no archit, infact read this small para from the link i posted-
However, the most common use of HP, as a unit, is to measure the power of an engine – which you can determine by hooking it to a dynamometer. What HP actually measures, is the maximum rate of acceleration and the top speed of the car.
On the other hand, Brake Horsepower measures the HP of an engine without considering the loss in power that is caused by some parts of the engine, like the generator, gearbox, water pump and other auxiliary parts.
Now before someone asks about " PS " (Its a unit like Hp,Bhp in which engine power is measured)
0.9866 PS = 1 Hp
A scottish guy named Watt figured that a horse could do 746 watts of work.
Germans estimated that their wimpier horses could only do 736 watts of work and they called their measurement Pferdestaerke or PS.
No, there is no exact OR constant relation between Hp & Bhp.
The Hp (engine power at axles) is mostly 15 - 20 % lower than Bhp (engine power at crank) depending on the gearbox,alternator,etc.(depending on them means considering their size,weight, no of moving parts,etc)
There is also WHP (wheel horse power) - This is the actual Horse Power in real condition.