Topic Moved and Approved.

Hi Neeraj,

The definitions of Torque and BHP can get really confusing at times as both of them are units used to measure power of an engine. I once came across a very simple definition for both of them in Overdrive and I will qoute it.

"Torque is the pulling power of an engine, BHP is how quickly Torque is put to road". To just make things a bit more simple in Layman terms. Trucks have huge torque as they need more pulling power and lesser BHP as they dont need to go quick. Cars have more BHP and lesser torque as compared to trucks because they need to go quicker and does not need that large pulling power.

When it comes which accelarates faster? A bike with slightly higher torque or slighlty higher BHP I think one cannot generalise because going faster for a bike also depends upon other factors like gearing, power loss etc (In other words how the power is put to road. Every bike does it differently).

Generally bikes with higher BHP should accelarate quicker but again you cannot generalise.
Bilkes with higher torque needs less gear changes as the engine has more pulling power in each gear again I am not generalising.


As for smoothness of engine. I dont think BHP or Torque can any way be related to engine smoothness. Only thing is under normal driving bike with higher torque should run more relaxed.

These are my 2 cents.

Rachit

In very simple terms, torque is the pulling power and the rpm up to which this pulling power is available defines the power of the engine.

from what i remember from the school physics, torque is the initial force required to move a object from a stand still position to start moving.
..

BHP is how fast you go (top speed) and torque is how fast you get there (acceleration)

Torque is the result of a force that causes an object to rotate about an axis.
The Horse Power is measured according to the rate of rotation of an object(here it's a wheel we're talking about).
BHP is just the HP/raw power of an engine measured against an engine brake.
Based on the design of an engine which includes various factors, the peak power(BHP) and the torque vary.

You can have an engine with more torque but less power and also an engine which has less torque and more power as rachitkdogra said. You can also have 2 engines with the same capacity but one with higher torque (lower Bore/Stroke ratio) and the other with higher BHP (higher Bore/Stroke ratio). The acceleration, top speed,etc. go by the design of the engine, transmission, weight and power losses.

I dont think thats correct.

I think the power is a function of torque and engine speed (RPM).

So an engine that produces less max torque but revs higher can produce a higher power output (e.g. Ninja 250R) than an engine which produces greater max torque but is unable to rev so high (e.g. Machismo 500 LB)

Acceleration is directly related to the power output of an engine. The amount of power that a bike generates at a given RPM decides how quickly that bike can accelerate from that RPM . Generally, torquier engines (means which have a wide RPM range through which they produce good amount of torque) are quicker off the block. But peakier engines (engines with a very narrow power band) tend to produce higher power (at higher RPM) but one needs to keep them within their power band to obtain brisk acceleration.

bhp means how fast u hit a wall

and

torque means how far u take the wall wen u hit it ..

Basically power = force X velocity


and force = mass X acceleration

so power = mass X acceleration X velocity


but velocity = distance/time

so substituting again,

power = mass X acceleration X distance / time


but mass X acceleration X distance = work

and since torque is the same as work,


power = torque/time


or in other words torque represents the work done and power
represents the rate at which work is done.

we can rewrite the above as,

power = torque X rpm

rpm basically stands for 1/time since it effectively it stands for rotations (a dimensionless quantity) divided by time.

So since power is the rate of work, it can be increase due to two factors. either by increase in work, or the increase in rate.

basically you can produce high power by doing a small work at a heavy rate, as well as by doing a heavy work at a small rate.

What is Torque (xxNM@xxxrpm)

hi,

I know high torque means more pulling power and less gear change(hope i am right.. correct me if i am not)

Just going through some motorcycle specifications - details comparission attached..

please help me to understand how to read or you can say best pulling power by reading bike Torque.with minimum gear change(like some ppls here said shorter gear and longer gear).. how i come to know that xyz bike having longer gear or shorter gear

I want to know like suppose stunner having torque of 11nm@6500 rpm and its photocopy Ignitor having 11nm@5000 rpm.

Please frd.. guide me i am confused how to read this equation on different bikes....

query approved and similar topics merged.

Thanks for approving the same, after LONG ONE day sir ji.. please kuch karo to speed up approval process.

Thanks again

This is going to be very long and sorry if in the end your confusion increases .

Well, as fuel is burnt in the combustion chamber, it pushes the piston down with a force. This force on the piston is transmitted to the crankshaft in form of torque. In very simple terms you can consider torque as a turning force.

A very simple example will help you understand the practical aspect of torque.

Go to any door near you and keep it closed. Now try to push the door near the pivot and open it. Try pushing with one finger.

Now try to open it by pushing it farther from the pivot, some where near the midpoint. Finally push it closest to the handle and see.

You will find that you need to apply maximum force near the pivot and least near the handle.

The mass of the door remains same, so the turning force must be same, how come you need to exert different forces at different time?

The reason being its not the force that is important it is the turning force or torque that is important to turn an object about its pivot.

This torque is the product of the force applied and the distance from the center of pivot about which to has to rotate. So as the distance from the pivot increased the force required to produce same torque is less.

I hope you understand what is torque from this example. Torque is the tendency of force applied to turn or twist an object.

So 1 N-m of torque basically means the turning ability of One Newton force applied perpendicularly on a lever at a distance of 1 meter from the center. Increase the distance force required reduces, reduce the distance you need to apply more force.

Similarly 11nm means turning ability equivalent to 11 Newtons force applied at a distance of 1 meter from the center.


How does it apply to our motorcycles?

The weight of the motorcycle and all forces restricting the movement of the motorcycle results in a restriction of movement of the wheels which through your transmission is transferred on to the engine shaft.

Now to make the motorcycle move, you need to apply force. Since it is the rotation of wheels that causes this movement, it means you need to apply a torque on the wheel to turn it.

I hope it is clear till now. You need to apply a force resulting on the turning of the wheels or in other words you need to apply torque to the wheels to make the motorcycle move. This torque is provided by the engine via the transmission.

This is very important point. What matters is the torque available at the wheels. If the engine produces 11N-m of torque at 5000 rpm, it does not mean it transmits 11N-m or torque to the wheels. We have to account for the gears. Gears transmit motion and torque and in the process multiply or reduce the torque and motion.

That is why at 5000 rpm in first gear you will be having much more torque at the wheels than in any other gear. How much your bike can pull depends on the torque available at the wheels which is a function of the engine torque and the gear ratios.

A very simple example.

Suppose there are two gears. One has 50 teeth and the other has 10, then when they mesh the ratio is 5:1. Suppose the first gear is the driving gear, then for every turn of the driving gear the driven will turn 5 times. That is suppose an engine rotates the first gear at 100 rpm, then the second one will be rotating at 500.

Similarly if the smaller one is the driving gear, for every 5 rotation of the driving gear the driven one turns one revolution. So if the engine is now connected to the other gear and is rotating it at 100 rpm, the larger one will be rotating at only 20 rpm.

In the first case you can see the final rpm has increased,but the torque transmitted would be only one fifth. So as the gear ratio increases the final rpm, it also reduces the final torque avaliable in equal proportions. This is what typically happens in higher gears.

In second case speed has decreased but the torque transmitted has increased by equal proportions. Typical example of what happens in lower gears.

Similarly shorter and longer gears.Assume two ratios of 5.5:1 and 5:1.

A ratio of 5.5:1 is longer than a ratio of 5:1 if the bigger gears are the driving gears. In first case as compared to the second case your torque transmitted has reduced but the final rpm has increased which in case of motorcycles means speed.

Hence having shorter gears gives you more torque at wheels which means more pulling power, but it eats away your top speed. Vice VErsa in case of longer gears.

Hope I ve not ended up making you more confused.

Cheers
Ride safe

So, it means that long stroke bikes (the length of the con rod being long) will have greater Torque & short stroke bikes will have lesser Torque.

An Enfield bike has more torque than a Pulsar.

Hope I am correct