Turbocharger

Turbocharger System Schematic:

The 7M-GTE engine is equipped with a Turbocharger system, designed to increase engine output by sending a greater air/fuel mixture to the engine than could normally be attained through natural aspiration. The Turbocharger utilizes spent exhaust gas heat and pressure to drive a turbine rotor, which is connected to an impeller wheel in the intake air pick-up. The impeller compresses the air in the intake manifold according to the amount of turbine revolutions. Only air is compressed, as the fuel is injected at the intake ports by the fuel injection system. However, when the fuel atomizes with the pressurized air, a larger mixture "charge" can be forced into the cylinders. Because engine output depends on the amount of air/fuel mixture ignited per unit of time, supplying a larger mixture amount can substantially increase output, without an increase in engine speed. This is accomplished by increasing "combustion pressure" in the cylinders.

The turbine speed increases with engine speed, (increased exhaust flow), causing intake manifold air pressure to increase, thus increasing engine output (performance). The turbocharger has an operational range of approximately 20,000 to 110,000 rpm. The Turbocharger turbine/impeller shaft rides on two full floating bearings, which are lubricated with crankcase oil under pressure from the engine oil pump. The housing also has coolant passages, which allows engine coolant to cool the turbo.

If Turbocharger pressure gets to high, predetonation (pinging) may occur, causing engine damage and poor performance. To reduce turbo pressure, a Wastegate Valve opens in the exhaust passage and bypasses exhaust flow around the turbine. This serves to slow the rotation of the turbine and therefore the impeller. The Wastegate Valve is opened by a pressure diaphragm that senses the pressure in the air intake, before the throttle valve. The turbo compresses air after the Airflow Meter, so that data sent to the ECU concerning intake air volume/temperature will not be affected and fuel can be injected accurately.