What is the difference between HP and Torque

I googled it to find out, but sites that came up had really complex explanations that I didnt understand.

I always thought HP was the more important spec, but I guess I was wrong.

Also, is 200HP & 205 ft-lbs @4500 RPM a good engine?

I googled it to find out, but sites that came up had really complex explanations that I didnt understand.
I always thought HP was the more important spec, but I guess I was wrong.


As simple as possible,.... HP is a unit of work. Torque is a unit of Force. The more force that can be applied over a given amount of time. the more work (HP). In a sense, Torque and HP are the same thing. However, if more torque can be applied over the same amount of time, more work (HP) can be done.



Also, is 200HP & 205 ft-lbs @4500 RPM a good engine?


"Good" engine? Don't know. Depends upon what you want it to do. Engines can be designed to produce lots of different torque at many different RPM points. It depends upon what you want that engine to do and at what RPM.

Jim
SR Racing

you need torque to get your vehicle moving and up to speed and horsepower to keep it going once you get there

you need torque to get your vehicle moving and up to speed and horsepower to keep it going once you get there


:smile: ???

No.. You need HP to do either. The more HP the better it can do either. The only difference is the final drive ratios you need and the point in RPM that you engine will pull best.

Again. HP is work... To do any work... accelerate a mass, keep a mass rolling and overcoming air resistance and wheel/road resistance requires HP. Torque is simply a measure of force that can be mapped against the RPM so you can determine WHERE in RPM that engine performs best.

HP = TORQUE x RPM / 5252. See?

Jim
SR Racing Inc.

Torque is actually a static measurement like you create with a wrench. Although you are moving, the point at which you cant turn anymore is the point where the bolt is giving back the same amount of torque force that your arms can generate. HP is like a swinging hammer. A 2-lb hammer can make a 100-lb impact when moving fast enough.

In an engine, torque is a bit abstract, but if an engine makes 100 ft-lbs, that means it would require 100 ft-lbs to stop it. Its a bit abstract because a stopped engine makes no torque but maybe that can illustrate it. HP is technically defined as torque over time. Going back to the hammer analogy, a resting hammer does no work, but get it swinging and it does work. If you start swinging it around in a circle it can do some damage. The faster you swing it, the more energy it has and therefore can do more damage.

Engines produce torque. As a function of their speed, torque produces HP.

horsepower is like a measurement of the "pulling force" at a certain speed-RPM in this case lets use this example; a car with 250bhp (brake horsepower) means it can pull the same amount of weight (?) as 250 horses at a given speed, or range of speed. torque is like a powerful, strong twisting force, like curtis said, using a wrench, because you use them slowly with lots of force. you cant use the same force if you're swingin a hammer, its just completely different force

you can swing a hammer with force, but its nothing like the force you use for tightening a bolt with a wrench, the reason why the peak torque is always at a lower RPM that the peak bhp (right ?) is because the engine generates the slower "twisting" force going slower that the "hammer-like" swinging/rotating force of the horsepower.

i hope thats clear

the reason why the peak torque is always at a lower RPM that the peak bhp (right ?) is because the engine generates the slower "twisting" force going slower that the "hammer-like" swinging/rotating force of the horsepower.


No. :smile:

The reason peak torque is always at a lower RPM than peak, HP is simply because Torque IS horsepower across time. I am not sure why this concept is so difficult to grasp.

You cannot simply say is torque or Hp better. One is a derivitive of the other.
Again. HP = (Torque x RPM) / 5252 (5252 converts the circular movement to time)

Based upon the above.. ALL engines produce the same torque and hp at 5252 RPM. This is simply a mathematical fact since Torque is HP across time.

EG. Two engines.. One produces 200 lbs of torque at 5252 RPM. At that point it is producing 200 HP.

Another produces 210 lbs of torque at 4800 RPM. At that point it is producing only 182 HP. However that same engine might produce 160 lbs of torque at 7500 RPM. At that point it is producing 228 HP.

Got it?

HP is WORK, Torque is force. (typically a circular force)

To convert this into something even simpler.

I have two laborers, pushing blocks of mass across the room. One can only push a 100 lb block and it takes him 20 seconds to move it 100 feet.
The other laborer can move a 200lb block but it takes him 45 seconds to move it 100 feet. The first laborer produces more HP (work). However the 2nd laborer produces more torque (force). In an hour, laborer number one will do more work. (HP)

Now for a selection of laborers.... IF I HAD to move 200 lb blocks. I would choose the 2nd laborer. He, at least can perform that work. If I simply had to move 100 lb blocks, I would choose the 2nd. He would be able to perform more work in a given time.

In the example above the second laborer is a Diesel, or big block low RPM engine. The first laborer is a small 18,000 RPM Indy car.

Given all the above, Torque/HP choice should be based upon the weight of the vehicle and what you plan to do with it. Gearing can be used to get the engines to comparable output torque, but gearing also has drawbacks.

There are lots more to this, but that is about as simple as I can make it.

Jim
SR Racing Inc.

my head hurts...

Well the way I've always understood this "abstract" concept is. TORQUE = WORK,TURNING FORCE, EFFORT. HORSE POWER is just a representation of the rate of speed that work is accomplished in! Example, I've got a 31Hp tracter that can outpull most 200HP cars because it produces lots of TORQUE! But its slow because the rate at which that torque is utilized is low (31Hp)! :2cents: A engine is costantly produceing torque even when its not being utilized for motion. This force is modified by the drivetrain to achieve required perameters for driveability. Horsepower stripped to the bone is basicly if one horse can move a load this far in this amount of time, then 2,3,4, ETC horses can perform that same feat this much faster! But the loads the same! :grinno: :useless: :sleeping: :sleep: :wtf: (You can wake up now!)

HP is like skittles, its bright and shiny. M&M's are like Torque, because some of them have nuts.

asemstr,

You got it right! (Except the horse to HP correlation. That was an estimate by Watt in the 18th century that turned out to be incorrect, but that was his best guess at the time.)

Jim
SR Racing

Torque is like a girl you'd marry; pretty, gets things done, reliable.

Horsepower is like a prostitute; sounds like a good idea when you buy it, but there's nothing on the inside you really want to experience.

By the way; that was the analogy we used internally at GM :)

:rofl: And that explains why GM guys are screwwed up! :screwy:

As simple as possible,.... HP is a unit of work. Torque is a unit of Force. The more force that can be applied over a given amount of time. the more work (HP). In a sense, Torque and HP are the same thing. However, if more torque can be applied over the same amount of time, more work (HP) can be done.




"Good" engine? Don't know. Depends upon what you want it to do. Engines can be designed to produce lots of different torque at many different RPM points. It depends upon what you want that engine to do and at what RPM.

Jim
SR Racing
GUYS THE DIFF. IS TORQUE IS JUST HOW MUCH HP THAT U PUT TO THE REAR TIRES AND TO THE PAVEMENT OR VICE VERSA. YOU NEVER WANT MORE HP THAN TORQUE

GUYS THE DIFF. IS TORQUE IS JUST HOW MUCH HP THAT U PUT TO THE REAR TIRES AND TO THE PAVEMENT OR VICE VERSA. YOU NEVER WANT MORE HP THAN TORQUE

Huh? I think you need to do some reading. You haven't quite grasped the concept.

Jim
SR Racing

Um yeah, thats completely wrong.

http://www.geocities.com/MotorCity/7177/torquehp.html

There is also a discussion in the Street/Track Racing Section under Honda about the same thing.

A horsepower is a unit of power. Torque is torque. Power is a function of torque and angular velocity. With the proper gearing, acceleration and top speed depend on power.

A horsepower is a unit of power. Torque is torque. Power is a function of torque and angular velocity. With the proper gearing, acceleration and top speed depend on power.
OK GUYS LETS RE GROUP.
read all the replys to this ? .. all say torque has somthing to do with acceleration, or your gear ratio. ok to any results out of gear ratio is for the real wheels to turn or the front what ever ok torque , sure it is A measure of force but the object has to move to get any amout of force. so forget it guys nothing you will say will change my theory of how you get deffinition. of what torque is . it is!!!!! the amout of horse power that is applied to the rear tires and to the pavement or vica versa if drive a front wheel drive . the guy dont want to no how u measure it but what is it . it is in all your replys but not in the right fase.

Sorry, Webster disagrees.

Torque
The moment of a force; the measure of a force's tendency to produce torsion and rotation about an axis, equal to the vector product of the radius vector from the axis of rotation to the point of application of the force and the force vector. A turning or twisting force.Horsepower
Abbr. hp A unit of power in the U.S. Customary System, equal to 745.7 watts or 33,000 foot-pounds per minute.Note that torque is measured in several ways, one of which is foot-lbs and one HP is equal to 33,000 ft-lbs/min. Technically, HP is torque over a period of measured time. Its an abstract thing, but torque is how much twisting force is being made at the crankshaft. Since torque is a static measurement and HP is a moving measurement, imagine HP as being the measurement of how many times or how fast that torque is being applied. If you could divide the 360 degrees of rotation into an infinite number and measure the torque at each one; that's horsepower. The faster it spins with the same torque, the more HP can be made.

I think someone is smoking something they shouldn't :)

A horsepower is a unit of power. Torque is torque. Power is a function of torque and angular velocity.

Finally, someone who realizes that this “Power vs. Torque” discussion is not limited to the U.S. customary system of units.

Horsepower vs Torque makes as much sense as Watts vs Torque, Power vs Pound-Feet, etc.


Note that torque is measured in several ways, one of which is foot-lbs and one HP is equal to 33,000 ft-lbs/min. Technically, HP is torque over a period of measured time.

Actually torque is measured in pound-feet (lb-ft), work is measured in feet-pound (ft-lb). Since work and torque are not equivalent, it cannot be said that power is simply torque measured over time (it is work over time).

To convert torque to power both time and distance are needed. Hence, RPM which has both a distance and time component.

It is this reason that torque by itself does not give any indication of an engine’s performance. At minimum torque and engine speed are needed.

As well, torque at the engine means little as it can be multiplied nearly indefinitely to the wheels. Of course the trade off of gearing is rotational speed or angular velocity, but the one constant factor is power.

sracing has it right. i think that it's just that some of you can't visualize what he's trying to tell you. horsepower & torque are two different viewpoints of the same equation regardless of how some of you seem to believe things are.... 1 horsepower is defined as the amount of energy needed to lift 550 pounds of weight a distance of 1 foot in 1 second. simply put, horsepower is the application of torque, over time, whereas torque itself is the amount of force generated by the twisting motion of an object, measured at a given distance (i.e. inches, feet, millimeters, what have you) from the center of the axis at a right angle. torque can be measured as either a static measurement (holding a given weight up) or dynamically as a peak potential quantity (i.e. max breakaway torque achievable @ a given rpm). it's really very concept to understand.

JESUS DON'T USE CAPS.

Please don't use all capital letters. It looks much better when you type normally.

And yes, that's why diesels tout potentially less hp than a big EFI counterpart, but puts out a load more torque: You might not get speed out of it, but you can pull more.

My inline 6 only has 145 hp (as opposed to 205 of my dad's 302 of the same model year) but it has the same torque, so we can haul the same load, he'll just do it with a bit more speed and ease.

You get onto someone for using caps in a four month old thread? Both are equally annoying.

I was searching threads and saw this. Neither here nor there, and I did put relative info in the thread.

Just dont confuse relative and useful.

Torque is defined as the sum of force vectors around an axis (of rotation). Basicly that means than on an axle torque is the force that will try to rotate the axle. We can have torque and no rotation and torque with rotation.

Torque can be used to do work. Work is defined as force multiplied with distance.

Horsepower is one unit of power, according to international standard power should be measured in watt. Horsepower was used as a measurement since some of the earliest steam engines replaced horses to power water pumps used in mining. One horsepower was the mean power produced by an average horse.

Power can be defined in many different ways depending on the situation, if we talk about engines the most common definition is power equals work per time unit.

What makes a car perform is the engine power, not torque. For example to make a car accelerate you need the power, P:

P = Fv = mav

m = mass
a = acceleration
v = velocity

Power is also what makes the top speed of a car. In order to drive at a certain speed the drag (aerodynamic and rolling friction) must be overcome. With a drag, F, the power, P, to drive at a certain velocity, v, is:

P = Fv

In order to offer a high performance a high power output at a certain rpm isn't enough. Instead the maximum output in a certain range is required, for example 6000-9000 rpm. What range is required depends on the application, a four speed gearbox will for example require a better range than a six speed gearbox.

So if it's power that do the all important stuff, what does the torque do. Well, torque is what makes your clutch slip, it's also what can overload the gearbox. Basicly torque itself has no function, but it is required to develope the power. Sometimes "torque" is incorrectly used to decsribe the low speed performance of an engine. Even though it's incorrect use of "torque", an engine that is powerful already at low speeds tend to have a good "range".

and with that description... this thread is closed. Too old for my tastes :)