A supercharger (15) is provided with a bypass pathway (17). A backflow preventer (20) is provided to the air intake pathway (8) between an airflow meter (10) and the bypass pathway (17). The backflow preventer (20) has: a casing (41) formed by locally expanding the cross-sectional area of the air intake pathway; and an inner tube (42) substantially constructing a duct for the mainstream of air intake. The inner tube (42) is supported by a flange portion (50) and the downstream end (42a) opens within the casing (41). During backflow when the bypass pathway (17) opens, a portion of the intake air enters into an exit-side space section (55), and the flow is prevented by the flange portion (50). Consequently, reverse flow is suppressed.

A pressuring system for a vehicle engine includes an intake manifold into which ambient gases flows. A control valve connects to the intake manifold. An engine block connects to the intake manifold and connected to a gases outlet. A timing belt cover connects to the engine block. A gases pipe connects between the control valve and the timing belt cover.

A combined mass airflow sensor and hydrocarbon trap is provided for absorbing evaporative hydrocarbon emissions from an air intake duct of an internal combustion engine. The combined mass airflow sensor and hydrocarbon trap comprises a duct that supports a hydrocarbon absorbing sheet in an unfolded configuration within a housing. The duct communicates an airstream from an air filter to the air intake duct during operation of the internal combustion engine. An opening in the housing receives a mass airflow sensor into the duct, such that the mass airflow sensor is disposed within the airstream. Guide vanes extending across the duct reduce air turbulence within the airstream passing by the mass airflow sensor. Ports disposed along the duct allow the evaporative hydrocarbon emissions to be drawn into the interior and arrested by the hydrocarbon absorbing sheet when the internal combustion engine is not operating.