Torque vs. Horsepower

[seanish4042]

This question has long plagued me. I know what the difference between torque and horsepower are...but how do they affect performance? I know from simple physics that torque is the rotational force put on the wheels by the crankshaft. And I know horsepower has to do with pulling or some shit. But what really makes a car perform? Say hypothetically the 30vq had 160hp (instead of 190) but still had 205 lb ft. of torque....would it run the same numbers? Or is there some ratio of torque to horsepower that affects performance? Any response is appreciated, and Im sure there will be plenty.

[Pick]

In all actuality, torque is more important than HP in acceleration. But maybe some of our more knowledgable members could enlighten us. I know the difference, but some probably know a little more.

[thrasher]

Like you said, torque is the actual force produced at the crankshaft...horsepower is simply a number derived from an equation.


Torque * RPM
___________ = HP

5252


So torque is what actually throws you back in your seat. Where HP becomes meaningful is in the upper RPM range, because it gives us an idea of how long the Torque will pull through any given gear. As RPM's rise, HP rises dramatically until well after the torque peak.

For example, that Max with 160 HP will throw you back in your seat exactly as hard as the 190 HP version...however, the 190 HP version will pull for LONGER in each gear, thus giving the 190 HP version the advantage.

The most important thing to keep in mind is this:
Torque determines how hard you are pushed back in your seat.
HP determines how LONG one will stay thrown back in the seat. The longer, the better. Everyone wonders why honda's are so fast with so little HP. Well, they spin to very high RPM's, and thus pull for longer in each gear than comparable cars with more Torque.

[NSX]

Originally posted by thrasher
Like you said, torque is the actual force produced at the crankshaft...horsepower is simply a number derived from an equation.


Torque * RPM
___________ = HP

5252

Then how do you come about the figures for MAX torque & power when they peak @ different revs?

[thrasher]

Originally posted by NSX


Then how do you come about the figures for MAX torque & power when they peak @ different revs?

because the torque doesn't just simply die at one point...if the RPM's are climbing faster than torque is falling, HP will keep increasing. that's why peak HP always comes later in the power band, because TQ has to be RAPIDLY decreasing for it to counteract the rising RPM's

[seanish4042]

thrasher...thanks a boatload, u know ur shit

[thrasher]

no prob dude

[biggunner]

i think of it in classical physics terms.

Torque is angular force. Usually its calculated by the dot product of Force and the distance from the fulcrum or centre of rotation. But since the engine is rotating, the angle of applicatication is constantly changing and combustion forces aren't always the easiest to , its not calculated but measured using a dynometer.

Energy, a term usually ingored in this analysis, is the product of angular force and angular distance, hence the torque X RPMs term. A flat torque curve will yield an increasing energy curve. However internal cumbustion is not perfect and lots of energy is lost. So who cares about that.

HP is a power term. The rate of change of energy. A.K.A., the first time derivitive of energy. Do the math and you get a HP curve. 1/5252 is a constant that converts units and takes into account time.

[bigb1876]

how about this- (a lesson from autoshop) torque gets you moving, horsepower keeps you going!!!

[bk2kmax]

Originally Posted by bigb1876

how about this- (a lesson from autoshop) torque gets you moving, horsepower keeps you going!!!

To make it more simplistic, just twist open a bottle cap, that motion that you are using is the torque.

Go to www.howstuffworks.com and get an even more definitive answer.