Outland

See? Wheens understands. Mdp and Raisedinabarn don't. You guys didn't pay attention in school...are you guys still not paying attention?

goodman888

Is there any pt to argue who paid attention or who didnt?

From http://home.att.net/~jroal/physics.htm

"If you lift a 550 pound object 1 foot you have done 550 foot pounds of work (not to be confused with foot pounds of torque which is a force, not work). This ignores inertia affects that would be very large in this example. If you do that work in one second, you have just applied one horsepower (or 746 Watts)."

"Torque is a force rating. A foot pound of torque is 1 pound of force applied perpendicular to a shaft 1 foot from the shaft centerline. Torque can be applied with no motion. A torque rating alone tells you some things about an engine however it does not tell you how much work the engine can do in a given time.

Power (HP or kW) is a rating of the amount of work that can be done in a given time. Power is really the rating you need to determine how fast you can go, how quick you can accelerate, or any other performance aspect of a vehicle, boat, or any powered machine. "

Let's look at the concept rather than arguing about the formula.
The formula just gives you a conversion rather than a practical view.

Power = Work Done / Time
Torque = Force X Perpendicular distance to the pivot

You can lift a 100kg weight and walk for 10 meters in 10 hours or in 1 seconds. They are the same work done. But the acceleration (power) and the rate of delivering energy is totally different.

See: http://imperialviolet.org/binary/apnotes.pdf
and
http://kipper.crk.umn.edu/physics/10...s/lesson11.pdf

I think some people mix up a derived formula with the actual physical implication here.

It just happens here (the confusion) that the engine is circular (RPM) and that people mix up with the concept of power and torque.

mdp c230k

Listen, torque is a force. HP is the rate at which it is delivered. Yes torque is important, I never said it was not. If you can not deliver the force at a high enough rate you will not accelerate. Diesel engines with gobs of torque are not used in race cars because the can not deliver it at a fast enough rate (hp). There is also no need to insult, especially when you do not understand what is being said. If you read the links I posted you will see that I am correct and it is you that fails the test. It takes force over time to accelerate, where is the time factor in a torque measurement? Get it? Yes it is the torque which provides the force, its measured in hp when dealing with accel.

goodman888

Failing the test...... you can use whatever term you like.

T = Moment of Inertia (Force) * Angular Acceleration (acceleration)
Moment of Inertia = Summation of mr*r (r being the radius)
Angular Acceleration = a/r

Hence T = mr*r * a /r = m * a * r or simple T = mar

It's very funny that if any passing students still insist that Torque is *more* important than Power in acceleration while NO links in google.com mention that.

T only mentions the Force. It's important of course but it's basic. You are arguing that a man needs lots of oxygen rather than super muscles and lungs in order to finish 100 meters in 9.7sec.

Well.. I think that's the end of discussion.

goodman888

I quoted the wrong message.... sorry....

My message is just a supplementary note and hope not to see any further argument.

goodman888

Do you know there's a practical difference between angular acceleration and linear acceleration?

Even by maths, Angular acceleration = Linear acceleration / angle in radian. Do u know what that radian implies practically?

Do you know in physics, angular and linear motions are, though interchangeable by formula, but conceptually different?

Outland

Exactly. Which is why HP is an abstract. Its a term INVENTED to describe work done in a linear fashion. A horse moving a load up a rope. Which is why torque is STILL the only force that is exerted. You need to actually go back and read all the posts.

mdp c230k

It is work done over time. Where is the time factor in torque? HP is not abstract, it is arbitrary and is set at 1hp=550ftlbs/sec. Torque is force but it is not work. It takes work to move an object. Work is force over time. Gee, hp is equal to force over time! HP must be the relavant unit of measure! Get it yet?

Outland

You understand about half of it now.

Quote:

Diesel engines with gobs of torque are not used in race cars because the can not deliver it at a fast enough rate (hp).

Diesels are stronger motors. They don't rev high enough. If HP was the only thing that mattered, why are all heavy machinery, large trucks, ships, etc powered by diesel motors?

Quote:

It takes force over time to accelerate, where is the time factor in a torque measurement? Get it? Yes it is the torque which provides the force, its measured in hp when dealing with accel.

Here's the part you don't yet understand. Going back to the angular momentum portion of this all, the high revving engines have to go 'twice the distance' to get the same work done. Is some of this sinking in yet?
The stronger the force, the less 'time' that force needs to applied. This is why a high revving motor that makes good top end HP but little torque is not a good match for a heavier vehicle....and the same reason that these motors are absolutely dead at lower rpms. And it still takes "time" for the motor to spin up to the 7K sweet spot.

mdp c230k

Diesel engines are able to deliver lots of force but not rapidly. To move large objects you need large forces. They are not able to deliver this large force at a fast rate so there hp rating is low despite their strength. Your last arguement is not to the right point. In order to provide the work needed the lower torque engine would have to spin at a higher rate, yes. But due to its lower hp at lower rpm it cant move the car quickly. If it was able to deliver more HP at the lower rpm the car would be quicker.

Outland

Yup. But they are still the stronger motor.

Quote:

Your last arguement is not to the right point. In order to provide the work needed the lower torque engine would have to spin at a higher rate, yes. But due to its lower hp at lower rpm it cant move the car quickly. If it was able to deliver more HP at the lower rpm the car would be quicker.

Yes, I muddled the last paragraph a bit. But I hope you understand my point now...its always been torque that moves you. Large low end torque will move you quicker than low torque will, at the same RPM. Thus, torque is what moves you off the line, what gives you that shove back in the seat.

When you have an engine with a high HP rating, but low torque, that you can only use the High HP in a very narrow range...it doesn't make that kind of power accross the whole rev band. The best motors have torque and HP that is relatively equal.

mdp c230k

Now you are getting it.
Also notice that none of the E.T. calculators use the torque value to get the time or the speed, they all use the HP and weight.

goodman888

Please give us the proof with regards to car motion.

I guess you may probably win a noble prize by proving to all physicians that Torque is more important than Power in acceleration.

goodman888

I'm getting confused what you want to convey indeed....

The best motors.... are the motors that suit the respective needs for a truck, sedan, or racing car etc. Different types of vehicles require different "best motors", right?

What I understand so far is, if either Power and Torque, there's no doubt that Power is more important than Torque because you can mechanically convert power into torque regardless to the power band but not vice versa. Of course, both are important to a vehicle for excellent performance.

It's like if you want to run fast, strong muscle or good oxygen supply, which is more important?

Outland

I have no idea what you are now arguing. Torque is still the only thing that moves your car. Not only that, torque is the only force that your motor makes. Deal with it.

Outland

For a car, to me anyway, a good motor has a torque rating relatively equal to its HP rating. That is a 200HP motor, that makes an honest 200ft lbs of torque, preferably on a flatter curve. Or a 300Hp motor that makes 300+ft-lbs of torque.

Torque is important for accelleration because maximum accelleration in any gear occurrs at the torque peak...that's the shove, that's the pull you *feel*. Torque is still the force that launches your car. This is not just my opinion, this is the way it works.

Quote:

What I understand so far is, if either Power and Torque, there's no doubt that Power is more important than Torque because you can mechanically convert power into torque regardless to the power band but not vice versa. Of course, both are important to a vehicle for excellent performance.

Its the combination that makes for all around performance. And HP is still torque...not some "other force".

Matt230K

I'm not going to chime in with any expertise. I have a basic understanding, even more so after reading this thread. But I can say that I also prefer engines that have about equal torque and HP. They are much better for driving at lower RPM's.

Even a Ferrari is probably not that fun to drive at low RPM's. They tend to be high HP and low torque engines and need to be revved up. The only one I have driven briefly is a 355 spider, and it didn't really feel that fast because I didn't push it to near redline.

Actually, after driving nearly ever Mercedes engine built, I am very happy with my 2.3L. Even though it does not have the most power, it is very driveable. With the pulley and extra boost, it drives just fine for me. It seems to pull at almost every RPM because it has a very flat torque band. So even though it isn't pulling as hard as other engines, it ALWAYS pulls and I like it.

darkfact

And I NEVER won any race.

PS. I always race C200, C230 and CLKs same classes.

mdp c230k

HP is work not force. Get the idea through your head. It takes work to move an object. Force over time is work. torque over time is hp is work. They are not the same thing as you keep implying. The more torque an engine can supply over time the more hp it can generate. Please go back to school and read the difference between force and work.

Matt230K

I'm not going to go back and read it all over again, but from what I remember, he always said that torque was a force, but HP was not. If you're referring to this quote:

I think this means that torque is a force, but HP is not some "other force" because it is not a force at all. You get it now?

C230 Sport Coup

May the force be with you.

Wheens

And not be so "torqued" at other's lack of understanding of basic physics!!

goodman888

HP is a rate not a force. Torque is a force but an angular force which has very different implication in linear force.

Outland

Perhaps your are illiterate, or ignorant. I grow tired with you implying that Ive said things that I HAVE NOT. AND IT DOES NOT TAKE WORK TO MOVE AN OBJECT...IT TAKES FORCE...THE ONLY FORCE A MOTOR MAKES IS TORQUE. IF YOU MOVE AN OBJECT OVER A DISTANCE, THEN YOUVE *DONE* WORK.

HP IS NOT A FORCE. SOMETHING THAT I SAID 3 PAGES AGO..

IVE SAID OVER AND OVER AND OVER THAT HP IS THE RATE TORQUE IS APPLIED. THE ONLY FRIGGEN FORCE DOING ANY WORK IS STILL TORQUE. GOT IT YET?

IF YOUR ENGINE MAKES 150ft-lbs of TORQUE AT 3000 AND ANOTHER ENGINE MAKES 300FT-LBS OF TORQUE AT 3000 RPM, THE OTHER MOTOR IS GOING TO PULL HARDER AT 3000RPM regardless of the HP rating.

This thread has lost all sense of usefullness.

Outland

LOL!