The turbocharger consists of turbine and compressor on a common shaft. The shaft bearing is constructed to higher rotation speed and lubricated by engine oil. The turbocharger is water cooled for improved durability. The turbine wheel is driven by exhaust emissions. The compressor wheel compresses the intake air. A bypass valve (Wastegate) regulates the charging pressure for generating a high pressure at low speed as well. At a defined charging pressure it regulates the way of the exhaust emission on bypassing the turbine wheel. The Wastegate valve is controlled pneumatic and electric from the pressure in the intake manifold. The pressure of exhaust emission is reduced by opening the Wastegate thereby reducing the intake pressure.
Scheme 27
Oil is applied under pressure to the crankshaft bearings (6), connecting rod bearings (7), camshaft bearings (2) and hydraulic lash adjusters (3). In addition the variable oil pump (9), variable camshaft phaser (1), and hydraulic chain tensioner (14) are supplied with pressurized oil. Oil is sucked from the oil pan through the fixed screen into the variable vane type oil pump. The pump is integrated in the front cover and directly driven by the crankshaft. Also integrated into the front cover is a pressure relieve valve (8) that opens when the oil pressure is too high at a cold start. When that valve is open some oil flows directly into the oil pan. Normally the pressurized oil passes into the engine oil gallery leading through the oil cooler (5) to the oil filter assembly (4). The oil is cleaned by passing the filter from the outer to the inner side of the filter. Then the oil flows into the main oil gallery. A filter by-pass valve in the oil filter ensures continues oil flow in case the oil filter should be restricted by more than 1.7 bar. From the oil filter the oil is distributed to the crankshaft bearings, oil pump displacement control chamber (10) and cylinder head feed (11). The connecting rod bearings are supplied by oil flow passages through the crankshaft connecting the main journals to the rod journals. A groove around each upper main bearing furnishes oil to the drilled crankshaft passages. In the cylinder head the oil is distributed to the variable camshaft phasers, chain tensioner, oil pressure switch (12) and through the restrictor orifice (13) into the camshaft feed oil gallery. From there the hydraulic valve lifters and camshaft bearings are supplied with oil.