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.

Methods and systems to control a temperature of a selective catalytic reduction catalyst are disclosed. In one example, a diverter valve that includes two butterfly valves that are coupled together via a shaft is adjusted to control a temperature at an inlet of the selective catalytic reduction catalyst so that the selective catalytic reduction catalyst may operate efficiently.

An ECM executes a catalyst early activation control at cold start of an engine such that the activation of a catalyzer is promoted by opening a WGV. Further, the ECM performs a diagnosis process of, during execution of the catalyst early activation control, repeating opening and closing of the WGV with a given period and diagnosing whether or not the WGV is stuck, based on whether or not a fluctuation component with the same period as the period of the opening and closing of the WGV is included in output from an intake manifold pressure sensor during the repetition.

Methods and systems to control a temperature of a selective catalytic reduction catalyst are disclosed. In one example, a diverter valve that includes two butterfly valves that are coupled together via a shaft is adjusted to control a temperature at an inlet of the selective catalytic reduction catalyst so that the selective catalytic reduction catalyst may operate efficiently.

An exhaust after-treatment system for treating an exhaust produced by an engine. The exhaust after-treatment system includes an exhaust passage, at least one catalytic exhaust after-treatment component in communication with the exhaust passage for treating the exhaust, and a water-removal device in communication with the exhaust passage that receives a portion of the exhaust therein at a location positioned upstream from the catalytic exhaust after-treatment component. The water-removal device is defined by a housing that includes a water-removal membrane that separates water from the portion of the exhaust to provide a permeate that is enriched with water, and to produce a retentate that is water depleted that facilitates the treating of the exhaust by the catalytic exhaust after-treatment component.

The present invention relates to a control unit for a waste heat recovery system, wherein the waste heat recovery system is operated in a first mode of operation after a first condition is fulfilled and the system is operated in a second mode of operation after a second condition is fulfilled. The invention also relates to a method for starting an expansion device in a waste heat recovery system.

An ECM executes a catalyst early activation control at cold start of an engine such that the activation of a catalyzer is promoted by opening a WGV. Further, the ECM performs a diagnosis process of, during execution of the catalyst early activation control, repeating opening and closing of the WGV with a given period and diagnosing whether or not the WGV is stuck, based on whether or not a fluctuation component with the same period as the period of the opening and closing of the WGV is included in output from an intake manifold pressure sensor during the repetition.

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.

Methods and systems are provided for diagnosing an active exhaust valve in an exhaust system based on thermal data. In one example, a method may include indicating degradation of a first active exhaust valve positioned in a first exhaust pipe of a first engine bank based on a difference between a first temperature of exhaust downstream of the first active exhaust valve and a second temperature of exhaust downstream of a second active exhaust valve positioned in a second exhaust pipe of a second engine bank. Degradation of the valve may be confirmed based on thermal image data acquired at outlets of the first and second exhaust pipes.

Methods and systems are provided for diagnosing an active exhaust valve in an exhaust system based on thermal data. In one example, a method may include indicating degradation of a first active exhaust valve positioned in a first exhaust pipe of a first engine bank based on a difference between a first temperature of exhaust downstream of the first active exhaust valve and a second temperature of exhaust downstream of a second active exhaust valve positioned in a second exhaust pipe of a second engine bank. Degradation of the valve may be confirmed based on thermal image data acquired at outlets of the first and second exhaust pipes.