horsepower is a useless number!!
everyone who allready knows this, you're allowed to laugh but im guessing that alott of people don't know this yet.

take you're engine's torque, mulitiply it by the rpm at which it is reached and divide by 5250. That is your horsepower at that rpm. I feel STOOPID! it simplifies a few aspects of things. It's all airflow fellas, and if you read how the term horsepower was created you'll wonder why we're still using that phrase at all, how dumb!! check it out on google, not a monumental thing but really i feel so retarded right now for not knowing this all along, i thought you could increase hp without torque but its just a multiplier!!! RETARD wondered why all the hp graphs crossed torque at 5250 rpm.

 

It's not useless. It's just a little misunderstood.

And yes, you can increase horsepower without increasing torque. You can make the same torque but at a higher RPM and you'll be increasing horsepower. Then you need to gear it and shift it so you are actually using that higher RPM range or, you're right, you're not going to go any quicker or faster.

 

It's not useless at all. But it would be helpful in the future if you DIDN'T post an attention grabbing look-at-me thread topic that mixes fact (hp = ftlbtorque*rpm/5252) with fiction (hp = useless number).

 

typically we term an engines power in hp, since the amount of hp is affected by rpm as well as torque it seems like a far less important number to pay attention to, an engine that can rev higher would supposedly have more power because if the torque curve is perfectly flat the hp would rise higher and higher due to an increase in rpms. in reality though it is just an engine that can rev higher,, soooo whats the deal?
perhaps useless was a little extreme and i found it humorous that i didnt know of this all this time so i apologize. whats hp good for measuring? its an artificial number that really doesnt relate to whats goin on in the motor, torque can be equated to air flow but hp rises even after torque falls, it's beyond me.

 

umm, dude.
any ONE number, is a useless number.

it takes more then one number, to tell you anything useful about an engine.

 

Power tells you something about the rate of work that can be done.

Torque doesn't.

THAT's why power is important.


Because the one with the higher output power can do the same work (force*distance) is less time for 2 engines with the same peak torque output.


Yes it does. You just don't understand it.

The torque curve rises, then falls, with rpm because the engine doesn't fill the cylinders evenly versus rpm. That's the effect of the volumetric efficiency of the engine, and it depends on the intake/exhaust/cam.

The reason why the hp curve can still rise even if the torque is falling is because the rate of power increase is greater than the rate of decrease in VE. When the two rates exactly balance, then power won't rise any more. After that, the rate of VE loss is greater than the increase from rpm, so power falls and you just went past the hp peak.

The torque curve tells you the work that can be done at each rpm; the hp curve tells you how quickly you can do the work at each rpm. Both curves have use and both are meaningful even if you didn't know why.

 

the rate at which you can do the work?? so 170 ft lbs of torque at 3000 rpm vs 2000 is better? im sorry but im still not grasping this, to come up with hp you just run torque through the equation, i get that hp will fall after the torque does because rpm is still increasing and when torque decrease is greater then rpm increase the hp peaks and then falls, thats just how the equation works. But why can't you get the very same info from torque? i think basically what you are saying is that hp shows you the VALUE of the torque at each rpm. in other words the 170 ft lbs you have at 2500 rpm isnt worth as much acceleration as the 150 ft lbs you have at 3500 rpm. am i correct??

 

work = force*distance

in SI units it would be measured in Newton*meter
in SAE (English) units it is measured in lbs*foot

The above works whether we're talking about dragging a stone block a distance on the ground, or whether we're talking about a load placed on an engine, where the engine output (the flywheel) rotates. For an engine the work ability at each rpm is described as the torque output of the engine.

power is the rate of work, or

power = force*distance/time

Need to move a 10 lb block a distance of 10 feet? That would be 100 ftlbs of work. If I gave you the choice between doing the job in 30 seconds, or a half second, you would need two different power outputs to get the job done: 3.33 ftlbs/sec or 200 ftlbs/sec.

A 350 with a very mild cam but very good VE, like the TBI Vortec engine, was rated at 230 fwhp and 330 ftlbs. Drop a LT4 HOT cam into the same engine and the peak torque will still be around 330 ftlbs, but the hp jumps to 350+. The one with the HOT cam has a much higher power output so it can do the same work (quarter mile of travel) is a MUCH shorter time period than the stock cammed engine. The work is the same (travel 1/4 mile) but the power needed to do it quickly is a lot higher.

The units of ftlb/sec can be converted into hp (or into Watts) but I'll skip that. The point is that one job is very easy, the other is not. So it's not enough to tell you the job, I need to also tell you how much time you have to get it done.

In the case of the engine, it's not enough to say that hp doesn't matter (remember: you said it was a useless number at the top of this thread), because it does matter. I just gave you a simple example why. To go deeper into the subject, you need to take an intro course in physics.

From the viewpoint of acceleration performance, yes. But if the car is a grocery-getter, maybe not.

Yes, you and anyone else can do that .... without understanding what it means.

You can always get one from the other, because of the precise relationship in the math (physics).

170*2500/5252 = 81 hp
150*3500/5252 = 100 hp

So one is obviously more powerful than the other. The acceleration question is harder to answer because you didn't give enough information about the gearing and road speeds. If the two engines were in identical cars, differing only in the engines, then one will be going faster than the other (because of the rpms involved), or they might be in different gears at similar or different speeds.

Don't get hung up on your example. Focus on this instead:

work = force*distance

power = rate of work = work/time

It's fair to say that if you had the full torque vs rpm curve, that you could also calculate the hp vs rpm curve... so there is no need to have both (if you know how to do the math). That doesn't mean hp is a useless number, for the reasons I gave above. In that case, it has nothing to do with the actual curves but rather what the peak output values are for torque and power, and the rpms where they occur. The hp tells you something about how fast the car could go, and the torque tells something about the peak force at the road to accelerate the car.

 

The important thing is that you actively pursue greater knowledge of how things work... keept it up and you'll learn more!

 

Sometimes two letters and a number work well enough though...

 

RPOs FTW!

 

STOCK LO3/L05, ROL.