Originally Posted by AndreyT
This is actually a slightly misleading statement.
The constant 5252 comes from specific measurement units which are used to represent power and torque: HP for power and lb-ft for torque. When power is expressed in HP and torque is expressed in lb-ft, then the adjustment constant is equal to 5252 and the graphs intersect at 5252 RPM. So, apparently what you really wanted to say is: your HP and your lb-ft graphs will always intersect at 5252 RPM point. Not just "torque", but specifically lb-ft graph of torque.
For different choice of measurement units the intersection point will be different. If you draw the same graphs in Watts and Nm units, they will intersect at around 10 RPM, meaning that on the real-life actual graph they won't intersect at all. If you draw the same graphs in kWatts and lb-ft units, you'll get yet another RPM for intersection point, and so on.
Additionally, all of the above only makes sense if the values along the Y-axis for power and torque are perfectly synchronized, as in the OP's graph. US-style dyno charts usually use the same Y-axis value for both HP and lb-ft graphs, meaning that you can expect to see the intersection at 5252 RPM all the time.
In some cases they prefer to use different scales along the Y-axis, meaning that the intersection point can end up virtually anywhere.
Thank you for clarifying.