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 gas purification system has a first exhaust gas purification element, a second exhaust gas purification element, a first exhaust gas part flow duct, and a second exhaust gas part flow duct. The second exhaust gas purification element is arranged geometrically after the first exhaust gas purification element. The first exhaust gas part flow duct has a first exhaust gas passage area and the second exhaust gas part flow duct has a second exhaust gas passage area. The exhaust gas passage areas are aligned parallel to a projection plane and the first and second exhaust gas part flow ducts are arranged geometrically one after another. The two exhaust gas part flow ducts are arranged such that a partial flow channel axis that is orthogonal to the projection plane passes through the first and second exhaust gas passage areas.

A vehicle exhaust system includes a component housing defining an internal cavity, a first exhaust gas treatment element positioned within the internal cavity, a second exhaust gas treatment element positioned within the internal cavity and axially spaced from the first exhaust gas treatment element by a gap, and a resonator volume in communication with the internal cavity.

A controlling method of exhaust gas purification system to which a lean combustion engine is applied and an LNT device, a DPF or an SDPF, and an SCR device are provided includes detecting vehicle information and determining whether the vehicle information satisfies nitrogen oxide desorption condition of the LNT device; desorbing the nitrogen oxide until the nitrogen oxide of the LNT reaches predetermined reference amount through engine rich combustion when vehicle information satisfies the nitrogen oxide desorption condition of the LNT device; injecting urea to purify the nitrogen oxide after a first period after ending of desorption of the nitrogen oxide of the LNT; desorbing sulfide of the LNT through the engine rich combustion; and injecting urea to purify the nitrogen oxide after a second period after ending of desorption of the sulfide rich combustion of the LNT.

An exhaust device includes an expansion chamber that expands an exhaust gas from an engine; a separator that partitions the expansion chamber; and a plurality of catalyst units arranged in the expansion chamber and supported in parallel by the separator. The separator is divided into upper and lower portions through a dividing plane, and the plurality of catalyst units are supported in such a manner as to be clamped from upper and lower sides at the dividing plane.

An exhaust pipe device of a saddle-riding vehicle, wherein a power unit is fixed to a body frame of a saddle-riding vehicle, includes an upstream-side exhaust pipe device for discharging exhaust gas from an internal combustion engine, a catalyst built-in pipe connected to a downstream end of the upstream-side exhaust pipe device, and a downstream-side exhaust pipe device connected to a downstream end of the catalyst built-in pipe. An exhaust muffler is connected to a downstream end of the downstream-side exhaust pipe device. The downstream-side exhaust pipe device has a main pipe portion and a branch pipe portion on a downstream side of an upstream end thereof where a branching portion is provided. An exhaust control valve is provided to the branching portion where the branch pipe portion is branched from the main pipe portion. The branch pipe portion overlaps, as seen in side view, with a vehicle center-side wall of the main pipe portion, and downstream ends of both the main and branch pipe portions are connected to the exhaust muffler. The above arrangement provides an exhaust pipe device wherein a branch pipe portion can be formed in a compact shape as viewed in side view, whereby excellent external appearance property is obtained, and a valve shaft of the exhaust control valve at the branching portion can be easily arranged with a required banking angle.

A straddle-type vehicle (100) includes a frame (20) and an engine (10) mounted on the frame (20), the engine (10) includes a cylinder head (11) positioned toward the rear end of the frame, and located below a saddle seat (80). The cylinder head laces toward the rear end of the frame, which allows the heated cylinder head of the engine and the exhaust pipe connected to the cylinder head to avoid contact with the vehicle the user's legs while riding the vehicle, so the effect of heat emitted from the cylinder head on the rider's experience is reduced.

An exhaust gas sensor mounting structure includes: an exhaust pipe attached to a vehicle engine; a catalyst unit which cleans exhaust gas of the engine; a silencer connected to a downstream portion of the exhaust pipe; and an exhaust gas sensor which detects a prescribed component of the exhaust gas; at least part of the catalyst unit is located in the silencer; at least part of a pipe that is connected to a downstream end portion of the catalyst unit extends alongside an outer surface of the silencer; and the exhaust gas sensor is attached so as to penetrate through an outer wall of the silencer and a wall of the pipe.

[Task] A task is to improve the flexibility for setting a muffler and sufficiently secure the length of a catalyst while making a V-type engine compact.

[Solution] A V-type engine (1) includes an engine body (3) including a crankcase (7) configured to rotatably support a crankshaft (11), and a first and second cylinder banks (8, 9) extending from the crankcase (7), an exhaust collecting pipe (31) connected to the first and second cylinder banks (8, 9), a catalyst (32) accommodated in the exhaust collecting pipe (31), and a muffler (33) detachably connected to the exhaust collecting pipe (31), wherein the catalyst (32) extends in a height direction of the engine body (3) from a base end side of the first cylinder bank (8) to a distal end side of the first cylinder bank (8).

An engine includes an exhaust-gas purification device. The exhaust-gas purification device purifies exhaust gas. The exhaust-gas purification device includes electrical components. The electrical components detect the states of the exhaust-gas purification device. The engine includes a cooling-water circulation mechanism for circulating cooling water for the engine. Further, a portion of the cooling water circulated by the cooling-water circulation mechanism cools the electrical components.