0397722 EVINRUDE CARBURETOR ASSEMBLY

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System Overview
The components of the air inlet and exhaust system control the quality and the amount of air that is available for combustion. There are eight separate turbochargers on the C175-20 cylinder. There are four low-pressure turbochargers, and there are four high-pressure turbochargers. The system is divided in four quadrants. Each quadrant has a high and a low-pressure turbocharger in series. The left quadrants feed the left cylinder bank and the right quadrants feed the right cylinder bank. The exhaust manifolds are mounted on top of the engine between the valve mechanism covers, in the center of the vee, and underneath the air system platform. The engine utilizes a single camshaft that runs down the top center of the engine block. The camshaft controls the movement of the valve system components. The engine utilizes cross flow cylinder heads to provide ventilation for the engine combustion system.
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Typical inlet air flow
(1) Inlet air supply
(2) Low-pressure turbochargers
(3) High-pressure turbochargers
(4) Supply to aftercooler
(5) Air return from aftercooler
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Typical exhaust air flow
(2) Low-pressure turbochargers
(3) High-pressure turbochargers
(6) Exhaust air from cylinder heads
(7) Exhaust manifold
(8) Exhaust gas outlet from turbochargers
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(1) Inlet air supply
(2) Low-pressure turbocharger
(3) High-pressure turbocharger
(4) Supply to aftercooler
(5) Return from aftercooler
(8) Exhaust gas outlet
(9) Air elbowsInlet air is pulled through the air filters into the air inlet (1) for each low-pressure turbocharger (2). The rotation of the low-pressure turbocharger compressor wheel forces the compressed air through air elbows (9) and into the inlet for the high-pressure turbochargers (3).The rotation of the compressor wheel in the high-pressure turbochargers further pressurizes the inlet air. Pressurizing the inlet air also increases the temperature of the inlet air. The compressed air exits the high-pressure turbochargers (3) and flows to the outlet to the aftercooler (4). The compressed air flows through the aftercoolers to the air intake manifolds (5). This cooled compressed air fills the inlet chambers in the cylinder heads. Air flow from the inlet chamber into the cylinder head is controlled by the intake valves.There are two intake valves and two exhaust valves for each cylinder. Refer to Systems Operation / Testing and Adjusting, "Valve Mechanism".The intake valves open when the piston moves down on the intake stroke. The cooled, compressed air is pulled into the cylinder from the inlet chamber. The intake valve closes 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 begins. The force that is generated by combustion pushes the piston downward on the power stroke.When the piston begins to move upward again, the piston is on the exhaust stroke. The exhaust valves open and the exhaust gases are pushed through the exhaust port into the exhaust manifold. After the exhaust stroke is complete, the exhaust valve closes and the cycle starts again.The HAA exhaust manifolds (7) are segmented by quadrant. The left rear cylinders go to the left rear quadrant high-pressure turbocharger (3), then to the low-pressure turbocharger (3). The two rear quadrants flow together through a Y-pipe and out the exhaust gas outlet.Note: The exhaust flow is the same for the right of the engine.After leaving the high-pressure turbochargers, the exhaust gases flow through exhaust tubing and down to the turbine wheels of the low-pressure turbochargers (2). The exhaust gases from each bank are split to provide flow to each of the four low-pressure turbochargers. The hot exhaust gases cause the turbine wheel of each turbocharger to rotate. The turbine wheels are directly connected to the shaft that drive the compressor wheels. After leaving the turbine, the exhaust exits the engine through outlet (8).