Originally Posted by PencilGeek
Granted it's been many years since we did this...but whenever we placed a bone stock motor on the (motor) dyno to get a baseline, they always produced the exact horsepower at the exact RPM the manufacturer claimed. We saw this with quite a few motors. These days, now that everybody is lawsuit happy, I'd be more inclined to think the published numbers are conservative.
It depends on the application. High end forced induction motors tend to be a bit underrated. BMW M motors are usually spot on, the S65 and S85 are good examples. The 335 is a bit underrated, no surprise, it would have upset E46 M3 owners (the peak dyno HP is virtually a wash).
The GT3 is underrated, along with the GT2, Carrera GT, and Ford GT.
So, just depends, the 03 cobra was underrated big time as well. Some cars are overrated, the RX8 being overrated to the point Mazda had to revise the hp rating on it due to owners asking what was up.