An engine system includes an intake passage, a non-deactivation exhaust passage, a second exhaust manifold, a first turbocharger including a first turbine rotated by exhaust gas flowing via the first exhaust manifold, a second turbocharger including a second turbine rotated by exhaust gas flowing via the second exhaust manifold, an exhaust outlet, a main intake circulation passage in communication with the intake passage via a compressor of the first turbocharger such that supercharging air is supplied to the intake passage, a sub intake circulation passage in communication with the main intake circulation passage via a compressor of the second turbocharger such that supercharging air is supplied to the main intake circulation passage, and a deactivation valve disposed on the sub intake circulation passage between the compressor of the second turbocharger and the main intake circulation passage so as to selectively open/close the sub intake circulation passage.

An engine system includes an intake passage, a non-deactivation exhaust passage, a second exhaust manifold, a first turbocharger including a first turbine rotated by exhaust gas flowing via the first exhaust manifold, a second turbocharger including a second turbine rotated by exhaust gas flowing via the second exhaust manifold, an exhaust outlet, a main intake circulation passage in communication with the intake passage via a compressor of the first turbocharger such that supercharging air is supplied to the intake passage, a sub intake circulation passage in communication with the main intake circulation passage via a compressor of the second turbocharger such that supercharging air is supplied to the main intake circulation passage, and a deactivation valve disposed on the sub intake circulation passage between the compressor of the second turbocharger and the main intake circulation passage so as to selectively open/close the sub intake circulation passage.

Methods and systems are provided for determining degradation of an EGR cooler based on differential pressure across the EGR cooler during EGR flow. In one example, the differential pressure across the EGR cooler may be based on differential pressure across an EGR valve and a pressure downstream from the EGR valve with and without EGR flow. The pressure downstream from the EGR valve may be a compressor inlet pressure or an intake manifold pressure in a low pressure EGR system or high pressure EGR system, respectively.

Methods and systems are provided for determining degradation of an EGR cooler based on differential pressure across the EGR cooler during EGR flow. In one example, the differential pressure across the EGR cooler may be based on differential pressure across an EGR valve and a pressure downstream from the EGR valve with and without EGR flow. The pressure downstream from the EGR valve may be a compressor inlet pressure or an intake manifold pressure in a low pressure EGR system or high pressure EGR system, respectively.

Various methods and systems are provided for controlling air flow in a two-stage turbocharger. In one example, an engine method comprises adjusting one or more exhaust gas recirculation valves to maintain a first turbocharger within a first air flow range, and adjusting a turbocharger bypass valve to maintain a second turbocharger within a second air flow range.

Various methods and systems are provided for controlling air flow in a two-stage turbocharger. In one example, an engine method comprises adjusting one or more exhaust gas recirculation valves to maintain a first turbocharger within a first air flow range, and adjusting a turbocharger bypass valve to maintain a second turbocharger within a second air flow range.

A method includes operating an air boosting apparatus of a two-stroke, opposed piston engine as a function of one or more factors including a first engine speed, a first torque, demand, a first altitude, a first transient rate, and one or more first ambient conditions to provide a first pressure S ratio (PR} of pre-turbine pressure (PTP) versus turbocharger compressor discharge pressure (CDP} and a first air-to-fuel ratio (AFR).

A power system that includes an engine, a first exhaust manifold, a second exhaust manifold, and a turbine. The first and second exhaust manifolds are positioned downstream of the engine. The turbine is positioned downstream of the first exhaust manifold, but is not positioned downstream of the second exhaust manifold.

The invention relates to a method for determining the pressure P.sub.avcm upstream of a mechanical compressor (3) equipped with a double supercharging circuit of a combustion engine. The pressure P.sub.avcm is determined by a dynamic model based on a law of conservation of flow rate in the volume upstream of the mechanical compressor. The model links the pressure P.sub.avcm upstream of the mechanical compressor (3) to a temperature T.sub.avcm upstream of the mechanical compressor (3), to a boost pressure P.sub.sural and boost temperature T.sub.sural on the intake side of the engine, and to an openness Bypass of the bypass valve (4).

The invention relates to a method for determining the pressure P.sub.avcm upstream of a mechanical compressor (3) equipped with a double supercharging circuit of a combustion engine. The pressure P.sub.avcm is determined by a dynamic model based on a law of conservation of flow rate in the volume upstream of the mechanical compressor. The model links the pressure P.sub.avcm upstream of the mechanical compressor (3) to a temperature T.sub.avcm upstream of the mechanical compressor (3), to a boost pressure P.sub.sural and boost temperature T.sub.sural on the intake side of the engine, and to an openness Bypass of the bypass valve (4).