885177 Mercruiser RETAINER

Illustration 1 g01356032
Air inlet and exhaust system
(1) Exhaust manifold
(2) Injector
(3) Glow plug
(4) Intake manifold
(5) Aftercooler core (if equipped)
(6) Exhaust outlet
(7) Turbine side of turbocharger
(8) Compressor side of turbocharger
(9) Air intake from the air cleaner
(10) Inlet valve
(11) Engine cylinder
(12) Exhaust valve The components of the air inlet and exhaust system control the quality of air and the amount of air that is available for combustion. The air inlet and exhaust system consists of the following components:
Air cleaner
Turbocharger
Aftercooler (if equipped)
intake manifold
Cylinder head, injectors and glow plugs
Valves and valve system components
Piston and cylinder
Exhaust manifoldEngines which are naturally aspirated pull outside air through an air cleaner directly into the intake manifold (4). The air flows from the intake manifold to the engine cylinders (11). The air mixes with the fuel and leads to combustion. After combustion, the exhaust gases flow directly to the outside air through the exhaust manifold (1).A turbocharger increases the temperature and the density of the air that is sent to the engine cylinder. This condition causes a lower temperature of ignition to develop earlier in the compression stroke. The compression stroke is also timed in a more accurate way with the fuel injection. Surplus air lowers the temperature of combustion. This surplus air also provides internal cooling.In turbocharged engines, air is drawn in through the air cleaner into the air intake of the turbocharger (9) by the turbocharger compressor wheel (8). The air is compressed and heated to about 150 °C (300 °F) before the air is forced to the aftercooler (5). As the air flows through the aftercooler the temperature of the compressed air lowers to about 50 °C (120 °F). Cooling of the intake air increases combustion efficiency. Increased combustion efficiency helps achieve the following benefits:
Lower fuel consumption
Increased horsepower output
Increased engine torque
Increased durability of the engine
Reduced particulate emissionFrom the aftercooler, air is forced into the intake manifold (4). Air flow from the intake manifold to the cylinders is controlled by inlet valves (10). There is one inlet valve and one exhaust valve for each cylinder. The inlet valves open when the piston moves down on the intake stroke. When the inlet valves open, cooled compressed air from the intake port is forced into the cylinder. The complete cycle consists of four strokes:
induction
Compression
Power
ExhaustOn the compression stroke, the piston moves back up the cylinder and the inlet valve (10) closes. The cool compressed air is compressed further. This additional compression generates more heat. Note: If the cold starting system is operating, the glow plugs (3) will also heat the air in the cylinder.Just before the piston reaches the Top Center (TC) position, fuel is injected into the cylinder. The air/fuel mixture ignites. The ignition of the gases initiates the power stroke. Both the inlet and the exhaust valves are closed and the expanding gases force the piston downward toward the Bottom Center (BC) position .From the BC position, the piston moves upward. This initiates the exhaust stroke. The exhaust valve (12) opens. The exhaust gases are forced through the open exhaust valve into the exhaust manifold (1).Exhaust gases from exhaust manifold (1) enter the turbine side (7) of the turbocharger in order to turn turbocharger turbine wheel. The turbine wheel is connected to the shaft that drives the compressor wheel. Exhaust gases from the turbocharger pass through exhaust outlet (6), a silencer and an exhaust pipe.Turbocharger
Illustration 2 g01263770
Turbocharger
(1) air intake
(2) Compressor housing
(3) Compressor wheel
(4) Bearing
(5) Oil inlet port
(6) Bearing
(7) Turbine housing
(8) Turbine wheel
(9) Exhaust outlet
(10) Oil outlet port
(11) Exhaust inlet The turbocharger is mounted on the outlet of the exhaust manifold in one of two positions on the right side of the engine, toward the top of the engine or to the side of the engine. The exhaust gas from the exhaust manifold enters the exhaust inlet (11) and passes through the turbine housing (7) of the turbocharger. Energy from the exhaust gas causes the turbine wheel (8) to rotate. The turbine wheel is connected by a shaft to the compressor wheel (3).As the turbine wheel rotates, the compressor wheel is rotated. This causes the intake air to be pressurized through the compressor housing (2) of the turbocharger.
Illustration 3 g01356055
Typical turbocharger with the wastegate
(12) Actuating lever
(13) Wastegate actuator
(14) Line (boost pressure) When the load on the engine increases, more fuel is injected into the cylinders. The combustion of this additional fuel produces more exhaust gases. The additional exhaust gases cause the turbine and the compressor wheels of the turbocharger to turn faster. As the compressor wheel turns faster, air is compressed to a higher pressure and more air is forced into the cylinders. The increased flow of air into the cylinders allows the fuel to be burnt with greater efficiency. This produces more power.A wastegate is installed on the turbine housing of the turbocharger. The wastegate is a valve that allows exhaust gas to bypass the turbine wheel of the turbocharger. The operation of the wastegate is dependent on the pressurized air (boost pressure) from the turbocharger compressor. The boost pressure acts on a diaphragm that is spring loaded in the wastegate actuator which varies the amount of exhaust gas that flows into the turbine.The turbocharger has a wastegate which is controlled by a diaphragm. One side of this diaphragm is open to the atmosphere. The other side of this diaphragm is open to the boost pressure in the intake manifold.The shaft that connects the turbine to the compressor wheel rotates in bearings (4 and 6). The bearings require oil under pressure for lubrication and cooling. The oil that flows to the lubricating oil inlet port (5) passes through the center of the turbocharger which retains the bearings. The oil exits the turbocharger from the lubricating oil outlet port (10) and returns to the oil pan.Cylinder Head And Valves
The valves and the valve mechanism control the flow of the air and the exhaust gases in the cylinder during engine operation. The cylinder head assembly has two valves for each cylinder. Each valve has one valve spring. The ports for the inlet