TM 5-2410-240-23-1
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ENGINE SYSTEMS CONTINUED
Turbocharger
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The turbocharger mounts on the exhaust manifold outlet on the right side of the engine. The turbocharger uses
energy from exhaust gas to compress inlet air to a higher pressure. Compressing inlet air forces more air into the
cylinders. Increased airflow into the cylinders allows fuel to burn with greater efficiency and produces more power.
Exhaust gas enters the turbine housing (Figure 5, Item 2). Energy from the exhaust gas rotates the turbine wheel
inside the turbine housing. The turbine wheel connects by shaft to the compressor wheel inside the compressor
housing (Figure 5, Item 1). As the engine load increases, so does the amount of exhaust gas. The additional
exhaust gas rotates the turbine wheel and compressor wheel faster. Air from the air filter enters the compressor
housing. The air is compressed and heated to about 300F (150C), and then forced into the engine aftercooler,
where it is cooled before entering the cylinders.
A wastegate (valve) on the turbine housing (Figure 5, Item 2) allows exhaust gas to bypass the turbine wheel. The
operation of the wastegate is dependent on pressurized air (boost pressure) from the turbocharger compressor.
The boost pressure acts on a spring-loaded diaphragm in the wastegate actuator (Figure 5, Item 4) to vary the
amount of exhaust gas that flows into the turbine.
The engine Electronic Control Module (ECM) uses input from multiple sensors to determine the optimum boost
pressure to achieve the best exhaust emissions and fuel consumption for any given engine operating condition.
The engine ECM uses a solenoid valve to regulate boost pressure to the wastegate actuator.
When high boost pressure is necessary for engine performance, the engine ECM signals the wastegate solenoid.
This causes low pressure in the air inlet pipe (Figure 5, Item 5) to act on the diaphragm within the wastegate
actuator (Figure 5, Item 4). In turn, the actuating rod (Figure 5, Item 3) acts upon the actuating lever to close the
wastegate. When the wastegate is closed, more exhaust gas is able to pass over the turbine wheel. This results in
an increase in turbocharger speed.
When low boost pressure is necessary for engine performance, the engine ECM signals the wastegate solenoid.
This causes high pressure in the air inlet pipe (Figure 5, Item 5) to act on the diaphragm within the wastegate
actuator (Figure 5, Item 4). The actuating rod (Figure 5, Item 3) acts upon the actuating lever to open the
wastegate. When the wastegate is open, more exhaust gas is able to bypass the turbine wheel. This results in a
decrease in turbocharger speed.
Figure 5. Turbocharger.
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