An exhaust gas purification structure of an outboard motor includes an exhaust gas pipe that has an exhaust gas passage through which exhaust gas of an engine can flow; and a catalyst that is provided in the exhaust gas passage and purifies the exhaust gas by allowing the exhaust gas to pass through the inside thereof. The exhaust gas pipe includes a coolant flow passage allowing a coolant that cools the exhaust gas to flow therethrough. An exhaust gas bypass passage allowing the exhaust gas to flow without passing through the catalyst is formed between the catalyst and an inner surface of the exhaust gas pipe forming the exhaust gas passage.

A method and system for controlling operation of a two-stroke engine having a turbocharger includes the two-stroke engine comprising an electronically controlled exhaust valve. A throttle position sensor generates a throttle position signal corresponding to a position of a throttle plate of a throttle. A boost box is coupled to the two-stroke engine. A boost box pressure sensor is coupled to the boost box and generates a boost box pressure signal corresponding to a pressure within the boost box. A controller is coupled to the boost box pressure signal controlling a position of the electronically controlled exhaust valve in response to the boost box pressure signal and the throttle position signal.

A heat exchanger including a honeycomb structure having partition walls defining fluid cells extending between inflow and outflow end faces, and inner and outer peripheral walls. A first outer cylinder contacts the outer peripheral wall. A first inner cylinder having inflow and outflow ports for the fluid has an outer peripheral surface that contacts the inner peripheral wall. A second inner cylinder having inflow and outflow ports for the fluid is spaced on a radially inner side of the inner peripheral wall. The inflow port of the first inner cylinder is closer to the inflow end face than the outflow end face in an axial direction of the honeycomb structure. The outflow port of the second inner cylinder is closer to the outflow end face than the inflow end face in the axial direction of the honeycomb structure.

An aftertreatment system includes: a selective catalytic reduction (SCR) system configured to decompose constituents of exhaust gas; an exhaust conduit configured to deliver the exhaust gas to the SCR system; a hydrocarbon insertion assembly; a valve operably coupled to the exhaust conduit, the valve configured to be selectively opened so as to allow a first gas to enter the exhaust conduit and mix with the exhaust gas; and a controller configured to: determine a SCR system temperature, in response to the SCR system temperature being less than a target temperature, instruct the hydrocarbon insertion assembly to insert hydrocarbons into the exhaust gas, and in response to the SCR system temperature being greater than the target temperature, instruct the valve to open so as to allow the first gas to enter the exhaust conduit, a first gas temperature of the first gas being lower than the SCR system temperature.

Methods and systems are provided for diagnostics of an exhaust tuning valve during vehicle-off conditions. In one example, the engine may be reverse rotated, unfueled while the position of the exhaust is varied and an intake air flow is estimated at each position of the exhaust tuning valve. The exhaust tuning valve may be diagnosed based on a change in air flow with the variation in the position of the exhaust tuning valve.

A post-treatment system includes two SCRs, a second SCR is connected to a booster in parallel, and a three-way valve is arranged before the second SCR and the booster, such that whether an exhaust gas flows through the second SCR or the booster is controlled by means of controlling the three-way valve. In the case of a low temperature, the three-way valve is controlled to close a branch of the booster, such that the exhaust gas flows through the second SCR and a first SCR that are connected in series, thereby reducing the energy loss caused by the exhaust gas flowing through the booster, and improving the NO.sub.x conversion efficiency in the case of a low temperature. In a case of a high temperature, the three-way valve is controlled to close a by-pass line, such that the exhaust gas flows through the booster and the first SCR.

A method and system for controlling operation of a two-stroke engine having a turbocharger includes the two-stroke engine comprising an electronically controlled exhaust valve. A throttle position sensor generates a throttle position signal corresponding to a position of a throttle plate of a throttle. A boost box is coupled to the two-stroke engine. A boost box pressure sensor is coupled to the boost box and generates a boost box pressure signal corresponding to a pressure within the boost box. A controller is coupled to the boost box pressure signal controlling a position of the electronically controlled exhaust valve in response to the boost box pressure signal and the throttle position signal.

An exhaust purification system may include at least one catalyst in an exhaust flow path of an internal combustion engine to decrease gaseous pollutants from an exhaust gas, a first particulate filter downstream of the catalyst, and a second particulate filter with a porosity lower and a lower mean pore size than the first particulate filter and in a bypass flow line downstream of the first particulate filter, the bypass flow line being configured to open and close based on at least one condition of the exhaust purification system or conditions of the exhaust gas. The second particulate filter may be configured to be removed and replaced when full. A method of purifying an exhaust gas through the exhaust purification system is also described.

A burner-based exhaust replication system that includes mechanisms for rapidly exchanging exhaust aftertreatment devices for testing. The exhaust replication system has a test leg for delivering exhaust to an exhaust aftertreatment device and a bypass leg for bypassing exhaust around the test leg. The test leg is equipped with a rotating drum that holds a number of exhaust aftertreatment devices. The drum is rotatable to selectively align the aftertreatment devices with the test leg and is moveable laterally in a direction parallel to the test leg to aid in sealing the test leg to the aftertreatment device.

A DEF system for use with an internal combustion engine, the DEF system including a primary flowpath extending between a first inlet and a first outlet, where the first inlet is open to and configured to receive exhaust gasses from the internal combustion engine. The DEF system also includes a secondary flowpath including a second inlet open to the primary flowpath downstream of the first inlet and upstream of the first outlet, a second outlet open to the primary flowpath downstream of the secondary inlet and upstream of the first outlet, and an injector assembly configured to inject DEF into the secondary flowpath.