Abstract: In the case of a method for operationally testing an exhaust gas turbocharger with a variable turbine geometry, actual values are detected of operating quantities which influence the operational capability of the exhaust gas turbocharger and which comprise main quantities which are used for deciding whether a fault exists in the exhaust gas turbocharger, as well as auxiliary quantities which describe a component of the exhaust gas turbocharger and are used for identifying faults in this component. In a first step, for fault detection, a quantity is measured as the main quantity which determines the engine air supply. In a second step, at least one auxiliary quantity is measured for the fault identification and, in the event of an unacceptable deviation of the actual auxiliary quantity value from the desired auxiliary quantity value, a fault signal is generated.

Abstract: In a piston for an internal combustion engine, which includes in its top an annular cooling oil passage which, at one side of the piston, is in communication with a cooling oil supply passage extending axially through the piston and has a bottom opening through which cooling oil is supplied by an injection nozzle, and, opposite the cooling oil supply passage, a cooling oil return passage in communication with the annular cooling oil passage for removing the cooling oil therefrom, at least the cooling oil supply passage includes cooling oil retaining pockets which retain, during outward movement of the piston, part of the cooling oil supplied to the cooling oil supply passage and from which the retained cooling oil is dislodged and moved to the annular cooling oil passage during inward movement of the piston.