Difference between Horsepower and Torque

[Spooled-up]

A friend of mine asked me what the difference was between torque and horsepower. Can anyone give me an idiot's version of the difference between the two? Can anyone give me the professor's version of the difference?



Thanks

 

[KatDiesel]

Read this : Torque and Horsepower Unveiled!

 

[Newf Limo]

Here is an attempt.

Torque gets you going, and horsepower keeps you going.



The sailors version of torque is not suitable for a family website, sorry



I believe torgue (as measured in lb/ft, expressed as foot pounds) is a measurement of work created by units in pounds of pressure applied across a lever that is one foot long, or something like that. Somebody will have a snazzy explanation of it. My physics knowledge is being eroded away by a lack of use.

I forgot how to explain horsepower. I think it has something to do with how big your picnic is and how many Clydesdales it takes to pull the appropriate amount of Budweiser to the location. It is all kinda' fuzzy. . .

 

[Papa Joe]

I'll volunteer as an idiot



Torque is a measure of rotational force. A torque wrench measures how many foot-pounds of torque you apply to, say cylinder heads. Or better yet, how many foot pounds at takes to turn a boat winch handle to pull a boat up onto a trailer. Not actually pull it up, but just start it to move.



Horsepower is a measure of the rate at which you can apply that force.



When you tighten a bolt and the wrench clicks - you stop and don't actually perform any work (except to apply the force to snap the torque wrench).



On the boat winch however, if you apply the necessary force to start the boat to move and continue to crank the winch - your'e working and applying horsepower. The faster you crank, the more horsepower. If you take your time, less horsepower.



550 foot-pounds force per second is a horsepower.



A torque converter (transmission) simply changes to rotation speed and varies the torque inversely while the horsepower remains unchanged (except for gear losses).



Sheesh, I'm through. Joe

 

[Max340]

Originally posted by DMKelley

A friend of mine asked me what the difference was between torque and horsepower. Can anyone give me an idiot's version of the difference between the two? Can anyone give me the professor's version of the difference?



Thanks

Well, Newf has it right. Torque gets ya going, and horsepower keeps ya going.



Torque is a rotational force. It can be measured in pounds per foot (force measured at the end of a foot long lever perpendicular to the axis of rotation).



To get to Horsepower mathematically, you must have revolutions per minute (RPM) This is because Hp is a measure of force over distance/time (revolution/minute)



T(ftlbs) x RPM

Hp= ----------------

5252



The idiots version?



Torque is what makes it so you should not grab the tire and attempt to stop it from spinning, and HP is what makes it so you should not attempt to catch the car by running after it.

 

[Skyjacked Ram]

I always thought horsepower is what gets you to 100mph and torque is what keeps you there. . is that right?

 

[HVAC]

What A Classic Question

"Torque is work"



Torque is what makes a heavy ram move, 6000 lbs for me.



"Horsepower is how fast the work can be done"



112 mph in the 1/4 mile in my case



You might have 600 horsepower but if you don't have any torque, you will struggle with large loads (think 2-cycle/no bottom end). Tractors have mucho torque and moderate horsepower, they can pull large loads slowly. A motorcycle can have 300 horsepower but it won't pull a plow a lick, no torque. A Ram with 300 hp and 650 torque does rather nicely with a 10,000 load, thank you mr. torque!



I love this topic!

 

[drawson]

As HVAC said Torque move weight and keeps it moving. Horsepower is torque at RPM.



I'll take torque over HP any time!!!!

 

[OO]

Torque is the force applied to your nuts by the EX. Horsepower is then measured after the torque has been applied

 

[Shovelhead]

Old racer's proverb. .



Horsepower wins Dyno wars..... Torque wins races.

 

[drawson]

Good link on HP

Here's a good link on Horse Power



http://www.howstuffworks.com/horsepower.htm

 

[RustyJC]

If you think of the linear version of torque, work = force x distance. If I lift 1 pound a vertical distance of 550 feet (regardless of how long it takes), I've done 550 lb-ft of work. Same thing applies to torque - if I pull a torque wrench a radial distance of 5 feet against a resistance of 110 lbs, I've done that same 550 lb-ft of work.



Horsepower is the rate at which work is done. If I lift that same 1 pound a vertical distance of 550 feet in 1 second, or if I pull that torque wrench 5 feet against a 110 lb resistance in 1 second, I'm doing work at the rate of 550 lb-ft/sec. It just so happens that 550 lb-ft/sec equals 1 horsepower.



Hope this helps!



Rusty

 

[JAK]

Torque is just a manipulation of horsepower. Aside from friction loss the power at the rear wheels is exactly equal to the power at the crankshaft. The torque is multiplied by the gear ratios and the speed is divided by the gear ratios, but the hp remains the same. If we put all of the above mentioned examples on a high efficiency hydrostatic transmission then the highest hp will always outperform the rest because we can operate the engine at it's peak hp continuously (at least until it melts down) and convert it to it's sub components (torque and speed) as needed to get the job done.

 

[Max340]

Originally posted by JAK

Torque is just a manipulation of horsepower.

Not really... ... HP is the "product" of torque and RPM. T and RPM can be manipulated. HP is merely the best way to express the power of torque and RPM combined.



[/i]Aside from friction loss the power at the rear wheels is exactly equal to the power at the crankshaft. The torque is multiplied by the gear ratios and the speed is divided by the gear ratios, but the hp remains the same. [/QUOTE]



Yup, but it does change if engine RPM goes up, because thats whats making the rest of the stuff go.



[/i]If we put all of the above mentioned examples on a high efficiency hydrostatic transmission then the highest hp will always outperform the rest because we can operate the engine at it's peak hp continuously (at least until it melts down) and convert it to it's sub components (torque and speed) as needed to get the job done. [/QUOTE]



Ok, thats true on paper. But lets ask the guys reading this... .



Would they want a 215hp/420ftlb Cummins, or a 235hp/320ftlb 360 gasser?

 

[RustyJC]

Originally posted by Max340





Ok, thats true on paper. But lets ask the guys reading this... .



Would they want a 215hp/420ftlb Cummins, or a 235hp/320ftlb 360 gasser?

Well, having just moved from a 300 BHP/450 lb-ft V-10 to a 245 BHP/505 lb-ft ETH, I feel qualified to respond. The V-10 makes more BHP, but the torque curve is all wrong for towing. With 3. 54 rear axle, the V-10 is only turning 2100 RPM in 3rd (OD locked out) at 60 MPH, our normal towing speed. The V-10 makes peak torque at 2800 RPM and peak BHP at 4000 RPM, so there just ain't much happening at 2100 RPM! When you hit a good grade pulling our 13,500 lb 5ver, it's 2nd gear/3600 RPM time with the V-10. In summary, to make the V-10 work, you have to rev the pi$$ out of it - that's not very relaxing over the long haul!



That's why we gave up BHP (at least in stock form - we'll see when I get the EZ and some other goodies installed) to get the ETH's 505 lb-ft of torque at 1600 RPM. With the 4. 10's, our Cummins is turning 2000 RPM at 60 MPH in 6th. Therefore, it's going to ride up the torque curve going up a grade since it's running above its torque peak - not like the V-10 that falls further off its torque curve as RPM's drop! The big rig guys call this diesel characteristic "torque rise", and it's a good thing!



Rusty

 

[Fireman]

idiots version

torque = low end power

Horse power = top end power



Fireman

 

[Steve M]

I'll probably get excused for this but, horsepower is how fast you get to the porcelain Powerstroke first thing in the morning. When you bend your connecting rod down to connect with the porcelain Powerstroke and your feet slide back, that's torque.

 

[JAK]

Not really... ... HP is the "product" of torque and RPM. T and RPM can be manipulated. HP is merely the bestway to express the power of torque and RPM combined.

Sorry about my poor choice of words. You are absolutely correct. And although the product is a specific manipulation, it is a much more proper way of expressing it.

Would they want a 215hp/420ftlb Cummins, or a 235hp/320ftlb 360 gasser?

I didn't mean to suggest that the higher hp was a better choice. But if you could match any engine speed with any ground speed, the higher hp will out work the lower hp. Torque curves wouldn't mean much if you operated the engine at 1 speed only. We can't do that because our transmissions have a finite number of ratios to select from. It isn't really the high torque of the diesel that makes it an excellent worker, but rather the shape of it's torque curve that gives us useable hp where we need it. Diesels actually have more hp in the cruising rpm range we typically run them in than a comparably powered gasser. Rusty pretty much nailed it with his explanation of "Torque Rise" Rarely do we operate any engine at its rated hp output because with a 5 speed that happens only at 5 distinct ground speeds. In the lower gears that will probably result in wheel spin and in the upper gears we would be speeding (100 mph? - I know some of us do that but I'm not one). At any other speed the shape of the torque curve determines what kind of power you will have. Sorry this was so long. I haven't taught physics in 6 years and even then I was never very good at explaining it thoroughly the first time.

 

[WadePatton]

great subject--one more simple version

Torque is power.

Horsepower is power/time.



What? Too simple?



Okay another stab.

Torque is a measure of power-absolute.

Horsepower is how quickly power can be applied.



or

Torque moves it, HP moves it quickly.



YOU NEED BOTH! I like mine in the ratio established by the 5. 9 Cummins-- a little more than twice as much torque as HP.



2. 33:1 in my case.

 

[jrobinson2]

Simple answer

Horsepower is the rate (how fast) your engine is making torque.

Jared