Abstract: In an exhaust gas recirculation arrangement comprising a housing forming a passage for an exhaust gas flow of an internal combustion engine and having a valve seat with a valve disc movably supported in the housing on a valve stem so as to be seated on the valve seat for closing the valve but being movable therefrom against the flow direction of the exhaust gas for opening the valve, a flow guide member is disposed in the valve housing upstream of the valve disc in such a way that, in its open position, the valve disc abuts the guide member and the guide member conducts the exhaust gas past the valve disc.

Abstract: A multi-cylinder internal combustion engine is provided which includes an exhaust gas driven turbocharger. Each cylinder includes at least one inlet port controllable by an inlet valve, at least one outlet port controlled by an outlet valve, and at least one separate additional auxiliary valve arranged in the cylinder head of the engine. A line for gas flow communicates with the additional auxiliary valves. The line from the auxiliary valve of at least a first cylinder is connected directly or indirectly with at least one second cylinder, and the gas flow through that line from the first cylinder to the second cylinder is controllably guided also to a pressure storage device and/or a turbine of the turbocharger.

Abstract: In an internal combustion engine with exhaust gas re-circulation including a fresh air supply duct extending from the charger of a turbocharger to the engine, an exhaust pipe extending from the engine to the turbine of the turbocharger for driving the turbocharger, and an exhaust gas re-circulation pipe extending from the exhaust pipe to the intake duct, the exhaust gas re-circulation pipe includes a flap valve having a pivotally supported flap which, in an open position of the flap valve, is disposed in a plane parallel to the direction of the exhaust gas flow through the flap valve for minimizing the flow resistance in the exhaust gas re-circulation pipe.

Abstract: A piston internal-combustion engine has a control system for controlling the number of strokes of the combustion process taking place inside a combustion space. As a function of operating parameters, the control system controls the engine operating process such that the process has a variable cycle of at least four strokes. A pushing of a charge out of a combustion space of the piston internal-combustion engine does not take place before one or several operating parameters have reached one defined limit value, respectively.

Abstract: A process for selective catalytic reduction of nitrogen oxides from exhaust gases, preferably those from diesel engines in vehicles, using pulsed superstoichiometric addition of NH.sub.3 or NH.sub.3 -releasing substances, comprises controlling the pulsed superstoichiometric addition of NH.sub.3 in such a way that, after it has started, the addition is interrupted again only when the amount of NH.sub.3 stored in the catalyst has reached a specific upper threshold value which is predetermined in accordance with the catalyst properties and the catalyst volume, the amount of NH.sub.3 stored being calculated from the difference between the metered amount of NH.sub.3 and the amount of NO.sub.x separated off, which is determined from the NO.sub.x concentration in the exhaust gas and the average degree of separation, and the addition of NH.sub.3 is resumed only when the amount of NH.sub.