Torque and Horsepower

[melicha82]

Here is a question that I never really don't know the answer to. What is torque and horsepower? How are they related and how are they different? and how does each affect a car? I have a slight idea what torque is but all the rest I don't know. Any help on this would be great...websites etc. Thanks

 

[APEXistud]

Well, this might help a bit.....Torque=acceleration and that's all I'm willing to help you out with. I would explain more, but I lack the lingo to help explain it in detail. Sorry man

 

[njaremka]

horse power = torque x rpm / 5252

that is how they are related. www.howstuffworks.com should have something to explain it better than any one here could.

 

[trobbins]

Here is another site http://www.revsearch.com/dynamometer/torque_vs_horsepower.html

But njaremka is right. Horsepower is calculated using RPM and torque.

If you dig into the formula HP = torque * RPM/5252 you will realize that at 5252RPM torque = HP.

Then anything above 5252 RPM, HP > torque and below 5252 RPM torque < HP. This explains the difference between a diesel truck and a honda civic. A diesel truck engine only runs at 1500 RPM or so, but it makes a ton of torque but not as much HP. A honda civic runs 8000 rpm and makes more HP but not a lot of torque. And the extreme of this is a motorcycle engine that turns 15000 RPM and creates a good amount of HP but hardly any torque.

So really, torque is probably a prefered number because on most high rpm engines you need to rev the hell out of them to get any power.

Hope this helps.

Tim

 

[big_ben]

Sorry, but a turbo diesel truck puts out over 1000 hp. I'm not sure if I misunderstood you or not when you said a diesel truck puts out lots of torque but little hp?

 

[trobbins]

From http://www.kenworth.com/6400_wor_mor.asp?file=790

Power comes from a Cat C-12 engine 395 h.p. at 2,100 r.p.m. The torque is 1,450 pounds at 1,200 r.p.m. The torque provides climbing power no matter what Im pulling .

395HP but 1450 lbs torque...

I am willing to bet 2100 RPM is very close to max engine speed.

These engines will have relitivly low HP compared to the torque.

If the engine you speak of makes 1000HP, it probably makes at least double that of torque.

Tim

 

[big_ben]

I stand corrected. I just remember a neighbor of mine when I was in high school was a trucker and owned his own truck. He had twin turbos and he said it had over 1500 hp. That's insane!

 

[JcsMP3]

Simplest way of explaining it;

Torque is the force that is used to get the wheel to turn.... used for acceleration.... (that is what makes burn out easy for a higher torquing (spelling??) engine)

HP is what is used to keep the wheel turning at that speed....

Go up a hill racing a Honda Si.. torque is in the range of 112 or something... you will see your torque work and whip his ass.

Jc