has served to heighten Godzilla's reputation as a mythological beast possessing supernatural powers. But some of these early tests have raised as many questions as they've answered. Over the next few days, we intend to answer them with rigorous testing of a fresh, production-ready U.S.-spec GT-R on flat, level ground.

Supercar Cred

The GT-R's official output ratings of 480 horsepower and 430 pound-feet of torque give it a weight-to-power ratio of about 8.1 pounds per horsepower -- that's 25 percent more weight per pony than its King Kong nemesis, the benchmark Porsche 911 Turbo and the Corvette Z06, its closest price competitor carry. Yet somehow early pairings of this anime animal consistently show it running neck and neck with those superstars through the quarter mile. Even if we credit its roughly 10-percent gearing advantage relative to the 911 Turbo for some of that disparity, that still suggests -- on paper at least -- that the car should need about 550-570 horses to keep up. Might Nissan be underreporting horsepower by 15 percent? Let's find out.

Which Dynamometer to Choose?

There are two basic types of dynos: load type and inertia type. The former generates electric or hydraulic resistance calculated to match a vehicle's on-road aerodynamics and friction. This type (Mustang and Dynapack are name brands) is best for simulating quarter-mile runs but suffers garbage-in-garbage-out inaccuracy if the aero and road-load assumptions are inaccurate (and such nitty-gritty engineering details are not yet widely available for the GT-R). Dynapack dynos bolt right to the wheel hubs, which can flummox high-tech cars like the GT-R, which expect to see four tire-pressure monitors whizzing by when the car is in motion. Inertia type dynos like the Dynojet use large, heavy rollers that employ a 4800-pound roller capable of measuring 1200 horsepower at each axle and measure the rate at which the drivetrain can accelerate them. This type is better for determining horsepower of high-output vehicles, as the power is measured directly (torque is mathematically calculated using engine rpm data recorded from a spark signal wire). For these reasons we chose a Dynojet, borrowing some time from the kind research and development team at filter experts K&N Engineering in Riverside, California.

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