Forgive my ignorance but all this talk of torque. What does torque mean on a car?

Is it not just the force that pushes the car forward? The force being determinant on weight and bhp? If so how can people say the S has poor torque? surely if its got quick acceleration it has good torque

so whats the difference then between acceleration and torque?

Can someone please explain in SIMPLE ENGLISH

yours confused......

numpty

 

Torque is a twisting force, produced by the engine and transferred to the wheels, see this link for a comparison of power vs torque...

http://www.lancs.ac.uk/ug/fairclok/power.html

 

Thats a nice explanation Ali - perhaps another thing for tech faq? mind this is general not S specific, sorry thinking out loud

 

Think of a screw and you have a screw driver in your hand. You grab hold of the driver and twist away. That is torque, even when the screw is not rotating you are exerting torque. Now the screw starts to turn. As it turns faster and faster you find you find you cannot apply the same twisting force, the force drops as the rate of rotation increases.

The power you are applying is the product of the torque and the rate of roataion.

Car engines have the same problem. The torque starts to reduce with increasing revs, though this effect only starts at rotation speed far higher than you or I can manage with a screwdriver. max torque occurs at a particular RPM value. For a diesel engine this is quite low copared to a petrol engine. The power is the product. Increasing the revs above the max torque value by a fraction, say 10% may result in a 5% reduction in torque, but the product of the two, power, in this case 110% x 95% which is greater than 100%, may still, and usually is still, greater than the power at the max torque point. Hence you have max power at a higher rev point than the max torque point. This goes on increasing until the torque fall begins to dominate and the max power point is passed. I beleive I am correct in saying in the case of the rotary Wankel engine this happens at incredible revs -but the engines fly apart first, and so are limited in revs.

Torque is more akin to brute muscle power. The old steam engines and water wheels had massive torque at very low revs, maybe 20 or 30 RPM. Speed them up and the torque drops dramatically. Think of a water wheel. Try to turn it faster and the buckets do not fill, hence the turning force falls, and power vanishes. A water wheel would give you incredible acceleration from 0 to 1 mph, then nothing! Bit big to go under the bonnet too!

 

Part II

You are right, it is torque that leads to acceleration, but it is power that overcomes all of the friction and air resistance. So the car engine has to be able to give the torque to accelerate the car while at the same time, and at the same RPMs, delivering the power needed to push the car forward.

 

How do you increase torque in the case of an engine. Does bigger capacity mean more torque or is it a function of the piston cylinder etc.

What I mean to say is why does the S2000 only have a measley 157nm!

P.S. Your explanation Xby2k is top.
Thank you.

 

[QUOTE]Originally posted by Gazzer
[B]How do you increase torque in the case of an engine. Does bigger capacity mean more torque or is it a function of the piston cylinder etc.

 

Start the engine. Get someone to rev the engine to the desired rpm. Grab hold of the flywheel and stop it. The force required to stop the flywheel is the amount of torque being output. Watch your fingernails!

 

Why does our 237bhp 2.0ltr only have 157ft-lb (thank u AB)?

 

brilliant

thanks everyone, Its now much clearer

hmmm what can lesson number 2 be

gazzer, from reading the thing that Ali posted, is it not because torque is somewhat limited by the engine size?

so overall then, acceleration is a combination of torque, engine size, weight, and gearing. and torque itself is a function of rpm