Do you talk power or drive torque?

Nice. Kinda wild that the old "Power V Torque" argument is still going on even now. hahaha

I'm too old too for chasing windmills, but there will always be arguments of such kind - torque vs power, thermionic tubes vs transistors, Adidas vs Nike, BMW vs Mercedes, porq vs beef.....
But I'm not to young not to say in one or two sentences what is mine opinion. After all, like Clint would say - Opinions are like a-beeep-les. Everybody got one and everybody think the other ones stink. :lol:
 
On any rolling road the power figures are originally from the flywheel then mechanical drag is then worked on the cool down. ;)



Torque is generally also measured at the flywheel (if measured at the drive wheels then xmission losses are added to give a flywheel figure).

Measuring a true flywheel figure would mean taking the engine out of the car.

Which is a lot of mucking about for a quick dyno run.

Cheers,

Rgds,

P.
 
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On any rolling road the power figures are originally from the flywheel then mechanical drag is then worked on the cool down. ;)

As these bhp threads always get pedantic................

The figures may come up expressed as flywheel figures and but the readings dont come from there - how do you get a reading directly from the flywheel without connecting to it

Readings are taken from the bits that move - you cant do it any other way



Or you could use a dynapak rolling road then the figures are at the hubs all the time with a correction for the flywheel figures



Dont you just love these threads :lol:
 
Power & Torque will always cross at 5252. If you are bright you will understand the basic maths below if your not just except the following is correct it will make life easier ;).

(Torque * engine speed)/5252 = Horsepower

The torque curve will always be higher before 5252 rpm and lower after 5252 rpm. Their curves cross over at 5252 rpm. This is a result of the conversion from pound-feet of torque to horsepower. Why that number? 1 horsepower is 550 foot-pounds per second while torque is measured in pound-feet. To convert from torque to horsepower, multiply by engine speed, which is measured in rpm (revolutions per minute); to convert horsepower to torque, divide by engine speed. A revolution uses radians, the length of an arc divided by the length of a radius, for units. Calculating for the circumference of a circle, there are 2 * pi radians in a revolution and 60 seconds in a minute so 1 rpm equals (2 * pi)/60, or 0.10472 rad/sec. 550 foot-pounds divided by 0.10472 radians per second equals 5252, our magic conversion number. "
 
And what about engines that don't rev up to 5252 RPM? And what is 5252? What is 7024? ;)
If you put torque in Nm you must use constant number = 7024 in that equation!
That is just constant conversion number, not an rule where you should cross max torque point. If your logic got sense then rest of metric world should aply 7024 RPM as reference point and, no doubt our engines would not work optimal once we cross border and enter into countrys with imperial system?
 
The 5252 is purely a number. It does NOT 5252rpm.

As Zwef asks, what about engines which don't rev that high?

If you measure torque in Nm rather than lbft then 5252 is absent from the equation.

In the same way as if you measure power in kW, 5252 will be absent from the equation.

All that this equation tells us is the power a engine is developing at a given speed based upon the torque is is generating at that speed. Nothing else.
 
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read any one of the explanations of the 5252 thing madrod puts it best

Power & Torque will always cross at 5252. If you are bright you will understand the basic maths if your not just except the following is correct it will make life easier

so if the car doesnt rev to that the curves wont cross ..................simplez

Oh and a formula doesnt need constants in it .If there were no variables it would be a sum with only one answer
 
And what about engines that don't rev up to 5252 RPM? And what is 5252? What is 7024? ;)

They wont cross simple as that.

Using metric units, the unit conversion constant is 9549, not 5252 like it was when pound-feet and horsepower were being used. This means that a graph of power and torque versus revs using metric units would have crossing curves at 9549RPM instead of 5252RPM.

5252RPM is not a significant point in a physical sense. It is merely the RPM at which a graph of torque in pound-feet and power in horsepower would cross when drawn on the same piece of paper. If different units were used, the curves would cross at a different point, yet the principles of operation would remain unchanged.​

horsepower-metric.png


I suggest you ring up James Watt if you dont believe the laws of physics he was a lot brighter than me. These are basic facts & are not up for debate. If you are struggling to understand them it pays to go away & study the subject.
 
It's not 5252rpm. It's just 5252. It's a ratio and has no units.

Power, whether measured in kW or bhp is a function of rotations per unit of time and torque which is a coupling force rotating about a common centre.
 
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I see lot of people can find Wikipedia. Like HDI fun said, it's a ratio not an unit. I don't doubt in equations posted here, just saying it is not obligatory that engine torque must drop above 5252 RPM, or engine torque MUST be hold its value untill 5252 RPM.
I know my english is not at best, but I'm sure it it understandable enough for those willing to read.
Say mr Watt hello for me when you see him!


For example, in which point crosses F1 engine? In which point crosses WRC engine?
WRC got about 300 HP and (reportedly) about 600-700 Nm of torque. Let's say it is 600 Nm ('tough i believe it is more). Crossed at 5252 RPM that brings us to about 450 HP (I rounded the number). Is it way more then 300 HP?

For the end, I think that is enough to make an point here and after this point thread will become "windmill chase case".
Like said before, I'm to old for chasing windmills, and to young to let common sence go away from me.

Roger and out!
 
I see lot of people can find Wikipedia. Like HDI fun said, it's a ratio not an unit. I don't doubt in equations posted here, just saying it is not obligatory that engine torque must drop above 5252 RPM, or engine torque MUST be hold its value untill 5252 RPM.
I know my english is not at best, but I'm sure it it understandable enough for those willing to read.
Say mr Watt hello for me when you see him!


For example, in which point crosses F1 engine? In which point crosses WRC engine?
WRC got about 300 HP and (reportedly) about 600-700 Nm of torque. Let's say it is 600 Nm ('tough i believe it is more). Crossed at 5252 RPM that brings us to about 450 HP (I rounded the number). Is it way more then 300 HP?

For the end, I think that is enough to make an point here and after this point thread will become "windmill chase case".
Like said before, I'm to old for chasing windmills, and to young to let common sence go away from me.

Roger and out!



.-No No :blink: Please the explanations again

Forget the numbers - as in the actual bhp/torque values thwey are not rellevant in themselves to the crossing point.

The fact is that the two will cross at that figure and that fact has no baring on how fast or slow the increase is before or after or on how high or how low the figures are before or after.

The crossing is ( for the nth time ) a consequence of the formula nothing more ......................................but it is a fact.
 
All these formulae are used for is to calculate engine power (the rate at which work is done) from measured torque and measured RPM.

5252 only arises as a result of it being the compaction of a whole bunch of conversion formulae.

Go and play around with the arithmetic. Take out the numbers and just work algebraically with the units alone.

There's no significance of curves crossing when one unit is power measured in bhp and the other is torque measured in lbft. It's arbitrary.
 
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Well, Sleeper,
That was egsactly my point!

We must be aware that whatever meassure unit we use that is just an amount of something we choose to use. Nature (or physic laws) does behave by almost* strict rules. People where forced to derivate meassuring units, and most of them are product of fiction. So in various parts of time and various parts of planet people have had developed various units. So we can see that 1 HP is given at various RPM depending on fact we use Kilograms or Ounces or...you name it - don't know english words for all mass or weight** units. Thing could be even more further then famous 5252 caracter if we decide to use any of numberous power meassure units. We even got american horse power versus "plain" horse power...
So, in mathematical expression with choosen units 1 HP will be reached at 5252 RPM, but egsact same amount of power can be reached anywhere in RPM if we use some of weight** units.


So, finally we agree that it is not benefitial to cross max torque with power line in anny determined point in revs when constructing an internal combustion engine.
Glad we understand each other after first posts in this "saga".

Now we can go to virtual pint of beer and chat about weather. :cheers:

*Why almost? Ask mr. Bor.
** I do think it is avoidable to strugle my english with mass-weight difference explaination.




EDIT: I started to write before HDI fun posted... You see by time difference how demanding to me is to speak technical in foreign language! :lol:
 
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We will put your translation skills as the reason for any misunderstanding then ......possibly thats what happens if you cut and paste in a second language.
 
Thank you for your kindness, Sleeper!

Next time HDI fun and myself shall translate wisselly. ;)
 
the lines will only cross at 5252rpm if power is measured in hp and torque is measured in lbft. think that might be where some confusion is.
 
Mr Watt gave us explanation how to determine 1 HP.... and that is all. That is not recomendation where to cross your max torque with power line in dyno chart nor does it mean that otherwise your engine will not runing fine.

Manufacturers crosses their torque and power lines wherever they find apropriate having in mind purposse and technical abillity of given engine.

For eg., my stock engine got max torque at only 1900 rpm (240 Nm) and max power at 4000 RPM (100 HP).
If I can make my engine hold max torque until 5252 revs at that moment that engine will make an output of 180 hp.
You see, a lot of 1,9 TDI makes even more output, but not as high as 5252 RPM!

Some constructors believe that ideal power distribution should look as follows:
Reach desired (or possible) torque as soon as possible and hold that value untill your engine reach desired (or possible) HP. After that point you decrease torque and hold max power trough revs as high as possible.

I will not be as rude as my oponents and say that they who can not understand that got no common sence, nor I will bite that translation demagogia after point is made.
Confusion is made because interpretation of correct formulaes in way that nature think and behave in imperial unit sistem. No, nature is behaving by nature laws and we made all of the units to explain processes to ourselfs. This is how numbers like 5252 or 9549 or 7024 apears.
 

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