Cylinder block
The biggest part of the engine is the cylinder block, which is also called an engine block (Figure). The cylinder block is a large casting of metal (cast iron or aluminum) that is drilled with holes to allow for the passage of lubricants and coolant through the block and to provide spaces for movement of mechanical parts. The block contains the cylinders, which are round passage ways fitted with pistons. The block houses or holds the major mechanical parts of the engine.
Cylinder Head
The cylinder head fits on top of the cylinder block to close off and seal the top of the cylinders. The combustion chamber is an area into which the air/fuel mixture is compressed and burned. The cylinder head contains all or most of the combustion chamber. The cylinder head also contains ports, which are passageways through which the air/fuel mixture enters and burned gases exit the cylinder. A cylinder head can be made of cast iron or aluminum.
Lubrication system
The moving parts of an engine need constant lubrication. Lubrication limits the amount of wear and reduces the amount of friction in the engine. Friction, which occurs when two objects rub against each other, generates heat. Motor or engine oil is the fluid used to lubricate the engine. Several quarts of oil are stored in an oil pan bolted to the bottom of the engine block. The oil pan is also called the crankcase or oil sump. When the engine is running, an oil pump draws oil from the pan and forces it through oil galleries, which are small passageways that direct the oil to the moving parts of the engine. Oil from the pan passes through an oil filter before moving through the engine. The filter removes dirt and metal particles from the oil. Premature wear and damage to parts can result from dirt in the oil.
Regular replacement of the oil filter and oil, is an important step in a preventive maintenance program.
MANIFOLDS
There are separate sets of pipes attached to the cylinder head which carry the air-fuel mixture and the exhaust gases. These are called manifolds. The inlet manifold carries the air-fuel mixture from the carburetor to the cylinders. The shape and size of the inlet manifold must be such as to prohibit the formation of fuel droplets without restricting the air flow. The manifold must be large enough to allow sufficient flow for maximum power yet it has to be small enough to maintain adequate velocities for keeping the fuel droplets in suspension in air. Further sharp bends in the inlet manifold tend to increase fuel separation. on account of its relatively lesser inertia. The air is able to travel through turns more quickly compared to the heavier fuel droplets. Rough interior surfaces of the manifold runners will increase the resistance to the mixture flow. Although a circular section runner has the largest cross-sectional area for its wall surface area, yet passenger car inlet manifold runners are often flat so that any liquid fuel dropping out of the charge may spread evenly on the manifold floor in a thin layer and evaporate quickly. Ribs and guide vanes are usually employed in the manifold runners, for uniform distribution of the charge to the various cylinders. The shape of inlet manifold for a 4-cylinder inline engine fed by a single carburettor, while the inlet manifold for the engine fed by two carburettors is various manifold passages are also called runners. Intake manifolds on v-8 engines are usually designed with runners on two levels and are fitted between the two heads. Cylinders, in the sequence of their firing order, are fed successively, alternatively from the upper and the lower runners. on in-line engines the inlet manifold is usually mounted on the same side of the engine on which exhaust manifold is located, to effect the transfer of heat from the exhaust gases in the later to the air-fuel mixture in the former, to aid its vaporization. This method is very effective in that the heat transfer takes place as soon as the engine is started. In some engines, alternative method of heating the inlet manifold by hot water from the engine cooling system is adopted. Though in this method, large area is heated uniformly, yet the heating is not immediate as in the former method. Therefore, this method is used where mechanical design makes it difficult to use exhaust heat. To avoid excessive heating, which could become a source of power loss due to reduction of air density, in some cases, the thermostatic control of heat flow is used. The exhaust manifold is the set of pipes carrying exhaust gases from the cylinder head to the exhaust system. It is generally made of cast iron so that it is able to withstand the heat of the exhaust gases. A smoother flow of exhaust gases is provided by the two-in-one manifold as compared to the simple one. The exhaust manifold is designed to minimize restriction to the flow of exhaust gases. For this sometimes cast-rib deflectors or dividers are employed inside the manifold so that exhaust gases are guided smoothly towards the outlet. In practice, exhaust manifolds are designed especially for the given engine-chassis combination since chassis front suspension, steering gear box etc. limit the space available for the exhaust manifolds. The exhaust manifolds on the modern engines.
GASKETS
Gaskets are used to provide a tight fitting joint between two surfaces : for example, the joint between cylinder head and block, between crankcase and oil pan, between the cylinder block and manifolds or water pump.
Main requirements of gaskets are :
1. Conformity. The gaskets must be able to conform to the mating surfaces which may have roughness or warpage.
2. Resistance. Due to temperature changes or vibrations the joint may become slightly loose. The gasket should be able to retain its sealing force under this situation.
3. Impermeability. The gaskets must be impermeable to the fluid it is expected to seal.
4. Resistance to chemical attack. The gaskets should be resistant to the chemicals with which it may come into contact, e.g. a cylinder head gasket should be resistant to the fuel, products of combustion, coolant and engine oil.
5. Resistance to operating conditions. As an example, the cylinder head gasket should be resistant to widely fluctuating and pulsating internal pressures and temperatures and exposure to flame.
6. Provision of apertures. The gaskets must have apertures for any studs, bolts. opening etc. For instance, the cylinder head gasket should have apertures for cylinders, coolant and lubrication passages, studs and bolts and valve push rods.
The function of the radiator is to ensure close contact of the hot coolant coming out of the engine with outside air, so as to ensure high rates of heat transfer from the coolant to air. A radiator consists of an upper (or header) tank, core and the lower (or collector) tank. Besides, an overflow pipe in the header tank and drain pipe in the lower tank are provided. Hot coolant from the engine enters the radiator at the top and is cooled by the cross-flow of air, while flowing down the radiator. The coolant collects in the collector tank from where it is pumped to the engine for cooling. There are two basic types of radiator cores, viz., tubular type and cellular type. In the former, it is the coolant that flows through tubes and air passes around them, while in the cellular type the air passes through the tubes and coolant flows in the spaces in between them. Out of these, tubular type cores are the most commonly used which are further classified depending upon the shape of the fins around the tubes which are meant to increase the area for heat transfer from coolant to the cooling air. Both the core tubes as well as the fins are made from thinnest possible material. Tubes are made from 0.1 mm to 0.3 mm sheet, whereas fins are made from about 0. 1 mm thick material. The materials used for radiators should be resistant to corrosion, possess higher thermal conductivity and form easily, apart from having adequate strength. Copper and yellow brass are the widely used materials for radiators. Aluminium is also used from weight and cost considerations. Some late model radiators have plastic tanks with aluminium cores.
AIR CLEANERS
As hundreds of cubic meters’ of air per hour are used by the engine of an automobile, it is very important that this air should be very clean. Impurities like dust in the air cause a very rapid wear of the engine, particularly of the cylinders, pistons, rings, valves and guides. Further if the dirty air enters the crankcase, it will contaminate the lubricating oil and ultimately damage the bearings and journals and decrease the service period of the lubrication system. It is, therefore customary to install air cleaner on the intake system of automotive engines. Apart from filtering the air, air cleaner also performs other functions :
( I ) It acts as a silencer for the carburation system. i.e., it reduce the engine induction noise to an acceptable level.
( II) In case the engine back fires, the air cleaner also acts as a flame arrester. Air cleaners offer, however, a resistance to air flow which is increased as the air cleaners get clogged with dirt. consequently air flow would get decreased, resulting in sluggish engine performance and higher consumption of fuel. These should, therefore, be cleaned regularly or replaced periodically, say, every 20,000 km.
IGNITION SYSTEM
FUNCTION
The function of the ignition system is to produce a spark in the engine cylinder towards the end of the compression stroke. In a four-stroke engine, a spark should occur in each cylinder after two revolutions of the crankshaft, whereas in a two-stroke engine a spark in each cylinder is required every revolution of the crankshaft. Thus, for instance, in a 6-cylinder 4 stroke engine running at 5000 r.p.m. the number of sparks required per minute will be 15000 and these have to be timed very accurately.
2. REQUIREMENTS OF AN IGNITION SYSTEM
1. Spark at the plug electrodes must be regular and synchronously timed with respect to the cylinder-piston position at all speeds and loads on the engine.
2. The spark should be sufficiently strong so as to start ignition of the charge. Since lean air fuel mixtures are less conductive, they require higher ignition voltages. Thus on modern emission- controlled engines that use lean mixtures, higher-voltage ignition system is required. Moreover, due to higher secondary voltage in these systems, it becomes necessary to increase the electrical insulation.
3. It should be light and compact.
4. The system must be easy to maintain.
5. It should be adaptable to mass production.
6. It must not cause radio interference.
3. TYPES OF IGNITION SYSTEM
A battery of 12 volts is generally employed. However, a very high voltage surge (of up to 25,000 volts in modern engines) is required for ignition purposes. The actual high voltage at which the spark occurs is called breakdown voltage and it depends upon so many factors, vie. the gap, polarity and condition of plug electrodes, condition of plug insulation, moisture on the distributor cap and spark plugs and pressure, temperature and type of mixture in the combustion chamber. Used spark plugs may require fairly higher voltage to fire than the new plugs because of increase in the gap and rounding off of the centre electrode. In a given engine the highest ignition voltage is required during part-thxottle acceleration because the fuel system is then supplying a lean mixture with increased combustion pressures. To produce such a high voltage, a special ignition system has to be employed. Two types of conventional ignition systems (called point type ignition systems) are in current use, viz, the 'battery ignition system' and the 'magneto ignition system'. However, both these systems have the major drawbacks of inertia of mechanical components like contact breaker and insufficient dwell period to build up adequate coil field at high engine speeds. Though for a long time, both these systems have been in use and giving satisfactory performance, yet since mid seventees, these are being fast replaced by 'electronic ignition systems'. Point-type and the solid-state (electronic) ignition systems operate in the same way except that they differ in the way the primary current is stopped and restarted.
BATTERY IGNITION SYSTEM
Battery of 12 volts is generally employed. Battery ignition system for a 4-cylinder engine . there are two basic circuits in the system viz, the primary and the secondary circuits. The battery, primary winding of the ignition coil, condenser and the contact breaker form the primary circuit, whereas the secondary winding of the ignition coil, the distributor and the spark plugs constitute the secondary circuit.
Battery system
An automotive battery is an electrochemical device that stores and provides electrical energy. When the battery is connected to an external load, an energy conversion occurs that results in current flow through the circuit to operate the load. Electrical energy is produced in the battery by the chemical reaction that occurs between two dissimilar metal plates that are immersed in an electrolyte solution. When the battery is discharging, it changes chemical energy into electrical energy. It is through this change that the battery releases stored energy. During charging, electrical energy is converted into chemical energy. As a result, the battery can store energy until it is needed. The storage battery is the heart of a vehicle's electrical and electronic systems. It plays an important role in the operation of the starting, charging, ignition, and accessory circuits. The largest demand placed on the battery occurs when it must supply current to operate the starter motor. The amperage requirements of a starter motor may be over several hundred amps. After the engine has started, the vehicle's charging system recharges the battery. It also provides the power to run the electrical accessories. If the vehicle's charging system fails, the battery must supply all the current needed to run the vehicle. Most batteries can supply 25 amperes for two hours before they become so low that they are unable to keep the engine running. The amount of time a battery can be discharged at a certain rate before the voltage drops to a specified level is referred to as the reserve capacity of the battery. An automotive storage battery has three main functions. It provides voltage and serves as a source of current for starting, lighting, and ignition. It acts as a voltage stabilizer for the entire electrical system of the vehicle. And, finally, it provides current whenever the vehicle's electrical demands exceed the output of the charging system. The battery must be able to maintain a good charge when the engine is off. The condition of the battery determines this capability, as do the electrical demands of the vehicle. When the engine is off, electrical power is still needed to maintain the memory in the various computers used in the vehicle and to keep clocks going .The electrical loads that are present when the ignition switch is off are called parasitic loads. At times the parasitic loads are so great that a battery will go dead if the vehicle has not been driven for a while. There are a variety of battery types in use today. The most common are the conventional battery the low-maintenance battery the maintenance-free battery the sealed maintenance-free battery the hybrid battery and the recombination battery.
CONVENTIONAL DESIGN BATTERY
The storage battery consists of grids, positive plates, negative plates, separators, elements, electrolyte, a container; cell covers, vent plugs, and cell containers .The grids form the basic framework of the battery plates. In a conventional battery the grids are made of lead alloyed with approximately 5 percent antimony for strength. Each grid holds the active materials of the plate within its borders. A positive plate consists of a grid filled with lead per-oxide as its active material. Lead peroxide (PbO2) is a dark brown, crystalline material. Its high degree of porosity allows the liquid electrolyte to penetrate freely. The material pasted onto the grids of the negative plates is sponge lead (P b).This porous gray lead allows the electrolyte to penetrate freely.
ELEMENTS AND CELLS
Each battery contains a number of elements. An element is a group of positive and negative plates. All of the positive plates are connected together, as are the negative plates. The plates are connected to each other by a plate strap. The positive and negative groups are then interlaced so the plates alternate. A separator is placed between groups to prevent contact between the positive and negative plates, which would cause the plates to lose their stored energy. A further separator requirement is that the electrolyte must flow easily back and forth between the plates. Everything from wood to porous rubber has been used as a separator, but sheets of porous fiberglass or polyethylene are now most popular. The plate straps, sometimes called post straps, extend up to provide terminals for connecting one element of the battery to another. When the element is placed inside the battery case and immersed in electrolyte, it becomes a cell. A 12-volt battery has six cells, which are connected in series with each other. Each cell has an open circuit voltage of approximately 2.1volts; therefore, a l2-volt storage battery has an actual open circuit voltage of 12.6 volts.
Electrolyte and Specific Gravity
As mentioned, the lead peroxide and sponge lead that fill the element plates are the active materials in the battery. However, these materials cannot become active until they are immersed in electrolyte, a liquid composed of water and sulfuric acid (H2SO4). The sulfuric acid of the electrolyte supplies sulfate, which chemically reacts with both the lead and lead per-oxide to release electrical energy. In addition, the sulfuric acid is the carrier for the electrons inside the battery between the positive and negative plates. The electrolyte of a fully charged battery is usually about 64% water and 36% sulfuric acid. This corresponds to a specific gravity of 1.270. Specific gravity is the weight of a given volume of any liquid divided by the weight of an equal volume of water. Pure water has a specific gravity of 1.000, while battery electrolyte should have a specific gravity of 1.260 to 1.280 at 80'F (26.7'C). In other words, the electrolyte of a fully charged battery is 1.260 to 1.280 times as heavy as water.
Checking Battery and Charging System:
Wear protective eye wear and clothing and remove all jewelry when checking your battery and charging system. Jewelry is a good conductor of electricity and is not recommended. Most batteries wear out every 3 to 5 years and need to be replaced. Always replace your battery with an equal replacement battery to assure proper operation.
Automotive batteries have a +positive terminal (red), - negative terminal (black). The battery in this illustration has a protective cover over the positive terminal to prevent short circuit in case of an accident. Electricity is stored in the battery and then supplied to the vehicle when the engine is not running. While the engine is running the vehicles alternator charges the battery for future use.
To check a battery surface voltage removes the positive terminal protective cover. Connect the +positive side meter lead (red) to the positive side battery terminal. Connect the - negative (black) side meter lead to the negative battery terminal. With the vehicle not running and the car sitting over night the battery voltage should be between 12.5 and 12.8 volts.
2. Identify Alternator
The alternator is rotated by a drive belt driven by the vehicles engine while it is running. Electrical voltage and amperage are generated to recharge the battery and supply voltage to the electrical system of the car. The alternator is held in place with mounting bolts. There is a main electrical wire on the rear of the alternator that supplies voltage to a main voltage junction box. If your alternator is not charging properly, your battery will slowly drain down from operating all the electrical systems in your car and stop the car from running.
3. Alternator Output
Connect the voltage meter lead the same way you would in a battery static voltage check, Start engine (do not drive) at engine idle the voltage should be between 13.6 to 14.3 volts. If not the alternator may need replacing.
The alternator provides electrical power to the battery while the car is in operation.
The multi rib belt is the single drive belt that drives the auxiliary systems in your car like the alternator and air conditioning compressor.
The car battery stores electrical power in reserve to be used at a later time.
Common Problems:
1. alternator stops producing electrical power and the car stops because the battery dies.
2. battery fails do to age or defect.
3. battery cables become loose causing the electrical system to fail..
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