What's the difference... I had someone explain it to me before but still wasn't clear on it..... Can someone explain it in 5th grader terms....

 

hp = passing power on the highway
torque = what you feel when you mash on the gas from a stop

 

That's way over-simplified and not too accurate but I'm too lazy to write up better definitions so I'll just give you the thumbs up and pretend like it's right until someone like Eric or Mike comes in here to educate.

 

To put it in bench press terms

Torque is how much you can bench once

HP is how much you can bench say 10x.

 

i believe hp is how strong u are, torque is how fast u make that strength. saw it on hp t.v. haha!!!

 

That would mean horsepower is endurance and torque is max weight, which would also be wrong.

Here try these definitions:

Horsepower
Measure of an engine's ability to perform work. How much mass it can move compared to what distance and what time. Or how much time it takes the engine to move a mass over a distance. Etc.

Torque
Measure of a force's tendency to produce torsion and rotation about an axis - turning or twisting power. This is what gets you started. The more torque the quicker you can get up to speed.

If you have a ton of horsepower but no torque it will take forever to get your car going but in the high end you would have great speed. If you have a lot of torque but little horsepower, your car will get up to speed much more quickly but would take longer in the high end to increase speed.

Torque matters off the line, horsepower matters once you're moving.

For better descriptions try:

http://www.howstuffworks.com/horsepower1.htm
http://www.howstuffworks.com/horsepower2.htm <--- compares torque to hp in a sidebar.

 

Aha.... that's what i was looking for....

 

Torque matters very little. All that accelerates the car and all you feel while driving is the application of torque over a period of time (which is horsepower by definition).

When anyone refers to "low end torque" or "torque gets you off the line" what they really mean is horsepower low in the rpm band.

 

Yup.

Errr... kinda. They explain this much better in the link I posted.

 

EZ.... HP and torque (in lb*ft)are defined by each other and at about 5252rpm they are equal ALWAYS

HP=Torque*(rpm/5252) (units of torque= lb*ft)

In dummy terms. if you have 200 lb*ft of torque @ 2000rpm... then you can just put this in the handy dandy equation and find that you have 76.16hp @ 2000 rpm. If you have a flat torque curve, then your horsepower increases linearly with engine speed. Another easy way to think of it is this. If you hold an electric motor in your hand (most of us have done that) and you hold the output shaft still, then turn it on, you can hold it stopped. If you let the shaft go, it's VERY hard to stop. The reason I say this is that permanent magnet motors have constant torque at all speeds 0 horsepower at 0 rpm and hp=torque at 5252rpm. Make sense?????

 

JROCK..... according to your definition.... HP is a measure of endurance.... "How much mass it can move compared to what distance and what time"

and torque is a measure of strength... "turning or twisting power".

Moo's simplified analogy is correct.

 

Moo had no reference to time in his analogy, though.

 

The Torque is related to HP and the formula is:
(HP * 5252)/RPM = Torque.
So, they are related by velocity

(If the speed of the applied force is less than the object you want to push, it isn’t going to help much!)

The torque is the actual "static" force (for a given gear) that is applied to move the car. The torque doesn't say anything about how fast that "force" can move...

For example, if I had a 4-wheel drive with a super low gear (redline would mean going 3-miles/hour), the amount of torque (force) available at the wheels could be huge, however, it would only accelerate a car up to 3-miles an hour!

HP is a measure of force over time (ability to do work). I can get a small 1/4HP motor with a gigantic gear down to lift a million pounds; the problem is, it will take a long, long time to lift it!

If I have a 10,000 HP, I have 40,000 times more power available and can use a more suitable gear ratio to lift that million pounds in much less time (1/40,000 the time to get the job done)

So, power is the ability to do work (its how much force available per unit time).

Torque is just the force (think of this in a static kind of way). The torque would relate to just how hard you would be pushed.

As an aside, the reason HP is so important is that a motor with very high HP, but low torque at a very high rpm can be geared down to make very high torque at the wheels. And, its the torque at the wheels that determines the acceleration for a given weight car: (F = ma)

If you take the torque at the engine and have a 1:1 gearbox, the change in speed at the output of the gearbox will be the same as that of the engine. The output torque will also match that of the engine.

Now, if you have a gearbox where the input gear -- that has half as many teeth as the output gear -- making two turns for every single turn of the output gear, the output speed will be reduced by half. The output gear speed will be 1/2 that of the input *and* the torque available at the output gear will be twice as great as the torque at the input. (The available power is still the same!)

Finally, if you have an engine with 300HP that revs to 20,000RPM, it can have very low torque available at the engine. But, the high revs means that the engine can be geared down to make a lot of torque at the wheels.


High HP means you can do a lot of work in a short amount of time.
AND
Very low hp means you can do a lot of work given a very long amount of time!


(Every wonder why the new rechargable drills with a small battery can drive screws through super thick hardwood? It's cause they have very little HP, but have a gearbox that transforms the tiny motor's wimpy torque (with very high RPMS) to a shitload of torque with very little speed!


If all of this just confused you more, check this link out:

http://www.vettenet.org/torquehp.html

 

I always thought of it as being;
HP -- How fast you can go.
Torque -- How quickly you get to that speed.

 

I feel like I'm on Mr. Wizard's World!!!!

 

See? I told you to wait for EricL to post. :P