An engine EGR system is provided, which includes an engine body, an intake passage, an exhaust passage and an EGR passage configured to recirculate exhaust gas as EGR gas to the intake passage. The EGR passage includes an EGR cooler and an EGR internal passage constituting the EGR passage upstream of the EGR cooler, and including a passage passing through a cylinder head. The EGR internal passage has a bent pipe part including a first bent portion at which an upstream portion of the EGR internal passage is bent away from a gas inflow port of the EGR cooler, a second bent portion located downstream of the first bent portion and bending the EGR internal passage toward the gas inflow port, and an intermediate portion connecting the first and the second bent portions by being disposed therebetween. The water-cooling passage is disposed around the bent pipe part.

A method of operating an engine includes igniting a combustible mixture in a combustion chamber of the engine, which produces exhaust gases. The exhaust gases are ejected into an exhaust manifold of the engine to create a primary exhaust stream. A portion of the exhaust gases is separated from the primary exhaust stream to create a secondary exhaust stream. Air and fuel are then mixed with the secondary exhaust stream to form a reformer feed mixture. The reformer feed mixture is reacted in a catalytic reformer to create a reformate exhaust stream, which is then mixed with an intake air stream to create a mixed air stream. The mixed air stream is the fed to the combustion chamber of the engine as the combustible mixture.

A first intake manifold is connected to a first group of cylinders, a second distinct intake manifold is connected to a second group of cylinders and a first, respectively a second, exhaust manifold for receiving the exhaust gas emitted from the first, respectively the second, group of cylinders. An EGR line is connected to the first and second exhaust manifolds. A mixing unit includes a four-way valve having a first inlet connected to an air line, a second inlet connected to the EGR line, a first outlet connected to the first intake manifold and a second outlet connected to the second intake manifold. The first inlet is connected to the air line, the second inlet is connected to the EGR line. The first outlet and said second outlet form a substantially X-shape. The first inlet and said second inlet are coaxial. The first outlet and second outlet are coaxial such that the first inlet is diagonally facing the second inlet and the first outlet is diagonally facing the second outlet.

A valve for m exhaust gas recirculation Mae in an engine includes a first barrel connectable to a first group of cylinders, a second barrel connectable to a second group of cylinders, and a center barrel between the first and second barrels and connectable to an intake of the engine, A poppet valve with two valve heads mounted on a valve stem is provided to open and close openings between the first and second barrels, with one of the valve beads of the poppet valve opening into the center barrel Vanes are provided in the center barrel to direct flow from the opening by the valve bead that opens into the center barrel toward the outlet opening.

An exhaust gas recirculation (EGR) passage is connected with an intake passage (a bypass passage bypassing a supercharger) of an engine. The EGR passage includes, in a position close to a connection port to the intake passage, an expanding portion in which a passage cross-sectional area expands and which lowers a flow speed of EGR gas so as to reduce an uneven flow, in the connection port, of the EGR gas flowing into the intake passage.

An exhaust gas recirculation (EGR) passage is connected with an intake passage (a bypass passage bypassing a supercharger) of an engine. The EGR passage includes, in a position close to a connection port to the intake passage, an expanding portion in which a passage cross-sectional area expands and which lowers a flow speed of EGR gas so as to reduce an uneven flow, in the connection port, of the EGR gas flowing into the intake passage.

A controller, in shifting the state of the EGR system from the EGR operating state to the EGR non-operating state at the time of performing the deceleration of the vehicle, calculates a provisional EGR ratio that is a provisional value of the current EGR ratio, estimates the provisional EGR ratio as the actual EGR ratio when a fore-and-aft differential pressure of the EGR valve is equal to or more than a predetermined value, performs correction to make the provisional EGR ratio smaller, and estimates the corrected provisional EGR ratio as the actual EGR ratio when the fore-and-aft differential pressure of the EGR valve is less than the predetermined value.

A controller, in shifting the state of the EGR system from the EGR operating state to the EGR non-operating state at the time of performing the deceleration of the vehicle, calculates a provisional EGR ratio that is a provisional value of the current EGR ratio, estimates the provisional EGR ratio as the actual EGR ratio when a fore-and-aft differential pressure of the EGR valve is equal to or more than a predetermined value, performs correction to make the provisional EGR ratio smaller, and estimates the corrected provisional EGR ratio as the actual EGR ratio when the fore-and-aft differential pressure of the EGR valve is less than the predetermined value.

An internal combustion engine having a turbocharger with variability at the compressor inlet, and a turbocharger. An internal combustion engine having a turbocharger, and a turbocharger, are described. A device which both performs a change in the cross section of the compressor inlet and brings about an adjustment of the exhaust gas recirculation rate is arranged in the region of the compressor inlet. As a result, the turbocharger is of space-saving and low-cost construction in the compressor inlet region.

An EGR system comprising at least one of an EGR cooler and an EGR valve is arranged above an intake manifold. A pair of facing surfaces which face each other with a space are provided at the EGR system attached to the intake manifold and the intake manifold. A damper plate having elasticity is arranged between these facing surfaces. The damper plate is configured to have a larger thickness than the above-described space and have a smaller Young's modulus than each of a lower-side facing-surface portion and an upper-side facing-surface portion, and the damper plate is clamped between the lower-side facing-surface portion and the upper-side facing-surface portion.