payeng

"Power" and "Torque" are two terms used to describe the performance of an engine.

There are many who are still confused between these two terms.


Can somebody come up with the simplest of explanation to describe the difference/relation/and units to describe the two terms..?? So that even a layman can understand it.

MG

Topic Approved

@payeng-There was a very good thread on the same lines which was started some time back and had some very good posts from Oldfox,arunmur and santoshxtra.I just hope that some members had saved those posts.

onlinesatish

Thx peyang for starting this thread!

Till date i have always failed to understand wat is the difference between BHP and torque. Though i have an idea abt torque i always fail to understand wat BHP is.

BHP - Brake Horse Power

All i know is this means it ability to pull with a power of some x no of horse!

If thts soo then wat does torque means? It also means the ablity to pull right

am always confused!

vinfreak

Torque is the power of a rotating force, which is the product of one of two equal, opposite, and parallel offset forces and the distance between them. When this is applied to a car this means the effort exerted on a shaft to move the vehicle along. When torque is great enough to move a shaft through a given distance in a given time this is expressed as power and measured as horsepower

Well simply this is power that has been measured on a brake or normally known now as a Dynamometer. This device provides a load for the engine to "drive" against and then measures the torque produced by the engine, which if it is then multiplied this by crankshaft revolutions per minute and adjusted with the standard figure, it provides a horsepower figure

You can find some info here:
Indiacar Infobank - Know your vehicle - For a world of automotive information at your fingertips

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locusjag

1 Hp is = 746W of energy.

How come "Brake" comes to be joined with "HP"? Do they mean, this much Braking HP is required to stop this machine of this much HP?

Trigger

The following is a link to a good article on HP and Torque. Its a bit long. Read thru it patiently.

NRHS - High Performance for your Harley Twin Cam, Evolution, Sportster or Buell!

onlinesatish

It would be better if someone can explain it without using physics terms like velocity etc.,........coz some of us dont have any idea abt it like me

vinfreak

All Credit that author (shantanu) for the write up..some credit to me for finding that

Check that out:
Torque and power are very much related. The amount of power an engine produces at a certain rpm depends on the amount of torque produced at that rpm.

For EG: the Vtec produces 132nm at 4700rpm. Now to calculate the power we will have to convert nm to lb ft which comes to 97.34 lb ft.

Now using the formula (bhp = torque * rpm/5252) we get 97.34 * 4700 /5252 = 87.10 bhp.

So the Vtec produces 87.10 bhp at 4700 rpm.

IMO the ideal torque curve would be if an engine were to produce max torque as low as 2000 rpm and keep it there for as long as possible.

If the Vtec engine was to keep that max torque of 97.34 lb ft beyond 4700 rpm, the engine would have produced 106 bhp at 5719.25 rpm and would have gone all the way to 126.03 bhp at 6800 rpm.

So the power of an engine depends on how much torque is produced at different engine speeds.

Diesel engines produce more torque mainly due to the high compression ratios the engines run on and the fact that they have a smaller bore and a longer stroke.

Actually it isn't that complicated but does take a lot of time before you start understanding it. When i started off with this, i was as confused as you are but when as i kept reading and discussing this with others, i've got a basic idea of what it's all about

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leon_nerd

"Brake" refers to how horsepower was originally measured and calculated, by means of a De Prony brake connected to the engine's output shaft. More recently, an engine dynamometer is used instead of a De Prony brake.

Torque, as mentioned by posts above, is the rotating force. I have previously given the example of the conventional tap to depict the torque action. When you open tap, you use your fingers and apply the force on tap on two different directions to rotate it. Now, torque is calculated as the force applied by your one finger multiplied by the the distance from the center. The Standard unit of force is N(Newton) & distance is m (metre). Hence, units are Newton meter (Nm). Now when we say the torque as, say, 1400 Nm then it depicts the force that will be applied by your one finger on the tap is 1400 Newtons and the distance from center is 1 metre.

nitrosatya

Now, horsepower is being measured in PS. What does it mean?