Converting Torque To horse power

[dragrcr]

this is realy a stupid idea, no offense, but there are SOOO many factors that determine a engins torque curve that a statement like this cannot be taken seriously, for example, there are small RC engines that make CRAZY HP numbers simply because of the fact that they rev at 50,000 + RPM. HP is simply the speed at wich a motor makes torque...

 

[hoss]

I thought all you had to do to convert HP to torque was to put down the 066 and pick up the 076.

 

[edisto]

this is realy a stupid idea, no offense, but there are SOOO many factors that determine a engins torque curve that a statement like this cannot be taken seriously, for example, there are small RC engines that make CRAZY HP numbers simply because of the fact that they rev at 50,000 + RPM. HP is simply the speed at wich a motor makes torque...

The idea is to get a ballpark for an engine. There is a lot of noise around the line, but there is a monotonic nondecreasing relationship between displacement and cc within a certain "class" of engines. There certainly are a lot of variables, but at the end of the day, bigger is better.

 

[hoss]

but at the end of the day, bigger is better.[/QUOTE]

I don't know that I need to hear anymore now.

 

[Under_Pressure]

The Horsepower = (5252 X torque) / RPM version also shows that horsepower is just a function of torque and RPM which kind of throws a spanner into the gears of all those long torque versus horsepower threads that turn up on bike and car forums every three weeks along with the oil threads.

Another neat thing about that formula is it shows that HP = torque at 5252 RPM and nowhere else. Torque must be greater than HP below 5252 RPM and HP must be greater than torque above 5252 RPM. So there are two and only two ways to increase power- build the engine to make more torque and/or build it to scream like heck. Both will get you to the same place- 700 hp is 700 hp whether it is a 2L Formula 1 engine or a 20L diesel. With the correct gearing the F1 engine will pull 100k lbs up a hill and the diesel will go 220 mph. But these examples show that building a lot of torque (reliably) in general will require relatively large, heavy components. Chainsaws are a perfect example of this- they use comparatively tiny engines that develop a bunch of power by winding to the moon. From a pure performance standpoint, larger, slower, "torquier" engines may be preferable, but in terms of the overall package, small high revving designs have won out.

 

[spacemule]

Did he specify whether this was for 2-strokes? It's a horrible underestimate for chainsaws, that gets worse as displacement increases.

I pulled some numbers off of Mike Acres site. The relationship between HP and displacement is non-linear, so I transformed displacement by squaring it.

The dots are the raw data points, the broken line is the displacement divided by 29, and the solid line I generated using a simple least-squares linear regression, which resulted in:

HP = 0.000536 * displacement^2 + 1.997

You've got too much time on your hands dude.

 

[demographic]

Another neat thing about that formula is it shows that HP = torque at 5252 RPM and nowhere else. Torque must be greater than HP below 5252 RPM and HP must be greater than torque above 5252 RPM. So there are two and only two ways to increase power- build the engine to make more torque and/or build it to scream like heck. Both will get you to the same place- 700 hp is 700 hp whether it is a 2L Formula 1 engine or a 20L diesel. With the correct gearing the F1 engine will pull 100k lbs up a hill and the diesel will go 220 mph. But these examples show that building a lot of torque (reliably) in general will require relatively large, heavy components. Chainsaws are a perfect example of this- they use comparatively tiny engines that develop a bunch of power by winding to the moon. From a pure performance standpoint, larger, slower, "torquier" engines may be preferable, but in terms of the overall package, small high revving designs have won out.

Pretty much covers it.

 

[edisto]

You've got too much time on your hands dude.

Some people like to play with numbers, some people like to troll. To each their own.

 

[EngineerDude]

To derive horsepower from torque you would use this formula.
Horsepower = (5252 X torque) / RPM

Actually, HP = (torque X RPM) / 5252

 

[FATGUY]

Actually, HP = (torque X RPM) / 5252

I stand corrected, I mistyped the equation, my apologies.

 

[edisto]

I stand corrected, I mistyped the equation, my apologies.

Maybe this will help: