K is a constant. For each engine, the value of this constant is fixed, which is related to the cylinder form of the engine, the length and angle of the crankshaft, etc. This constant is different for different engines. Let me talk about torque again. Simply put, torque is actually how much traction the engine can output.

As mentioned above, power is not only related to torque, but also to speed. This can explain why the torque will decrease when it rises to a certain value. Assume that the torque of an engine is 1000, and the power is 50 when the speed is 1000 rpm. Then increase the speed. When the speed is increased to 2000, if the torque is still 100, then the power is 100. When the speed is increased to 4000, but the power is only increased to 150, the torque is reduced to 75.