Abstract: An air induction control device for an internal combustion engine comprises means defining a communication passageway for communicating between air at atmospheric pressure and the air in the downstream passageway from a throttle valve. A valve member is disposed in the communication passageway and is moveable toward the downstream direction thereof to open the communication passageway in response to an atmospheric pressure greater than pressure in the downstream passageway. A valve biasing means is disposed to apply force to and bias the valve member in the upstream direction to close the communication passageway in response to the pressure differential between atmospheric pressure and the air pressure int he downstream passageway. A flow restriction element positioned downstream of the valve member comprises calibrated openings defining a primary chamber and secondary chamber, wherein the volumetric proportion of the primary chamber: second chamber: calibrated openings is about 50-70: 25-35: 0.8-1.2.

Abstract: An air induction control device for an internal combustion engine comprises means defining a communication passageway for communicating between air at atmospheric pressure and the air in the downstream passageway from a throttle valve. A valve member is disposed in the communciation passageway and is moveable toward the downstream direction thereof to open the communication passageway in response to an atmospheric pressure greater than pressure in the downstream passageway. A valve biasing means is disposed to apply force to and bias the valve member in the upstream direction to close the communication passageway in response to the pressure differential between atmospheric pressure and the air pressure in the downstream passageway. A flow restriction element positioned downstream of the valve member comprises calibrated openings defining a primary chamber and secondary chamber, wherein the volumetric proportion of the primary chamber:second chamber:calibrated openings is about 50-70:25-35:0.0-1.2.