lol, it does seem to be an American thing not to understand BHP. Not a dig, but an observation as I have had this discussion twice this week already.
HP or Horse Power is basically the measure. It is an imperial unit, and originated by a horse pulling X weight over Y distance and time. James Watt invented the system to rate his steam engines with. So a 6hp engine would do the work of 6 horses.
There are many types of horse power, some are a measurement and some a calculation. But HOW they are derived is important.
To find out the horse power of an engine we use a 'brake' device, hence the B as this denominates the type of horse power we are referring to.
BHP is a calculated measurement, this is done by measuring torque.
HP = torque (lb ft) x rpm / 5252
So, to mearly state you car has HP is actually very inaccurate. As dyno's, engine and chassis such as Mustang and Dynojet are all BRAKE devices.
Once you have derived the BHP yes you can indicate WHERE the measurement was taken.
Most common is the flywheel, but usually this is not stated on it's own but it IS noted, I'll explain in a bit.
But you could also derive BHP at the propshaft (many boats are), the wheel hubs (such as chassis dyno's like a Rototest Dyno) or indeed at the driven wheels themself.
Thus for the sake of correctness rwhp, should really be rwbhp.
rw = rear wheels, the WHERE
b = brake the type and the HOW
hp = the unit
Now the reason you don't see manufactures claim fwbhp (flywheel), is because they also state SAE Net.
SAE Net is a standard dictated by the Society of Automotive Engineers. This dictates exactly HOW and WHERE the reading should be taken, it also covers such things as engine ancilliary devices, fuel grade, astmospheric conditions and so on.
SAE Net is ALWAYS measured at the flywheel.
So remember, when referring to HP in terms of automotive use, it should ALWAYS be BHP, then any addtions you wish to add, to denominate where the measurement was derived.
As I said there are many types of HP:
ihp - this is indicated HP, and was commonly used in the 19 Century. It is a calculation using cylinder pressure of steam engines. This will give a very different number to that of BHP, yet it is still HP
dbhp - drawbar horsepower. This is for trains as a rule. This is a MEASURED as opposed to a CALCULATED like BHP is. Basically a train pulls a special carriage which meausres the amount of pull. I think this would be intersting for cars to be measured by.
RAC HP - This was used in Britiain in the early 20th Century, it is calculated by measuring the internal dimensions of the engine and certain assumptions of efficency. I think following this logic a ZR1 Corvette would only produce ~120RAC HP
There are also many other types as well. Plus there are metric equiverlents too. A metirc HP is still a horse lifting X weight over Y distance and time. But it uses metres and KG, instead of feet and pounds.
1 Metric HP is slightly smaller than 1 Imperial HP.
Metric HP may still be listed as HP or commonly as PS.
Bascially it all gets rather confusing, and there really is nothing else quite like it.
The closest comparison I can think of is money.
What is $1.00?
Well it would depend on the type of dollar, as Australian, Canadian and American dollars all have different monetary values.
$1.00US has a different value and thus spending power to $1.00Aus eventhough they are both the same physical number.
I agree what's TFH? I'm in the military where everything has to have at least one acronym to exist and was a auto mechanic before and still haven't seen this one in relation to motors and HP.
