Abstract: Managing firing fraction transitions of a variable displacement internal combustion engines by (a) avoiding transport delays in an Exhaust Gas Recirculation (EGR) feed by starting movement of an EGR valve position after a decision to transition to a new firing fraction has been made, but prior to the start of the transition and (b) adjusting the EGR valve as needed during the transition so as to maintain an EGR fraction within a predetermined range during the transition. By performing both (a) and (b), spikes of nitrous oxide (NOx) and/or hydrocarbon emissions are reduced or altogether eliminated during the transition.

Abstract: Various methods and systems are provided for diagnosing a condition of a component in an exhaust gas recirculation system. In one example, a method includes selectively routing exhaust from a first subset of engine cylinders to an exhaust passage via a first valve and to an intake passage via a second valve and determining a respective condition of each of the first valve and second valve based on a first exhaust pressure of the first subset of engine cylinders and a second exhaust pressure of a second subset of engine cylinders.

Abstract: Methods and systems are provided for an engine including a first turbocharger having a first compressor and a second turbocharger having a second compressor. An EGR differential between the first compressor and the second compressor may be increased under a condensation condition, and decreased under a surge condition. The EGR differential may also be decreased when a compressor outlet temperature exceeds an outlet temperature threshold.

Abstract: It is intended to provide an EGR device for an engine in which a cooling structure such as an EGR cooler is not required and which reduces Nox contained in the exhaust gas in the whole operation areas, so as to correspond to recent exhaust gas regulation. An EGR device 30 for an engine comprises an EGR pipe 14 for continuously connecting an exhaust manifold 4 and an intake manifold 3 of an engine 1, an EGR valve 9 for controlling a passage area of the EGR pipe 14, an ECU 6 for controlling the EGR valve 9. The EGR device 30 further comprises a bypass passage 24 for bypassing the EGR valve 9 and a restrictor 25 is installed in the bypass passage 24.