Whew...glad that got settled!! I was about to go crazy!! As stated, 5252 is the function of plotting both BOTH HP and Torque no matter what...EVER. 5252 is the number that the two will always intersect. In fact, some builders build their motors specifically so that 5252 (or in that neighborhood) is the shift point and they gear the car accordingly. Go math!

 

Who knows where 5252 comes from though. I do

 

James Watt said an average horse can lift 550lbs. 1ft in one second (Equals 550ft/lbs. per second or 33,000 ft/lbs. per minute)
The measure of torque is one revolution assuming 1 pound of resistance. (Pi x 2ft circle)
So assuming that one pound resistance over one full revolution you get 6.2832 ft/lbs of work.
Now divide 33,000 ft/lbs of horsepower by the work it takes to turn one pound of resistance over one full revolution (6.2832) and you get 5252 rotations per minute to equal one horsepower. That is why HP and Torque have to meet at 5252 to justify the equation. They have to eqaul 1.

Therefore Horsepower = (Torquex Rpm) /5252

So now everyone knows

 

wow, emperial system blows. thank Goddness for SI units, go metric.