Turbocharger: Description and Operation

Turbo Charger:

PURPOSE AND LOCATION
The turbo charger, bolted to the intake manifold, provides an effective way of boosting the power output of an engine without increasing its cubic capacity.

Turbo Charger And Parts (Typical):

CONSTRUCTION AND OPERATION
The turbo charger consists two bladed rotors mounted on a shaft. The first of these (the turbine) is propelled by the exhaust gases exiting the cylinders, while the second (compressor) is used to compress the intake air.
Since compressed air contains more oxygen per unit of volume (higher air density), it can fill the cylinder to a higher degree, therefore increasing engine horse power.
The maximum speed of the turbo charger rotors is approx. 120,000 RPM, this requires that the rotors are carefully ballanced.
To regulate the maximum charge pressure, the turbo charger houses a wastegate valve. When the exhaust gas pressure gets to high, the wastegate valve opens a by-pass around the turbine wheel, reducing the exhaust gas pressure in the manifold. This will result in lower turbo rotor speeds and as a result, it will lower the boost pressure in the intake manifold.
The lubrication of the turbo charger is accomplished by the normal engine lubrication system. A supply line feeds the turbo charger with pressurized oil from the oil system. The engine oil lubricates the floating bearings, where the charger shaft floats on a film of oil, then returns into the crankcase through the return line.
The turbo charger is cooled by the regular cooling system. Engine coolant gets routed through the charger housing via an inlet and outlet line. The coolant's main function is to cool the turbo bearings.

CAUTION: 1. The engine oil (amount and purity) is an important factor in the service life of the turbo charger. Always change the engine oil/filter as often as Volvo recommends and refill with the correct oil quality/grade.
2. Never race the engine immediately after start-up. Allow the engine to idle for a while so the turbo charger can be properly lubricated.
3. Allow the engine to idle before shut-down. If the engine is turned off at high Rpm, the turbo will rotate without lubrication for a long time. This can ruin the turbo charger shaft and bearings under extreme conditions. By letting the engine idle for a while before turning off, the turbo charger has time to slow down and reduce its temperature.