Colt L4-1597cc 1.6L SOHC Turbo (1984)
Turbocharger: Description and Operation
Fig. 57 Typical turbocharger.
Fig. 58 Turbocharger cross sectional view
The turbocharger, Figs. 57 and 58, is an exhaust driven device which compresses the air being delivered to the engine through the intake system. The
turbocharger is used to increase engine power on a demand basis, allowing a smaller more economical engine to be used.
Exhaust gasses flow through a turbine which is connected through a shaft to the impeller (compressor). During normal, steady operation, the turbine
does not rotate fast enough to boost pressure. As speed increases, the mixture is compressed, allowing a denser mixture to enter the combustion
chambers and develop more engine power during the combustion process.
The intake manifold pressure (boost pressure) is controlled by a wastegate valve which is used to bypass a portion of the exhaust gasses around the
turbine at a predetermined point in the cycle, limiting boost pressure.
The turbocharger shaft bearings are lubricated by engine oil pressure, and on some models the turbocharger center section is water cooled. Due to the
extreme high heat and high RPM operating conditions, a constant supply of clean oil is essential to proper turbocharger operation and service life. The
engine should never be shut off immediately after driving, as flow of oil to the turbocharger bearings will be stopped while the shaft is still rotating, and
excessive heat build-up during the ``hot soak'' period after engine shut down will cause residual oil on the turbocharger bearings to carbonize. Rather the
engine should be allowed to idle for several minutes after driving to allow the turbocharger to cool and to maintain oil pressure until the turbine shaft
slows down or stops.
