Turbocharger: Description and Operation

Forward Turbocharger W/ Accessories And All Piping:

Rear Turbocharger W/ Accessories And All Piping:

The turbochargers are used to increase engine output by providing a denser air/fuel charge to the engine than could normally be attained through natural aspiration. Each turbocharger utilizes spent exhaust gas pressure to drive a turbine rotor, which is connected to and drives an impeller wheel in the intake air piping. The impeller compresses the air in the intake manifold according to the amount of turbine revolutions. This vehicle is equipped with two turbochargers. The primary reason for this is to allow the installation of smaller diameter turbine wheels which have a lower rotary inertia. The lower inertia allows the turbine sections to accelerate much quicker than a single turbine of equal output. This configuration makes for a dramatic reduction in the driveability problem know as "turbo lag".

Only air is compressed, as fuel is injected at the intake ports by the fuel injection system. However, when the fuel atomizes with the pressurized air, a larger volume "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.

The turbine speed increases with exhaust gas flow, (approximately equivalent to engine speed times throttle opening), 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 contains coolant passages, which allow engine coolant to cool the turbocharger.

If Turbocharger pressure gets too high, predetonation (pinging) may occur, causing engine damage and poor performance. To limit 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, prior to the throttle valve. To insure that fuel injection can be metered accurately, the turbocharger is positioned in the piping after the Airflow Meter, therefore data sent to the ECU concerning intake air volume/temperature is not affected by intake charge pressurization.