Kopierat från megamanual.com:
"Torque and Horsepower
The force of the piston(s) on the crankshaft (through the connecting rod) becomes a rotational force called 'torque', and is measured in ft·lbs. Work is done when force is exerted over a distance (measured in lb·ft) such as lifting 100 pounds 330 feet. Power is the rate at which work can be done (lifting 100 pounds 330 feet in 60 seconds, for example).
The rate at which the engine can produce torque is a function of rpm, and is called 'horsepower ' (HP). In particular, horsepower is defined as the ability to do 33000 lb·ft of work in one minute (ex. 1 horsepower can raise 330 pounds 100 feet in a minute, or 33 pounds 1000 feet in one minute, or 1000 pounds 33 feet in one minute, etc.).
For a rotating engine crankshaft, the torque tells us the force at a radius of 1 foot. In one revolution, that force will be exerted over the circumference of a 1 foot circle, so a force of F = torque÷r, over a distance of D = 2πr, where r = 1 (but note that the r in both equations cancel each other out when we calculate the work done: W = F × D).
The result is that the work (W) done per revolution is 2π × torque. This work is done rpm times per minute. So the functional relationship for horsepower is:
HP = (2pi*torque*rpm)/33000
One effect of this relationship is that the same torque at a higher rpm makes more horsepower (which is why 2.4 liter F1 engines with just 200 lb·ft of torque - less than many passenger cars - can make over 700 HP at their 19000 rpm maximum speed). And it is horsepower that makes the vehicle accelerate. Also, note that HP = torque at 5252 rpm (so take any dyno results where that isn't true with a big grain of salt).
The tradeoff is that engines run best only over a certain limited rev range. A stock engine might produce useful power over a range from 1500 rpm to 5500 rpm, while a race engine might make power from 5500 to 9500 rpm because of its cam timing, compression ratio, intake/exhaust design, etc. The stock engine would break if it was rev'd like a race engine, the race engine would have no power off idle for cruising around town (and would have poor fuel economy, high emissions, suspect reliability, etc.).
You may hear people talk about street engines needing torque for best performance, race engines needing horsepower. What they mean is that street engines need to be built for lower rpm, race engine for high rpm. Both cases would like to have as much horsepower as possible, *and* as much torque. But on the street, you don't want to have to downshift twice and rev to 5500 rpm every time you want maximum power (such as at a stop light). "
Notera att formeln gäller vridmoment i lb·ft.
Står ni fortfarande kvar vid era åsikter om att det är "vridet" som accelerar bilen och allt vad ni tjatar om så rekomenderar jag att ni läser om Fysik A.
