Fuel Delivery and Air Induction: Description and Operation

Fig. 1 Turbocharger assembly.:

Fig. 2 Turbocharger assembly.:

Fig. 3 Turbocharger assembly.:

Fig. 4 Turbocharger assembly. 3S-GTE gasoline engine:

The turbocharger assembly, Figs. 1 through 4, utilize hot exhaust gasses to drive a turbine wheel, which in turn drives a compressor impeller, in order to pressurize air entering the engine. The turbine wheel and compressor impeller are mounted on a common shaft which rides on a floating, sliding contact bearing that receives pressure lubrication from the engine oil system. The turbocharger is mounted directly adjacent to the exhaust ports in order to take maximum advantage of exhaust gas energy, and the compressed air is routed into the intake manifold through the fuel injection air flow sensor or air flow meter assembly from the air cleaner.
Lubricating oil is supplied through a special line directly from the engine oil pump, providing sufficient flow to allow the shaft to ``float'' on a film of oil. Oil is returned to the engine pan through a large diameter drain tube. The turbine (exhaust) and compressor (intake) housings are sealed from the bearing housing by means of piston ring type sealing rings that are fitted into grooves in the shaft.
Boost pressure in the intake manifold is primarily controlled by engine RPM and load, however, pressure is limited during high RPM operation by a boost pressure regulator (wastegate). The wastegate is located on the engine exhaust side, and directs exhaust gas flow through a by-pass duct when boost pressure exceeds the calibration point of the actuator diaphragm installed in the compressor housing.
An intercooler assembly is used on 7M-GTE and 3S-GTE engines. The intercooler cools the intake air charge (turbocharged air), expelled by the turbocharger assembly, increasing the air density. As the air intake charge efficiency increases, the exhaust gas temperature supplied to the combustion chambers decreases, producing more engine power. The intercooler used on the 3S-GTE engine is a water cooled type and is located at the front of the vehicle, utilizing the vehicle windstream to cool the turbocharged air. The intercooler used on the 7M-GTE engine is an air cooled type and is also located at the front of the vehicle.