49178 - 00500 Excavator Turbocharger ME080098 Oil Cooled for 4D31 Engine

Characteristic

The compressor wheel and turbine wheel are connected via a steel shaft. In a traditional turbocharger, this shaft rides in a bearing system within a cast-iron housing. The bearing system consists of journal bearings to control radial movement and a thrust bearing to control axial movement. Radial clearances are specified in ten-thousandths of an inch.

Smaller turbochargers can easily exceed 200,000 rpm. Lubriion is critical and oil provides a thin boundary layer in which the bearings and shaft rotate. Oil also plays an important role in removing heat from the system. Piston rings are used on either end of the shaft to contain the oil and prevent exhaust/boost pressure from entering the center section. Due to the high exhaust temperatures in gasoline appliions, water cooling is typically applied to reduce temperatures in the bearing housing and prevent oil coking during heat soak conditions.