Horsepower terms are a bit confusing and subject to many different standards. Although the true hp of an engine is entirely independent of test equipment and process the actual measured values are not. bhp is brake horsepower as measured using a brake system (brake dyno) on the engine driveshaft (not the cars brakes). Any measurement that included any drivetrain components would further complicate testing and would always report lower power numbers from parasitic drivetrain losses. Sometimes auxiliary hp robing equipment such as alternator or water pump is can be left out of the measurement process (getting you a higher number). In the US we (often) use SAE (Society of Automotive Engineers) standards to test hp. We call it hp rather than bhp although it is measured by a brake dyno as well. The old SAE standard was from 1971, the newest one from SAE is called J2723 and specifies precise test conditions to eliminate any advantages or variability in the test (http://www.sae.org/certifiedpower/). PS figures only further complicates the matter. This German unit of power is lawfully not supposed to be used anymore but you still hear it a lot from Europe. Their new official power unit is kW (kilowatt, the metric MKS standard). PS and kw are defined exaclty by:
1 PS = 0.73549875 kW = 0.9863201652997627 hp (SAE)
Also hp numners differ from EU to US (models) because the engines and cars are actually equiped differently and do produce a different amount of power. Hope this helps.
Swamp - please tell me you cut and paste this info from somewhere and you don't go to bed at night dreaming about this stuff!!!