The fuel consumption at idle is mainly determined by idle speed and efficiency.
It is advantageous to have as low an idle speed as possible, as idling is of considerable importance when driving in dense traffic (for minimizing fuel consumption).
However, the selected idle speed must be sufficient to ensure that, under any conditions (e.g. when the air conditioning is switched on, or the vehicle electrical system is heavily loaded), it does not drop so low that the engine starts to run roughly or stalls.
To regulate the idle speed, the injected fuel quantity is varied by the idle speed controller until the measured actual engine speed is the same as the specified target engine speed.
The specified engine speed and the control characteristic are influenced by the CHT.
Other parameters are:
โข vehicle speed (engine speed compensation system),
โข generator control (smart charging) – this can raise the idle speed,
โข speed control system.