Abstract: A catalytic converter is adapted to retard spark timing to increase the temperature of the converter catalyst when a temperature sensor within the converter senses low exhaust temperature. A vacuum advance mechanism is responsive to intake manifold vacuum conducted thereto via an intake vacuum passageway to advance spark timing for the engine. The temperature of exhaust gas from a catalytic converter for exhaust emissions is sensed. When the sensed temperature of the exhaust is below a predetermined value, a comparator outputs an actuation signal which is used to cause a solenoid valve to open an air passageway to admit atmospheric air into the vacuum advance mechanism so that spark timing will be retarded, thereby increasing the temperature of the catalyst.

Abstract: The accumulator chamber communicates with the atmosphere through a passage which is formed therein with a restriction for restricting the cross sectional area of the passage or which is provided therein with a pressure control valve for opening the passage in response to a difference between the atmospheric pressure and the vacuum in the accumulator chamber which difference is above a predetermined value to maintain the vacuum differential between the accumulator and vacuum chambers above a predetermined value when the engine suction vacuum is above a predetermined value.