I like it. It's true.

 

Maybe this will help with the original question about "power" ...

The more torque you have, the faster the car will accelerate to its top speed.

The top speed is determined by horsepower (all else being equal).

So, take the Z06 versus the "stock" C5. While the Z06 has more HP, it actually has a higher final gear ratio, so the top speed of a Z06 is LESS than a stock C5. However, a Z06 will cover the quarter mile faster than a stock C5. Which is more "powerful" ???

Depends on what you're looking for ... speed or acceleration.

Given that the top speed of any of our cars is higher than we can use almost anywhere, most people would be looking to increase torque as the major goal.

HTH

 

horse power determines how fast you go
torque determines how fast you get there.

 

Ahhhh. If there were a Mr. Horsepower, he would be turning over in his grave right about now.
Nobody has posted a correct answer for the difference between hp and torque yet.

If you really want to know the difference. Spend the time and read this article. You will be glad you did.


http://www.ls2.com/boggs/torques/handt.htm

 

Brother,,,,,that says it all!

I've never seen it in that light!



BC

 

wow, back to physics class. good article

 

You beat me to the article.

I've read a few articles on HP vs. Torque, and that article is the best one I've read to date. Clear, consise and explained in 'layman' terms.

 

Ok. It is an excellent article. Thank you. Now explain where I was wrong? It described everything I said including the same formula that I posted.

 

(Horse)power is what wins races. Period.

The best way I can put this is:

I can make 250 ft*lb of torque on a bolt with my arms. But somehow, I can't connect my arms to a set of pedals and make a honda go faster than an engine which makes 110 ft*lb of torque. The difference is the engine makes a lot more power than I can, and the reason for this is power takes into account velocity, or in the rotational analog, RPM.

Assuming you can hook up, it is the integral of power*dt, (i.e. average power * time) which matters... which means a nicely shaped power curve is what wins races.

The reason for the torque urban legend that goes around is that when an engine has a large maximum torque number, it usually has a nicely shaped power curve. That, and it usually makes most of its power at low rpm so when people are tooling around town, they're closer to the engine's maximum power without a downshift.

Power is the scalar F*v where F is a force vector and v is a velocity vector; another way to look at it is P=dE/dt, i.e. how fast you can add energy to something. Consider: kinetic energy is related to speed via T=m/2*v^2 (I've always used the non-bold T to mean kinetic energy). So the bigger the speed, the bigger the kinetic energy. If you look at that, you'll notice the faster you can give something energy, the faster it gets to a certain speed... but energy is power * time. If you get to a speed faster, your average speed is higher, which means you're in front... and this is done by having a bigger power*time than your competitor As said by other posters, horsepower is given as |Torque|(ft*lb)*RPM/5252. Another thing about this is it takes into account your rotational velocity and therefore it also takes into account any gear multplication scheme you use.

Torque is defined as the vector product rxF; it is the rotational analog of force. Note: there is -no- mention of RPM (or velocity here); when someone talks about 'low end torque' what they are actually talking about is low end power, because the words 'low end' imply an rpm or speed...and when you consider speed, you are, by definition, talking about power.

 

Come Again....this time in ENGLISH. J/K!

 

Re: the original post... a couple examples...

Some mods will make more 'torque' because they add power at lower rpm as opposed to high rpm. e.g. a cam with a large duration will tend to make more power at higher rpm because it exploits the effects of a column of air moving rapidly to stuff more air in an engine. Basically, the valves will open much sooner and close much later then they 'should' and they count on a rapidly moving column of gas to stuff more air in / suck more gas out while they're open even though the piston will still be moving up when the intake valve opens....

Something like long intake and exhaust runners tend to move the power curve to a lower rpm because by their shape, they produce a long moving column of air which will stuff air in / suck it out very well at a low rpm, but by the nature of increased surface area (longer and narrower) there is more friction which becomes more important at high rpm/high power levels.

Changing the rod/stroke ratio affects the shape of the power curve because piston accelerations at a given rpm near tdc and bdc are changed.

and so on.

 

Does it not also depend on the inteded use?

Drag racing - 1320' under 11 sec. vs Road racing, 2500-redline, 4-6 times every 1:30 for 20 to 45 min at a time?

 

Just what I was going to post. you can find it here as well.

http://vettenet.org/torquehp.html