The difference between horsepower, and torque in a car.
In: Physics
The relationship between horsepower and torque is speed. High torque at low speed have the same horsepower as low torque at high speed. A gearbox changes the speed but not the horsepower going through it. You can therefore get high torque at low speed or low torque at high speed out of the same engine just by changing the gears.
You often see just a single number being quoted for an engine. This is usually the peak horsepower and torque respectively. So how many horsepower can it produce at the optimal speed, typically a very high speed, and how much torque can it produce at a different optimal speed for torque. These numbers can be misleading as the engine rarely stay at optimal speed for either of these numbers. Peak horsepower might be related to maximum speed but when you are accelerating the engine have to go through a lot of different speeds for each gear. The torque curve for an engine tends to be more flat so peak torque tends to be something you can get at any speed. So high peak torque engines tends to accelerate better as they often have a descent amount of horsepower outside of the optimal speeds as well.
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