Image source: www.dekuyperphoto.com
People regularly confuse the difference between brake horse power (bhp) and wheel horse power (whp)
, and when they do - and when they try
to correct what they see as a mistake - you know they're going to get owned in the comments section
. No-one wants to be that guy...
To save you from comments ownership - and for your general knowledge - here are the differences between bhp
Image source: Mustangandfords.com
1. Brake Horse Power (bhp)
This is the power output of any engine measured at the engine's flywheel
. (A flywheel is a disc with teeth on it. It's connected to the rear of the engine and its purpose is for the smooth transfer of power to the transmission from the engine.)
2. Wheel Horse Power
Unlike bhp, whp is the power output measured at the wheels
. This is the information a dyno run provides and usually reads around *15 per cent less than the power measured at the engine (bhp
) - this is because power is lost in the driveline (including clutch and transmission).
*Four-wheel drive cars lose between 20-25 percent of their quoted bhp figure because of the increased friction.
1. The term brake horsepower
) refers to a device called ‘Prony Brake’
(invented by Gaspard de Prony), which was used to measure engine power in the early 1900s.
2. You don't need to increase an engine's bhp to get an increase in a vehicle's whp. You can achieve higher whp by reducing the rotational mass in your drivetrain, such as the wheels, tyres, brakes, clutch, flywheel, etc.
Dynoing a rear-wheel drive Miata at the front...that'll be 0whp, then!