MONITORING AN IC ENGINE OF A FOREST HARVESTER

The method for controlling a forest harvester (10) includes measuring, when carrying out an operation, rotational speed of an engine (22); automatically determining, in a control electronics (100), a relative or absolute difference between the measured rotational speed of the engine and a predetermined guideline for the rotational speed of the engine, the guideline defining a preferred rotational speed or a range of preferred rotational speeds for the operation that is being carried out; and automatically notifying, by the control electronics, an operator of the forest harvester, that the determined difference either follows the guideline or the determined difference deviates from the guideline. The engine being adapted to deliver predetermined power levels during the operation.