Auxiliary Air Valve (Idle Speed): Description and Operation

Auxiliary Air Valve





In order to maintain idling speed during cold start and warm up, more air than that supplied by the normal idle bypass is required.

This extra air is supplied by the auxiliary air valve which is temperature sensitive so that the idle speed can be controlled throughout the warm-up phase.The auxiliary air valve consists of a variable orifice, controlled by an expansion element. It is mounted on the engine cylinder head where it is responsive to coolant temperatures. By adjusting the profile of the variable orifice according to coolant temperature the engine idle speed can be controlled.