Study of the indicated diagram of a thermal engine.

The indicated diagram is the graph that represents this cycle.

The indicated diagram is the diagram that represents the real cycle of a heat engine (a diesel engine or an Otto engine).

The same deformation of the indicated diagram occurs in the case of a slow combustion.

The indicator is a device used to obtain the indicated diagram of a thermal engine cycle.

A negative surface (D, in the figure), corresponding to the lost work, is created in the indicated diagram.

Let us examine, then, in its main details, the indicated diagram taking as reference the 4-stroke engine.

This defect is also cause of reduction in the surface of the indicated diagram, that is, of a loss of useful work.