Cyber ITR

which is more important , big power or big torque ? and how do they related to each other ?
sorry if it sounds kinda a dumb question

Etylorcen

If you mean horsepower from power, it is derived from torque. HP = Torque* RPM/ 5252.

poison

what's more important is BOTH, you want as much out of both as you can.
In an engine, there is bore and stroke. (bore x stroke) x # of cyl = displacement (correct me if i am wrong).

Torque comes out of the Stroke, which is how much travel a Piston comes down and back up.

Horsepower comes from the Bore, which is how big the diameter (combustion camber), so when under compression, how much force it pushes down on the piston.

Stock@$$GSR

Is there other ways to change the stroke of the engine besides changing the crank?

Sonny

Nope!

Sonny

poison

yes connecting rods

SEFIxCivic

no that won't work.

ion_four

Questions:
Changing the rods would just change the compression, right?
HP (ignoring gearing) determines topspeed and torque determines how fast you get there, right?

Answers in the form of questions:
Still thinking: If HP=torque x rpm / 5252...I don't think the bore would have anything to do with determining the HP, since you could derive an equation for HP that only uses the stroke (as related to the torque).
It seems that experience on the street shows that torque is more important, as a non-vtec SOHC with a 55shot would be faster than a B16 swap in the same chassis. Though the HP are about equal...the SOHC would have gobs more torque and thus rape it.

Though, as a converse...I raced a e36 BMW 325i up a mountain this weekend and since it was pretty goddamned steep, I was topped out in fourth at about 98(really damn steep mountain, heh) and slowly pulling away from him...he had a fair bit more torque/weight, while I had more HP/weight...so, I schooled him, since we were already up and runnin fast before we started. From a stop on level ground he would have probably taken me...

long post, my bad.


[Modified by ion_four, 4:21 AM 5/16/2002]

noel

When you're told it depends it really does. The statement you as much as both as you can get is also true. If you are building a car that is gonna go 5000mph then you'll need lots of hp. Torque is really important for accelerating. If you want a car to go light to light I think you should worry more about torque.

As far as how much torque your engine produces I think it comes down to the displacement between the rods and the centerline of the piston. It's a moment arm (force x distance). Keep in mind that 1hp = 550lb ft/s. That really put into perspective how much power my engine produces. Kinda scary at times.

This help any? and of course correct me if I'm wrong.

Noel

Turdblow rex

which is more important hp or torque? the answer to this is simple, kinda. Hp is not measured by anything it is computed off of how much torque the engine makes. Because of this, hp and torque are allways the same at 5252 rpm. If you look at every dyno graph ever run you will see this, so what you need to realize is the point in rpm that the engine makes peak "power" determines wether you will have more torque or more hp. If the peak is over 5252 rpm you will have more hp than torque, in the case of a honda where this occurs at 7-8 grand you end up with alot of hp and no torque. if you look at the other end of the scale at a diesel engine that makes peak power at under 3000 rpm you end up with numbers like 225 hp and like 500 lbs torque. it is all in the math.

So which do you want? It doesnt matter, well kinda. power is power, a certian amount of power allows a certian amount of work to be done in a certian amount of time (accelerate a vehicle). this is where gearing comes into play, but that is a whole different discussion. as long as the transmission is geared "correctly" for the power curve of the engine it will go fast. For high rpm engines you need low geared tranies and short tires and for low rpm engines you need taller gears.

There is alot more to this but this gives you the jist of it

TheSwift1

perfect explanation...

Xerxes

"Horsepower sells cars. Torque wins races."

-Xerxes