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I'm confused on the whole horsepower vs. Torque. A lot of the litter bikes boast 150+ horsepower engines but only about 70+ lbs of torque. Not much more torque than bigger monsters but I know they are a lot faster. Not that that's important. I'm wondering what is the difference and where do you feel each on the bike?
 

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HP is a function of both torque and RPM

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
 

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Re: Horsepower vs. Torque

the bottom line is torque is the actual twisting power that is applied to your rear wheel, which is what you need to get the bike going.
 

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Re: Horsepower vs. Torque

I am confused by Filmore's statement that all engines make equal hp and torque at 5252 rpm. Does that mean that all engines make the same hp/tq or a given engines hp/tq are equal at that rpm?
 

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Re: Horsepower vs. Torque

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...
 

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Re: Horsepower vs. Torque

Yeah, I didn't think so. Just wasn't sure if I was reading it wrong or someone was smoking something. :)
 

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Re: Horsepower vs. Torque

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.
 
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Re: Horsepower vs. Torque

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

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Re: Horsepower vs. Torque

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
 
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Re: Horsepower vs. Torque

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

Now the burning question...which one is better V-twins or I4s? ;D
 
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Re: Horsepower vs. Torque

V-twin=more torque b/c of a greater bore
i4=less torque greater hp, revs higher
Most of it is preference
 
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Re: Horsepower vs. Torque

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

Cheers!
 
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