Abstract: An engine air intake system for vehicles such as snowmobiles. The air intake system helps prevent airborne contaminants from entering the vehicle engine through the air intake. The intake includes an elongated channel with openings on either end that provides a throughway for contaminants entering the channel. A wall of the channel includes at least one aperture leading to an intake port on an engine cylinder. The intake port is positioned generally parallel to the direction of airflow through the channel.

Abstract: A variable exhaust resonance chamber valve system for internal combustion engine. The engine includes a cylinder having an exhaust port with an axial extent along the axis of the cylinder structure. An exhaust passage having a resonance port extends from the exhaust port to exhaust the engine. A resonance chamber extends from the resonance port and communicates with the exhaust passage through the resonance port. A port valve is adjustable between a second position, in which the port valve exposes the exhaust port throughout its axial extent and occludes the resonance port, and a first position, in which the port valve restricts the axial extent of the exhaust port and exposes the resonance port. A valve control module is connected to the port valve and functions to adjust the port valve between first and second positions in response to engine conditions. At low speeds and low output conditions, the valve is in its first position.