What are speed characteristics and external characteristics? What is the meaning of external characteristics?

Rotational speed characteristics: the relationship between engine performance index (Me, Ne, ge) and rotational speed when the position of engine fuel supply adjusting mechanism is fixed. When the throttle opening is maximum or the rack position of the fuel injection pump is at the maximum fuel supply position, the engine speed characteristics are called full load speed characteristics or external characteristics, and others are called partial load speed characteristics.

Significance of external characteristics: 1, evaluation of engine power 2, working stability of expensive engine.