Abstract: In a method for the operation of a four-stroke reciprocating piston internal combustion engine with alternating compression. ignition and spark ignition, fuel is injected directly, fresh charge is delivered and combustion exhaust gas is led off. At low and medium partial load a partially homogenized, lean basic mixture of air, fuel and retained exhaust gas is formed for the compression ignition, and at higher partial load and at full load a homogeneous, stoichiometric mixture is formed for the spark ignition. Further features include exhaust gas retention, a build-up of exhaust gas and activation injection into the retained exhaust gas. For a smooth transition between the two operating modes, in addition to the co-ordinated interaction of exhaust gas retention, build up of exhaust gas, restriction of the fresh charge, and of the ignition advance angle in spark ignition, together with the quantity and the timing of the fuel injection, use is also made of exhaust gas recirculation.

Abstract: In a four-stroke reciprocating-piston internal combustion engine, a method is carried out for operating the latter with a homogeneous lean basic mixture of air, fuel and retained exhaust gas and with compression ignition and direct fuel injection into a combustion space. In order to avoid ignition problems during compression ignition and in the case of a low load, in an activation phase, the retained exhaust gas is compressed in the region of the gas-exchange dead center and is subsequently expanded, and, in this phase of the work cycle, activation fuel is injected into the combustion space in order to stabilize main combustion.

Abstract: A method for operating a four-stroke internal combustion engine which allows the combustion-chamber pressure to be equalized in a cylinder-selective manner consistent with the cycle, in which the quantity of exhaust gas retained with valve closure overlap selected is controlled or preset as a function of the engine speed and load by an exhaust throttle valve affecting all the combustion chambers, and the pressure in the individual combustion chambers when the inlet members are opened is equalized by corresponding cylinder-selective activating injection in a manner consistent with the cycle.

Abstract: The invention concerns a method for operation of a four-stroke reciprocating internal combustion engine with a homogenous lean base mixture of air, fuel and retained exhaust, as well as with compression ignition and direct fuel injection into a combustion chamber with gas displacement devices.In order to keep the design cost low for this concept, the reciprocating internal combustion engine is operated at partial load with compression ignition and preferably mechanically controlled exhaust retention, whereas operation in the full load and high partial load range occurs as a spark ignition engine.