Horsepower vs. Torque - Ranger-Forums - The Ultimate Ford Ranger Resource


4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

Reply
 
LinkBack Thread Tools Search this Thread
  #1  
Old 03-05-2009
DaReallyPoGigolo's Avatar
Member
Thread Starter
 
Join Date: Jan 2009
Location: Chino Hills, CA
Posts: 11
Horsepower vs. Torque

Hey everyone.

I've been a long time reader on the forum, but this is the first time I've actually decided to make a post.

Recently I was reading through a thread that got a little out of hand on the subject of torque and horsepower, the thread nor the names of those involved being of any relevant importance as mentioning them would just add fuel to the fire, and I thought that I would take it upon myself to explain how each is measured, calculated, used, and give some common, physical examples of each one in action and how each is important.

DISCLAIMER: THIS IS BY NO MEANS AN ATTEMPT TO START ANY SORT OF FIGHT OR TO TAKE SIDES WITH ANYBODY!!!

With that said, any questions are more than welcome and are encouraged, as I am happy to clarify anything I've said or anything that anyone might be feeling a little vague on.

Oh, the reason I know a thing or two about this is because I'm a Mechanical Engineering student soon to graduate with a strong background in Physics, Statics, and Dynamics.



To begin, I'll start by defining the base quantities of any and all Newtonian equations:

Time (t)
Mass (m)
Length (l)




The most basic equation is VELOCITY. Velocity is the distance traveled in a given amount of time. There are two kinds of velocity. LINEAR VELOCITY is the velocity when traveling in a straight line, and is written as

V = ( l / t )

ANGULAR VELOCITY (sometimes called rotational velocity) is the angle traveled in a given amount of time and is written as

V = (change in angle / t ).

An example of linear velocity, think of a truck that travels 60 miles in two hours. 60 miles divided by 2 hours comes to a velocity of 30 mph.

An example of angular velocity, think of a tire spinning on a car. If the tire is spinning at 100 rpm, that's 360 degrees one hundred times in one minute, or 36000 degrees per minute. This comes to 600 degrees of rotation per second.




After velocity comes one that we all know and love, ACCELERATION. Acceleration is the change in velocity per amount of time, otherwise known as the rate at which velocity changes.

A = (change in velocity/time) = ( l/t/t ) = ( l/t^2)

For instance, if you're traveling at 50 feet per second and then accelerate to 100 feet per second in a matter of 10 seconds, the linear acceleration is
[(100ft/s - 50ft/s)/10s] = 5ft/s^2

For an angular example, if a wheel is rotating at 600 degrees per second angular velocity and then increases to 1200 degrees per second angular velocity in a matter of 10 seconds, the angular acceleration is
[(1200 deg/s - 600 deg/s)/10s] = 60 deg/s^2





Next after acceleration comes FORCE. Force is an acceleration applied to a mass.

F = m*A = (m)( l/t^2)

Weight is the most common example of force. A human being has a certain mass, and the acceleration acting on the mass is gravity. Gravity has a value of 32.2 ft/s^2 at sea level on the planet Earth. Multiply your mass by gravity and you get your weight.

An example of angular force would be a flywheel of a given mass being acted on by an angular acceleration.




Next is one of the big ones in this discussion, WORK. Work is defined as a force applied across a displaced distance.

W = F*l = m*A*l = (m)( l/t^2)(l) = (m)(l^2/t^2)

For linear applications, work is simple. It's simply the force applied across a distance. For example, if someone pushes a box with a force of 100 lbs and it moves 10 ft, the work done is (100 lbs)(10 ft) = 1000 ft-lb

For angular applications, work is more commonly known as TORQUE. Torque is the force applied perpendicular to the distance from the center of rotation to the point where force is applied. For example, if you have a ratchet (acts as a lever arm), and the ratchet is 2 ft long, and you pull on the ratchet so that your arm makes a perfect L with the ratchet (ratchet is 90 degrees to your arm) with a force of 50 lbs, the work, or TORQUE, is (2 ft)(50 lb) = 100 ft-lb of torque.




And finally is the second big one in this discussion, POWER. Power is simply work (or torque) divided by time. More specifically, power is the change in work per a given period of time

P = W/t = (F*l)/t = (m*A*l)/t = (m)(l^2/t^2)/t = (m)(l^2/t^3)

A good example of power would be a person attempting to turn a very heavy wheel with your hands. You must apply a torque to the wheel to turn it, but you can't turn it very fast because, oh, let's say you're tired. You can however keep it turning at a steady, slow pace. Even if applying a large torque to the wheel, it's spinning very slowly (time to rotate is very great), so now your torque is being divided by a large number, so the power applied to the wheel is low.

Now, let's say that you just woke up and had a few energy drinks. You apply the same torque to the same wheel, but now you're full of energy and can move your hands much faster, rotating the wheel at a faster rate (time to rotate is now very small), so now your torque is being divided by a small number, so the power applied to the wheel is high.



Here's where the big difference between power and torque comes into place.

Torque is a force applied across a distance. Let's say a 4000 lb truck with 36 inch tires and 4.56 gears with a 3:1 first gear ratio is going up a 30 degree incline. Doing a few small trigonometry calculations will yield a force along the slope of 2000 lb. So now we have 2000 lbs acting perpendicular to a tire with a distance from center to outside of 18 inches, or 1.5 ft. The torque created on the truck's axle by gravity will now be (2000 lb)(1.5 ft) = 3000 ft-lb. So, the torque created by the engine and transferred through the gears must overcome the 3000 ft-lb. If you take a Ranger 4.0 SOHC with approximately 240 ft-lb of torque through the gear ratios mentioned, you get (240 ft-lb)(4.56)(3.0) = 3283.2 ft-lb. Therefore, this setup would be able to overcome torque on the truck due to gravity and move forward.

Power is a measure of how quickly torque is applied, or in other words, the rate at which torque is applied. If we take our torque example, we have the truck making 3283.2 ft-lb uphill and gravity making 3000 ft-lb downhill. This gives us a 283.2 ft-lb favor uphill. Now, if the engine (and therefore axle) is turning relatively slowly, the time between each revolution will be relatively large, let's say, half a second. Take our 283.2 ft-lb of torque and divide by 0.5 seconds and we'll get 566.4 ft-lb/s, which is only slightly over one horsepower (1 HP = 550 ft-lb/s). Now, let's say we have the engine (and therefore axle) rotating 5 times faster than before. Now each revolution will only take 0.1 seconds. Take our 283.2 ft-lb or torque and divide by 0.1 seconds and we get 2832 ft-lb/s, which is just over five horsepower. The difference between the two situations is that, although they have the same torque and therefore can haul the same load, the one with more horsepower can haul that same load at a higher speed.

So here we can see the big difference between torque and horsepower. Torque implies how much of a load something can haul, where as horsepower implies how fast it can be hauled. For instance, a motor with 150 horsepower and 300 ft-lb of torque at a given rpm can haul a 1000 lb load at half the speed that a motor with 300 horsepower and 300 ft-lb of torque at the same rpm can haul it at.

This is why a diesel with 300 HP and 600 ft-lb of torque can haul twice the load at the same speed as a half ton gasoline with 300 HP and 300 ft-lb of torque.

Finally, I'm going to address whether or not horsepower is real. Horsepower is just a unit of power. It is very real, but to say it's just a calculation isn't very correct. For some reason, the standard English system decided that 1 HP had to equal 550 ft-lb/s, something to do with horses and buckets of water, etc. So while that is just a calculated combination of other units, it does have unique use and meaning as I've pointed out in the previous few paragraphs. Both TORQUE and POWER (horsepower simply being a unit of power) are different but critical to automotive function. If we look at their formulas in terms of the base quantities we see that:

TORQUE = (m)(l^2/t^2) and POWER = (m)(l^2/t^3)

So yes, power is torque divided by time, but if you look at them, neither are by any means their own thing. They're both just the ba$tard children of mass, length, and time. With this said, all machines that measure any of the quantities (velocity, acceleration, work, etc.) that i mentioned above, they're really only measuring a combination of mass, length, and time, sometimes with known values such as that of gravity. At any rate though, whether it's a floor scale or a dyno, it's all based off of mass, length, and time. Being a little more specific in the case of the dyno, a dyno doesn't measure horsepower or torque, it measures values of length and time and uses a known value of mass for the roller to calculate both torque and power (see equations above).

Ok, it's 2:30 in the morning and I'm done with the technical discussion. I would like to address a few things about this discussion before I go though:

1. I realize that there are indeed more complex explanations and examples that could have been used for this discussion, but simplicity more often than not yields the best results and I feel that in this case, that couldn't have been more true.

2. I focused most of the detailed explanation on linear equations. I put detail into the angular equations when needed, but didn't go too far into them because I feel that to fully understand them one needs a fairly thorough knowledge of trigonometry. Not everybody has that, so I tried my best to explain things with the most basic math possible that just about anyone can make sense of. Again, simplicity is good

3. I didn't list any equations for horsepower or torque because I wouldn't have felt right doing that without explaining exactly how they work (things like why torque and horsepower cross at 5252 rpm, etc), and again that takes a lot of trig or at the very least geometry. If anything else, I just didn't think it necessary to go into this, but if anyone wants to know, feel free to ask.

4. This was made to be a simple explanation of torque and horsepower, how they work, and their differences. I hope everyone enjoyed this


Again I'd like to state that by no means am I taking sides with anyone in any sort of argument. I would however LOVE if people came up with any sorts of questions. I'd be happy to answer them. I hope everyone enjoys my first post, and I'm looking forward to contributing to the Ranger-Forums community!
Reply With Quote
  #2  
Old 03-05-2009
Roddy's Avatar
Member
 
Join Date: Mar 2008
Location: Canada
Posts: 1,332
r u serious?
Reply With Quote
  #3  
Old 03-05-2009
wydopnthrtl's Avatar
Member
iTrader: (2)
 
Join Date: Dec 2005
Location: SE, Mi
Posts: 2,342
Quote:
Originally Posted by DaReallyPoGigolo View Post

TORQUE = (m)(l^2/t^2) and POWER = (m)(l^2/t^3)

So yes, power is torque divided by time, but if you look at them, neither are by any means their own thing. They're both just the ba$tard children of mass, length, and time.

An excellent point. During that other thread I was thinking that at the end of the day... torque is still math. But I wasn't going to give bob 1/3rd of a "bat" to beat me up with.

But... "horsepower" is just so wrong. Had the opposition said "power" I'd have been in agreement and just let the terminology slide.

In america we follow so many "cow paths" it makes your head spin. Proof of this is the American mentality to not comprehend why we should embrace and switch to metric units. Our grandfathered in ways (aka cow paths) are self destructive and only serve to confuse the simple minds.

Excellent post!

regards,
Rich
Reply With Quote
  #4  
Old 03-05-2009
VW TANK's Avatar
Member
iTrader: (1)
 
Join Date: Feb 2008
Location: Ridgewood,NJ
Posts: 162
i think its a great post
Reply With Quote
  #5  
Old 03-05-2009
RF Veteran
 
Join Date: May 2005
Location: College Station, TX
Posts: 5,782
Great post indeed!

And horsepower is a unit of measure for power, so I think the distinction would have a minimal impact on the discussion, wouldn't it?
Reply With Quote
  #6  
Old 03-05-2009
Level I Supporter
 
Join Date: Aug 2006
Location: Durham, NC
Posts: 3,657
Great post!!!! Just one question, do you believe in Santa Claus?
Reply With Quote
  #7  
Old 03-05-2009
RF Veteran
 
Join Date: May 2005
Location: College Station, TX
Posts: 5,782
Reply With Quote
  #8  
Old 03-05-2009
zabeard's Avatar
who?
iTrader: (8)
 
Join Date: Nov 2004
Location: IN
Posts: 26,045
Quote:
Originally Posted by Gearhead61 View Post
Hey now dont give up his location!
Reply With Quote
  #9  
Old 03-05-2009
Level I Supporter
 
Join Date: Aug 2006
Location: Durham, NC
Posts: 3,657
Quote:
Originally Posted by wydopnthrtl View Post

But... "horsepower" is just so wrong. Had the opposition said "power" I'd have been in agreement and just let the terminology slide.

I Did, Rich.....my post #23:


Quote:
Originally Posted by wydopnthrtl
I personaly wish that "horsepower" was never conjured up. Its a term that has zero bearing on todays understanding of power. Yet we Americans hang onto it and try to justify one motor against another using a make believe and completely fictitous math equasion.

It only serves to confuse people. Santa clause is not real.. and neither is horsepower.


Take a look at torque curves between the two and you'll understand where each makes the meat of thier tq.



I guess Ford, and everybody else in the industry is WRONG!!!!

Rich, torque is a rotational force, power (HP) = WORK/TIME



And again in post #28:


But this pretty much sums it up for you:

"Torque is a measure of the ability of an engine to do work. It's a component of, but not the same as, the (horse) power of the engine, which is the rate at which work can be done."

Last edited by Takeda; 03-05-2009 at 08:33 AM.
Reply With Quote
  #10  
Old 03-05-2009
03bamaGT's Avatar
Member
 
Join Date: Aug 2006
Location: B'ham, AL
Posts: 1,752
I think Carol Shelby said it best...

Horsepower sells cars, torque wins races.

I don't feel like reading the whole because it is too early for math, but definitely will later. So my post might be a little OT.
Reply With Quote
  #11  
Old 03-05-2009
wydopnthrtl's Avatar
Member
iTrader: (2)
 
Join Date: Dec 2005
Location: SE, Mi
Posts: 2,342
Bob, Mike laid it all out. Your gonna think what you think based on your perceptions of science. I think what I think based on my understanding science, and then take stands because of things I can measure.

Your clearly stalking me. A repetitive behavior I might add... Stop it.

Regards, Rich
Reply With Quote
  #12  
Old 03-05-2009
Level I Supporter
 
Join Date: Aug 2006
Location: Durham, NC
Posts: 3,657
Quote:
Originally Posted by wydopnthrtl View Post
Bob, Mike laid it all out. Your gonna think what you think based on your perceptions of science. I think what I think based on my understanding science, and then take stands because of things I can measure.

Your clearly stalking me. A repetitive behavior I might add... Stop it.

Regards, Rich

Rich, face it, you screwed up!!!

And you were wrong AGAIN, by this statement, I used the term POWER several times:

Had the opposition said "power" I'd have been in agreement and just let the terminology slide

Last edited by Takeda; 03-05-2009 at 10:28 AM.
Reply With Quote
  #13  
Old 03-05-2009
Hanks Rangers's Avatar
Member
 
Join Date: Sep 2008
Location: Sandpoint, ID
Posts: 821
wow here we go again..... somebody just give it up
Reply With Quote
  #14  
Old 03-05-2009
God,Country,FORD's Avatar
Member
iTrader: (1)
 
Join Date: Nov 2007
Location: Red Oak, IA
Posts: 2,468
Mike, awsome post, eccept i feel like im back in math class.. lol..

and that was my post you were talking about.. and you just opened up a whole new thread for bob and rich to squabble in.. but atleast we will all get our humor for the day.. lol..
Reply With Quote
  #15  
Old 03-05-2009
God,Country,FORD's Avatar
Member
iTrader: (1)
 
Join Date: Nov 2007
Location: Red Oak, IA
Posts: 2,468
btw, your avatar makes me LOL.. i know. simple pleasures for simple minds.. but i laugh every time i see it like its the first:)
Reply With Quote
  #16  
Old 03-05-2009
Level I Supporter
 
Join Date: Aug 2006
Location: Durham, NC
Posts: 3,657
Thanks Mike!!! I would think that any M.E. would know, and understand, the material you posted.

"Finally, I'm going to address whether or not horsepower is real. Horsepower is just a unit of power. It is very real, but to say it's just a calculation isn't very correct."

Last edited by Takeda; 03-05-2009 at 11:26 AM.
Reply With Quote
  #17  
Old 03-05-2009
monkeysteeler12's Avatar
Member
 
Join Date: Nov 2008
Location: vienna va
Posts: 663
too much time on your hands... lol

jk! good wright up! this should be a sticky
Reply With Quote
  #18  
Old 03-05-2009
Urandaman's Avatar
Member
 
Join Date: Oct 2006
Location: wher ever uncle sam wants
Posts: 1,193
torque is a movie...
yal are dumb
Reply With Quote
  #19  
Old 03-05-2009
whippersnapper02's Avatar
RF Veteran
iTrader: (1)
 
Join Date: Sep 2006
Location: Earth, Milky Way Galaxy
Posts: 7,415
Quote:
Originally Posted by Urandaman View Post
torque is a movie...
yal are dumb
The funny thing is that the movies were about crotch rockets. Crotch rockets don't make that much torque.
Reply With Quote
  #20  
Old 03-05-2009
wydopnthrtl's Avatar
Member
iTrader: (2)
 
Join Date: Dec 2005
Location: SE, Mi
Posts: 2,342
Quote:
Originally Posted by Takeda View Post
"Finally, I'm going to address whether or not horsepower is real. Horsepower is just a unit of power. It is very real, but to say it's just a calculation isn't very correct."
I missed that in Mikes statement. I take back the compliment!


Horsepower is a math calc. and so is power.

And as of yet.. Mr Stalker has yet to post up a picture of a horsepower wrench. I again challenge him and anyone else to show me a physical thing that measures "horsepower". (horses can't be involved)

Go ahead. Prove me wrong. Show me.

This whole idea of horsepower is just stupid. The simple minds that try to claim a physicality of "horsepower" (without using an actual horse) are just ignorant of simple mathmatics.

And what's worse.. is that this whole term came from a marketting excersize!

There is no such thing as horsepower in an internal combution engine.

Prove me wrong and I'll gladly eat some crow. You can't use a horse.. and you can't use math to prove it. Show me!
Reply With Quote
  #21  
Old 03-05-2009
wydopnthrtl's Avatar
Member
iTrader: (2)
 
Join Date: Dec 2005
Location: SE, Mi
Posts: 2,342
Quote:
Originally Posted by fddriver02 View Post
The funny thing is that the movies were about crotch rockets. Crotch rockets don't make that much torque.
Power to weight ratio, gear ratios, and rates of acceleration are what make for good or poor acceleration.
Reply With Quote
  #22  
Old 03-05-2009
03bamaGT's Avatar
Member
 
Join Date: Aug 2006
Location: B'ham, AL
Posts: 1,752
Quote:
Originally Posted by wydopnthrtl View Post
I missed that in Mikes statement. I take back the compliment!


Horsepower is a math calc. and so is power.

And as of yet.. Mr Stalker has yet to post up a picture of a horsepower wrench. I again challenge him and anyone else to show me a physical thing that measures "horsepower". (horses can't be involved)

Go ahead. Prove me wrong. Show me.

This whole idea of horsepower is just stupid. The simple minds that try to claim a physicality of "horsepower" (without using an actual horse) are just ignorant of simple mathmatics.

And what's worse.. is that this whole term came from a marketting excersize!

There is no such thing as horsepower in an internal combution engine.

Prove me wrong and I'll gladly eat some crow. You can't use a horse.. and you can't use math to prove it. Show me!
I agree with you for the most part...HP formulated from the torque used to spin a Dyno.
Reply With Quote
  #23  
Old 03-05-2009
wydopnthrtl's Avatar
Member
iTrader: (2)
 
Join Date: Dec 2005
Location: SE, Mi
Posts: 2,342
Quote:
Originally Posted by 03bamaGT View Post
I agree with you for the most part...HP formulated from the torque used to spin a Dyno.
You know it very well could be the terminology that I'm using?

Torque is easily measured. Horsepower can't be measured because without a actual horse involved.. it's only a math calc. used to make dummies understand how much work can be done via a machine creating torque.

I really don't know how to say this in a more simple way?


And btw.. the only reason I keep posting is for those who are reading and trying to understand. I keep doing this in spite of the idiot stalker.
Reply With Quote
  #24  
Old 03-05-2009
whippersnapper02's Avatar
RF Veteran
iTrader: (1)
 
Join Date: Sep 2006
Location: Earth, Milky Way Galaxy
Posts: 7,415
I believe the term horsepower came from the early car days when people where switching from horse drawn carriages to cars. Where ever it came from I have always heard that horsepower is a calculation of torque and that horsepower is not real measurement of the power of an engine.
Reply With Quote
  #25  
Old 03-05-2009
03bamaGT's Avatar
Member
 
Join Date: Aug 2006
Location: B'ham, AL
Posts: 1,752
We will soon be going to kW anyways...
Reply With Quote
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Horsepower TV: E3 spark plugs add 5-7 horsepower dixie_boysles 4.0L OHV & SOHC V6 Tech 20 08-15-2009 09:28 PM
question about horsepower and torque texasbullseye89 General Technical & Electrical 15 11-27-2007 11:54 PM
simple...more horsepower! NinetyEight4.0L 4.0L OHV & SOHC V6 Tech 14 01-01-2007 09:45 PM
Ebay:Accelerator Horsepower Enhancer FMD General Ford Ranger Discussion 18 11-30-2005 03:22 PM
stock horsepower crawly1025 4.0L OHV & SOHC V6 Tech 9 10-09-2005 08:34 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -6. The time now is 02:36 AM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.