0385949 JOHNSON DRIVE ASSY

Illustration 1 g00350753
Callouts (1) through (11) follow the air flow from the air cleaner to the muffler. (1) Air cleaner (2) Clean inlet air (3) Turbocharger (4) Clean, hot, pressurized inlet air (5) Air-to-air aftercooler (chassis assembly) (6) Clean, cool, pressurized air (7) Inlet manifold (8) Exhaust manifold (9) Hot exhaust gases (10) Cooler exhaust gases (11) Muffler (12) Fan (13) Radiator
Illustration 2 g00340186
Schematic of Air Inlet and Exhaust System (8) Exhaust manifold. (5) Air-to-air aftercooler core. (14) Exhaust valve. (15) Inlet valve. (7) Inlet manifold (cylinder head). (16) Air piping from turbocharger to aftercooler. (17) Exhaust outlet. (18) Air inlet. (19) Compressor side of turbocharger. (20) Turbocharger shaft. (21) Turbine side of turbocharger.In an air-to-air aftercooler system, compressed, turbocharged air is directed to a mounted cooler in front of the radiator. Air (ambient temperature) is moved across the aftercooler. This allows the aftercooler to lower the inlet valve's air temperature to approximately 43°C (109°F). The air then flows to inlet manifold (7), which is part of the cylinder head. The cooling of the inlet air increases combustion efficiency, which provides two main benefits:
Lower fuel consumption
Increased horsepower outputClean inlet air (2) from air cleaner (1) is pulled through air inlet (18). This inlet air is pulled into the compressor side of turbocharger (19) by rotating compressor wheel (22). The rotating compressor wheel pressurizes the inlet air. Consequently, this compressor wheel heats up the inlet air. This pressurized, hot inlet air is then forced through the air piping from the turbocharger to aftercooler (16). The air-to-air aftercooler core (5) then cools the inlet air. This cool air provides dense, high pressure air to inlet manifold (7) in the cylinder head. When inlet valves (15) open, the cool, dense, high pressure air flows into the combustion chamber. At this point, the cool air mixes with the fuel spray that has been injected for combustion during the compression stroke.When exhaust valves (14) open, hot exhaust gases flow into exhaust manifold (8). These hot exhaust gases flow to the turbine side of the turbocharger (21) and out exhaust outlet (17). When the hot gases pass through both the turbine wheel and the compressor wheel (air inlet side), the exhaust gases' energy turns these wheels via turbocharger shaft (20) .Turbocharger
Illustration 3 g00365373
Turbocharger Cartridge (22) Turbocharger compressor wheel (23) Ring (24) Turbine housing (25) Turbocharger bearing (26) Oil inlet port (27) Ring (28) Deflector (29) Oil outlet port (30) Ring (31) Turbocharger bearing (32) RingThe turbocharger is mounted to exhaust manifold (8). All the exhaust gases flow from exhaust manifold (8) through the turbocharger. The exhaust gases then flow into turbine housing (24) through the exhaust inlet. These gases push the blades of turbine wheel. The turbine wheel is connected by a shaft to turbocharger compressor wheel (22). 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 (18) by the rotation of turbocharger compressor wheel (22). The action of the compressor wheel blades causes compression of the inlet air. Compressed air provides more power to the engine, because more air is available for filling the combustion chamber after inlet valves (15) open.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's compressor wheels turn faster.As the compressor wheels turn 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 (25) and (31) use engine oil under pressure for lubrication. The oil enters the turbocharger through oil inlet port (26). Then, the oil flows through passages in the center section for lubrication of the turbocharger bearings. Oil from the turbocharger escapes through oil outlet port (29) in the bottom of the center section. 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
CamshaftThe 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.