Tell me about torque?

[yambabe]

Can someone throw some numbers at me about torque and what it means?

Himself reckons there's no point in my having a bike with mega bhp cos I'd never use most of it, but he says a strong motor with lots of torque would be ideal. I kind of know that torque is related to acceleration and is a kind of thrusty effect but that's about it as far as my knowledge goes.

So what is "good" or "high" torque in terms of numbers?

The bike I have my eye on for my next one has a mere 52 bhp according to the spec sheet, and it has 69 Nm of torque. Is that good?

Does that mean I'll have plenty of acceleration at fairly low revs to make stuff like overtaking easier? (Which is what I want.......)
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[veeeffarr]

Torque = Acceleration
BHP = Speed (Torque with a factor of time applied)

Torque is basically a rotating force, like opening the lid of a jam jar. BHP is the rate at which work can be done...

Gah, stupid words... HTH

[Kickstart]

Hi

Trouble is that torque has 2 different meanings. The engineering meaning (turning effect of a force) and the more generally used (how flexable an engine is). They are not the same thing by a long way (a highly tuned 2 stroke will tend to have a very good max torque figure, but few people would claim the bike is flexable).

First one is the one that the numbers on a spec sheet refer to (in ft/lb). Second is not really mentioned, although possibly the best way to see it from a spec sheet is how far apart the rpm are for max power and max torque.

Power is just torque x rpm.

All the best

Keith
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[yambabe]

Max power is at 6000 rpm, max torque is at 3500 rpm apparently.
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[Blau Zedong]

Sometimes people confuse torque with "spread of power". A highly tuned 2 stroke will produce alot of specific torque, but It will coincide with peak power and will in no way be "flexible" or have "a nice spread of power".
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[G]

As Keith said - people usually say 'power' and talk about peak power but talk about the range of torque an engine has when they say 'torque'.
However, they could quite reasonably talk about a high peak torque and the range or power an engine has.

An engine with a good range of torque will generally have relatively (to it's peak power) a wide range of power through out the rev range.

I disagree with Toby. Torque does not mean acceleration.
High power gives you good acceleration and a high top speed.
High torque allows you to pull heavy things up hills.

A tractor will probably have very high torque, but won't accelerate very well. A cbr250 has a high power output for it's capacity, but would be useless at pulling a plough.


If you are not one to rev your engine to the red line every time, you may find that an engine with a wide range of torque to better suit your riding style. This doesn't have to mean a lack of power - for instance a GSXR1000 K1 had the highest peak power in it's class at the time, but also had the widest range of torque / power across it's rev range.

[lilredmachine]

I would say you are more concerned with power delivery than the amount of torque and power itself. As Blue said, having a lot of torque does not mean that a bike will be flexible or easy to use, it just means it has a lot of torque.

What is far more important is how it is delivered and the area of the rev range it appears in.
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[yambabe]

OK I'm kind of getting it I think, but I could still do with you giving me some numbers!

So as a comparison, the "max" figures are

"my" bike 52PS (bhp?) at 6000 revs, 69Nm at 3500 revs

GSF650S Bandit 77.5 PS (bhp?) at 10100 revs, 59.2Nm at 4000 revs.

So "my" bike has less overall power than a bandit, and less top speed, because it has a much lower rev range. However, it has the potential to pull a little harder in the low revs and may have better acceleration? But the bandit would be described as having better "torque" in everyday usage because it has a much broader range to spread it over and therefore more flexibility?
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[wristjob]

[veeeffarr]

[lilredmachine]

[lilredmachine]

Another example of that is the little Skoda Fabia VRS.

It has 130hp as stock and about 220lb/ft torque, as you would expect for a low power high torque diesel the 0-60 is slow, 9.5 seconds, but the in gear acceleration times are (for a car) very quick.

Superchips will flash the ECU and dyno tune it for a fee, this on average gives about 165hp and 330lb/ft of torque. Despite only receiving a 35hp increase the 0-60 drops almost 2.5 seconds to 7 and the top speed increases to over 145mph from 125. This seems to suggest that torque may have a little more to do with acceleration than G is letting on...

The torque is produced later on into the rev range, so whilst hp is not dramatically increased in pure numbers, the torque providing it is there stronger and for a longer amount of time, hence the dramatic performance increase.
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[mr.z]

This is how i like to think of it, how accurate it is I'm unsure but i don't worry about that sort of thing..

Say your hitting somebody with sticks..

Now say your using a big stick full of lead and hitting hard, this is torque

Now you hit with the sticks a little faster, this isbhp

RPM is how many sticks are employed at the time.



Both stick beatings produce the desired result, but in different ways..
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[G]

[Sharpy]

[bazza]

"Torque vs bhp"? "V twins"?

You realise G will be stuck in this honeypot thread for days, don't you?

Nice.
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[lozzypop1]