875546 Volvo.Penta Piston

Illustration 1 g01107004
Basic air inlet and exhaust system
(1) Inlet valves
(2) Exhaust valves
(3) Inlet manifold
(4) Exhaust manifold
(5) Air to air aftercooler
(6) Air inlet
(7) Exhaust outlet
(8) Compressor
(9) TurbineThe 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
Cylinder head
Valves and valve system components
Piston and cylinder
Inlet manifold
Exhaust manifoldNote: The following description of the operation of the air inlet and exhaust system assumes that the engine is developing boost pressure.Inlet air passes through the air cleaner into the air inlet (6) of the turbocharger compressor (8). A turbocharger is used to increase the flow of air into the engine. This increase in air flow pressurizes the combustion air supply for the engine. The pressure that is placed on the inlet air allows a larger volume of air to be compressed into the cylinder. This compressing of the inlet air is referred to as engine boost.The compressing of air causes the air temperature to rise to about 204 °C (400 °F). As the air flows through aftercooler (5), the temperature of the compressed air is cooled to about 46 °C (115 °F). The aftercooler utilizes a heat exchanger to cool the inlet air. Cooling the inlet air causes the air to become more dense. Compressing and cooling the inlet air increases the combustion efficiency of the engine. This also increases the horsepower output.From the aftercooler, air enters the inlet manifold (3). Air flow from the inlet manifold to the cylinders is controlled by inlet valves (1). There are two inlet valves and two exhaust valves (2) for each cylinder. The inlet valves open at the top center position of the piston. When the inlet valves open, cooled compressed air enters the cylinder through the inlet ports. The inlet valves close as the piston reaches the bottom center position. This is called the inlet stroke of the engine. As the piston begins to travel back to the top center position on the compression stroke, the air in the cylinder is compressed to a high temperature. When the piston is near the end of the compression stroke, fuel is injected into the cylinder and mixes with the compressed air. This action causes combustion to start in the cylinder. Once combustion starts, the combustion force pushes the piston toward the bottom center position. This is called the power stroke. The exhaust valves open when the piston moves toward the bottom center position and the exhaust gases are pushed through the exhaust port into exhaust manifold (4) as the piston travels toward top center on the exhaust stroke. The exhaust valves close and the cycle repeats. The complete cycle consists of four strokes:
Inlet
Compression
Power
ExhaustThe exhaust gases from the cylinder are forced into exhaust manifold (4). The flow of exhaust gases from the exhaust manifold enters the turbine side of the turbocharger. The flow of the exhaust gas and the heat of the exhaust gas causes the turbine wheel in the turbine (9) to spin. The turbine wheel is connected to a shaft that drives the compressor wheel. Exhaust gases from the turbine wheel then exit the turbocharger (8).Turbocharger
Illustration 2 g01748913
Turbocharger
(10) Compressor inlet
(11) Compressor housing
(12) Compressor wheel
(13) Shaft bearing
(14) Oil Inlet port
(15) Shaft bearing
(16) Turbine wheel
(17) Turbine outlet
(18) Turbine inlet
(19) Oil outlet portAll of the air that enters the engine passes through the compressor. All of the exhaust gases from the engine pass through the turbine.The exhaust gases enter through turbine inlet (18). The flow of the exhaust gas pushes the blades of the turbine wheel (167) and exits through the turbine outlet (17). The turbine wheel is connected by a shaft to compressor wheel (12).As the compressor wheel rotates, a vacuum is created in the compressor housing (11). Air is pulled through the air filters into the compressor housing through the compressor inlet (10). Impeller vanes are manufactured into the compressor wheel. The vanes are used to compress the incoming air. The compressed air is directed to the compressor outlet into the inlet piping. The air is then directed toward the inlet side of the engine. Boost pressure is created as the flow that is developed by the compressor wheel exceeds the needs of the engine. This results in a positive inlet manifold pressure that exceeds atmospheric pressure. The increased pressure allows the engine to burn more fuel during fuel combustion. Through optimum fuel efficiency, this strategy allows the engine to produce more power and lower emission levels.When the throttle is opened, more fuel is injected into the cylinders. The combustion of this additional fuel produces an increased flow of exhaust and greater exhaust temperature. The additional flow and the increased temperature of the exhaust causes the turbine and the compressor wheels of the turbocharger to turn faster. As the compressor wheel turns faster, air flow into the air inlet system creates an increase in the pressure that is in the inlet manifold. This increased air pressure allows the engine to burn extra fuel with greater efficiency.The shaft bearings (13) and (15) use pressurized oil from the engine for lubrication and for cooling. The oil comes in through oil inlet port (14). The oil then goes through passages in the center section to lubricate the bearings. This oil also cools the bearings. Oil from the turbocharger goes out through oil outlet port (13) in the bottom of the center section. The oil then flows back to the engine oil pan.Valve System Components
Illustration 3 g01748993
Valve system components
(20) Rocker arm
(21) Valve adjustment screw
(22) Rocker arm shaft
(23) Camshaft follower
(24) Camshaft
(25) Valve bridge
(26) Valve rotator
(27) Valve spring
(28) Valve
(29) Valve seatThe valve train controls the flow of inlet air into the cylinders and the flow of exhaust gases out of the cylinders during engine operation. Machined lobes on the camshaft (24) control the following aspects of valve function:
Height of valve lift
Timing of valve lift
Duration of valve liftThe crankshaft gear drives the camshaft gear through an idler gear. The camshaft must be