Torque and horsepower: What they mean and why they’re different

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You may have heard it before: “Horsepower sells cars; couple win races.” But what is torque and why does it matter? We’re not engineers here, even if we play them on YouTube, so we’re going to give you the non-engineer explanation and try our best not to make you feel like a photography major in a gen-ed math class. Let’s dive in.

Couple

Torque is how you get things done, mechanically. Turning a knob, opening a flap, operating a lever – these are everyday applications of the concept. Essentially, it is a measurement of the amount of work done by something. Or, put more clearly (and unscientifically), it’s a measure of leverage.

Your typical physics teacher will probably demonstrate the concept with some sort of simple lever, but this is Autoblog, not West Crestfield Senior High, so let’s use car stuff, shall we? The best way to easily visualize torque is not with engine components, but with a wheel wrench.

Why a spanner? Because torque is a multiplicative measurement of an amount of force delivered over a certain distance. That’s why a car’s engine torque is expressed in pound-feet; you apply a force (in pounds) over a distance (in feet).

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Scenario: You have entered a parking space with a flat tire. You have a well-inflated spare, a jack and a typical wheel wrench. For this example, let’s say the wheel wrench handle is one foot (12 inches) long. You put the jack on the right spot and you’re ready to loosen those lug nuts before putting the wheel in the air. You put the lug wrench on it and give it a good, assertive yank counterclockwise… and nothing happens.

What are you doing? Go ahead, shout the answer if you know it. If you said “get a longer wheel wrench”, you’re right. “Jerk harder” would also have been correct, because increasing the distance (wrench handle length) or force (jerking harder) would increase the amount of torque you applied to that lug nut.

But you can only jerk so hard, and the more you try, the more tired you get. You can replace yourself with a bigger, more powerful human (diesels have a torque; try Vin) or you can get a better tool. But there are no wheel wrench shops nearby (what, don’t you have wheel wrench shops?), just a one-window hardware store, a liquor store, and a few hair and nail salons. So you wander to the hardware store and ask the clerk if they have wheel wrenches.

They do not. Just your luck! But since you now understand how torque works, you know that all you need is something that will allow your wheel wrench to handle longer, such as a length of pipe that fits over the handle. So you buy a four-foot metal pipe, walk out and unscrew those suction cups like this, because now you’re applying four times the force you would with that one foot wrench.

horsepower

Now that you understand torque, it is much easier to understand the difference between torque and power. The great thing about torque is that it’s very simple “can it be done?” formula. You have to move something that requires X force and you have Y foot-pounds of leverage to apply. If Y is greater than or equal to X, you can move it. So why do we care about horsepower?

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Horsepower is a more complex measurement because it takes time into account, mathematically referred to as speed. In other words, if torque tells you if you can do something, horsepower tells you how quickly you can get it done. To calculate it, multiply the torque (in pound-feet) by the speed (in RPM, in the case of a car) and divide the total by 5,252. Why 5,252? Because it’s a mathematical constant, as in “Why are you constantly asking us questions we don’t want to answer?”

Let’s go back to that scenario with a flat tire. Let’s say the hardware store was fresh out of anything you could use to make the wheel wrench longer and Vin Diesel ghosted your Insta chat. So while you can’t make yourself stronger, you may be able to find ways to increase the force you exert on the end of the key. Like using a hammer, for example.

That hammer will allow you to apply more force to the end of the wrench’s handle, but you’re not just going to be using it to help you jerk, right? You’re going to hit the thing. Each of these momentary bursts of force is greater than the constant amount you can apply to the handle by pulling on it, and sure enough, each impact starts to loosen the lug nut.

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Pop. Pop. Pop. Ultimately, it’s loose enough that you can use the wrench (and eventually your fingers) to do the rest. No, you didn’t exert as much torque as with a longer wrench, so it took a little longer. The speed with which you completed the work slowed down, but eventually you got it done. This is the same premise behind a hand-operated percussion pistol. You deliver quick, powerful bursts of torque time after time to apply leverage incrementally.

So, yes, if you had a big enough percussion gun you could use it to turn your car’s crankshaft and move it across the road, but even a hypothetical monster percussion gun can’t quite handle much… a thousand pound vehicle. get on the road quickly. It has the leverage (torque) to get it going, in other words, but not very fast (hp).

Essentially this is how an internal combustion engine works, only you have multiple wrenches (your connecting rods) that apply torque to your nut (the crankshaft) hundreds of times per second. And to take that analogy further, the crankshaft in turn (sorry) becomes a giant wrench that you use to turn your flywheel.

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This is the point where a motor’s torque is actually measured. Every part of your drivetrain downstream from the crankshaft is just another wrench turning yet another part, and with this analogy, your transmission is basically a box of different sized wrenches so you can choose the best one for the job you’re trying to do. to be carried out . Keys. Keys everywhere.

So which is better?

There is a saying in racing: to finish first, you have to finish first. Koppel, represented by the big red Ford pickup above in this article, is the “can it be done?” figure, so it goes without saying that this is the most critical measure of an engine’s potential. But if you’re in a race, represented by the little red Ferrari F1 car up there, wheel-to-wheel or against the clock, “how fast?” is an incredibly pertinent question. Neither torque nor horsepower tell the whole story. Look no further than the Jeep Wrangler Rubicon 392 for a perfect illustration of the fact that many factors come into play, including tire choice, aerodynamics, suspension design and (perhaps the most critical) acceleration. But that’s a topic for another time.

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