899912013 Mercury TAPPET, (3.258)

Illustration 1 g01108450
Air Inlet and Exhaust System (1) Exhaust manifold (2) Aftercooler (If Equipped) (3) Exhaust valve (4) Inlet valve (5) Cylinder (6) Air inlet (7) Turbocharger compressor wheel (8) Turbocharger turbine wheel (9) Exhaust outletClean inlet air from the air cleaner is pulled through air inlet (6) of the turbocharger. The compressor wheel (7) causes the air to compress. The air then goes into the aftercooler (2) (if equipped). When the inlet valve (4) opens the air goes into the cylinder (5). When the exhaust valve (3) opens, hot exhaust gases flow into exhaust manifold (1). These hot exhaust gases flow into the turbine side of the turbocharger and out exhaust outlet (9) of the turbocharger.
Illustration 2 g01108467
Turbocharger and Jacket Water Aftercooler (If Equipped) (1) Exhaust manifold (5) Cylinder (6) Air inlet (9) Exhaust Outlet (10) Housing for Jacket Water Aftercooler (If Equipped) (11) Turbine wheel housing (12) Air outlet (13) Compressor wheel housing (14) Cylinder head (15) Exhaust inletThe water cooled aftercooler cools the turbocharged air. The compressed air flows into the engine mounted cooler. Cold jacket water from the radiator flows through the aftercooler core. The cold jacket water cools the hot inlet air temperature. The cooler air improves combustion efficiency, which provides two main benefits.
Lower fuel consumption
Increased horsepower outputIn a turbocharged system without an aftercooler, the compressed air flows directly into the inlet manifold. Lower engine ratings and properly designed turbochargers reduce compressed air temperatures. This helps extend the life of the engine.Turbocharger
Illustration 3 g01108481
Turbocharger (1) Air inlet (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 inletThe turbocharger is mounted to the exhaust manifold. All the exhaust gases flow from the exhaust manifold through the turbocharger. The exhaust gases then flow into turbine housing (7) through the exhaust inlet. These gases push the blades of the turbine wheel (8). The turbine wheel is connected by a shaft to the turbocharger compressor wheel (3). Therefore, the exhaust gases cause the two wheels to turn at very high speeds.Clean air from the air cleaner is pulled through the air inlet (1) by the rotation of turbocharger compressor wheel (3). The action of the compressor wheel blades causes compression of the inlet air. Compressed air provides more power to the engine. Additional air is available to fill the combustion chamber after the inlet valve opens.When the load on the engine increases, more fuel is injected into the cylinders. This creates more gases and hotter gases, which will cause the turbine to turn faster. Therefore, the turbocharger compressor wheel will turn faster.As the compressor wheel turns faster, more air is forced into the engine. The increased air flow provides more power to the engine, because the engine can then burn additional fuel with greater efficiency.The following conditions control the maximum rpm of the turbocharger:
Fuel setting
High idle speed setting
Height above sea level
If the high idle rpm or the engine rating is higher than given in the Technical Marketing Information (TMI) for the height above sea level at which the engine is operated, there can be damage to engine or to turbocharger parts. Damage will result when increased heat and/or friction due to the higher engine output goes beyond the engine cooling and lubrication system's abilities.
The factory establishes the fuel setting adjustment for a specific engine application. The governor housing and the turbocharger are sealed. This seal prevents these possible changes:
Adjustment of the fuel
High idle speed settingThe turbocharger's bearings (4) and (6) use engine oil under pressure for lubrication. The oil enters the turbocharger through oil inlet port (5). The oil then flows through passages in the center section for lubrication of the turbocharger bearings. Oil from the turbocharger escapes through the oil outlet port (10). Finally, the oil flows back to the engine lubrication system.Cylinder Head and Cylinder Valves
Each cylinder has one inlet valve and one exhaust valve. Each inlet valve and each exhaust valve has a valve rotator. The valve rotator causes the cylinder valve to turn by a small amount for the opening and for the closing of this cylinder valve. This action helps prevent carbon deposits from forming on the valve face and on the valve seat.The cylinder head has valve seats that can be replaced. The valve guides can also be replaced. Threads on the inside diameter of the valve guides hold oil that lubricates the valve stem. Valve Mechanism
The valve mechanism controls the flow of both the inlet air and the exhaust gases in and out of the cylinders. The valve mechanism consists of the following components: rocker arms, pushrods, valve lifters and camshaft.The crankshaft drives the camshaft. The camshaft is timed to the crankshaft. When the camshaft turns, the camshaft lobes move the valve lifters up and down. The valve lifters move the pushrods that move the rocker arms. Movement of the rocker arms opens the inlet valves and the exhaust valves. The valves open according to the firing order (injection sequence) of the engine. A valve spring closes each cylinder valve, and the valve spring holds each cylinder valve closed.