Announcement

**Samarth 619** · 02-16-2012, 10:07 PM

@ madhav parashar: A smaller gear ratio compromises between torque on wheel and speed obtained, not power.
Your "more torque and less power" is not correct. Because, if I take to 8000 rpm in 1st gear, I'm getting maximum power but not enough speed.

In other words, power results in more overall work done (which is balanced between acceleration OR speed, depending on the gear ratio).

@ asif & rachit: Couldn't get your point. Power and torque are basically the same, except for the rpm/ revving. Separating them makes it all the more difficult to define them.

Torque means the force applied. And Power is the actual work done (in the attributes of acceleration, push, speed, etc.). As simple as that.

Also, can we say trucks have low bhp? We can't COMPARE them to anything similar. Even trucks have upto 500~ bhp, and that's no small figure unless we're comparing with motorcycles and cars.

**asif** · 02-17-2012, 10:57 AM

**Samarth 619** · 02-17-2012, 07:21 PM

@ arif: I said, they're same except for the movement caused (rpm). And so it is. Power = Torque X rpm. How "time" is involved in this definition, is beyond me...

For your example, its possible that P180 has 17.02 PS and 13.5 Torque @ same 8500 rpm.
And it is possible that P180 gives 14.22 NM torque and about 13 PS power @ 6500 rpm.
And also, its possible that the bike gives 8 PS and 7 NM torque at 4000 rpm.

Every bike has a powerband and a torque graph, is what I'm saying. (figures are just fictional to explain a point).

My point here is for a bike torque is always at a lower rpm than power, hence its only required to get you to go from zero to running and power is something that helps to maintain that running.

So, maybe you mean "Maximum torque" rpm is always lower than "Maximum power" rpm. Being accurate is necessary to clarify such stuff.

Yes, torque gets you from zero to running and more running too. But the power determines your overall "drive/ push".

**asif** · 02-17-2012, 10:03 PM

hahahhah.
rpm translates to rotation per "minute", and thats where exactly TIME came from. I never said the rpm is the same for the max. torque or max.power, please read again.

FYI P180 makes Max. power of 17hp@ 8500 rpm and max. torque of 14.22 Nm@6500 rrpm.

Originally posted by Samarth 619 View Post

Every bike has a powerband and a torque graph, is what I'm saying. (figures are just fictional to explain a point).

Please explain how are they fictional?

Lastly the name is Asif not Arif

!!!

**sunny_** · 02-19-2012, 09:15 PM

Originally posted by asif View Post

By definition,

Originally posted by Samarth 619 View Post

@ arif: I said, they're same except for the movement caused (rpm). And so it is. Power = Torque X rpm. How "time" is involved in this definition, is beyond me...

Samarth bro, from the basic definition of Power, it is the rate of work done, that is, work done per unit time, therefore it is related to time. Yes, the relation you gave also shows this point.

Originally posted by asif View Post

FYI P180 makes Max. power of 17hp@ 8500 rpm and max. torque of 14.22 Nm@6500 rrpm.

Please explain how are they fictional?

Samarth bro tried to explain various torque/power at various rpms, not only at rpm where that quantity is max.

**psr** · 02-19-2012, 11:59 PM

Here is a link to explain the various factors in simple words...
HowStuffWorks "How Force, Power, Torque and Energy Work"

**asif** · 02-20-2012, 10:44 AM

Originally posted by sunny_ View Post

Samarth bro tried to explain various torque/power at various rpms, not only at rpm where that quantity is max.

That part is understood and is clear. You misunderstood what is being asked.
Why are the figures called "fictional" is my question.How can you talk about torque curve and say that figures are fictional.

**Samarth 619** · 02-20-2012, 05:32 PM

@ Asif: Sorry dude, for misspelling your name.

RPM is by itself a measure of engine speed, and yes its time related as you say.

About the Fictional part: We know that P180 makes 17~PS max @ 8500 and 14.22 NM max @ 6500. These are real.

But, I was explaining that torque/ power exists even at other spots on the powerband and to explain this point I used fictional figures like (13PS @ 6500 and 8 PS/ 7NM @ 4000 rpm).

Overall point is just that, different power and torque figures exist from the idle rpm to the rev limiter. Only the maximums are quoted by companies usually like 17.03PS and 14.22NM.

@ sunny_: Thanks for explaining the fictional part. You're right.

**ajmalrasi** · 02-29-2012, 02:55 AM

Originally posted by epic.fail.engineer View Post

First of all, I think this is an excellent topic to discuss for motorcycle enthusiasts. I think its very important to know these things as they are very basic and it makes a healthy "biker's discussion".

What I am going to write here is purely my understanding on the subject. Any remarks/criticism is most welcome. I am not going into the units and technical information on any of the following terms, I'll probably go into it as the discussion progresses. This is how I'd put it to a layman.

Power: Everything starts from the engine. Power is purely a parameter of the engine. It depends on the engine size(capacity), tuning(discuss later), Compression ratio, 'bore X stroke' etc. But whatever the parameters, power depends purely on how the engine is built. By the definition of power, it is the energy put out by the engine (as a result of combustion of fuel) per unit time.

This was the easy part.

Torque: To understand torque, you need to understand the concept of power applied in an angular fashion(discussed earlier). But when it comes to motorcyles, the power output of the engine or the resultant torque doesn't directly run the motorcycle. Here is where gears play a very important role. A good understanding of gear ratios will put all your doubts to rest. Consider the following picture:

Lets say one of them is the input gear (driven by the engine directly), one of them is the output gear (driving the motorcycle). (No. of teeth in output gear / No. of teeth in input gear) = Gear Ratio = (Torque output / Torque input).

For different gears (1st, 2nd, 3rd etc), the gear ratios are different, and hence the torque output is different. Therefore, your vehicle's behavior is different.

It is practically impossible to be able to estimate a bike's performance purely by peak-power and peak-torque figures(provided on the spec sheet), unless it is known to have a more-or-less "linear torque curve".

Enough for now..

Thoughts?

Great .. now i understand it

**hunkofgals** · 02-29-2012, 07:08 PM

hey guys
quite an interesting topic out here

but ive got a small doubt

if our engine produces some 15bhp @ 8500 rpm
is there any way we can get that 15bhp @ a lesser rpm

example :
15bhp @ 7000 rpm or 6000rpm ???

**Samarth 619** · 02-29-2012, 11:08 PM

Originally posted by hunkofgals View Post

hey guys
quite an interesting topic out here

but ive got a small doubt

if our engine produces some 15bhp @ 8500 rpm
is there any way we can get that 15bhp @ a lesser rpm

example :
15bhp @ 7000 rpm or 6000rpm ???

If rpm is made lesser, then torque should increase... It can be increased by modification. Modifying it should give 15 bhp @ 7000 rpm, but maybe it will make 16.5 @ 8000 then... It can't be exacted to the figure you mentioned.

You can choose good exhausts, performance air filters, ECU changes, reboring, etc. to get same or more power at lesser rpm.

**liionheart** · 04-25-2012, 06:09 PM

rpm vs peak power?

One Question:-

Let us consider My bike have max. power 17 BHP@8500rpm then why bike accelerate by increasing throttle(i.e. rpm) after 8500rpm in same gear??

**arun.bk** · 05-04-2012, 09:46 PM

Originally posted by liionheart View Post

One Question:-

Let us consider My bike have max. power 17 BHP@8500rpm then why bike accelerate by increasing throttle(i.e. rpm) after 8500rpm in same gear??

Its because power s still produced beyond the specific rpm, but its nt the max output..thats it

**stoneboy** · 05-10-2012, 10:55 AM

For everyone interested in more of such stuff, you can always dig in How Stuff Works.

Here is a couple of sources of information from the same portal -
How Horsepower Works
How Force, Power, Torque and Energy Work

**abhisheklalnediya** · 05-10-2012, 12:10 PM

consider 2 bykes alls specs are same like weight, tyre, transmission....
say 2 150 cc bykes with 15bhp

but only difference is one have 10Nm and another have 15Nm ,
if i rider both what difference i can feel?

Announcement

What is "Power", what is "Torque"..??

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment