Torque for dummies

MadCat360

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I admit I have absolutely no idea how torque vs hp vs gearing works and unfortunately this thread has done nothing to change that unfortunate situation.

Good day. My brain is fried.
 

NooDle

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it's true that F1 engines have relatively little torque, only 200 lb/ft or something, and even then, their torque band is very narrow (something like 16.000-18.000 rpm). The rest of the time those things just will.not.rev. Heck, they idle at 4,500 rpm, which is kinda high

however, because they make an insane amount of revs, they can make 700-800 hp, while having only little torque. So torque isn't what wins races, otherwise my car would be able to keep up with an F1 car, which it obviously doesn't...
 

speck123

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...

I mentioned a rocket engine as an extreme example of an engine that has measurable horsepower (expressed as thrust) and no torque at all.

...
Say what?

Rocket engines don't spin around, so of course there is no torque. I do suggest, however, that you read up on Newton's Laws of Motion

Especially this part:

"A body continues to maintain its state of rest or of uniform motion unless acted upon by an external unbalanced force."

Put simply: to get the rocket moving, you need a force acting in the opposite direction of the (intended) motion.

Torque plays a similar role for our purposes. That is, it is torque that overcomes friction (from tires, etc) and aerodynamic drag.
 

SirEdward

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I think we're making a mess:

Torque is a force. Being a force it accelerates objects.

The mess starts when we don't consider time. A force of a Newton is a force capable of accelerating a mass of 1 kg to the speed of 1 m/s in a time of 1s . A Netwon/meter, measure of torque, can do the same thing (rotating) to an object tied to a lever which is 1 meter long.

But a Newton can be a Newton even if it's not applied for one second. It can be, for example, the force capable of accelerating a mass of 1 kg to the speed of 0,04 m/s in a time of 0,2s. It will remain 1N.

So it is for engines. You are all talking of peak torque, but since the engine is revving, the important thing is not exactly what the peak of torque is, because it will be applied for a brief instant. What is important is the curve of torque, so if you have an engine capable of delivering 300 Nm of torque from 5000 to 7000 rpm (and 10 Nm outside this range), it will accelerate the same car faster than an engine capable of delivering 300 Nm of torque but only from 6000 to 6500 rpm (and 10 Nm outside this range), because, the first engine will give the same amount of acceleration for more time than the second one.

But hey! (and here comes the importance of transmission in real world) you can equip your car with a CVT automatic gearbox, that will maintain your engine in the best possible rev range, providing the car, with either one of this two engines, with the same final acceleration. So, in real life, transmission in important.

However, using the same car, if you choose the first one of these two engines, you will achieve a higher top speed than using the second one, because the first one will still deliver 300 Nm at 7000 rpm, while the other one will only produce that amount up to 6500. The first one, following the formulas that describe this, will have more horsepower.

Torque doesn't win races alone, but it does together with horsepower, a good good way of delivering the energy to the road, a good good way of controlling the car when is moving and a good good way to stop it at will without destroying it.
 
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HumansAreDead

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Torque is the effectiveness to turn an axis, or twisting force. It has NOTHING to do with acceleration.
Wrong.

Torque = Force x Distance
Force = Mass x Acceleration

Therefore with a little rearranging
Acceleration = Torque/(Mass*Distance)

And from that
Acceleration is proportional to the torque QED :p

Torque is a measure of power. Horsepower is a measure of power/time.
I think the clue might be in the name horsePOWER and that the units are Watts which is a measure of power not Ws^-1 as you suggest. :)
 

edkwon

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Here's the simplest explanation: Horsepower makes you go fast. Torque makes you feel like you are going fast; it gives you that kick in the back when you push the gas.

/thread
Even tho what i say isnt entirely accurate, i like to simply as such:

hp = determines top speed

tq = determines force of acceleration to get to that top speed
 

Karoug

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it's true that F1 engines have relatively little torque, only 200 lb/ft or something, and even then, their torque band is very narrow (something like 16.000-18.000 rpm). The rest of the time those things just will.not.rev. Heck, they idle at 4,500 rpm, which is kinda high

however, because they make an insane amount of revs, they can make 700-800 hp, while having only little torque. So torque isn't what wins races, otherwise my car would be able to keep up with an F1 car, which it obviously doesn't...
I found an interesting bike test (bare with me) between a Sook GSX-R 750 and a Honda CBR 900, despite having almost 20% less torque the sook was always faster than the Honda, and they posted similar hp, weight and top speed.
 

SirEdward

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I found an interesting bike test (bare with me) between a Sook GSX-R 750 and a Honda CBR 900, despite having almost 20% less torque the sook was always faster than the Honda, and they posted similar hp, weight and top speed.
Probably (apart from gearbox's magic) is because, while having less torque as a peak, it has a better distribution of torque, a better torque curve.

If this is the case, then when at the peak of torque, the sook accelerate less than the CBR, but on average (before or after that point) the sook delivers more torque than the CBR.

Real world is different from theory, though. Maybe the gears are specifically set, maybe the weight is different, maybe the electronic on the CBR is slowing it down. Who knows...
 

NooDle

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^yup, the flatter the torque curve the better. It also means you don't have to shift every 3 seconds, you can basically accelerate in any gear at any speed if you have a very flat torque curve
 

satcomvato

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Very nice, I love the front end twisted like that. I had a buddy who put a small block chevy in an old Datsun 240z and when he got on it the first time he cracked the t-tops.
 

kurthest

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I still dont think I understand.

That being said, I guess Jonus' Audi 90 has lots of torque on this vid (racing a 850 horsepower ricecooker (Supra) ):

[YOUTUBE]http://www.youtube.com/watch?v=bMz24kRG0gA[/YOUTUBE]
 

Lupul

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Doubt that...

It might be the fastest accelerating audi on the planet but i don't think it can beat any Le Mans versions when it comes to being fast (by which i mean high top speed). Surely the car in the video has lots of torque, but it also probably has a short ratio gearbox thus being able to weave trough the fast. On a highway run the supra would have probably toasted it.

Not takin' sides.

Great idea of creating such a topic, awfull involvement of gears to make it seem a lot more complicated than it is. Why not settle for the output at the flywheel and then, in a separate topic post different speeds, various ratio type gearboxes could achieve with one engine producing that much torque and that much horsepower.
 

ediesbra

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So with F1 cars, am I right in thinking that if they had a higher torque output with lower revs, producing roughly the same horsepower, would the top speed be less? :think:
 

NooDle

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^yes, because they wouldn't be able to rev so high, thus not make as much hp
 
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