The temperature of exhaust gas discharged from a compact air-cooled engine used as a power source for an engine-driven working machine is reduced. An engine has a muffler mounted directly to the exhaust opening of the cylinder, and a resin muffler cover covering the muffler. An exhaust gas restriction member is provided to a wall surface of the muffler, and two exhaust passages serving as outlets for exhaust gas are formed in the exhaust gas restriction member. The exhaust passages are arranged independent of each other, and the streams of discharged exhaust gas are discharged to be slightly separated from each other as the streams flow away from the exhaust openings. The separated streams of discharged exhaust gas form a negative pressure space between the streams promoting the introduction of a cooling air stream into the negative pressure portion. Thus, the temperature of the exhaust gas can be reduced.

An exhaust manifold assembly with a thermal barrier coating for an opposed-piston engine reduces heat rejection to coolant, while increasing exhaust temperatures, fuel efficiency, and quicker exhaust after-treatment light-off. The exhaust manifold assembly can include a coating on the inside surface of the manifold assembly. The coated exhaust manifold assembly can ensure structural robustness of the exhaust manifold assembly over a larger range of operating temperatures.

The present disclosure improves serviceability of an automotive powertrain unit without deteriorating NVH characteristics. A powertrain includes an engine having a cylinder head; and a transmission coupled to the engine. The engine includes an EGR connected between an intake passage and an exhaust passage. The transmission is provided below the cylinder head in a vehicle height direction. The EGR is provided along a side of the cylinder head toward the transmission, and supported by the transmission.

An engine device including an exhaust manifold provided on an exhaust side surface of a cylinder head, and an exhaust pressure sensor configured to detect an exhaust gas pressure in the exhaust manifold. The exhaust pressure sensor is attached to the cylinder head. The exhaust pressure sensor is connected to the exhaust manifold through an exhaust pressure bypass path provided in the cylinder head and an exhaust pressure detection pipe connecting the exhaust pressure bypass path to the exhaust manifold. A cooling water passage is provided nearby the exhaust pressure bypass path, in the cylinder head.

There is provided a secondary air introduction device configured to introduce air into an exhaust port provided in a cylinder head of an engine by using a negative pressure in the exhaust port. A back-flow restriction member is provided between a reed valve and the exhaust port in an air introduction passage, and includes a plate part intersecting with an extension direction of the air introduction passage. The plate part has an air passing region in which the air flowing through the air introduction passage from an air intake unit toward the exhaust port is enabled to pass therethrough and a back-flow cutoff region in which exhaust air, which flows in a direction of directly colliding with at least a valve body of the reed valve, of exhaust air flowing back through the air introduction passage from the exhaust port is cut off.

An exhaust pipe structure for an in-line four-cylinder internal combustion engine includes: an in-line four-cylinder internal combustion engine; four exhaust pipes connected with respective exhaust ports in respective cylinders of the internal combustion engine; and a converging exhaust pipe connected with a converging portion at which downstream ends of all the exhaust pipes converge. In this exhaust pipe structure, the exhaust pipes are each configured as a dual pipe including an outer pipe and an inner pipe disposed inside the outer pipe. At the converging portion, the four exhaust pipes are arrayed linearly in parallel with each other, and the outer pipes of adjacent ones of the exhaust pipes are directly welded with each other at the downstream ends.

An internal combustion engine has a cylinder head having an integrated exhaust manifold which has multiple exhaust ducts; and a secondary air system for supplying ambient air that is additionally supplied through an inlet as secondary air into the exhaust manifold into the exhaust gas flow downstream from the exhaust valves of the internal combustion engine during the cold-start phase. For fresh air supply, the secondary air system has a plurality of supply ducts that connect a distributor block of the secondary air system to an exhaust duct and are arranged in the integrated exhaust manifold and each provided with a valve assembly. Each valve assembly has a blocking means in the form of a closure flap that is pivotable about a pivot axis at a distance from the center of mass of the blocking means. According to the installation position of the internal combustion engine in a motor vehicle, and owing to this eccentric arrangement of the pivot axis, the blocking means assumes a defined closed position under the influence of gravity when there is no pressure difference between the exhaust manifold and the secondary air system and opens automatically under the influence of a relative overpressure in the gas pressure on the side of the secondary air system in relation to the gas pressure on the side of the exhaust manifold.

A turbine connector (40) in an engine exhaust manifold (30) includes a turbine foot (54) attached to incoming exhaust conduits (42,46). The turbine foot (54) has an outer perimetric edge (72) defining a trapezoidal shape, and inner perimetric edges (86,90) forming exhaust outlets (88,92) from the incoming exhaust conduits (42,46). The inner perimetric edges (86,90) have varied perimetric curvatures largest in finite curvature size upon a web (94) extending between the exhaust outlets (88,92), and together forming an hourglass web profile in a turbine-mounting plane defined by the turbine foot (54).

A multi-cylinder engine having an engine body with a cylinder head is provided. The engine includes first and second cylinder groups, each having a plurality of independent exhaust passage parts provided to the cylinder head and connected to cylinders of the first and second cylinder groups, respectively, and first and second collective exhaust passage parts collecting the first and second pluralities of independent exhaust passage parts at a location downstream in an exhaust gas flow direction, and having an opening formed in the side surface part of the cylinder head, first and second exhaust-pipe parts each connected to the openings of the first and second collective exhaust passage parts, respectively, an exhaust gas recirculation (EGR) passage connected at one end to the first exhaust passage group and connected at the other end to an intake passage, and an exhaust gas temperature sensor provided to the first exhaust-pipe part.

A multi-cylinder engine having an engine body with a cylinder head, and mounted on a vehicle is provided. The engine includes first and second cylinder groups each provided to the engine body and comprised of first and second pluralities of cylinders, first and second exhaust passage groups each having first and second pluralities of independent exhaust passage parts provided to the cylinder head and connected to the first and second cylinder groups, respectively, and first and second collective exhaust passage parts provided to the cylinder head and collecting the first and second pluralities of independent passage parts downstream in an exhaust gas flow direction, and a cooling medium passage provided in the cylinder head, through which a cooling medium flows, and having an intermediate passage part provided between the first collective exhaust passage part and the second collective exhaust passage part.