What about the internal combustion engines that sit under the bonnet of the cars, SUVs, and utes most of us drive? Their power isn’t measured by hitching up to a 33,000 lb concrete block and hitting the throttle. No, it’s all more scientific than that.
So there are some basics to remember. Torque, or pulling power as it is also known, is the rotational force produced by an engine’s crankshaft. The ‘work’ is that force acting over a distance, where ‘power’ is how much work is being generated. The power number is arrived at by multiplying torque by engine speed.
The basic rule is the more power generated the more work is done and the faster your vehicle can accelerate from 0-100kmh, the higher the top speed, and so on (there are lots of provisos here: gearing, vehicle weight, aerodynamics, etc; but the fundamental rule is correct).
Traditionally, the bigger the engine, the better off you are because there is inevitably more torque to work with.
Turbocharged and supercharged engines also have more torque because they pump more air into the cylinder. More air leads to more torque, which leads to, yep, more power.
Why some people love power
In an internal combustion engine, power tends to increase with revolutions per minute (rpm) but not in a purely linear way. This is because torque is not constant through the rpm range.
Torque tends to be very low at low rpm, peaks at mid-rpm, where the ability of the engine to maximise the amount of air going into each cylinder is at its optimum and then drops away at higher rpm.
Because power equals torque multiplied by rpm, power tends to increase the more you rev the engine, even as torque is dropping off at high rpm.
So that’s an explanation of why horsepower is the term focussed on by performance car lovers and in motorsport - because maximum throttle high-rpm tuning works in that environment.
Of course, boys love to compare, so there are pub bragging rights about power numbers. Through the generations of locally-built Ford and Holden performance cars, peak power kept creeping up with each new iteration of Falcon and Commodore V8 topping the other by a few kilowatts.
It is not unusual for the peak power figure to also become part of a car name. Jaguar, Land Rover, Lotus, Renault, Skoda, and Volkswagen all currently do this, for a wide variety of vehicles including quite bland entry-level models.