5005653 JOHNSON Service Manual - English

Illustration 1 g01102550
(1) Exhaust valve
(2) Inlet valve
(3) Aftercooler core
(4) Precooler
(5) High pressure turbocharger
(6) Exhaust inlet for the high pressure turbocharger
(7) Wastegate
(8) Outlet for the inlet air on the high pressure turbocharger
(9) High pressure turbocharger exhaust outlet
(10) Inlet for the inlet air on the high pressure turbocharger
(11) Exhaust inlet for the low pressure turbocharger
(12) Wastegate pressure line
(13) Exhaust outlet for the low pressure turbocharger
(14) Outlet for the inlet air on the low pressure turbocharger
(15) Low pressure turbocharger
(16) Inlet for the inlet air on the low pressure turbocharger The engine components of the air inlet and exhaust system control the quality of air and the amount of air that is available for combustion. The components of the air inlet and exhaust system are the following components:
Air cleaner
Turbochargers
Precooler
Aftercooler
Cylinder head
Valves and valve system components
Piston and cylinder
Exhaust manifoldThe low pressure turbocharger compressor wheel pulls inlet air through the air cleaner and into air inlet (16). The air is compressed by low pressure turbocharger (15). Pressurizing the inlet air causes the air to heat up. The pressurized air exits the low pressure turbocharger through outlet (14) and the air is forced into inlet (10) of high pressure turbocharger (5).The high pressure turbocharger is used in order to compress the air to a higher pressure. This increase in pressure continues to cause the inlet air's temperature to increase. As the air is compressed, the air is forced through the high pressure turbocharger's outlet (8) and into the air lines to precooler (4).The pressurized inlet air is cooled by the precooler prior to being sent to the aftercooler. The precooler uses engine coolant to cool the air. Without the precooler, the inlet air would be too hot in order to be cooled sufficiently by the aftercooler. The inlet air then enters aftercooler core (3). The inlet air is cooled further by transferring heat to the ambient air. The combustion efficiency increases as the temperature of the inlet air decreases. Combustion efficiency helps to provide increased fuel efficiency and increased horsepower output. The aftercooler core is a separate cooler core that is mounted in front of the engine radiator. The engine fan and the ram effect of the forward motion of the vehicle causes ambient air to move across the core.Inlet air is forced from the aftercooler into the engine's intake manifold. The airflow from the intake manifold into the cylinders and out of the cylinders is controlled by engine's valve mechanisms.Each cylinder has two inlet valves (2) and two exhaust valves (1) that are mounted in the cylinder head. The inlet valves open when the piston moves downward on the inlet stroke. When the inlet valves open, cooled, compressed air from the intake manifold is pulled into the cylinder. The inlet valves close when the piston begins to move upward on the compression stroke. The air in the cylinder is compressed by the piston. As the air is compressed by the piston, the temperature of the air in the cylinder is heated. Fuel is injected into the cylinder when the piston is near the top of the compression stroke. Combustion begins when the fuel mixes with the hot, pressurized air. The force of combustion pushes the piston downward on the power stroke. The exhaust valves are opened as the piston travels upward to the top of the cylinder. The exhaust gases are pushed through the exhaust port into the exhaust manifold. After the piston completes the exhaust stroke, the exhaust valves close and the cycle begins again.Exhaust gases from the exhaust manifold flow into the high pressure turbocharger's exhaust inlet (6). The hot gases that are expelled from the engine are used to turn the turbine wheel of the turbocharger. The turbine wheel drives the compressor wheel that is used in order to compress the inlet air that enters the inlet side of the turbocharger. The exhaust gas exits from the high pressure turbocharger through the high pressure turbocharger's exhaust outlet (9).Wastegate (7) is used by the high pressure turbocharger to prevent an overspeed condition of the turbocharger's turbine wheel during engine acceleration. The wastegate also prevents excessive boost of the engine during engine acceleration. The wastegate is controlled by the boost pressure that is felt in the air hose assembly that connects the inlet side of the two turbochargers. Wastegate pressure line (12) provides the air pressure to the wastegate's diaphragm. As the diaphragm reacts to high boost pressure, a valve is actuated. The valve allows exhaust gas to bypass the high pressure turbocharger's turbine. This effectively controls the speed of the turbine.The exhaust gases then enter the exhaust inlet for the low pressure turbocharger (11). The exhaust gases drive the turbocharger's turbine. This energy is used in order to compress the inlet air in the same manner as the high pressure turbocharger. The exhaust gases then exit the low pressure turbocharger through the exhaust outlet for the low pressure turbocharger (13). The exhaust gases are then expelled into the vehicle's exhaust system.Turbochargers
Illustration 2 g01102627
Turbochargers
(1) Wastegate
(2) High pressure turbocharger
(3) Low pressure turbocharger High pressure turbocharger (2) is mounted to the exhaust manifold of the engine. Low pressure turbocharger (3) is located below the high pressure turbocharger on the engine. The exhaust gas from the low pressure turbocharger is fed into the vehicle's exhaust system. Wastegate (1) is used in order to control the amount of exhaust gas that enters the turbocharger's turbine during engine acceleration.
Illustration 3 g01102643
Typical example of a turbocharger
(4) Air inlet
(5) Compressor housing
(6) Compressor wheel
(7) Bearing
(8) Oil inlet port
(9) Bearing
(10) Turbine housing
(11) Turbine wheel
(12) Exhaust outlet
(13) Oil outlet port
(14) Exhaust inlet The exhaust gas from the engine enters the turbocharger's turbine housing (10) through exhaust inlet (14). The blades of the turbocharger's turbine wheel (11) are caused to rotate. As the turbine rotates, the exhaust gas flows around the turbine and exits through the turbocharger's exhaust outlet (12). Because the turbocharger's turbine wheel is connected by a shaft to the turbocharger's compressor wheel (6), the turbine wheel and the compressor wheel are caused to rotate at