Fast idle carburetor system

Abstract

A carburetor system has a fast idle cam to hold the throttle plate in a fast idle position for facilitating engine operation during warm-up after starting. The cam is movable to a second position after engine warm-up to permit the throttle plate to move to its low idle position in response to a bias. A control has thermally expansible material disposed in a chamber to move a piston to move the cam to its second position with a positive force when the material is heated. Two electrical heaters are disposed in heat-transfer relation to the material. One of the heaters is connected to a power source when the engine is first started and a thermally responsive switch operable above a selected ambient temperature level connects the other heater to the power source when the ambient temperature is above that level to accelerate heating of the thermally expansible material. The material undergoes a change of physical state and a rapid expansion when heated to a temperature above the selected ambient temperature and the heaters comprise elements of a material of positive temperature coefficient of resistivity which display a sharp increase in resistivity at a temperature above the change-of-state temperature.