Idle Speed
Idle speed is the minimum speed at which the engine runs stably with no load while the throttle lever is at its lowest position. On diesel engines it is typically in the 700–900 rpm range. On an electronic throttle kit it is the lower reference point of the working range and is set by the engine's own idle adjustment.
Idle speed is determined by the engine, not the kit: the idle adjustment screw of the injection pump or of the carburettor sets this value. The electronic throttle kit only releases the throttle lever down to the idle position; the speed at which the engine settles where the lever is released is the engine's own setting.
- If idle is set too low the engine runs roughly and can stall when load is applied.
- If it is set too high the working range of the kit narrows; the resolution of the potentiometer drops.
The installation order therefore matters: first the engine's idle is set correctly, then the cable is tensioned so that with the engine at idle it has no slack but is not pulling either. In GS740-3P calibration this is exactly the first step — with the potentiometer at its lowest position the cable is tightened taut, then the upper limit is taught. On the GS740, a short button press toggles between idle and the stored work speed.
Context in which this term is used: Electronic speed and throttle control on diesel engines