What is/what use is torque

[WOODYTHEWISE]

Just been reading my handbook for the CL. Under the heading 'Engine' it lists the following.
CL600 500BHP Torque 800nm at 1800RPM to 3500RPM...............
CL55AMG 500BHP Torque 700 at 2750RPM to 4000RPM................
Now the 0.60mph is the same for both cars at 4.8sec and the top speed for both is 155mph.
So my question is..'What does the extra 100nm in the CL give you'? would it for instance provide better acceleration over the 60mph on to the 155 top speed.
Both cars are pretty nippy

 

[Dieselman]

So my question is..'What does the extra 100nm in the CL give you'?

Noticeable quicker in gear acceleration, without the need to change down.

Model| 40-60mph|50-70mph
Cl600|4.6|5.2
Cl55|5.4|6.9

 

[bolide]

0-60 figures are a fairly useless metric for real-life motoring whereas 50-70 times are pretty useful. At those speeds the measurements are not (usually) traction-limited and give a good measure of performance

The other benefit of more torque is the reduction in the need to change down to overtake - the result being a more relaxing driving experience

Nick Froome

 

[WOODYTHEWISE]

0-60 figures are a fairly useless metric for real-life motoring whereas 50-70 times are pretty useful. At those speeds the measurements are not (usually) traction-limited and give a good measure of performance

The other benefit of more torque is the reduction in the need to change down to overtake - the result being a more relaxing driving experience

Nick Froome

Very true, it would take someone well versed in rapid take off to get the most out of a standing start even in good road conditions. The 50 to 70 is, as you say very useful.
I had an 87 560 SEL that had a great 50 to 70 time.

Thank you both to DM and yourself.

 

[NISFAN]

Torque on it's own has little relevance, power is the more useful measure out of the two.

The difference in acceleration would be due to the area under the curve being higher in the case of the CL600, not due to it's higher torque figure.

 

[davidjpowell]

Diesel has torque which is why it is better

 

[Fastard]

the area under the curve .

What is the area under the curve ? Please explain.

 

[grober]

Just been reading my handbook for the CL. Under the heading 'Engine' it lists the following.
CL600 500BHP Torque 800nm at 1800RPM to 3500RPM...............
CL55AMG 500BHP Torque 700 at 2750RPM to 4000RPM................
Now the 0.60mph is the same for both cars at 4.8sec and the top speed for both is 155mph.
So my question is..'What does the extra 100nm in the CL give you'? would it for instance provide better acceleration over the 60mph on to the 155 top speed.
Both cars are pretty nippy

The other difference will be the 600 ---V12 will be a heavier engine rather than the tuned V8 of the CL55 AMG meaning more power is required to accelerate it to 60 mph thus offsetting any power advantage. In addition gearbox or rear axle ratios may be slightly different and equipment levels [ weight] also. In two light stripped down racers 100Nm would make a huge difference in "in-gear performance" but in two heavy GT cars built with an eye for comfort as well as speed may not be quite so noticeable?

 

[finisterre]

The area under the curve?

Hmmm, that is making me think. I don't know what it would represent. Normally a torque curve has rpm on the x axis and the y is power or torque. Power and torque being interchangeable, a linear function.

Can anyone help me out? integrating a function to find the area under a curve is often done and normally tells you something but in this case I am baffled as to what it would amount to. Differentiating to give a rate of change .ie. acceleration has some meaning in speed time curves, has this caused a misunderstanding?

 

[sars]

Torque makes you accelerate, power makes you go faster, however both these figures are related by the equation torque x rpm/5252 = power.

Diesels have much more torque but have a lower maximum RPM and thus the gearing is different than a petrol which have lower torque but higher rpm. Thus the lower gearing on a diesel equates to a similar force level at the contact point between tyre and road as the petrol engine giving similar acceleration figures.

 

[finisterre]

hello sars!

 

[sars]

Hi fin

Not sure what relevance the area under the curve has in relationship to how quickly a car accelerates and thus calculus might not be the best use of your time my friend.

 

[grober]

What is the area under the curve ? Please explain.

Think the OP was referring to the visual combination of engine rev range with the torque output curve which when combined together would give a visual representation "by area" of the "available torque" over the entire engine rev range. Usual contrast being the older fairly sharp peaked curve coming in at relatively high rpm versus the "loaf of bread" curve found in some many of today's turbocharged direct injection cars where peak torque is achieved at very low rpm and remains fairly constant throughout the rev range.

 

[Bellow]

So my question is..'What does the extra 100nm in the CL give you'?

Wheelspin off the line.
For reasons of traction, 0-60 figures are too dependent on other factors other than power/torque to be absolute.

 

[Bellow]

Can anyone help me out? integrating a function to find the area under a curve is often done and normally tells you something but in this case I am baffled as to what it would amount to. Differentiating to give a rate of change .ie. acceleration has some meaning in speed time curves, has this caused a misunderstanding?

What the graph shows is where the required torque and power are in relation to rpm. From there the gear ratios can be selected and translated into 'load curves' (cascades) which when compared to the 'road load' (what it takes to drive the vehicle) give the surplus torque available for acceleration.

What has to be achieved is that on each up shift of gear, the torque doesn't fall to too low a level - which is why 'peaky' motors require close ratio gearboxes to give of their best.

 

[V12]

Noticeable quicker in gear acceleration, without the need to change down.

Model| 40-60mph|50-70mph
Cl600|4.6|5.2
Cl55|5.4|6.9

Where do you source this info?

 

[marc.l]

When I asked my father to explain the difference between torque and hp many many years go his reply was
Bhp will determine how fast you crash into the hedge and torque how far through the hedge you will go .
A bit simplistic I guess but a easy way to explain it .

 

[Stratman]

Torque is a turning force, measured in units of force multiplied by units of distance.

Take your torque wrench and set it to 100Nm. That's a force of 100 Newtons applied at a distance of 1 metre. Because the wrench is less than 1 metre long you need to apply more force, 200 Newtons if it's half a metre long to make it click. The turning force at the pivot point is the same as long as the force multiplied by the distance at which it's applied is the same.

A single cylinder internal combustion applies a turning force to the crankshaft. The pressure of the burning gases on the piston is the force and the distance between the crankshaft centre and the big end centre is the distance. Because the piston is constrained in the cylinder the force is always applied vertically downwards, so the distance part of the equation varies between zero at top (and bottom) dead centre to a maximum (the crankshaft throw) when the piston is halfway between the two extremes.

Each time the engine fires it can do some work, such as moving a plough or a car. If it fires ten times per second it can clearly move the car a given distance ten times quicker than if it fired once per second. In both cases the engine has moved the same force (the car's resistance to motion, mostly friction and a bit of air resistance) through the same distance (force times distance is equal to work done), but the faster rotating engine has performed the work ten times quicker.

The rate at which work is done is Power. Using 'dimensional analysis' (sums using only units without numbers) it can be shown that* Power = Torque x Revs, that's why F1 engines rev the way they do. The Revs part of the equation is 18,000 which gets them off to a good start.

When you put an engine in a real car there is a gearbox and rear axle in the equation. The gearbox multiplies torque at its output shaft but reduces the revs by the same factor, so ignoring losses within the box the power output is the same. What it means on the road is that if one engine produces more torque than another at the same engine revs, and the gearbox and axle ratios are the same, the car with more torque will produce more power at the same revs. If the car manufacturer changes the ratios of the transmission or axle then it's all down to how they've been changed.


* Torque is force (Newtons) times distance (Metres).
Revs are just the reciprocal of Time , so they're 1/T
Work, measured in Joules is the product of Force and the distance through it's been applied.


So, Work (J) = FxD = NM (Newton Metres)
Power is the rate of work, so Power = FxD/T

Using the metric system power is measured in Watts (W) so that equates to W=NM/S

 

[sinewave]

Simplistically Torque gives pulling power/acceleration.

BHP gives you the Top end speed.

This is why small capacity but high BHP engines are quick top end but their acceleration can let them down and make them 'thrashy' to drive much like a Bike engine.

Big capacity petrol engines whilst having good BHP offer only the similar Torque levels of a Diesel engine some 2.5 litres smaller i.e. AMG 6.2 V8 versus a 3 litre Diesel.

Looking at the Tractor world we have engines of 15 litres or so in the big John Deere's but BHP's of only 400 or so, but look at the Torque figures of 2500 NM

Pulling Power is King!

 

[Bellow]

This is why small capacity but high BHP engines are quick top end but their acceleration can let them down

Not if you are in the correct gear. Why else are they configured thus for motorcycles where acceleration is all?