Abstract: A process operates a piston engine in which at least one intake valve and at least one exhaust valve are assigned to each of the cylinders of the piston engine. The piston engine is equipped with a valve actuator permitting variable opening and closing times. An engine control system of the piston engine determines a current actual value of an exhaust gas mass proportion. The value forms the contents of the cylinders together with a fresh gas mass proportion after the fresh gas has been supplied and before combustion. The engine control system actuates the valve actuator in order to set a desired value for the exhaust gas mass proportion.

Abstract: In a method for entering program data into a control unit in a motor vehicle, the program data are provided by a data transfer point, via the following steps: a program data acceptance request is sent to the control unit, the control unit changes to a program data acceptance state, the program data are transmitted to the control unit, and the program data are accepted by the control unit. Before the control unit changes to the program data acceptance state, the control unit checks whether program data acceptance conditions prescribed for the control unit exist.