TOPIC 1
ENGINE MAIN COMPONENTS
Engines Main Components
This topic deals with the general construction of the engine and its main components, and also some engine design features.
While multi cylinder engines contain parts which perform the same functions as those in a single cylinder engine, they are more complex and have many more parts. However, it is easier to understand how an engine is constructed if it is first broken down into sections before considering the complete engine.
For our purpose, this will be done by looking at parts at the top of the engine, the front of the engine, the rear of the engine, the bottom of the engine, the main internal parts, and finally the components of an engine assembly.
Components at the top of the engine
Parts that can be identified in the illustration are:
1. Timing Belt
2. Camshaft Timing Pulley
3. Camshaft
4. Rocker Arms And Shafts.
5. Valve and valve spring.
Component at the top of an engine
The Parts Work Like This
The timing belt drives the camshaft pulley, which is attached to the camshaft. The cams on the camshaft operate the rocker arms, which pivot on their shafts to open and close the valves. The intake valves are opened to admit air-fuel mixture, and the exhaust valves are opened to discharge the burnt gases.
Components at the front of the engine
The figure shows parts located at the front of the engine, including those in the previous illustration. These are :
1. Crankshaft Timing Pulley (Sprocket)
2. TimingBelt
3. Crankshaft Pulley and Balancer.
Component at the front of an engine.
The Parts Work Like This
The piston is shown on top dead-center (TDC). On the power stroke, combustion pressure forces the piston down on the power stroke. Through the connecting rod, this rotates the crankshaft so that the engine operates.
The crankshaft timing pulley (or sprocket) drives the timing belt, and this rotates the camshaft to operate the valves as described before. The crankshaft pulley (drive pulley) is a different one to the timing pulley and is used to drive parts on the outside of the engine - the fan, water pump, alternator, power steering and the air conditioning compressor (these parts are not shown). The pulley is part of a vibration damper that helps to reduce engine vibration.
Components at the rear of the engine
The figure show a section of the rear of the engine . The parts shown are :
1. Starter Ring Gear
2. Flywheel
3. Crankshaft Flange
Component at the rear of an engine
The Parts Work Like This
The starter has a pinion which engages with the ring gear on the flywheel. When the starter is operated, it spins the crankshaft, the pistons are moved up and down, and fuel is taken into the cylinders. The fuel is ignited by the spark plugs so that the engine starts and runs
The flywheel is bolted to a flange on the rear end of the crankshaft. It is a heavy cast iron wheel that is used to help the engine run smoothly. It does this by absorbing energy during a power stroke and releasing energy during the other strokes.
Components at the bottom of the engine
The figure show the lower part of the engine. The parts shown are:
1. four pistons
2. connecting rods
3. crankshaft
4. crankshaft balance weights
5. crankshaft main-bearing journals.
Internal components at the bottom of engine.
The Parts Work Like This
The crankshaft has a number of cranks to which the connecting rods are attached. A bearing between the connecting rod and the crank pin reduces friction and wear. The upper end of the connecting rod is connected to the piston with a large piston pin. This is sometimes called a gudgeon pin. This allows the connecting rod to move in relation to the piston, with a wrist like action.
The crankshaft is supported in the crankcase by main bearings. Only the journals are shown. The journals are the parts of the shaft that run in the bearings. They are accurately ground to produce a fine surface finish.
The crankshaft has a number of balance weights. These masses are located opposite the crank pinS to balance the crankshaft.
The crankshaft and its bearings are sometimes
referred to as the bottom end because they are near the bottom of the engine. The bottom end of the connecting rod is sometimes referred to as the big end because it is the larger end of the connecting rod.
Internal components of the engine
The figure combines all the previous parts of the engine and shows all the main operating parts. These are the valve mechanism, timing belt, crankshaft, pistons, connecting rods, and the flywheel.
Internal parts of an engine
The Parts Work Like This
There are four valves per cylinder in the enginetwo intake and two exhaust. The camshaft pulley is twice the size of the crankshaft timing pulley, so that the camshaft rotates at half the engine speed. The timing pulleys are connected by the timing belt. This has teeth which mesh with the teeth on the pulleys.
The camshaft has a cam for each valve and is designed with its cams in the correct position to open the right valve at the right time. Also.
the camshaft is timed to the crankshaft so that the valves open and close at the correct times in relation to the positions of the pistons.
The pistons are fitted with piston rings which seal against the cylinder walls. To identify the pistons, they are numbered from front to rear: No. 1 and No. 4 pistons are shown at the top of their stroke (TDC) and No. 2 and No. 3 pistons are at the bottom of their stroke (BDC).
Written Activity #2
1. Name the six parts which make up the top end of typical small OHC engine.
1. ----------
2. ---------
3. ----------
4.----------
5.---------
6. ---------
2. Name the parts indicated on this diagram .
3. Name the parts found at the front of a small OHC engine.
1.
2.
3.
4. Name the parts indicated on this diagram.
1.-------------------------
2.-------------------------
6. Name the parts indicated on this diagram .
7. What are the main components to be found at the bottom of an engine ?
1.
2.
3.
4.
8. Name the parts indicated on this diagram.
9. Name all of the parts indicated in this complete engine.
TOPIC 2
ENGINE ASSEMBLY.
Components of an Engine Assembly
The figure shows the complete engine with some of its ancillaries attached to the outside. The cylinder block and cylinder head have been cut away to show the internal parts of the engine which were in the previous illustrations.
The following are parts that can be identified: cylinder block, cylinder head, valve cover, oil pan, exhaust manifold, intake manifold, throttle body, fan, water pump, distributor with cables and spark plugs, oil filter, and oil pump.
The cylinder head is usually made of aluminum and is shaped above each cylinder to form the combustion chambers in which the air-fuel mixture is burnt. It carries the valves and the valve operating mechanism. On overhead camshaft engines, it has bearings for the camshaft. It has intake and exhaust ports which are opened and closed by the valves.
Valve Cover
The valve cover (rocker cover) fits on top of the cylinder head and covers the valve mechanism. It is made of aluminum alloy on most engines.
Oil pan
The oil pan, or sump, is attached to the bottom of the crankcase and closes off the internal parts. It also acts as a reservoir for the engine oil, on a four-stroke engine which is circulated throughout the engine by the oil pump.
Exhaust manifold
The exhaust manifold has a flange which is bolted to the cylinder head over the exhaust ports. Pipes or branches of the manifold carry the burnt gases away when the exhaust valve opens. It is made of cast iron to resist heat.
Intake manifold and throttle body
This is bolted to the opposite side of the cylinder head to the exhaust manifold on this engine. It carries the air-fuel mixture to the engine. The engine illustrated in Figure 6 has electronic fuel injection (EFI), and this has a throttle body attached to the intake manifold. On carburetor engines, the carburetor is mounted on top of the manifold.
Fan
The fan at the front of the engine provides a flow of air through the radiator for cooling. This engine has a variable speed fan, but electric fans are also used.
Water pump
The water pump is driven by the fan belt from the crankshaft pulley. It circulates coolant throughout the engine for cooling purposes.
Distributor, cables and spark plugs
The distributor is at the rear of the cylinder head and is driven by the camshaft. It distributes high voltage to each spark plug at the right time. This provides the spark which ignites the air-fuel mixture. The cables from the distributor are connected to the spark plugs which, on this engine, are located in the center of the cylinder head.
The firing order for a four cylinder engine is 1- 3-4-2 or 1-2-4-3. This is the sequence in which the pistons deliver their strokes.
Oil filter and oil pump
The oil pump picks up oil from the oil pan and circulates it throughout the engine. The oil passes through the oil filter, which removes particles of carbon or any other foreign material from the oil.
Written Activity #2
Answer all of the following questions (all questions refer to section 2.1).
1. What is the biggest on main part of on engine?
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2. For small petrol engines, what is the cylinder head made of?
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3. What is fitted between the engine block and head?
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4. What is fitted over the head and valves?
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5. What is another name for the oil pan?
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6. What carries the burnt gasses away from the engine?
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7. Where would you find the carborattor?
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8. What does the fan do?
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9. What does the water pump do?
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10. What does the distributor do?
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11. What does the oil pump do ?
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12. Name all of the parts as shown as the following diagram.
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TOPIC 2
ENGINE FEATURES.
Engine futures
The figure shows a four cylinder engine for a small passenger vehicle. This is a carburetor engine. It has a chain drive to the overhead camshaft.
Cross sectional view of engine
The figture shows a cross sectional view of a basic engine. This has been cut right through the valve cover, cylinder head, cylinder block and oil pan to show the construction of the parts.
Items that can be identified are water jackets in the cylinder head and cylinder block, intake and exhaust valves and their ports, the cylinder head gasket, the construction of the piston, and the construction of the crankshaft and connecting rod bearings
Horizontal engine.
The arrangement of a horizontal engine, often referred to as a flat engine because of its construction, is shown in figure . This is a four cylinder engine with its cylinders horizontally opposed. Its various features are identified tin the illustration
Arrangement of a horizontally opposed engine.
Diesel engine
The basic construction of a diesel engine can be seen in figure. This is an overhead valve engine with the camshaft mounted in the cylinder block. Cam followers operate on the cams of the camshaft, and push rods transfer movement to the rocker arms on top of the cylinder head. The camshaft is driven by timing gears, which also drive an auxiliary shaft. This, in turn, drives the injection pump and a vacuum pump.
Cross sectional view of an engine, showing the internal
Being a diesel engine, injectors are fitted to the cylinder head. It also has long pistons, which have a combustion chamber in the piston head. The components of a diesel engine carry greater stress than those of a petrol engine and so are generally of heavier construction.
Diesel engine construction.
KEY ANSWER OF WRITTEN ACTIVITY
Written Activity 2
1. Name the six parts which make up the top end of typical small OHC engine.
1. Timing belt.
2. Camshaft Pulley.
3. Camshaft.
4. Rocker Arms.
5. Rocker Shaft.
6. Valves and Valve Springs.
2. Name the parts indicated on this diagram.
2. Name the parts found at the front of a small OHC engine.
1. Timing belt.
2. Crankshaft pulley and balance.
3. Crankshaft timing pulley.
3. Name the parts indicated on this diagram.
4. What main components are located at the rear of an engine ?
1. Starting ring gear.
2. Flywheel.
5. Name the parts indicated on this diagram
6. What are the main components to be found at the bottom of an engine ?
1. Connecting rods.
2. Crankshaft.
3. Crankshaft balance weight.
4. Crankshaft main bearing journals.
7. Name all of the parts indicated in this complete engine.
TOPIC 2
ENGINE ASSEMBLY.
Written Activity #11. To pass this topic you have to be able to identify eleven components which are attached to an engine. List them below.
1. Cylinder block
2. Cylinder head
3. Valve cover
4. Oil pan
5. Exhaust manifold
6. Fan
7. water pump
8. Distributor, cabels and sprak plug
9. Oil filters
10. Oil pump.
Written Activity 2
1. What is the biggest and main part of on engine?
The cylinder block on engine block.
2. For small petrol engines, what is the cylinder head made of?
Aluminium
3. What is fitted between the engine block and head?
Head gasket
4. What is fitted over the head and valves?
Valve or rocker cover
5. What is another name for the oil pan?
Sump
6. What carries the burnt gasses away from the engine?
Exhaust manifold - exhaust system
7. What does the fan do?
Creates a flow of air through the rdiator
8. What does the fan do?
Creates a flow of air through the radiator.
9. What does the water pump do?
Circulates water or coolant throughout the engine
10. What does the distributor do?
Distributor a high tension voltage to each spark plug
11. What does the oil pump do?
Circulate oil through out the engine
12. Name all of the parts as shown as the following diagram.
13. How would you describe this engine?
4 Cylinder, in-line, petrol, water cooled, OHC EFI engine
TOPIC 3
ENGINE FEATURES
Written Activity #1
What are the four types of engines you will need to identify to pass this topic.
1. Light Petrol.
2. Aorrozitally apposed or flat.
3. Small diesel.
4. Medium to large diesel.
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ENGINE MAIN COMPONENTS
Reviewed by heri
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4:53 AM
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Reviewed by heri
on
4:53 AM
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