in heat engines, the maximum power that can be developed over a limited time period, for example, in handling excessive loads. Higher-than-rated power is attainable through increases in the rotational speed of the engine’s shaft or increases in torque. In the former case, the power developed is limited by the limiting values of the inertial forces on the various engine parts or by deterioration in the lubrication of the parts. In the latter case, the power is limited by the increase in pressure of the working fluid, which leads to an increase in the mechanical stresses imposed on the engine parts or to an increase in the temperature of the parts accompanied by an increase in heat stress. The limiting value of boosted power also depends on the type of engine, the design features of the engine, and the method used to regulate power.
The length of time that an engine producing boosted power may be operated is determined by the ability of the engine parts to withstand increased heat loads before reaching temperatures that cause a deterioration in normal operation or failure; as a rule, it should not exceed 10 percent of the nominal engine life.