Torque and Horsepower!

[John Wilson]

http://impulsengine.com/performance/moreav.shtml

[John Wilson]

P. S. I've away's said the V6 sould have had more torque....same HP but 280 ft lbs of torque. JW

[John Wilson]

Have you ever looked at the specs of an engine in a magazine and seen something like "this engine makes 300 pound-feet of torque at 4,000 RPM," and wondered how much power that was? How much horsepower are we talking about here? You can calculate how many foot-pounds of horsepower this engine produces using a common equation:

(Torque x Engine speed) / 5,252 = Horsepower
The engine that makes 300 pound-feet of torque at 4,000 RPM produces [(300 x 4,000) / 5,252] 228 horsepower at 4,000 RPM. But where does the number 5,252 come from?

To get from pound-feet of torque to horsepower, you need to go through a few conversions. The number 5,252 is the result of lumping several different conversion factors together into one number.

First, 1 horsepower is defined as 550 foot-pounds per second (read How Horsepower Works to find out how they got that number). The units of torque are pound-feet. So to get from torque to horsepower, you need the "per second" term. You get that by multiplying the torque by the engine speed.

But engine speed is normally referred to in revolutions per minute (RPM). Since we want a "per second," we need to convert RPMs to "something per second." The seconds are easy -- we just divide by 60 to get from minutes to seconds. Now what we need is a dimensionless unit for revolutions: a radian. A radian is actually a ratio of the length of an arc divided by the length of a radius, so the units of length cancel out and you're left with a dimensionless measure.

You can think of a revolution as a measurement of an angle. One revolution is 360 degrees of a circle. Since the circumference of a circle is (2 x pi x radius), there are 2-pi radians in a revolution. To convert revolutions per minute to radians per second, you multiply RPM by (2-pi/60), which equals 0.10472 radians per second. This gives us the "per second" we need to calculate horsepower.

Let's put this all together. We need to get to horsepower, which is 550 foot-pounds per second, using torque (pound-feet) and engine speed (RPM). If we divide the 550 foot-pounds by the 0.10472 radians per second (engine speed), we get 550/0.10472, which equals 5,252.

So if you multiply torque (in pound-feet) by engine speed (in RPM) and divide the product by 5,252, RPM is converted to "radians per second" and you can get from torque to horsepower -- from "pound-feet" to "foot-pounds per second."

[p71]

sounds like a conversation we had somewhere hmmm charlie?
5252 for life!

[R.Penguin]

Um......oh, yeah.........I um......I knew that!

WTF? :p

[p71]

or you can admit that horsepower is a fake made up number and that all it does is describe the shape of the torque curve... a high tq low hp motor has lots of low end, (like a deisel motor) a high hp low tq motor has lots of top end (like a sports bike or an s2000)... one with relatively equal numbers is mor balanced, like a g8. This is a rule of thumb.

[John Wilson]

Um......oh, yeah.........I um......I knew that!

WTF? :p

Did not mean to bore you guys...

[GRRRR8]

sounds like a conversation we had somewhere hmmm charlie?
5252 for life!

This feels so Dejavuish! LOL

[-Ray-]

Did not mean to bore you guys...

I never wondered. I'm also not good in math, so I didn't even read the full post.

[R.Penguin]

Did not mean to bore you guys...
I was NOT bored. However, my head exploded violently several seconds after I posted. They say with some hospital time and a bit of luck, I might be able to come home for Christmas. :p

[John Wilson]

I was NOT bored. However, my head exploded violently several seconds after I posted. They say with some hospital time and a bit of luck, I might be able to come home for Christmas. :p

Good luck. I know longer have to wonder why people don't post on this forum very much...it's just so warm and friendly. LOOK OUT! Here comes a tumble weed rolling across my screen. JW

[p71]

Good luck. I know longer have to wonder why people don't post on this forum very much...it's just so warm and friendly. LOOK OUT! Here comes a tumble weed rolling across my screen. JW

Dude you need to chill... most of the guys on here either already know this, or do not care about it. Your description was nicely succinct and made for a good read but it is over most peoples heads who are just doing a casual read.

[GRRRR8]

Good luck. I know longer have to wonder why people don't post on this forum very much...it's just so warm and friendly. LOOK OUT! Here comes a tumble weed rolling across my screen. JW

John I didnt see anything offensive in the posts. I personally was part of a post like this and it is how I met many members. Tumble weed?!?! This site passed all sites but 1 in 3 months! I know people sometimes dont see in a post what you do, but that doesnt make the site bad.