An exhaust system for an internal combustion engine and having at least an exhaust duct, which originates from the internal combustion engine and has an end part, which ends with an outlet opening, through which exhaust gases are released into the atmosphere. The end part of the exhaust duct has at least one movable wall, which can be moved to different positions to vary the width of the outlet opening. There are provided a motor-driven actuator device, which is configured to move the movable wall and can be electronically controlled, and a control unit, which is configured to vary, by controlling the actuator device, the position of the movable wall depending on a rotation speed of the internal combustion engine and on an engine load of the internal combustion engine.

A multi-mode muffler for an exhaust system of an internal combustion engine provides a rotary plate that modulates exhaust gas flow between a first and second flow path. Each flow path may provide different sound dampening characteristics, thereby providing different sound profiles with the same muffler. In a disclosed embodiment, the rotary plate is driven by a shaft coupled to an external actuator. Also, a third possible position of the rotary plate may allow flow through both the first and second flow paths, thereby providing a third possible noise profile. One of the sound profiles may be louder than the other thereby allowing the muffler to switch between “loud” and “quiet” modes of operation.

Exhaust systems for a vehicle are provided. In one example, an exhaust system includes a muffler, a first exhaust outlet pipe fluidly coupled to a first outlet of the muffler, a second exhaust outlet pipe fluidly coupled to a second outlet of the muffler, a bypass duct fluidly coupled to a third outlet of the muffler, and a combined X-Y shaped intersection at which the first exhaust outlet pipe, the second exhaust outlet pipe, and the bypass duct are fluidly coupled to each other.

Systems and methods for operating an engine that includes an exhaust tuning valve in its exhaust system are described. In one example, a position of the exhaust tuning valve may be adjusted to reduce a possibility of the exhaust tuning valve becoming stuck due to freezing water. In particular, the exhaust tuning valve may be cycled as ambient temperature approaches a temperature at which water freezes.

Methods and systems are provided for an exhaust muffler system with multiple inlets of different diameters. In one example, the muffler system may include multiple sets of inlet pipes to a muffler with each set of inlet pipes including pipes of different diameters with valves controlling exhaust flow into the inlet pipes. Exhaust from an engine bank may flow to a distinct set of inlet pipes and a distinct outlet pipe of the muffler via a separate exhaust passage.

An exhaust pipe structure having a variable confluence portion may include a first pipe to discharge exhaust gas generated by engine cylinders disposed in a first line, a second pipe to discharge exhaust gas generated by engine cylinders disposed in a second line, a confluence pipe provided with a first end connected to the first pipe for communication with the first pipe and a second end connected to the second pipe for communication with the second pipe, and a valve plate disposed in the confluence pipe and selectively opened and closed, in which the confluence pipe may include a main connection tube disposed at the first end of the confluence pipe and an entry confluence tube and a sub-entry confluence tube branched off from a middle of the confluence pipe and disposed at the second end of the confluence pipe.

An exhaust system for an engine has a volume element such as a muffler or a silencer. First and second exhaust pipes are connected as dual exhaust pipes upstream of or downstream of the volume element. The first exhaust pipe has a first length (L1). A valve is positioned in the second exhaust pipe at a distance (D) from the volume element. The distance D is a fraction of L1 such that the second pipe is a resonator for the first pipe with the valve in a closed position. A method of controlling exhaust noise includes positioning a valve in the first exhaust pipe at a distance (D) from a volume element with D being a specified fraction of a length of the second exhaust pipe, and closing the valve such that the first pipe provides a resonator for the second pipe to counteract standing wave in the second pipe.

A road vehicle comprising: a passenger compartment; an internal combustion engine; an exhaust system, which releases into the atmosphere the gases generated by the combustion, is connected to the internal combustion engine, and ends with at least one silencer having at least one outlet pipe; and an exhaust noise transmission device, which is provided with a transmission conduit, which originates close to the outlet pipe of the silencer, ends in the area of a wall of the passenger compartment, and is provided, on the inside, with at least one insulating element, which is arranged inside the transmission conduit so as to tightly seal the transmission conduit.

A slip-type active noise control muffler reducing exhaust noise of a vehicle may include at least two guides connected to an inner wall of a housing accommodating exhaust gas in the muffler and formed in a pipe shape in a longitudinal direction of the muffler, and a baffle positioned in a plane shape partitioning the interior of the housing and including an electromagnet on the plane shape to control an interval of the baffles through a movement signal by current applied to the electromagnet according to frequency calculated from the exhaust gas, in which the interval of the baffles may be controlled and the exhaust noise may be reduced by controlling the number of wavelengths depending on the frequency.

Methods and systems are provided for adjusting a position of an exhaust valve that regulates engine exhaust noise. In one example, the position of the exhaust valve is adjusted according to a road grade estimate. The road grade estimate may be based on a vehicle's present position on a road or a position that is a distance away from the vehicle's present position.