The Electric Choke for Improved Cold Start Control

During the warm-up period of a carbureted spark ignition engine, a choke control is required to provide the rich fuel-air mixture necessary to achieve combustion. Over the past decade, a new type of choke control, which uses electrically generated heat, has been widely applied to this function. This control uses a PTC ceramic heater to rotate a bimetal coil with a level of control not achievable in previous choking systems. The purpose of this paper is to describe the operation and construction of this electric choke control as it is presently applied to production vehicles.