torque or horsepower

[tschultz]

I have had this debate many times and while torque is what you feel and what moves the car...HP is what makes it useful because it represents torque x rpm. Rpm is critical here because it is the number of revolutions over time. Torque by itself is meaningless when it comes to how powerful an engine is. In contrast, higher rpm's can get more power to the wheels through shorter gearing. Now the debate goes on and on because people who are pro-torque are actually talking about HP. There's a reason we use it to rate engines.

Look at our cars..

Eta engine has 170 ft/lbs torque but only 121hp @4200 rpms 2.79 or 2.93 final drive.
325I engine has 165ft/lbs torque but 168hp @5800 rpms 3.73 final drive.

We know the 325i is faster than the eta because the 325I is getting more power to the wheels. It's area under the curve is actually greater than the eta even though it has more torque because the eta cannot rev past 5000 rpm while the 325I still has a couple thousand rpm's to play with. In layman's terms the eta is fast off the line but it can't sustain it over time. If you put a 3.73 in the eta, it will be faster upto a point but it will run out of rpm's faster and it's top speed will be limited.

This is why 1.6 liter Honda engines can be fast in a sprint. They can make good HP and put it down through very short gearing. Cars like the s2000, e30 m3, itr all have similar traits...high hp/rpms from small displacement. This is the basis for road race engines. Few people like peaky cars on the street though so for stoplight racing most prefer to have more low end torque.

Good post.

[digger]

because you can't!

you havent made a single argument that was valid for why engine torque is more useful than engine hp when looking at performance potential. when you do that come back otherwise GTFO of this thread

[digger]

good post.

+1

[QUKBMER]

I have always liked this video. You dont have to have alot of HP to go fast. http://www.streetfire.net/video/hors...hit_179480.htm

[digger]

I have always liked this video. You dont have to have alot of HP to go fast. http://www.streetfire.net/video/hors...hit_179480.htm

its usually and cheape to remove 20% weight than gain 20% hp and the braking and handling would also benefit so best BFYB

[digger]

Here's my last dyno with a 3.73 gear 235/60/15 tire and 265 gear box.

now i see your graph you make alot of midrange power such that the power curve is flat. so the hp is always there on tap. if you had a more linear increasing type curve such as a centrifugall blower with less area under the curve but higher peak you would need alot of closely spaced gears to be quicker if at all. graph below "only" shows 520hp but you get the idea about area under the curve and hp that is available in midrange being lower. yours has 500hp for 2500 band of rpms the other for 600rpm



so your midrange torque helps but it is the power that results from this that helps (more midrange torque = more mid range power). if you had the same midrange torque but topend torque fell off quickly and hp peaked alot lower you would be quite a bit slower

[digger]

the reason why power and energy are useful concepts is as follows

to go up a hill in a requires a change of potential energy as you do work against gravity.

the faster you want to go up the hill means you do it in less time then the more power you need because work/time is POWER

also

if you want to change speed from say 60mph to 120mph this requires a change in kinetic energy

the faster you want to do this i.e. in less time the more power you need because work/time is POWER


torque without rpm is useless for acceleration and motion thats why anyone that works with things moving trys to maximise power that is available as this inhenrently maximise forces the provide propulsion