What is the GT-R's Real Horsepower ?

Car and Driver.com

Despite what Nissan claims, the GT-R is not making the advertised 480 horsepower.

In this case its more power. Nissans answer has been an efficient driveline. It might be efficient, or maybe this car just rewrites some of the correction factors that people use.

On MotorCity Speed’s Mustang dyno in Commerce Township, Michigan, GT-R No. 4 produced a peak of 415 horsepower at the wheels. Based on our 20-percent loss estimate, the engine output was 519, or 39 horsepower more than Nissan’s stated 480.

So what’s up? We called Nissan, and the company says the first four cars we tested were early-build versions that received regular engine-computer software updates, which may account for the varied results we recorded. We then wondered which engine-computer calibration was the one real-world GT-R buyers would receive.

Three weeks later, a fifth GT-R arrived. This one, allegedly, was a production version with the latest—and final—engine calibration. We took it both to the test track and MotorCity’s dyno.

This car performed nearly identically to the fourth car. It smoked the quarter-mile in 11.6 seconds at 120 mph and produced 420 wheel horsepower. We also measured the turbo boost pressure in both cars, and the curves were basically identical.

There are a couple of dyno charts, and boost pressure charts on the Car and Driver site. The prototype car actually made less boost than the production car.