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R

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HP= torque x RPM / 5252

Therefore, all motors have equal torque & HP at 5252 RPM and the bikes that make big HP with moderate torque must do it at higher RPMs.

Torque is more a function of displacement, compression ratio, and other stuff that people smarter than I know about. This is why our desmo twins with big pistons are noted for fat bottom ends and great mid-range, while the I-4 yamakawazukidas are known as revvers...

--Fillmore

If you look at a graph that plots both torque and horsepower as a function of speed, the lines for torque and horsepower will cross at 5250 RPM. (It's in the equation...)

So, "no", not all engines produce the same torque and/or horsepower at 5250 RPM...

I am confused by Filmore's statement that all engines make equal hp and torque at 5252 rpm.

S

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can't remember where i saw this article (to credit the author) but it's a fun read:

http://www.ducatipipemod.com/misc/torque-vs-hp.html

T

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I don

torque is not an 'amount of work'. hp is the rate of

work (ft-lbf / sec. in english units), and torque is the applied

moment (ft-lbf). a weight hanging from a cantelever beam applies torque, but no work is done, so no power is extracted.

let the weight fall as it applies torque, and power can

be extracted. torque is not conserved between the

engine and contact patch, whereas power is (disregarding

drive line losses). if the engine makes 150 Hp and 75

ft-lbf torque, the contact patch will see 150 Hp (minus

losses), but the torque will depend critically on the

gearing between crank and rear wheel. do the math ....

75 ft-lbf isn't nearly enough to lift the front wheel. but

run it through a 10:1 gear, and you've got 750 ft-lbf.

since power = torque * rpm (disregarding the constant of

proportionality), when you amplify torque by gear reduction,

the rpm goes down (rear tyre spins slower than engine)

so that power is conserved as required.

R

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I always thought that torque is what gets you to speed and HP is what holds that speed ???

Your practical definition is what you feel on the street in particular. Torque is "quick" and horsepower is "fast". For instance, my M1000S makes more torque than my 03 Kawi Z1000 and feels quicker in most street riding. It isn't until the Z1000 really gets moving that the 125HP gets felt.

I always thought that torque is what gets you to speed and HP is what holds that speed

D

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Thanks for the clarification guys, I have often wondered this myself.

Now the burning question...which one is better V-twins or I4s? ;D

X

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V-twin=more torque b/c of a greater bore

i4=less torque greater hp, revs higher

Most of it is preference

R

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My ear prefers I4 on 12K rpm and above.... Led Zeppelin music to my ears baby!Now the burning question...which one is better V-twins or I4s? ;D

But my commute in the city traffic demands torque.

Cheers!

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