You're right there Dollyboy! You could work out the BHP of the engine on a rolling road, without transmission losses (but it would not be very accurate!)
What follows is a public service announcment!
BHP (Brake horsepower) actually refers to the power measured at the crankshaft using a braking system brake - an engine dynometer. It used to be that engine power was measured using the deflection resulting from this braking being applied - nowadays it refers to the braking system that is used to measure torque during the run, which can then be used to calulate power afterwards (multiply the torque by engine speed in revs per second and then by the circumference of the braking band to give the power)
Rear wheel horsepower is the measure of what the car is actually delivering to the wheels (or wheel horsepower, for 4 wheel drive vehicles and front wheel drives). This is measured on a rolling road and accounts for the all the losses resulting from ancilleries such as air conditioning, the alternator and of course the transmission losses from gearbox and axle.
The two primary US measurements were gross and net horsepower. Net is now the common one.
Gross horsepower is the now outdated power measurement at the crankshaft without any ancilleries - anything driven by the engine that's not absolutely essential - such as alternators, power steering pumps and with the fuelling and ignition system in 'ideal' configuration.
Prior to 1973, horsepower specifications were listed by the manufacturers as gross horsepower. After 1972, manufacturers provided net horsepower specifications as they were more reflective on the actual outputs of the engine. Net horsepower is the same concept (power measured at the crankshaft) but includes the losses of all the ancilleries - these are both effectively the same as BHP...
I bet they'd be disappointed if they rolling roaded that TR7
- Then again, it may well be 240 at the crank....
Drivetrain losses are usually in the region of about 10 to 25%, can be more for complicated powertrains such as the Imprezas 4x4 system and so on.
Shorty's shaker Fordson was a devil of a machine and that probably could make 300BHP......but it was made to take half that in N20
Quote:
2.1 triumph dolomite sprint engine full race spec with new block lightened & balenced bottom end with steel rods,1 off JE racing pistons machined in the states,comp head 3 angle valve seats, 306 duration piper cam,twin 45 webbers with K&N filters,msd blaster coil,moroso leads,msd digital6 ignition system,NOS fogger kit with 75bhp jets at mo but engine built to take 150bhp
Was a fast maachiiiiinneeee!