An exhaust control device for engine configures an exhaust system by joining exhaust pipes at a collecting pipe. The exhaust pipes are coupled to a plurality of respective cylinders. At least two types of exhaust valves are configured to perform an exhaust control at different parts in the exhaust system. The exhaust control device for engine includes first exhaust valves, a second exhaust valve, and an actuator. The first exhaust valves are mounted to a plurality of communicating pipes and communicating the predetermined exhaust pipes. The second exhaust valve is mounted to the collecting pipe. The actuator is configured to drive to open and close the second exhaust valve. The first exhaust valves are configured to be driven to open and close corresponding to an actuating region of the second exhaust valve.

Mufflers with unique configurations which, in certain (but not all) embodiments, improve engine performance. In other embodiments, improved manufacturing processes and methods for making mufflers. In particularly preferred embodiments, methods for making motorcycle mufflers with swaging techniques. In still other preferred embodiments, swaged motorcycle mufflers with improved exhaust flow. In still other embodiments, aftermarket mufflers which can be assembled to a variety of engine exhaust systems utilizing a universal coupler.

A muffler in an exhaust device of an engine includes a casing, a first expansion chamber, a second expansion chamber, and a third expansion chamber separately formed in the casing, and a first communication pipe, a second communication pipe, and a third communication pipe provided in the casing. The rear exhaust pipe is connected to the first expansion chamber, the first expansion chamber communicates with the third expansion chamber via the first communication pipe, the first expansion chamber communicates with the second expansion chamber via the second communication pipe, and the second expansion chamber communicates with an outside of the casing via the third communication pipe. The third expansion chamber does not communicate with an outside of the third expansion chamber except that the third expansion chamber communicates with the first expansion chamber via the first communication pipe.

In a saddle-ride type vehicle in which a cylinder head of a single-cylinder engine main unit has a front wall and a rear wall, an exhaust system being connected to the front wall and an intake system being connected to the rear wall, a joining surface of the cylinder head to a head cover is formed on a plane crossing a cylinder axis, the plane being inclined downward toward a front. Rotation axes of camshafts are arranged on the plane. An axis of a valve stem of a throttle valve is arranged on the plane. A curve cover curved so as to cover driven sprockets fixed to the camshafts is formed on one side in a vehicle width direction of the head cover. A drum housing box housing a throttle drum fixed to one end of the valve stem is arranged close to the curve cover.

The present invention relates to an exhaust gas sensor arrangement structure comprising: an exhaust pipe 6 extending from an engine 3 to form a part of an exhaust flow path; an exhaust valve 7 that adjusts an aperture of the exhaust flow path; and a first exhaust gas sensor 8a that detects a predetermined component in an exhaust gas flowing through the exhaust flow path. The first exhaust gas sensor has a detector 80 arranged to protrude into the exhaust flow path. The exhaust valve includes a plate-like valve body 70 that expands and reduces a flow path cross section of the exhaust flow path, and a rotating shaft 71 extending in a direction intersecting with an axial direction of the exhaust flow path and serving as a rotation center of the valve body. A downstream end of the valve body approaches the detector as the valve body is rotated in a direction of reducing the flow path cross section.

A straddle-type vehicle comprises an engine which generates driving power and emits an exhaust gas; an exhaust device including: a catalyst which cleans the exhaust gas, an inner tube in which the catalyst is disposed and through which the exhaust gas flows, the inner tube extending to a location downstream of the catalyst; and an outer tube which covers an outer peripheral surface of the inner tube in an axial direction of the inner tube, and has a muffling space through which the exhaust gas discharged from the inner tube is flowed to reduce an exhaust noise radiated from the engine; at least one exhaust pipe through which the exhaust gas is led to the catalyst; and a downstream oxygen sensor which detects an oxygen concentration of the exhaust gas after flowing through the catalyst, at a location downstream of the catalyst in the inner tube.

A vehicle exhaust device includes a muffler body that has an interior space divided into a plurality of expansion chambers by a partition wall, and an exhaust control valve that switches an exhaust passage in the muffler body. The exhaust passage includes a first exhaust passage and a second exhaust passage. The first exhaust passage connects an upstream end and a downstream end of the muffler body straight. The second exhaust passage passes through the plurality of expansion chambers via a connecting pipe that connects the plurality of expansion chambers. A center of the first exhaust passage is located above a center of the muffler body in a vehicle upper-lower direction, and the second exhaust passage is located below the first exhaust passage.

An exhaust emission control device for an internal combustion engine including multiple reed valve chambers which are provided to cylinder head portions of a multi-cylinder engine. The reed valve chambers are formed by covering recessed portions in the cylinder head portion with reed valve covers. Upstream sides of the reed valve chambers communicate with the atmosphere via a secondary air supply pipe. Downstream sides of the reed valve chambers communicate with exhaust ports via communication passages provided to the cylinder head portion. The reed valves are interposed between the upstream sides and the downstream sides of the reed valve chambers, and are opened by exhaust pulsation pressure. In the cylinder head portion, the multiple reed valve chambers are disposed with spaces therebetween. The reed valve covers communicate individually with the secondary air supply pipe, and the reed valve covers are connected in series by the secondary air supply pipe.

In a vehicle, a rod of a waste gate valve actuator reciprocates along a virtual plane which is parallel to both the central axis of a connecting shaft of a turbocharger and the cylinder axis of a cylinder hole. When viewed in the left or right direction of the vehicle, a main catalyst of a catalyst portion is provided forward of the cylinder axis of the cylinder hole. The flow direction of the exhaust gas in the main catalyst intersects with the reciprocating direction of the rod of the waste gate valve actuator when viewed in a direction orthogonal to both the central axis of the connecting shaft of the turbocharger and the central axis of the cylinder hole.

An exhaust system for the engine includes two exhaust pipes for discharging therethrough exhaust gases from the engine, a muffler for silencing the exhaust gases, an introducing pipe for introducing the exhaust gases into the muffler and a collecting duct for merging the exhaust gases from the two exhaust pipes together and then to introduce them into the introducing pipe. The collecting duct has a single outlet opening within an interior of the introducing pipe, which single outlet opening has a first passage area that is chosen to be smaller than the sum of respective second passage areas of discharge openings of the exhaust pipes and also to be smaller than a third passage area of the introducing pipe.