What exactly is the difference between horsepower and torque?

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There's a battle of words that occurs when a group of people begin arguing over who has the fastest machine. All sorts of performance metrics are thrown around, and it can quickly become a miasma of uninformed soup. Some think they're going to win a race because they have more horsepower, while others scream from the hilltops that torque is king. What's the real difference between the two anyway? Jason Fenkse from Engineering Explained is here to unlock the knowledge you need in understanding horsepower versus torque.

To fully understand how torque and horsepower unfold in the automotive space, we need to first grasp what it is we're dealing with on a physical level. Put simply, torque is the measure of force multiplied by distance. It's the measure of a force acting at a radial point. An easy way to visualize this is to imagine a wrench. You put one end on a bolt, grasp the other end with your hand, and you tighten that bolt on a screw. Your hand is applying force on one end of the wrench, which is a given distance away from the bolt. You're generating torque.

Now on the flip side of this discussion, we have horsepower, or power in general. In basic engineering terms, power is the rate at which work is done. Jason does a great job of illustrating this concept by way of a toy race car. If the car were real, and the driver wanted to get from point A to point B, the amount of power required to do so would vary based on how quickly the driver needed to move between the points. That's because the rate of the work being done would be different, and thus the power required to travel the distance would change.

So it's the power that gives you the ability to move more quickly. However, you need the torque to start the action. What happens if you line up equal vehicles where the only differences are the torque and horsepower available. Jason puts two hypothetical vehicles on the table before him, and it's the one with more horsepower that will accelerate more quickly. That's because the car with more horsepower can achieve the same amount of work at a faster rate.

Horsepower fans, don't rejoice just yet. You can't have horsepower without torque, as that provides the ability for the engine to do the work across a given rate. Finally, once you add in differing gears and gear ratios, there's a whole new variable to explore in this battle of physics and engine engineering.

The old saying "Horsepower sells cars, but torque wins races" isn't exactly true. Click play on the video above to see what we mean, and hear Jason break down all of the science for you.

 
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