torque and horse power

**rfrogger120** · 10-04-2007, 06:49 PM

Would someone be able to explain to me what is the differance between torque and horse power?

**davekc** · 10-04-2007, 06:49 PM

Horsepower is the rating of power that a engine produces at certain RPM's.
In layman's terms, torque is a conversion of that power at the drive wheels. Often measured in so many foot pounds.

http://en.wikipedia.org/wiki/Torque#Explanation

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**rfrogger120** · 10-04-2007, 07:00 PM

Davekc, If a truck is slowing down while going up hill, what is it lacking torque, horse power or both?

**LDB** · 10-04-2007, 07:10 PM

My understanding is that torque is what creates movement and horsepower is what sustains it. You have to have plenty of torque to get moving from a stop. You have to have sufficient horsepower to maintain momentum once you are up to speed. If you are slowing down on hills it is a lack of horsepower moreso than torque, although both are required. I'm just an old country boy, not an engineer, so I could have it all confuzzled but I believe that's correct.

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**RichM** · 10-04-2007, 07:25 PM

Leo is correct,torgue gets you moving and HP keeps you moving.

**davekc** · 10-04-2007, 07:30 PM

I second that. Leo's explanation is correct.
If you are slowing down, it could be low horsepower and or, improper gearing that is reducing the torque and transfer of horsepower in order to sustain a certain speed.
A Hino comes to mind with 260 horses and 585 pounds on the torque.
That combo is a sign of a slow hill climb. Add some weight, and you go much slower, or backwards.

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**x06col** · 10-04-2007, 08:16 PM

Also, it can be caused by not "driving" the truck. ie If you have a lower HP/TQ truck, you can"t just set the cruise and wait till it runs outa breath and "then" change gears. You need to keep your "little" truck in it's RPM range for max HP/TQ. So.... drive it an don't let it run outa breath, if, thats your problem.

**arkjarhead** · 10-05-2007, 01:12 AM

I heard that col. they just ain't windin up thier rubberband tight enough.

**RLENT** · 10-05-2007, 11:22 AM

Another thing to be aware of is that the peak in the torque curve (over the rpm range) is usually at a much lower point than the peak of the horsepower curve.

**dhalltoyo** · 10-05-2007, 11:43 AM

Ditto with both answers from Leo and the x06col.

One factor to also consider is the multiplication factor.

The RPM's at the tranny's tailpiece and the ring and pinion ratio's in the final drive.

If you got enough gearing (i.e. multiplication factor), there is a compensation factor for reduced horsepower. And, when you are not climbing hills, the smaller HP engine does quite well with fuel economy.

If you are going to be hauling coal through the hills of West Virginia, by all means, buy yourself a 700hp Cat Engine and get 4 miles per gallon. Of course, that is not our business. Is it?

PS. Fuel savings has to be a huge consideration when one is looking to purchase a truck.

**DocRushing** · 10-06-2007, 08:53 PM

This is somewhat oversimplified, but it makes a basic point:
The horsepower rating of an engine is a measure of its capacity to accelerate, whereas the torque rating is a measure of its capacity to pull hills (and otherwise move a mass).
The higher the horsepower, the more quickly can an engine accelerate.
The higher the torque rating, the more easily can the engine maintain a particular speed on a particular upgrade.
If a truck loses speed on an upgrade at full throttle -- assuming that the driver has selected the right gear -- then the engine has reached its max torque capability.
That's why the driver will need to downshift when the engine reaches the lower end of its r.p.m. operating range -- the left end of the green sector on the tachometer -- so that the engine can maintain road speed in the proper gear with the engine in the green range on the tachometer.
Best wishes to all,
Doc.
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(Chauffeur's license or CDL since 1963.)

**unorthodoxneon** · 10-07-2007, 09:14 PM

Torque is a turning of something. If your turn a wrench on a bolt you are exerting torque. The engine turning the tranny and wheels is exerting torque. Horsepower is what keeps you going or energy. It would be like racing in track. The person with the most energy would go fastest, even against someone who had more muscle (aka torque) He might be able to power his way off the line but wouldnt be able to run as fast as someone with more energy.

Horsepower is what you would need to make it up that hill. Torque is important as well but usually with horsepower comes torque and vice versa.