First off BHP= BRAKE HORSEPOWER.
Brake horspower is basically measure of an engine's horsepower without the loss in power caused by the gearbox, generator, water pump and other paristic effects. When you read the specifications from dealers, they always tell you the BHP.
The actual horsepower delivered to the driving wheels is less. The actual horspower delivered to the wheels is called
WHP= Wheel Horspower. The true way to find out WHP is run it on a dyno.