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09-26-2018, 04:51 PM | #1 |
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What torque and horsepower mean for cars
I'm trying to understand what torque and horsepower are, and what they actually do for a car. Here's what I think I know.
Torque is rotational force. In high school physics we measured force in newtons, but that was for forces in a straight line. As a rotational force, torque is measured in newton meters, or pound feet. If you use a wrench to turn a nut, and you apply 10 pounds of force at the end of the 1 foot handle, you're applying 10 pounds * 1 foot = 10 pound feet of torque. For a car, the torque is the rotational force applied to the engine's wiener. (What's the technical term?) Power is a measure of how fast you're getting shit done. It's work / time, or force * distance / time. For cars the unit of power is the horsepower (1 hp = 550 foot pounds per second), and the term horsepower is often used interchangably with power even though one is a unit and one is a concept. A handy formula relates torque to power: Power (hp) = torque (lb-ft) * RPM / 5252 That formula works because power is force * distance / time, and torque is force, and RPM is not exactly distance / time, but I guess rotational force has to go with rotations / time? But what do torque and power mean for a car's performance? I've always heard that torque gets you moving and horsepower keeps you moving, but that doesn't seem right. It seems like power is what actually moves a car, and torque does nothing for you per se, but is important only because it's a big factor in determining power. A car with more torque can generate the same power at lower RPMs, but a car that allows higher RPMs can generate the same power with less torque. So at the end of the day, horsepower is all that matters, whether it comes from torque or RPMs. Yes, no, maybe so? |
09-26-2018, 06:20 PM | #2 | |
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Torquing about which is more important is meaningless; torque and power are 2 sides of the same coin.
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09-26-2018, 06:24 PM | #3 |
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having high torque at a given rpm mean you feel the push more
having high power means you end up going faster then the other car in the end. (*not counting aero/weight of the car) |
09-26-2018, 06:33 PM | #4 |
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09-26-2018, 06:44 PM | #5 |
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Yesssss!!
This is something that is usually not mentioned in these power vs torque threads.
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09-26-2018, 06:47 PM | #6 |
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@Johnny Horsepower
It reads like you've done some research. I'm guessing you would have seen a gazillion other posts about this subject.
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09-26-2018, 06:56 PM | #7 |
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09-26-2018, 07:43 PM | #8 | |||
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Yes, aero/weight/gearing are certainly important, just not the focus of this particular thread.
Quote:
Quote:
...but also having high rpm at a given torque means you feel the push more. So high power means you feel the push more, right? Quote:
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09-26-2018, 08:05 PM | #9 |
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Horsepower is how fast you hit the wall; torque is how far you move it.
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09-26-2018, 08:24 PM | #10 |
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09-26-2018, 08:25 PM | #11 | |
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Horse power and torque are not two isolated things and you can not have acceleration without both AND all the other considerations.
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09-26-2018, 08:37 PM | #12 |
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09-26-2018, 08:50 PM | #13 | ||
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Quote:
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I think it's reasonable to assume that cars A and B have the same weight, aerodynamics, and gearing, even if that's not quite realistic. (Like more torque might mean a bigger engine, which changes other things.) If that's too much to assume, then OK, let's say this is for entertainment purposes only, to provide a simple illustration of the concepts of power and torque. |
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09-26-2018, 08:57 PM | #14 | |
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The video in the link you gave explains it all perfectly. If you can't get it from that then I give up.
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Last edited by Tcoat; 09-26-2018 at 09:13 PM. |
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