C3.3 Industrial Engine Caterpillar

Air Inlet and Exhaust System

Usage:

C3.3 E3K

Turbocharged Engines

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Illustration 1	g01237037
Air inlet and exhaust system (1) Exhaust manifold (2) Fuel injection nozzle (3) Glow plug (4) Inlet manifold (5) Exhaust outlet (6) Turbocharger turbine wheel (7) Turbocharger compressor wheel (8) Air inlet (9) Inlet valve (10) Engine cylinder (11) 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
Inlet manifold that is integral with the cylinder head
Cylinder head, injectors and glow plugs
Valves and valve system components
Piston and cylinder
Exhaust manifold

Air is drawn in through the air cleaner into the air inlet of the turbocharger (8) by the turbocharger compressor wheel (7). The air is compressed and heated.

Air is forced into the inlet manifold (4). Air flow from the inlet manifold to the engine cylinders (10) is controlled by the inlet valves (9). There is one inlet valve and one exhaust valve (11) for each cylinder. The inlet valve opens when the piston moves down on the intake stroke. When the inlet valve opens, compressed air from the inlet port is forced into the cylinder. The complete cycle consists of four strokes:

Inlet
Compression
Power
Exhaust

On the compression stroke, the piston moves back up the cylinder and the inlet valve (9) closes. The air is compressed and this 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 TC position, fuel is injected into the cylinder via the fuel injection nozzle (2). 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 (11) 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 of the turbocharger in order to turn turbocharger turbine wheel (6). The turbocharger turbine wheel is connected to the shaft that drives the turbocharger compressor wheel (7). Exhaust gases from the turbocharger, pass through the exhaust outlet (5), and an exhaust pipe and a silencer.

Naturally Aspirated Engines

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Illustration 2	g01237212
Air inlet and exhaust system (1) Exhaust manifold (2) Fuel injection nozzle (3) Glow plug (4) Inlet manifold (5) Exhaust outlet (6) Air inlet (7) Inlet valve (8) Engine cylinder (9) Exhaust valve

Air cleaner
Inlet manifold
Cylinder head, injectors and glow plugs
Valves and valve system components
Piston and cylinder
Exhaust manifold

Air is drawn in through the air cleaner into the air inlet (6) of the inlet manifold (4). Air flow from the inlet manifold to the engine cylinders (8) is controlled by the inlet valves (7). There is one inlet valve and one exhaust valve (9) for each cylinder. The inlet valve opens when the piston moves down on the intake stroke. When the inlet valve opens, air from the inlet port is forced into the cylinder. The complete cycle consists of four strokes:

Inlet
Compression
Power
Exhaust

On the compression stroke, the piston moves back up the cylinder and the inlet valve (7) closes. The air is compressed and this compression generates more heat.

Note: If the cold starting system is operating, the glow plugs (3) will also heat the air in the cylinder.

From the BC position, the piston moves upward. This initiates the exhaust stroke. The exhaust valve (9) opens. The exhaust gases are forced through the open exhaust valve into the exhaust manifold (1) .

Exhaust gases from exhaust manifold (1), pass through exhaust outlet (5), and an exhaust pipe and a silencer.

Turbocharger

Note: The turbocharger is not serviceable.

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.

A turbocharger improves the following aspects of engine performance:

Power output is increased.
Fuel efficiency is improved.
Engine torque is increased.
Durability of the engine is improved.
Emissions from the engine are reduced.

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Illustration 3	g01263770
Typical example Components of a turbocharger (typical example) (1) Air inlet (2) Compressor housing (3) Turbocharger compressor wheel (4) Bearing (5) Oil inlet port (6) Bearing (7) Turbine housing (8) Turbocharger turbine wheel (9) Exhaust outlet (10) Oil outlet port (11) Exhaust inlet

A turbocharger is installed between the exhaust and inlet manifolds. The turbocharger is driven by exhaust gases which flow through the exhaust inlet (11). The energy of the exhaust gas turns the turbine wheel (8). Then, the exhaust gas flows out of the turbine housing (7) through the exhaust outlet (9) .

The turbocharger turbine wheel and the turbocharger compressor wheel (3) are installed on the same shaft. Therefore, the turbocharger turbine wheel and the turbocharger compressor wheel rotate at the same rpm. The turbocharger compressor wheel is enclosed by the compressor housing (2). The turbocharger compressor wheel compresses the air that is drawn in from the air intake (1). The air flows into the engine cylinders through the inlet valves of the cylinders.

The oil from the main gallery of the cylinder block flows through the oil inlet port (5) in order to lubricate the turbocharger bearings (4) and (6). The pressurized oil passes through the bearing housing of the turbocharger. The oil is returned through the oil outlet port (10) to the oil pan.

The turbocharger has a wastegate. The wastegate is controlled by the boost pressure. This allows some of the exhaust to bypass the turbocharger at higher engine speeds. The wastegate is a type of valve that automatically opens at a preset level of boost pressure in order to allow exhaust gas to flow around the turbine. The wastegate allows the design of the turbocharger to be more effective at lower engine speeds.

The wastegate 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 manifold pressure.

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 valves are on the left side of the cylinder head. The ports for the exhaust valves are on the right side of the cylinder head. Steel valve seat inserts are installed in the cylinder head for both the inlet and the exhaust valves. The valve seat inserts can be replaced.

The valves are installed in valve guides. The valve guides can be replaced. The stem of the exhaust valve is shaped in order to prevent the seizure of the valve. The seizure of a valve can be caused by a buildup of carbon under the head of the valve.

The inlet and the exhaust valves are opened and closed by the rotation and movement of the following components:

Crankshaft
Camshaft
Valve lifters
Pushrods
Rocker arms
Valve springs

The camshaft gear is driven by the crankshaft gear. The camshaft and the crankshaft are timed together. When the camshaft turns, the valve lifters and the pushrods are moved up and down. The pushrods move the rocker arms. The movement of the rocker arms open the valves. The opening and closing of the valves is timed with the firing sequence of the engine. The valve springs push the valves back to the closed position.