The cylinder head includes an intake port communicating with a cylinder of a cylinder block, a cylinder head main body having an exhaust port communicating with the cylinder, and a rocker housing integrally formed on the cylinder head main body and an inner side of which is defined as a valve-system accommodating space. The rocker housing includes a lateral wall having a lateral wall main body and a base end portion which extends along a lower end of the lateral wall main body, connects the lateral wall main body to the cylinder head main body, and has a thickness thicker than that of the lateral wall body. A flow path which extends in an extending direction of the base end portion and through which a fluid flow is formed in the base end portion.

In an engine that includes a blow-by-gas returning system configured to direct blow-by gas within a crankcase to an intake system through an inside of a head cover, the intake system includes a cover intake-passage disposed at a blow-by-gas outlet of the head cover, and the cover intake-passage communicates with a blow-by-gas passage of the blow-by-gas outlet.

An air intake system is provided that supplies charge air to multiple cylinders in an in-line configuration in an uniflow-scavenged, two-stroke opposed-piston engine. The engine is configured such that the intake ports of the cylinders are situated in one intake chamber within the engine block. The air intake chamber includes a feature to balance the mass of air that reaches the intake port of each cylinder in the engine.

An intake manifold is provided and includes a runner that is connected between a plenum and a cylinder head to allow air introduced into the plenum to enter the cylinder head. A dent is formed at the runner such that the dent extends along a channel of the runner while having an inner surface with a protruding shape. The runner has, at an end thereof, an inner surface formed to be flat without being formed with the dent. The inner surface of the runner is connected to the cylinder head.

A cooling device includes a surrounding member, an air inlet, an air outlet, and a flow-path-formation mechanism. The surrounding member is configured to surround an engine. The air inlet is formed in the surrounding member. The air outlet is formed in the surrounding member and is to be coupled to an intake pipe of the engine. The flow-path-formation mechanism is configured to form a flow path that allows outside air to circulate to the air outlet from the air inlet when a temperature of the engine or a temperature inside the surrounding member is greater than or equal to a predetermined temperature.

A side-by-side vehicle comprises a vehicle body frame including a cabin frame part surrounding a riding space in which seats for a driver and a passenger are provided; an engine which is mounted on the vehicle body frame and generates driving power for allowing the side-by-side vehicle to travel; an air-intake unit including in an inside thereof, an air-intake passage through which intake-air flows to the engine, and an air inlet through which the intake-air is introduced into the air-intake passage; and a cargo carrier having a loading space with a depressed shape in a state in which the cargo carrier is supported by the vehicle body frame, and the air-intake unit is disposed so that the air inlet is directed downward and faces a surface of the cargo carrier.

A saddle riding vehicle includes a body frame, an exhaust pipe, a muffler, and a catalyst. The body frame includes a main frame, a seat frame that extends rearward from the main frame and supports a seat for occupant, and a rear frame that extends from the main frame upward to a rear and is connected to the seat frame. The exhaust pipe extends rearward of the vehicle from an exhaust port of an engine. The muffler is connected to a rear end portion of the exhaust pipe. The catalyst is disposed in the muffler. An air cleaner box is disposed rearward of the engine. The catalyst disposed in the muffler is disposed in a space surrounded by the main frame, the seat frame, and the rear frame and overlaps with the air cleaner box as viewed in a side view of the vehicle.

An engine includes: an exhaust manifold 7 close to one of left and right side surfaces of an engine; a turbocharger 60 having an exhaust-side inlet connected to the exhaust manifold 7; and a rocker-arm-chamber-integrated intake manifold 8 being disposed on an upper surface of a cylinder head 5 and integrally including a rocker arm chamber 90 and an intake manifold 6. The intake manifold 8 has a wall 101 dividing the rocker arm chamber 90 close to the one of the left and right side surfaces of the engine 1 and the intake manifold 6 close to the other of the left and right side surfaces to isolate the rocker arm chamber 90 and the intake manifold 6 from each other. The rocker arm chamber 90 has, in its upper portion, a positive crankcase ventilation device 69 protruding therefrom and being configured to return blowby gas to an intake system. The positive crankcase ventilation device 69 has, in its side surface, a blowby-gas discharge port 67 connected with a gas conduit 68 through which blowby gas is delivered to an intake-side inlet of the turbocharger 60.

An air intake circuit for a heat engine is intended to be positioned between an air compression element and at least an upper portion of a hollow combustion chamber in a cylinder head of the engine. The air intake circuit includes the cylinder head, an air intake manifold, and at least one air intake duct. The circuit also includes at least one concave receptacle turned towards the outside of the engine, housed in a cavity of the cylinder head, and connected to a tubular element pushed into the at least one air intake duct.

An engine including: an exhaust manifold provided near one side surface of an engine; a turbocharger having an exhaust-side inlet connected to the exhaust manifold; and a rocker-arm-chamber-integrated intake manifold disposed on a cylinder head and integrally including a rocker arm chamber and an intake manifold. The intake manifold has a wall dividing the rocker arm chamber provided near one side surface of the engine and the intake manifold provided near another side surface thereof to isolate the rocker arm chamber and the intake manifold from each other. The rocker arm chamber has, in its upper portion, a positive crankcase ventilation device protruding therefrom and returning blowby gas to an intake system. The positive crankcase ventilation device has a blowby-gas discharge port connected with a gas conduit through which blowby gas is delivered to an intake-side inlet of the turbocharger.