I recently saw the horsepower and torque specs for the 2005 Pontiac GTO:

Horsepower (advertised): 400 @ 5200 rpm

Torque (advertised): 400 ft-lbs @ 4000 rpm

Those familiar with auto math should notice something wrong right away.

Recall that the formula for horsepower is HP = Torque x rpm / 5252. So Torque = HP x 5252 / rpm.

Now, if the '05 GTO develops 400 horsepower at the stated engine speed, then the torque at 5200 should be 404 lb-ft, which is higher than

what the peak torque is supposed to be (400 ft lb @ 4000.)

So this means that either the peak torque is understated or the peak horsepower is overstated, assuming the engine speeds to be correct.

Explanations? (I'm awaiting a response from Pontiac but am not holding my breath.)