What are Horsepower and Torque?

[Motofool]

Copied from
http://www.roadrunner.travel/2015/06...mance-metrics/

In the early days of automobiles—or horseless carriages as they were initially called—it seemed only natural that the power output of these new fangled machines would be expressed in relation to the amount of work that the most commonly known and used source of motive power was back then—a horse. The generally accepted definition of one horsepower is the energy it takes to move a 330-pound object 100 feet in one minute.

Torque, which is a component in the horsepower formula, is the twisting force that rotates an object (e.g., a crankshaft). Torque is usually quoted in pounds-feet, which is the force measured in pounds pushing on the end of a lever measured in feet.

Horsepower is calculated by a formula that includes units of force produced (torque) and how fast that force is applied (RPM). As a result the amount of torque and horsepower produced by an engine varies, depending on the RPM at which the engine is spinning. Single horsepower and torque specifications quoted for motorcycles are usually the maximum amounts produced over the motor’s entire RPM range. (OK, I know this is getting a little technical and if your eyes are starting to glaze over, feel free to skip the next two paragraphs.)

Generally there are two ways of measuring horsepower and torque: at the crankshaft (aka “brake horsepower”) or at the motorcycle’s rear wheel. The difference in the two measurements is the amount of power lost through the primary drive mechanism, which can be a chain, belt or driveshaft. Different bikes will vary, but horsepower loss of around 10-percent is a rough rule of thumb. A bike with a driveshaft, though, usually will lose more power between the crankshaft and the rear wheel than one with a chain drive. Manufacturers usually quote horsepower and torque figures measured at the crankshaft. Independent bike tests, however, usually report power output measured at the rear wheel on a dynamometer. Obviously, power delivered to a bike’s rear wheel is what really counts out on the road.

Some motors are designed to produce their maximum power at high RPMs (e.g., sport bikes with in-line four-cylinder engines), while others reach their peak power at lower RPMs (cruiser V-twins) and still other engine designs are usually somewhere in-between. From a seat-of-the-pants perspective, a rider feels power building as RPMs increase, but the motive force of engines with a high level of torque at low RPMs will be felt almost immediately, with a twist of the wrist, but then may quickly drop off.

[Somchai]

Thank you for this write-up, Hernan

[Aufitt]

Both measurements.

Horsepower is how hard you hit the wall,

Torque is how far you take the wall with you.

[Klondike1020]

Horsepower/// is what crotch rocket riders brag about.

Torque /// is what Harley riders brag about.


Ride a bone stock Vrod and a stock R1.

or a Stock Cheiftan and a stock GSXR 750.

Which feels more powerful.?> you decide.

Very different feelings but the cruisers do not make my guts churn and adrenaline course the same as a sport bike.

I still want a bagger ....

[Aufitt]

A cbr250 single feels powerful because it has high torque for its low Hp.
A Ninja 250 feels gutless because it has very low torque.

But the Ninja is faster.

[Somchai]

Originally Posted by Aufitt

Both measurements.

Horsepower is how hard you hit the wall,

Torque is how far you take the wall with you.

Aufitt a great word, never heard that before

[Panda]

super simply
torque is a force
horsepower is a rate of work (f*d)

[sharky nrk]

Originally Posted by Panda

super simply
torque is a force
horsepower is a rate of work (f*d)

*also known as = things a N250 does not have much of lol

[Motofool]

Originally Posted by Panda

super simply
torque is a force
horsepower is a rate of work (f*d)

Originally Posted by sharky nrk

*also known as = things a N250 does not have much of lol

According to this, and judging for the distance that @NevadaWolf has covered, her Nijette is the one with more H.P.

Please, see
Mega Massive Road Trip

[sharky nrk]

Originally Posted by Motofool

According to this, and judging for the distance that @NevadaWolf has covered, her Nijette is the one with more H.P.

Please, see
Mega Massive Road Trip

LOL, NevadaWolf certainly has some kinda awesome distance riding H.P.

[agentbad]

Horsepower


Torque

[FrugalNinja250]

Another way of putting it is that torque is the force at any given moment, and horsepower is the result of that force working over time. The formula for HP is (torque x RPM) / 5252. Here's where the 5252 comes from: http://www.epi-eng.com/piston_engine...and_torque.htm

It's all basic algebra.

A bit of trivia: If you ever see a dynochart where the HP and torque are not identical at 5,252 RPM it's been faked. Also, the torque is always more than HP below that point, and the reverse is true above that point.

[xorbe]

HP is Torque * RPM / 5252 ... uh yah what FrugalNinja said up there ^^^

[Biker's]

That's quiet informative. But i am still

This is what Wikipedia shows me about my bike (VFR800)
"
Power 104 hp (78 kW) @ 10,250 rpm
Torque 55 ft·lb (75 N·m) @ 8,500 rpm
"
I am not good in maths so just tell me in simple words.

[FrugalNinja250]

Originally Posted by Biker's

That's quiet informative. But i am still

This is what Wikipedia shows me about my bike (VFR800)
"
Power 104 hp (78 kW) @ 10,250 rpm
Torque 55 ft·lb (75 N·m) @ 8,500 rpm
"
I am not good in maths so just tell me in simple words.

Not sure of what your question is?

If your maximum torque is 55 ft-lbs at 8,500 RPM, then (55x8,500)/5,252=89.0HP at that RPM. At 10,250 RPM you're making (5,252x104)/10,250=53.3 ft-lbs of torque.

Here's a sample dyno chart showing HP and torque at any given RPM:



You can see that the two curves each has a peak. One curve is for torque, the other for resulting HP from the torque at that particular RPM. In your case, the two numbers you have are the peak torque and peak HP, and the RPMs that each of those peaks is at. The torque curve is fairly flat since it's basically how much turning force the motor can put out, but the HP curve rises as RPM rises.

Since HP is always derived from torque and RPM as a calculated number, the HP will rise with RPM until the point in the RPM band where the torque falls faster than the RPM climbs. Engine design often times requires giving up low RPM torque to get more high RPM torque, thus giving you more HP at the high end. Two-strokes and F1 engines are like that. Or, engines can be designed to give more low end torque and thus HP but lose more HP at the high end. For trucks, RVs, etc, low-end torque is preferred because it saves wear and tear on things like clutches. Also, the faster you spin an engine the more torque you lose to internal friction and what's called pumping losses, or the power consumed internally just to suck the air in past the throttle plates and intake valves and then push the exhaust gasses out through the exhaust valves and muffler/piping system. That torque is lost regardless of the amount of HP produced, so it's beneficial for efficiency (as measured in pounds of fuel needed to produce X amount of horsepower) to design an engine to run at lower RPMs yet develop lots of torque. Hence diesels.