Abstract: An internal-combustion engine is equipped with a ventilation system which is used for ventilating the crankcase. The ventilation system cooperates with an oil separator, is connected with an intake pipe and, furthermore, is provided with throttles. For expanding the application range and optimizing the effect of the ventilation system, the latter comprises the crankcase ventilation and a turbocharger ventilation, the crankcase ventilation and the turbocharger ventilation being connected to a distributor unit assigned to the oil separator. The distributor unit has a first throttle and a second throttle. In this case, with the insertion of the oil separator, the first throttle is connected with a first pipe connected to the intake pipe; the second throttle is connected with the intake pipe by way of a second pipe. In the suction operation, the ventilation system operates by way of the second pipe and, in the charger operation, it operates by way of the first pipe.

Abstract: In order to prevent penetration of lubricant into the combustion chamber, a piston for an internal combustion engine has a labyrinthine pressure equalizing passage between the combustion chamber and the crankcase. For this purpose, the piston ring closest to the combustion chamber is guided with relatively large axial play in the matching annular groove. The piston rings located farther from the combustion chamber are each provided with recesses that connect the annular chamber between the adjacent piston rings with the bottom of the respective annular groove. A bore is also provided in the annular groove that is farthest from the combustion chamber, the bore connecting the bottom of the annular groove with an interior chamber defined in the piston. In this way, the pressure can equalize between the combustion chamber and the crankcase.