Turbo Charger

Fig. 1 Turbocharger System:

PURPOSE AND LOCATION
The turbo charger, bolted to the exhaust 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 of two rotors mounted on a common shaft. The first rotor (the turbine) is propelled by exhaust gases exiting the cylinders, while the second (the compressor) compresses the intake air.

Since compressed air contains more oxygen per unit of volume (higher air density), it fills the cylinder to a higher degree, increasing engine horse power.

Turbine Speed
Maximum speed of the turbo charger rotors is approx. 120,000 RPM. This requires that the rotors are carefully balanced.

Wastegate Valve
To regulate the charge pressure, the turbo charger uses a wastegate valve. When the intake manifold pressure gets too high, the wastegate valve opens a by-pass around the turbine wheel, reducing the exhaust gas pressure in the manifold. This results in lower turbine rotor speed and as a result, lowers the boost pressure in the intake manifold.

Lubrication
The turbo charger is lubricated by the engine lubrication system. A supply line feeds the turbo charger with pressurized oil from the engine lubrication system. The engine oil lubricates the floating bearings where the charger shaft floats on a film of oil. Engine oil returns into the crankcase via the return pipe.

Fig. 3 Water-Cooled Turbo:

Cooling
The charger uses the engine cooling system to control bearing temperature. A supply and return line route coolant through the turbo charger bearing housing. The coolant, together with the engine oil, reduce the turbo temperatures by approximately 50% over engine oil cooled units. This reduces the overall thermal load and increases turbo charger reliability and service life.