BHP is a type of HP, it is the HP at the engine/crank itself. If you stick a car that makes 210bhp on a dyno, you will get a lower # like 180hp, because the dyno will tell the actual amount of HP making it to the wheels. You can lose a good 10%-20% of the crank HP in the drivetrain, etc... The difference between BHP and WHP
Brake horsepower: (BHP) A measurement of the actual usable power (not calculated power) measured at the output shaft (usually the crankshaft) rather than at the driveshaft or the wheels. Thus none of the auxiliaries (gearbox, generator, alternator, differential, water pump, etc.) are attached. It is called the brake horsepower because the shaft power is usually measured by an absorption dynamometer or "brake." This is not the brake on the vehicle's wheels but a testing device applied to the shaft. This instrument is applied to stop or absorb the rotation of the output shaft and returns a value.
SAE horsepower: A simple formula of long standing is used to determine horsepower. The formula is: (bore diameter) squared times (number of cylinders) divided by 2.5. This formula is used primarily for licensing purposes and is not very accurate for determining actual brake horsepower. Also called rated horsepower.
SAE net horsepower: The brake power (power available at the flywheel or output shaft -- usually the crankshaft) of a fully equipped engine fitted with all the accessories necessary to perform its intended functions unaided. In 1973, automobile manufacturers began publishing their engine specifications in "net" horsepower and "net" torque instead of "gross" figures. In many cases the published numbers were significantly lower in 1973 than in 1972. Some of the decrease was attributed to the addition of pollution equipment, the lowering of compression, and the use of regular unleaded gasoline instead of premium leaded fuel. However most of the decrease in number was a switch to "net" figures.
SAE gross horsepower: A production engine's actual power available at the flywheel or output shaft (usually crankshaft) as tested with an absorption dynamometer. It differs from SAE net horsepower in that many of the accessories (such as alternator, water pump, etc.) are not attached. Engines before 1973 were primarily measured with these "gross" numbers. Since 1973, "net" figures were published. This confusion caused many people to suppose that their engine had been seriously de-tuned when they saw that the same engine in 1972 had 400 hp but in 1973 had only 235 hp. (This example is from the Cadillac 500 cubic inch engine).
