Delta 88 V6-231 3.8L (1983)
As engine load increases and the throttle opens, more air-fuel mixture is drawn into the combustion chambers. As the increased volume is burned, a
larger volume of high energy exhaust gasses enters the engine exhaust system and is directed through the turbocharger turbine housing, Fig. 16. Some of
the exhaust gas energy is used to increase the speed of the turbine wheel which is connected to the compressor wheel. The increased speed of the
compressor wheel compresses the air-fuel mixture and delivers the compressed air-fuel mixture to the intake manifold, Fig. 16. The high pressure in the
intake manifold allows a denser charge to enter the combustion chambers, in turn developing more engine power during the combustion cycle.
The intake manifold pressure (Boost) is controlled to a maximum value by an exhaust gas bypass valve (Wastegate). The wastegate allows a portion of
the exhaust gas to bypass the turbine wheel, thereby not increasing turbine speed. On 1982-83 models, the wastegate is operated by a spring loaded
diaphragm device sensing the pressure differential across the compressor. When intake manifold pressure reaches a set value above ambient pressure, the
wastegate begins to bypass the exhaust gas. On 1984-87 models, an electronic wastegate is used. In this system, a pulse width modulated solenoid has
been positioned between the manifold and wastegate diaphragm. Information regarding air flow, engine RPM, transmission gear and detonation is
collected and analyzed by the Electronic Control Module. If the engine will tolerate additional boost, the solenoid signals the wastegate accordingly.
Inside the wastegate, the exhaust divert valve is normally closed, allowing boost pressure to rise until the mass air flow called for by the ECM is
satisfied. When air flow reaches this level, the exhaust divert valve opens, allowing the exhaust gas to divert around the turbine and flow directly into the
exhaust system.
