Torque vs. Horsepower

[240Dave]

Torque vs Horsepower

The basic premise is “Torque is how much power your engine makes while horsepower is how often your engine can make that power.”
Most of what I know on the subject I learned from howstuffworks.com

So, obviously you want a lot of both when building a fast car, but how much is too much? Maybe there is no such thing as too much, only compromises between the two…

You have a 1.6L engine in an 1800LB (fictional) vehicle that makes 70tq at its peak and say 200hp up at 10,000rpm
Compare that to a 10L engine in a 10,000LB (fictional) vehicle making 2000tq at its peak and 200hp at 3,500rpm.

Slap that big engine in the light car and it should really haul right? Well…maybe not, else more people would do it, no?

Ok, so torque is for heavy cars and horsepower is for light cars right?
Hrm…not good enough for me.

Rather than make this post any longer describing what I think I know, my guesses and likely off theory…why don’t you all explain to me why you would sacrifice torque for horsepower(revs) or the other way around.


Dave-
Who is desperately trying to shake things up a bit...no pun intended ;)

[hookedup240]

Been discussed already.

http://www.zilvia.net/f/showthread.php?s=&threadid=35788&highlight=torque+vs+horsepower

I am under the impression that you need torque to get moving especially in a bigger car. But overall high hp #'s get you going fast. I have this assumption from being in my Friends 94 mustang GT vert. Stock 215hp 285 torque, and it weights 3800pounds. I assume that without all this torque this car would go nowhere. I have driven this car many times, he has some basic bolt ons done to it and he ran a 14.8. Its fun to drive because its a lot faster than my car. But its only fun to drive around town with all that torque, and runs out of steam at like 5400.

Overall i think that it all depends on the car, and what you plan on doing with it.

[240Stilo]

I don't think Dave's idea was discussed in that thread. As long as you can put all that power to the floor and get the car to move instead of just burning rubber then your hypothetical super engine light car should haul ass like no other.


EDIT!: If you could make a go-cart that's powered by a KA....MAAAN! That would be a pretty fast ride. $300 for KA and who knows how much for the rest of the project. Just a crazy idea though.:D

[Jeff240sx]

Whats with this torque is to get going and horsepower is to get top speed ****? Who told you that?
Horsepower is a function of torque. HP = Torque * RPM / 5252. HP is simply a made-up number, that can't be measured. Torque is what dynos rely on, and why when you dyno, the computer needs to know that you're in a 1:1 gear ratio, otherwise you'll have higher RPM at either the engine or tires, and throw off the reading.
10,000 hp at 10,000 rpm means you only need 5252 ft/lbs. 10,000 hp at 20,000 rpm only needs 2626 ft/lbs of torque. On the other end of the spectrum, 10,000hp at a cruise-liner 2000 rpms needs 26,260. See? This is a completely related function, and you won't have horsepower without torque, and your car won't move without torque. And dynos don't read horsepower, they calculate it from torque. And all rotating force is measured in torque, Length * (cosx)Force.
So, as you can see, horsepower has nothing to do with top speed, or how often you can accelerate, or any other miserable comparisons.
-Jeff

[DuffMan]

Not all dynos calculate torque and derive HP. Only brake dynos work like that.

Dynos that use a free rolling drum measure the acceleration of the drum to get HP. Don't need to input your tire sizes or final gear ratio to use these. Then torque is derived from the HP numbers.

[240 2NR]

READ THIS!!!! (http://vettenet.org/torquehp.html)

[RedlineRacer]

Not trying to steal the thread. But, I gotta ask this, becuase a friend of mine (a honda driver) and I always get in an arguement about corrected dyno hp. Isn't corrected dyno hp effected by the humidity and tempurature? He will argue with me all day that it is the weight. This is his analogy:

"If you take a B18 out of a Integra and drop it in an accord, it will dyno with lower hp because the accord weighs more."

I try to tell him that the calculation for hp has nothing to do with weight, but he is so hard headed. Which one is right? I see that the integra will be faster with the b18 because it is lighter and will go faster, but have the same hp (granted it has the same drivetrain).

[Andy5]

b18 into an accord is stupid :). but i know thats not ur question. The motor should dyno the same into anycar because the motor is a motor its not changed. I think ur friend is hard headed :rolleyes: