BadSaver said:
Horsepower is a measure of power. Torque is not a measure of power. It is a measurement of twisting force.
The point was, the measure of power (as in the study of physics - matter & motion) is horsepower.
Trust me, I do understand the engineering and the physical difference. Quite often, I try to distill complex subjects so that they can be understood by people asking questions and reading these articles. In fact, that is one of the guidelines of this forum. I'm attempting to make it easier to understand, rather than quote physics principles and formulas, which I try to avoid, as well as electronics formulas...(long story there too).
The very fact that vehicle engine ratings are DIRECTLY mathematically related means they can BOTH be used almost interchangeably for power output specs, and are very often done so in the real world. If you have
one, you can 'calculate' the
other, based on an assumption about expected RPM, say, when pulling a mountain grade.
As iTripper points out, its WHERE in the RPM curve that matters when it comes to towing with a truck, as opposed to a sports car that might have very high horsepower ratings at 6000 RPM, but much less torque at, say, 1200 RPM.
BTW, ALL torque vs horsepower rating curve charts cross at 5252 RPM. This is no coincidence, its
evidence of the mathematical and direct relationship between torque and horsepower.
Engineers and scientists in the labs will separate them, but in the real world of driving vehicles with internal combustion engines, in many ways, more HP (at a given RPM) almost always means more torque, and vice versa.
In the world of large 15 liter diesel engines, if my truck's engine is rated at 1500 lb-ft of torque (at 1400 RPM) and I have the mechanic hook up the laptop and reprogram it for 1700 lb-ft, (at 1400 RPM) I just instantly got more
power, as a result of the new injector settings. Coincidentally, the displayed horsepower on a chassis dyno will also go up, because the engine now produces more power, by raising the torque ratings.
The two specs ARE directly related in the real world of internal combustion engines.
Wanna talk electric motors? Yep....very different now....You can have MAXIMUM torque at zero RPM with ZERO horsepower being produced.
But with diesel and gas engines, they have a range of productive RPM, so if either rating is changed, the other one changes also.