30-35bhp. Depends to ambient temps (which affect the temp of the gearbox oil etc). Also if a car is run several times, the losses will decrease. This will reflect in the Engine Power that the RR Run produces (will probably be less because Engine Power = Wheel Power + Transmission Losses).

Here is another example. Take a look at the Norris Designs Evo and also the RC Developements Evo. They both quote figures around and in excess of 800bhp. But they have 250-300bhp Transmission loss and around 600bhp at the wheels. How does that happen??!! What happens when a cars horsepower increases that affects the resistance of the transmission?? Always baffled me that one.