LINK (L.H.) 1S1864 - Caterpillar

The components of the air inlet and exhaust system control the quality and the amount of air that is available for combustion. There are separate turbochargers and exhaust manifolds on each side of the engine. A common aftercooler is located between the cylinder heads in the center of the engine. The inlet manifold is a series of elbows that connect the aftercooler chamber to the inlet ports (passages) of the cylinder heads. There is one camshaft in each side of the block. The two camshafts control the movement of the valve system components.
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Air Inlet And Exhaust System
(1) NOx reduction system (NRS) cooler
(2) Exhaust manifold
(3) Aftercooler (ATAAC or SCAC)
(4) Exhaust outlet
(5) Turbine wheel
(6) Compressor wheel
(7) Air inlet
(8) Inlet valve
(9) Exhaust valveClean inlet air from the air cleaners is pulled through air inlet (7) into the turbocharger compressor by compressor wheel (6). The rotation of the compressor wheel compresses the air. The rotation of the turbocharger compressor wheel then forces the air through a tube to aftercooler (3). The aftercooler lowers the temperature of the compressed air before the air enters the inlet chamber in each cylinder head. Air flow from the inlet chamber into the cylinder heads is controlled by the inlet valves.There are two inlet valves and two exhaust valves for each cylinder. Refer to Systems Operation, "Valve Mechanism". The inlet valves open when the piston moves down on the inlet stroke. The cooled, compressed air is pulled into the cylinder from the inlet chamber.The inlet valves close and the piston moves up on the compression stroke. When the piston is near the top of the compression stroke, fuel is injected into the cylinder. The fuel mixes with the air and combustion starts. The force of the combustion pushes the piston downward on the power stroke. When the piston moves upward again, the piston is on the exhaust stroke. The exhaust valves open and the exhaust gases are pushed through the exhaust port into exhaust manifold (1). After the piston makes the exhaust stroke, the exhaust valves close and the cycle begins again.Exhaust gases from exhaust manifold (2) go into the turbine side of the turbocharger. The exhaust gases cause turbine wheel (5) to turn. The turbine wheel is connected to the shaft that drives the turbocharger compressor wheel (6). The exhaust gases exit through exhaust outlet (4).NOx Reduction System (NRS)
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(3) NOx reduction system (NRS) cooler
(2) NRS venturi
(3) NRS valve assembly
Illustration 3 g06208207
(4) NOx reduction system (NRS) cooler
(1) NRS venturi
(2) NRS valve assembly
(3) ERVThe NOx Reduction System (NRS) sends hot exhaust gas from the exhaust manifold through the NRS system and back into the intake. In order for exhaust gas to be able to mix with pressurized air in the intake, back pressure is needed in the exhaust system. This back pressure is created by the Exhaust Restriction Valve (ERV). The ERV is at the end of the exhaust manifold between cylinders 10 and 12. When NRS flow is requested by the ECM, the ERV valve will