Power Vs Torque

[AnnuityAdviser]

Someone please explain the difference!

[otolith]

The higher the rpm you make torque at, the more useful it is. We have a measure of this "torque and revs" thing, which we call "power".

[FreeLitres]

Petrols have power.
Diesels have torque and are quicker in the real world.

Something like that.

[mrmr96]

[Patrick Bateman]

People need to understand there is no 'versus'.

[fozzymandeus]

An engine's torque is it's ability to transfer turning force to the flywheel, ergo cause a change in rotational momentum. Large torque means the engine is capable of changing the velocity of a drivetrain quickly, hence make the car accelerate.

Power is about transfer of energy: the engine's ability to transfer the energy in the fuel into kinetic energy (if we're talking about output power). High powered engines will be able to cause a rapid transfer of energy, therefore make the subject of the transfer reach high momentum.

The best measure of a car's expected performance is its power to weight ratio.

The best measure of a car's ability to gain traction against significant load (e.g a trailer or a caravan or a highly resistive drivetrain) is torque.

[vonhosen]

Power = how fast the engine punches.
Torque = how hard the engine punches.

[redgriff500]

Tractors have torque
Motorbikes have power

One is a function of the other and you need sufficient amounts of both

[otolith]

If you want an analogy, "how much torque do you have?" is like asking "what denomination notes are you carrying?" and "how much power do you have?" is like "how much money do you have?".

[FreeLitres]

otolith said:

If you want an analogy, "how much torque do you have?" is like asking "what denomination notes are you carrying?" and "how much power do you have?" is like "how much money do you have?".

I have 80p in 20p coins. How fast am I?

[otolith]

FreeLitres said:

I have 80p in 20p coins. How fast am I?

Not very, but you have a broad spread of coinage

[nottyash]

otolith said:

The higher the rpm you make torque at, the more useful it is. We have a measure of this "torque and revs" thing, which we call "power".

Well I dont think thats the case.

[cuprabob]

Horsepower = Torque X RPM / 5250

They both have a direct relationship with each other

[redgriff500]

otolith said:

The higher the rpm you make torque at, the more useful it is.

Do you want to rephrase that..

I presume you meant LOWER

[otolith]

redgriff500 said:

otolith said:

The higher the rpm you make torque at, the more useful it is.

Do you want to rephrase that..

I presume you meant LOWER

Nope. Higher. If you make 250lbft @ 8000rpm, you will have a much faster car than if you make it at 1200rpm.

[Jacobyte]

Power is only a calculation. Torque is actually doing the work. But if you do it twice as many times in a minute (e.g. 81ftlb at 6500 rpm rather than 3250 rpm) you will have twice the power output.

Power = Revs x Torque / 5252

E.G.
100bhp = 6500 x 81 ftlb / 5252
50bhp = 3250 x 81ftlb / 5252

Taking the £1 analogy:
£1 = 100 x 1p pieces
£1 = 2 x 50p pieces

Edited by Jacobyte on Monday 9th July 20:59

[otolith]

nottyash said:

otolith said:

The higher the rpm you make torque at, the more useful it is. We have a measure of this "torque and revs" thing, which we call "power".

Well I dont think thats the case.

The higher the revs you make the torque at, the more you can multiply it by gearing it down.

[jagnet]

otolith said:

Nope. Higher. If you make 250lbft @ 8000rpm, you will have a much faster car than if you make it at 1200rpm.

Agreed

A water wheel can easily generate 1,500 ft.lbs of torque, and rotates at say 10 rpm. That gives us nearly 3 whole bhp!

But it's got loads of torque, so in the real world it's faster than an M3

[nottyash]

otolith said:

nottyash said:

otolith said:

The higher the rpm you make torque at, the more useful it is. We have a measure of this "torque and revs" thing, which we call "power".

Well I dont think thats the case.

The higher the revs you make the torque at, the more you can multiply it by gearing it down.

I prefer torque at low revs but linear up the rev range. The whole point is so you dont have top bother using gears. Get into 6th gear at 1800 rpm, and no need to change just ride the torque

[SSBB]

Torque is measured in Nm.
Power is measured in Nm/s.

If you haven't ever studied mechanics, you may not get this.

For speed, power is key. Whether you achieve this through high torque (turbo-diesel), or high rpm (bikes) it doesn't really matter.