Horsepower vs. Torque ?

[cbdtran_imp]

ok I'm no engineer but the new BMW s1000rr makes 83 ft lbs of torque and 193 horsepower

a Harley Davidson electra glide make 95 ft lbs of torque and 76 horsepower

The new Indian Chieftan makes 119 ft lbs of torque no reported hp figures I can find

I'm thinking the Harley will pull more weight as evidenced by it GVWR, but the BMW is going to run a heck of a lot faster through the quarter mile, and regardless of massive torque figures the Indian isn't going to be much quicker through the quarter than the Harley

dyno graph is a narrow angle of how engine work, torque peaks, let's say at 7k RPM, but horse power peak at 12K RMP. At 12 RPM, torque is significant lower than its peak at 7K.

it all come to how much energy an engine generates at any RPM, and how they gear the engine by transmission. Torque and horse are the same, it represent the energy of an engine at any particular RPM and how it is geared.

A Cummis truck engine of 15L generate around 650 lbs of torque but 300 horsepower, they design the engine to tow heavy load not top speed, and less energy for engine longevity, so are boat engine

[JustPassinThru_imp]

Look at any dyno graph and torque and hp always cross at 5250 rpm. Torque is twisting force - newton meters or lb ft, gets you off the line and pushes a lot of weight. HP describes how much work is done over a given period of time, or the rate which work is done, so speed. If I knew more about physics, I might be able to explain why the two cross paths at 5250 rpm. Maybe a trip through the googlesphere will help...

That's probably the best way of putting it.

A comparison might be this: Thirty years ago, in the dark ages of emission controls on old-school carburetors...some OHC fours, specifically Ford's fours, made more horsepower than their 1950s six-cylinder engines.

But that was deceptive, as anyone who'd driven both knows. Step on the gas with a six, even in those years, you could feel that thing lift you off, right from idle. Like a tractor when you pop the clutch.

With that 2.3 Four, it would whine "Who, ME?" You'd have to stand on it to get moving, and hold the flow of traffic. Yet in dynamometer tests, it showed more horsepower, not less, than the sixes.

Torque. Power applied in a twisting motion - just as with a "torque wrench." As opposed to horsepower, which is the power needed to lift a given quantity of water, one foot, at sea level.

[Dakota_imp]

[/quote] Torque and horse are the same, it represent the energy of an engine at any particular RPM and how it is geared.

A Cummis truck engine of 15L generate around 650 lbs of torque but 300 horsepower, they design the engine to tow heavy load not top speed, and less energy for engine longevity, so are boat engine
[/quote]

Torque and horsepower are NOT the same. Good Lord, my grade school son read this thread and asked what was wrong with you folks.

[flynrider]

Torque and horse are the same, it represent the energy of an engine at any particular RPM and how it is geared.

A Cummis truck engine of 15L generate around 650 lbs of torque but 300 horsepower, they design the engine to tow heavy load not top speed, and less energy for engine longevity, so are boat engine
[/quote]

Torque and horsepower are NOT the same. Good Lord, my grade school son read this thread and asked what was wrong with you folks.
[/quote]

HP = Torque x RPM / 5252

If they were the same, the equation would look much simpler :

HP = Torque

[ChipBeck_imp]

Horsepower does work and is what accelerates the vehicle. Torque is a simple force and can be increased or decreased without a change in horsepower. Torque X speed = horsepower. Neither one is energy.

I don't understand why anybody even talks about horsepower. To elaborate a little bit on what Dakota said:

Horsepower = Torque x RPM

If you know the torque curve, then you know the horsepower curve automatically. The confusion between torque and energy is that they share the same unit, the newton-meter (http://en.wikipedia.org/wiki/Torque#Units). Torque is a measure of how much force is transferred to the crank each rotation, so you multiply by how fast the rotations are to get the total power.

Gentlemen,

DBXXX nailed it in the post quoted above. Forget everything else that has been guessed or theorized about in this thread. Torque is turning force at the crank. Horsepower is that turning force multiplied by the number of times that force is generated in one minute. If torque is 10 and RPM is 10 that is the same amount of horsepower as another engine where torque is 5 and RPM is 20.

To create a mental picture think of an engine that is built to lift weight straight up on a pulley. If one rotation of the crank would lift one pound of weight one foot high then the torque is 1 foot pound. But that doesn't tell us squat about the work that engine will do without knowing how many rotations per minute the engine will turn. If a motor with 1 foot pound of torque only turns 10 times a minute (10 RPM) it will lift that 1 pound weight 10 feet in a minute. Another engine with the exact same torque that spins at 30 rotations per minute will lift that 1 pound weight 30 feet in one minute. Horsepower is a measure of how much work an engine will do. Torque is only a measure of turning force.

Now if you cut the torque in half but double the RPM, horsepower remains constant. In the last example above we have an engine with 1 foot pound of torque turning 30 RPM lifting a 1 pound weight 30 feet in a minute. A different engine with half the torque that spins at 100 RPM will lift that 1 pound weight 50 feet in a minute.

This is a simplified example for engines that run at constant RPM but you get the idea. Torque is meaningless as a measure of power without multiplying it by RPM. Given optimum gearing and holding other variables constant, two motorcycles with 100 HP engines will accelerate at the same rate even if one of them has only half the peak torque of the other. The lower torque engine must turn twice the RPM to do the same amount of work.

In short, it is horsepower, not torque, that determines how fast a motorcycle will accelerate or how much total work any engine will do.

Some people like the feel of slow turning engines that chug along at 2000 RPM like Harley Davidsons. High torque per turn is important here as that turning force is only being generated 2000 times a minute in 6th gear at 50 mph. A 600cc sport bike that is turning 6000 times a minute in 6th gear at 50 mph may only have half the torque per revolution but that turning force is being generated 6000 times per minute or 3x as often. So that sport bike will have 1.5 times the power of the Harley and will accelerate much faster. Comprende'?

Cheers.

Chip

[the Ferret]

Answer me this Mr Peabody ( that means anyone smart enough to explain it to a dumb guy)

Why isn't torque or horsepower linear thru a rev range..for example see torque charts on several sport bikes below. Notice how the torque rises and falls, then rises again then falls as rpms increase until the torque graph looks like a mountain range. Why does the torque fall off between 3500 and 5000 rpms even though rpms or cycles per minute is increasing?

http://www.sportrider.com/sites/sportrid...e_dyno.jpg

Now look at the horsepower and torque of the CB 1100 (couldn't find an example of just the torque graph). Notice how the torque line is pretty much a constant as rpms increase

http://www.motorcycle.com/gallery/galler...OISSES_PMT

If both are a byproduct of each other, so much so that there is a formula for it, why does it dip on one chart and not on the other chart?

Confused in sw Ohio

[rboe]

Now you have introduced the dirty real world. To create that power you have to pump fuel and air into the motor then pump the by products out. That process is messing and frought with compromises on the intake side and exhaust side. You can tune the intake manifold for certain rpm ranges but not all, same for the exhaust (e.g. the old two cycle motors that would suddenly "come on the pipe" as the pipe design would help the pumping action).

Then you toss in regulations for clean burning (and typically the engineers, knowing how the tests for clean burning are done will design to the tests to a degree), or the job the motor is intended to do (steady running at lower rpms like in a cargo ship vs. a dragster) then the mechanical slop in gearing or chain that controls the valve train - it gets pretty messy.

I think the Honda engineers designed the torque curve for riders, not to look good in the quarter mile in the latest Cycle Magazine - kudo's to them for that.

[CIP57_imp]

http://s29.postimg.org/3zeyq8m2v/screenshot_47.png

Here is the graph for a cbr1000RR, aside from rpm's the torque curve is very similar to our bikes. Most Honda's have very smooth torque curves even there sport bikes which make them a pleasure to ride at slow speeds.

Looking at the chart is why that HD comparison is a joke, bring this bike out of the hole at 7000rpms and your in the meat of the HP and torque curve.

Mickey, all bikes will have different torque curves based on cams, pistions, intake, exhaust etc. Suzuki's are monsters on top and not as much torque in the mid-range as Honda, where Honda is known to be dead on top regarding HP.

http://s29.postimg.org/ulrff7q9z/screenshot_48.png

Without looking at the V's Honda is the most rid-able of all the inline 4's with the best torque curve of the bunch.

[metallyguitarded_imp]

I have decided I don't want to know about horsepower and torque and rpm and acceleration, about tractors or pulleys or marine engines. I do not like them Sam I Am. I will not learn this on a boat. I will not learn this on a goat. I will not, cannot on a plane. All this talk drives me insane. I do not like them Sam I am.

[the Ferret]

Lol MG

Steve.. What I don't understand is if there is this symbiotic relationship between torque and hp expressed in the formula

Torque x rpm = HP,

Why don't the lines on dyno charts reflect this relationship and mirror each other? ..why would the lines be any different. Why does it not show a corresponding dip in horsepower where it shows a dip in torque? Why would there be a dip in torque when rpm is increasing. One chart is going up in the same spot the other chart is going down and vice versa.

Do you see what I am saying?

As far as carbs and cams and valves go, they are the same ones in the motor when you start the dyno runs as when you end the dyno runs, and they are made of metal so they don't radically alter shape ( lift duration etc) from 2000-6000 rpms where the dip in torque shows up on the dyno chart of 600s I posted.

I will probably never understand this so the explanation is moot I suppose. it just doesn't make any sense to me.

With my last breaths I will probably still be saying torque makes you go and hp makes you go fast lol