This maybe a little off topic but here is a link about HP vs Torque.

http://www.v8914.com/Horsepower-v-torque.htm

 

Eureka...I've got it!

 

scale meaning the way the numbers on the axis showing must be identical.
Example like the graph I provided, scaled at 100-500HP and 100-500 TQ. Some dyno technician like to do something like 100-500HP and 100-300TQ, then the 5252rpm won't apply.

example:



This one is not crossed at 5252rpm.
The equation don't change but the question was asked about how to read dyno chart and why some don't cross at 5252rpm.

 

OK, from the physicist:

Torque and power are not the same thing. Power measure energy per unit of time. Torque measures twisting force. Power (from rotary motion) is indeed calculated as torque times rate of spin. But this must be in consistent units, which the customary units are not, so a conversion factor is also required.

But the 5252 (actually 5252.113122...) is entirely an artifact of the scale. If you use different scales you get a different number. 5252 is the number for the so called "english" system no longer used in England (at least officially) but still used in the US.

There are three scales in operation in this calculation. HP for power, pound-feet for torque and revs per minute for spin rate. Why has no one asked where the 5252 came from? It's (550 x 60) / (2 x pi).

The 550 comes from 1 hp = 550 ft-lb. The 60 converts minutes (as in revs per minute) to seconds, and the 2xpi converts revs to radians. There are 2 pi radians in one revolution.

In the rest of the world, which uses newton-meters (NM) for torque and Kilowatts (KW) for power the magic revs is 9549.2965855... Which is (1000 x 60) / ( 2 x pi). The 1000 converts watts to Kilowatts.

If you used watts instead of KW the magic revs is 9.549...

If you used hp and pound-feet but revs per second (rather than per minute), the magic number would be 87.53...

If you were really English and used stones, rods, and revs per fortnight. Never mind.


Again, the 5252 is not a law of nature. It is completely an artifact of the scales chosen for power, torque and rate of spin. And it has nothing to do with kind of engine. The end of the crackshaft does not care what spins it, only how hard and how fast.


[QUOTE]Originally posted by wickerbill
[B]

The horsepower will ALWAYS be equal to the torque at 5252 RPM's.

 

But we're not in another country. We're in America. Using good ol' American horsepower and lb/ft for torque, isn't it always the same at 5252 RPM's. I'm aware that there are other units, but using the standard US units is that not correct?

 

Gregg is right. 5252 rpm crossover is just a reference point. It's purely mathematic calculation. No matter you have 1000 horse power motor or a Geo metro motor, if the scale of horsepower and torque are the same, the cross point is at 5252 rpm. I don't know why so many people are interested in 5252 rpm, show you nothing how the motor is running.

 

i just scanned through here seen where there was a dyno test with 500 horse power was that for a honda s2000 cause i've never seen that much in one and i'd like to knwo whos it is and where to see the specs on it.

 

Sorry, that was not an S2000. It was a Civic. I might have one soon in three weeks that might break 500HP if the motor is stable enough.

 

Is this only in cars? or is this the case for Motorcycles also??

 

"this" = what?