Experiment No

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Engine Cylinder: The engine cylinders are contained in the engine block. The block has traditionally been mady of gray cast iron because of its good wear resistance and low cost.

Wet Liners or Dry Liners: Heavy duty and truck engines often use removable cylinder sleeves pressed into the block that can whether the sleeve is in direct contact with the cooling water.

Crankcase: Iron cylinder liners may be inserted at the casting stage or later on in the machining and assemble process. The crankcase is often integrate with the cylinder block.

Crankshaft: The crankshaft is usually a steel forging although the advent of large stiff crankshaft with relatively low stresses allowed cast iron to be substituted as a means of reducing costs.

Main Bearings: The crankshaft is supported in main bearings, in heavy duty engine, the number of bearings is one greater than the number of cylinders.

Crank Pin: At the end of the cranks throw is located crank pin which holds the correcting rod bearing.

Oil Pan: A pressed-steel oil seals the block assemble and serves as an oil slump or reservoir for the lubricating oil.

Piston: A piston is made of aluminum, cast steel or iron and its main function is to transmit the force created by the combustion process to the connecting rod.

Piston Rings: The piston is fitted with at least three piston rings. The upper rings are called compression rings because their purpose is to contain the high pressure gases in the cylinder and so prevent below by into the crankcase on the compression and power strokes. The lowering is usually an oil-control ring. The purpose of the ring is to scrape surplus oil from the wall and transfer it through slots in the ring to drainage holes in the piston that allow the oil to return to oil pan.

Connecting Rod: The forged steel connecting rod of I-beam section joins the piston and crankshaft.

Piston Pin: Connecting rod may be rifle drilled to conduct lubricating oil from the connecting rod bearing to the piston pin, or it may have a small hole, to spray oil to the piston pin as well as to the crankshaft and cylinder walls.

Camshaft: The camshaft made of cast iron or forged steel with one cam per valve is used to open and close the valves. The cam surfaces are hardened to obtain adequate life. In 4-Stroke cycle engines, camshafts turn at one half the crankshaft speed.

Valves: The valve type normally used in four stroke engines are poppet valves, although a few engines are made with either slide valves or rotary valves.

Intake and Exhaust Valves: The intake valve is made of a chromium-nickel alloy steel, while the smaller exhaust valve, which operates at higher temperature (about 1200 degree Fahrenheit) is made from a silichrome alloy. The exhaust valve leads a particularly severe life because it is opened at a time when the combustion gases may be above 3000 degree Fahrenheit, and these hot gases stream at high velocity past the face of the valve.

Cylinder heads: The cylinder head seals off the cylinders and is made of cast iron or aluminum. It must be strong and rigid to distribute the gas forces acting on the head as uniformly as possible through the engine block.

Valve Stem: The valve stem moves in a valve can be integral part of the cylinder head (or block for L-head engines), or may be a separate unit passed into the head (or block).

Valve Spring: A valve spring, attached to the valve stem with a spring washer and split keeper, holds the valve closed.

Carburetor: It is the device which is used to supply fuel air mixture for the I.C.E. In small engines, carburetors are attached directly while in big engines, carburetor is attached with inlet manifold.

Distributor or Leads: A device which produces spark in the cylinder when it is required.

Alternator: Altering current generator used in automobiles in which alternating current in charged into direct current by a rectifier.

Ball Bearings: An anti-friction bearing consisting of a hardened inner and outer race with hardened steel balls between the two valves.

Booster: A device to boost the power applied by the operator in operating clutch, brake, steering etc.

Brake Shoe: The carrier to which the brake lining is attached and which is used to force the lining in contact with the brake drum.

Cam: An ecentric projection on a revolving shaft designed to give some repuisite linear motion to a follower or tappet.

Chasis: Machine portion or frame work of an automobile excluding cab and body.

Filter: A unit containing filtering element to eliminate foreign particles from the fluid being filtered.

Float Chamber: A small fuel contained with the carburetor which contains a float operate valve at its entrance.

Float Piston: A piston pin which is not locked in the connecting rods or the piston but is free to turn in both the connecting rod and the piston.

Push rod: A connecting link in an operating mechanism such as rod placed between the tappet and rocker arm.

The purpose of the cooling system is to take heat from the hot parts of an engine and dissipated into the atmosphere. There are two types of cooling systems.

This system employs water as coolant. The water removes heat from the engine/ cylinder/ head and rejects it to the air via a radiator.

Water Jackets/Passages: These are present in the head and around the cylinders cooling water flows through cavities in the block and head in order to remove heat.

Water Pump: It is a small centrifugal pump driven by a V-belt off the crankshaft. It pumps water around the closed cycle from the engine to radiator and vice versa.

Hoses/Pipes: Connects the engine to the radiator and carry hot water from engine to radiator and cooled water from radiator to engine. These are generally made of rubber.

Radiator: It's a heat exchanger and is used to transfer the heat from the hot water coming from the engine to the atmosphere. It consist of the fined tubes through which water flows. Air is blown (in automobiles, air is sucked through a fan, assisted by the movement of car) across the fins to cool down the water. The cooled water is fed back to the water jacket.

Fan: It flows air through a radiator may be driven by the camshaft or electrically by a motor.

This system uses air as coolant. It more suited in the application in places where temperature is generally low.

Cooling Fins: These are either out into the cylinder or onto the smooth cylinder. Their purpose is to increase the surface area form which heat can be dissipated.

Blower/Fan: A fan driven off the crankshaft by a V-belt constantly blows air through the cooling fins to cool the cylinder block/head.

No.	Engine RPM	Coupling Force (N) F	Torque N.m *T = F L**	Excitation I	Power Watt P 2x3.142xNxT/60	Power H.P HP P / 746
1	3200	-	-	-	-	-
2	3000	9	8.5941	0.2	3014	4.04
3	2800	16	15.2784	0.3	4480	6
4	2600	22	21.0078	0.35	5720	7.6
5	2400	29	27.6921	0.45	6960	9.32
6	2200	40	38.196	0.5	8800	11.8
7	2000	48	45.8352	0.59	9600	12.8

A dynamometer is essentially a device for measuring the forces or couples which tend to change the state of rest or of uniform motion of a body.

There are many kinds of dynamometers, but reference can only be made to a few of the types used in measuring the power available from a uniformly revolving shaft. Broadly, two main types may be distinguished, namely,

As the name imply, an absorption dynamometer absorbs the available power in doing work, usually against friction.

Transmission dynamometers transmits the available power unchanged, except for the small amount of absorbed by friction at the joints of the dynamometer.

A simple type, known as Prony Brake. It consists of two blocks of wood, each of which embraces rather less than one half of the pulley rim. The two blocks can be drawn together by means of bolts, pushioned by springs, so as to increase the pressure on the pulley. One block carries an arm to the end of which a pull can be applied by means of a dead weight or spring balance. A second are projects from the block in the opposite direction and carries a balance weight B, which balances the brake when unloaded. The friction torque on the pulley may be increased by screwing up the bolts, until it balances the torque due to the available power. For counter clockwise rotation of the drum, the arm L will float between the stops S with a weight W suspended from it. The torque on the drum is given by WL and, knowing the speed rotation of the pulley, the power absorbed may be calculated.

An alternative arrangement, which is much better for the absorption of larger powers, is so to arrange the brake that the end of the lever L rests on the platform of weighing machine.

This type of brake is generally much steadier in operation than the Prony Brake. It is also suitable for the absorption of a wider range of powers. In generally two or more ropes rest on the pulley rim. They are spaced evenly across the width of the rim by means of three or four wooden blocks at different points round the rim. The total pull S on the slack ends of the ropes is registered on a spring balance, while the pull W on the right ends is provided by dead weights. The brake torque is then given by (W-S)r, where r is the effective radius of the drum to the rope centre.

This dynamometer is very widely used for the absorption of a wide range of powers and is suitable for a wide range of speeds. It was invented by William Froude in 1877.

A rotor A is keyed to the main shaft, to which the power to be measured is supplied. Surrounding the rotor is a stator fixed to its outer casing. The main shaft is supported on ball bearings in the outer casing, and the outer casing is, in turn, supported to ball bearings C carried by brackets on the bed plate. Water is supplied through a flexible pipe to the branch D. In each face of the rotor and in the adjacent faces of the stator there are semi oval channels.

This dynamometer consists of an electric generator, the field system of which is mounted on trunnions so as to be able to revolve freely. The arrangement is similar to that of the outer casing of the hydraulic dynamometer.

Although strictly speaking this is an absorption dynamometer, the electrical energy generated can be fed back to the supply lines and usefully employed in lighting, etc. This constitutes one of this advantage of the type over the hydraulic dynamometer, but the chief advantage lies in fact that the generator may be run as a motor.

The disadvantages of the swinging field dynamometer are that it is only suitable for comparatively high speeds and small powers, and it is much less robust than the hydraulic dynamometer.

This class of dynamometer is designed in order to allow of the measurement of the power which is usefully employed by an machine. The general principles which underlie the design of the various types will be briefly explained.

A simple epicyclic train or spur or bevel wheels, may be placed between the source of power and the machine and used to measure the power transmitted.

In this type of dynamometer, the design is such that while the belt is transmitting power, the difference between the tensions on the tight and slack sides may be measured.

One of the oldest forms of dynamometer is the Eddy Current Dynamometer. The simples form consist of a disc which is driven by the engine under test, turns in a magnetic field. The strength of the field is controlled by varying current through a series of coil located on both sides of the disc. The revolving disc acts as a conductor cutting the magnetic field. Current are induced in the disc and since no external circuit exists the induced current that heat the discs. For large power absorption the heating of the disc becomes excessive and difficult to control.

1.	Design	4-cylinder, 4 cycle, 4 stroke, double carburetor
2.	Arrangement of cylinder	Horizontally opposed flat four cylinders
3.	Bore	85.5mm, 3.75"
4.	Swept volume:-	1584 c.c.
5.	Compression Ratio	7.7:1
6.	Turning direction of fly wheel	Anti clock wise
7.	Valve activating mechanism	Cam follower, Push rod, and rocker arm
8.	No. of valves (2) Over head	Over head position, one intake, one exhaust
9.	Valve clearance	Intake 0.10mm, Exhaust 0.10mm
10.	Mean Position Speed	6.9 m/s at 3000 rpm
11.	Air cooled	Radial blower on crankshaft
12.	Amount of cooling air	Approx. 500 lit at 3600 rpm
13.	Lubrication	Force feed by gear pump
14.	Oil cooling	Flat tube cooler in air stream
15.	Fuel supply	By mechanical fuel pump
16.	Fuel used	90 Octane
17.	Carburetor	Down draft SOLE x 28 VFIS
18.	Ignition	6V / 12V battery
19.	Breaker Point Gape	0.4 mm (0.016")
20.	Spark plug Gape	0.6 - 0.7mm (0.024 - 0.028")
21.	Spark plug Detail	BOSHW 145-T1 BERU 145-14
22.	Firing Order	1-4-3-2
23.	Firing Point	10^o before TDC
24.	Governor	Centrifugal governor with toothed belt drive acting or carburetor throttle valve.
25.	Starting System	6V electric starter motor arranged horizontally.
26.	Crank case	Magnesium alloy
27.	Crankshaft	4 Plain bearing of Al-alloy
28.	Pistons	Light metal alloy with steel inserts
29.	Cylinder Head	Al-Alloy one head for two cylinders
30.	Cylinder	Special gray cast iron
31.	Spark plug	Heart range 145, Thread 14mm, BOSH W145T, BERU 145-14

1.	Accelaration due to gravity 'g'	9.8 m/s² or 1.27x10¹¹mm/hrs²
2.	Coefficient of discharge of air intake Nozzle	0.95
3.	Density of water 'fw'	1000 kg/m³
4.	Density of intake air 'fa'	1.3 kg/m³ at 20^oC
5.	Density of fuel (petrol)	0.76 gm/ml
6.	Diameter of throat of intake Nozzle	49.6mm
7.	Area of throat of intake Nozzle	1.932x10³ mm²
8.	Length of Lever Arm	0.954 m
9.	Diameter of piston 'D'	0.088 m
10.	Length of Stroke	69.8mm

ma = Coefficient of discharge Cd x Area of intake nozzle x Density of intake air

The Inlet system for two stroke cycle engine is quite different in nature from that of four stroke engine and, therefore, it will be discussed separtely.

In four stroke engines, admission takes place mainly during downward motion of the piston. As the piston moves down, the cylinder volume increases causing drop in cylinder pressure. The intake valves opens a few degrees of crank rotation before the top dead center. When the pressure inside the cylinder drops below the pressure of ambient air by a value drop to pressure in the intake system and the inlet valve opens, fresh air or charge begin to enter the cylinder. This drop of pressure depends on the speed of the engine, the resistance of flow and density of the charge. Usually the exhaust valve remains open ever after the inlet valve opens and it closes after a few degrees of crank motion from the TDC. This period of valve overlap, during which both inlet and exhaust valve remain open, helps in driving out the exhaust gases more efficiently. The process of admission continues upto the BDC position of piston and beyond. It ends when the inlet valve closes. Upto the BDC, admission of charge is mainly due to piston motion. The decrease in cylinder volume, due to piston motion (per degree crank travel) near the dead center positions, is very small. Therefore, the pressure at inlet remains higher than the pressure inside the cylinder even after the BDC (the volume of charge inside the cylinder decreases during this period) and the process of admission continues until the inlet valve closes. The velocity head of charge in the intake system is also used in forcing more charge into the cylinder. Pressure wave propagation in the intake system due to periodic opening and closing of the inlet valve may also help in increasing the flow of charge in the cylinder.

The inlet valve opens 10-20 degree before TDC and the exhaust valve closed 15-30 degree after TDC. Therefore, both the valves remain open for a certain period of crank rotation during initial period of admission. During earlier part of valve overlap some combustion gas may enter the intake system, but during the later part the combustion gases move out creating a local pressure drop. As a result fresh charge enters the cylinder pushing out the exhaust gases. It is common practice to keep the inlet valve wide open during the main period of charging and to make best use of inertia of charge in the intake system.

The exhaust valve opens ahead of the BDC, when the expansion process is still continuing. The pressure of the products at the moment is much higher than the exhaust pressure and burnt products flow through the exhaust at sonic velocity. After the piston crosses the BDC the burnt gases whose pressure has dropped to exhaust pressure are forced out of the cylinder due to upward motion of the piston. The gas velocity during this period is much lower. During the first phase of exhaust some work of expansion is lost and during the second phase some work is lost in expelling the brunt gases. Too early or too late opening of exhaust valve increases the work lost during exhaust. For a particular design of engine there is a particular moment of exhaust opening which produces minimum work loss.

The exhaust process in two stroke engine begins as soon as the exhaust port is uncovered by piston during it downward motion. The pressure of burnt gas from previous cycle being higher that the critical pressure the burnt gases flow out with sonic velocity. The pressure of burnt gas gradually reduces and finally the gas pressure equals the exhaust pressure. This is the first phase of exhaust and called the blowdown phase. As the piston moves further downwards in its expansion stroke the inlet ports are uncovered by the piston. Fresh charge, admitted into inlet ports are uncovered by the piston. Fresh charge, admitted into the crank case and compressed inside it previously, enters the cylinder through inlet ports at a pressure above the exhaust gas pressure (crank case scavenged engine). In blower scavenged engines the pressure of fresh charge is increased by a blower or a compressor and the charge enters the cylinder as soon as the inlet ports are uncovered. The high pressure charge drives out the burnt gases from the cylinder through the exhaust ports and fills the cylinder with fresh charge. This combine process of discharging and burnt gases and filling the cylinder with fresh charge is called scavenging. This phase continues during the period when both inlet and exhaust ports are open. The piston starts its upward motion after crossing the BDC position. The admission process is complete with closing of the inlet ports by piston during its upward motion. The exhaust process continues for a small period until the piston covers the exhaust port and the scavenging process is complete.

Internal combustion engine operate at comparatively high speed. When increased in speed after starting the peripheral speed of the journal grows. High peripheral speed causes increased lubricating oil pressure in the journal bearing. The temperatures of the piston assembly and the bearings appreciably grow after continuous operation at high speed. The function of the lubrication system will be to provide oil between bearing parts in order to cool the bearing surfaces by maintaining sufficient rate of oil flow through these surfaces. Lubricating oil also washes out any wear product from journals or other mating parts. Two types of lubrication systems are commonly used depending on the power output and operating conditions of the engine.

The lubricating system with a wet sump. The lubricating oil is stored in a pat at the bottom of the crank case. The oil pan is separated from the crank case space by a screen. Oil is delivered under pressure to different sections of the engine by a delivery pump. The parts which are supplied with oil under pressure are main bearing, the crank pin bearing, piston pin bearing, the cam shaft bearing and the valve operating mechanism. Oil is generally sprayed from connecting rod big end to the cylinder liner and the cams. A course filter is in series with the oil line and a fine filter is connected to the oil line in parallel. The course filter usually cleans all the oil supplied to the engine. System with high circulation rate is provided with oil cooler where the oil is cooled by air or water.

In this system major part of oil is stored in a tank outside the engine or the crank case. The oil flows down into small recesses at the bottom of crank case. It is continuously pumped out from these recesses into the storage tank by a pump and there is practically no storage of oil in the sump. The delivery pump installed inside the storage tank delivers oil under pressure through oil cooler and filter to different sections of the engine. This system of lubrication is employed only in high power engine and in low height engine.

The oil, after lubricating different parts, flows down into the recesses both in front and rear of crank case. The oil from the recess is continuously pumped out into the storage tank. A separate delivery pump is provided in the oil tank which delivers oil through the oil cooler and filters into the main line. A bypass valve is provided before the oil cooler to return any excess oil delivered by the pump. Usually a drain valve is provided in the main line. This valve ensures constant oil pressure before the bearing irrespective of varying speed and temperature of the engine.

Gear pump with external meshing of gears is extensively used for oil circulation. Spur and helical are both used in this pump. Rotary pump with internal meshing gears is also coming into practice.

The lubricating oil receives heat generated in the bearing surfaces due to friction. It also gets heat owing to its contact with heated surfaces of piston. If the heat is not removed during operation, the temperature of oil will go on increasing. The viscosity of the oil will decrease rapidly as the temperature increases and if the oil supplied to the bearing surface becomes too hot the film of lubricating oil may break down resulting in metallic contact between journal and bushing. In order to overcome this difficulty the lubricating system of engine is provided with oil cooler. The coolers may be water cooled or air cooled type.

The oil circulated to bearing surfaces should be filtered and cleaned of minute solid particles to such a degree that the size of the left over particles is less than the minimum clearance between bearing surfaces.

The lubricating system in common use employs on coarse and one fine filter. The entire flow of oil is passed through the coarse filter before it is circulated. The fine filter with high resistance of filtering element is placed parallel to the flow line. Only a part of the oil flow is passed through this filter and then returned to the oil sump.

The exhaust hot air form exhaust valve is entered into the turbo charger. In turbo charger there is a turbine. The blades of turbine is rotated by hot air and this turbine starts working. The turbine is connected to a compressor by means of a shaft. The compressor sucks the air from atmosphere. The air from filter is compressed to inlet manifold by means of a compressor.

The air compressed by turbo charge into inlet manifold has greater mass, high temperature and pressure. For an efficient process we need air of high pressure and low temperature. For the same purpose we install an inter cooler between turbo charger and Inlet manifold. This inter cooler is nothin but a simple radiator consisting of a fan and fins for the exchange by heat. Only fraction of pressure is decreased but temperature is lowered down from it.

The first major component in the electrical system is the battery. The battery is used to store power for starting, and for running auxiliary devices such as clocks, radios and alarms when the engine is off. The next major component is the starter motor, which is used to start the engine. The third component is a charging device powered by the engine, known as the alternator. It powers the electrical system when the car is running, and restores the charge within the battery. With these basic components, the car maintains its supply of electricity. A device called the voltage regulator keeps the power level stabilized, and the fuse box keeps minor problems from becoming major ones.

The car's initial source of electricity is a battery, whose most important function is to start the engine. Once the engine is running, an alternator takes over to supply the car's electrical needs and to restore energy to the battery.

A 12-volt storage battery consists of layers of positively and negatively charged lead plates that, together with their insulated separators, make up each of six two-volt cells. The cells are filled with an electricity-conducting liquid (electrolyte) that is usually two-thirds distilled water and one-third sulfuric acid. Spaces between the immersed plates provide the most exposure to the electrolyte. The interaction of the plates and the electrolyte produces chemical energy that becomes electricity when a circuit is formed between the negative and positive battery terminals.

The starter converts electricity to mechanical energy in two stages. Turning on the ignition switch releases a small amount of power from the battery to the solenoid above the starter. This creates a magnetic field that pulls the solenoid plunger forward, forcing the attached shift yoke to move the starter drive so that its pinion gear meshes with the engine's crankshaft flywheel. When the plunger completes its travels, it strikes a contact that permits a greater amount of current to flow from the battery to the starter motor. The motor then spins the drive and turns the meshed gears to provide power to the crankshaft, which prepares each cylinder for ignition. After the engine starts, the ignition key is released to break the starting circuit. The solenoid's magnetic field collapses and the return spring pulls the plunger back, automatically shutting off the starter motor and disengaging the starter drive.

When the starter is not in use, the drive unit is retracted so that its pinion is disengaged from the flywheel. As soon as the starter is activated, the forward movement of the solenoid plunger causes the shift yoke to move the drive in the opposite direction and engage the pinion and flywheel. The pinion is locked to its shaft by a clutch that unlocks if the engine starts up and the flywheel begins turning the pinion faster than its normal speed. By allowing the pinion to spin freely for a moment, the clutch protects the motor from damage until the drive is retracted.

The alternating-current generator, or alternator, is the electrical system's chief source of power while the engine is running. Its shaft is driven by the same belt that spins the fan. It converts mechanical energy into alternating-current electricity, which is then channeled through diodes that alter it to direct current for the electrical system and for recharging the battery.

A spark plug is a device, inserted into the combustion chamber of an engine, containing a side electrode and insulated center electrode spaced to provide a gap for firing an electrical spark to ignite air-fuel mixtures.

The high-voltage burst from the coil via the distributor is received at the spark plug's terminal and conducted down a center electrode protected by a porcelain insulator. At the bottom of the plug, which projects into the cylinder, the voltage must be powerful enough to jump a gap between the center and side electrodes through a thick atmosphere of fuel mixture. When the spark bridges the gap, it ignites the fuel in the cylinder.

The spark plugs ignite the fuel mixture in the cylinders by means of a burst of high-voltage electricity carried from the distributor. The ability of the spark to ignite the fuel is badly affected if the plugs are damaged or the spark gaps are abnormal. It is therefore important to examine used spark plugs closely and to clean them periodically. The gaps of old and new plugs should also be checked before installing them. There are three basic types of spark plug fouling: "carbon" fouling, "high speed" or "lead" fouling, and "oil/carbon" fouling.

Carbon fouling is caused from low-speed operation or a fuel mixture that is too rich. It causes missing or roughness and creates soft black soot that is easily removed. Lead fouling is caused by tetraethyl lead used in some fuels and by extended high speed operation. Lead compounds which are added to the gasoline have a bad effect on some spark plug insulators. At high temperatures, it is a good conductor and may give good results under light loads, but often fails under full loads and high combustion temperatures. In some cases, it is possible to run the engine at a speed just below the point where missing will occur; then, increase the speed (always keeping below the missing speed) to burn off the lead fouling. Lead fouling appears as a heavy, crusty formation, or as tiny globules.

The third type of fouling is found on engines that are so badly worn that excess oil reaches the combustion chamber past the piston ring, or the valve guides.

In all cases of fouling or wear, it is best to replace the plugs. To avoid having to replace plugs one at a time as they wear out, always replace the entire set, even though only one plug may be bad. Plugs should normally be replaced about every 12,000 miles.

The coil is a compact, electrical transformer that boosts the battery's 12 volts to as high as 20,000 volts. The incoming 12 volts of electricity pass through a primary winding of about 200 turns of copper wire that raises the power to about 250 volts. Inside the distributor, this low-voltage circuit is continuously broken by the opening and closing of the points, each interruption causing a breakdown in the coil's electromagnetic field. Each time the field collapses, a surge of electricity passes to a secondary winding made up of more than a mile of hair-like wire twisted into 25,000 turns. At this point, the current is boosted to the high voltage needed for ignition and is then relayed to the rotor.

The distributor is separated into three sections: the upper, middle, and lower. In the middle section, the corners of the spinning breaker cam strike the breaker arm and separate the points some 160 miles an hour. (standard ignition) High-voltage surges generated by the action of the coil travel to the rotor that whirls inside a circle of high-tension terminals in the distributor cap. At each terminal, current is transferred to wires that lead to the spark plugs. Two other devices - the vacuum advance and the centrifugal advance - precisely coordinate the functions of the points and the rotor assembly as the requirements of the engine vary.

The automotive storage battery is not capable of supplying the demands of the electrical system for an extended period of time. Every vehicle must be equipped with a means of replacing the current being drawn from the battery. A charging system is used to restore the electrical power to the battery that was used during engine starting. In addition, the charging system must be able to react quickly to high load demands required of the electrical system. It is the vehicle's charging system that generates the current to operate all of the electrical accessories while the engine is running.

The purpose of the charging system is to provide the electrical energy needed to charge the battery and to power all the electrical components and systems on the automobile. When the engine is not running, the battery provides this electrical energy. When the engine is running, the charging system takes over. The basic parts of a charging system are shown. The alternator is the heart of the charging system. It is an alternating-current generator mounted on the engine, which is driven by a belt from the crankshaft. The alternator develops alternating current, which is changed to direct current. Alternating current changes from positive (+) to negative (-) at a regular cycle. Direct current does not change from positive (+) to negative (-). Only direct current can be used to charge a battery.

A voltage regulator, either inside or outside the alternator, senses the electrical needs of the vehicle and adjusts the output of the alternator accordingly. An indicator light on the instrument panel allows the driver to observe whether the system is operating properly. The battery is connected electrically to the alternator, so that either one may supply the electrical needs, and so that the alternator can charge the battery.

Two basic types of charging systems have been used. The first was a DC generator, which was discontinued in the 1960s. Since that time the AC alternator has been the predominant charging device. The DC generator and the AC alternator both use similar operating principles.

As the battery drain continues, and engine speed increases, the charging system is able to produce more voltage than the battery can deliver. When this occurs, the electrons from the charging device are able to flow in a reverse direction through the battery's positive terminal. The charging device is now supplying the electrical system's load requirements; the reserve electrons build up and recharge the battery.

If there is an increase in the electrical demand and a drop in the charging system's output equal to the voltage of the battery, the battery and charging system work together to supply the required current.

When the conductor is parallel with the magnetic field, the conductor is not cut by any flux lines. At this point in the revolution there is zero voltage and current being produced.

As the conductor is rotated 90 degrees, the magnetic field is at a right angle to the conductor. At this point in the revolution the maximum number of flux lines cut the conductor at the north pole. With the maximum amount of flux lines cutting the conductor, voltage and current are at maximum positive values.

When the conductor is rotated an additional 90 degrees, the conductor returns to being parallel with the magnetic field. Once again no flux lines cut the conductor, and voltage and current drop to zero.

An additional 90-degree revolution of the conductor results in the magnetic field being reversed at the top conductor. At this point in the revolution, the maximum number of flux lines cuts the conductor at the south pole. Voltage and current are now at maximum negative values.

When the conductor completes one full revolution, it returns to a parallel position with the magnetic field. Voltage and current return to zero. The sine wave is determined by the angle between the magnetic field and the conductor. It is based on the trigonometry sine function of angles. The sine wave shown plots the voltage generated during one revolution.

It is the function of the drive belt to turn the conductor. Drive belt tension should be checked periodically to assure proper charging system operation. A loose belt can inhibit charging system efficiency, and a belt that is too tight can cause early bearing failure.

The DC generator is similar to the DC starter motor used to crank the engine. The housing contains two field coils that create a magnetic field. Output voltage is generated in the wire loops of the armature as it rotates inside the magnetic field. This current is sent to the battery through the brushes.

The components must be polarized whenever a replacement DC generator or voltage regulator is installed. To polarize an externally grounded field circuit (A-type field circuit), use a jumper wire and connect between the BAT terminal and the ARM terminal of the voltage regulator. Make this jumper connection for just an instant. Do not hold the jumper wire on the terminals. For an internally grounded field circuit (B-type), jump the F terminal and the BAT terminal.

In C.I engines, the fuel must be injected at the correct instant. Early or late injection results in loss of power. If the fuel is injected too early in the cycle, compression will not be at the maximum, the temperature will be low and ignition will be delayed. When the fuel injection is late, the piston will be past top center and power will be less because maximum expansion of the burned fuel will not take place. The injection must therefore start instantly, continue for the prescribed time, and then stop abruptly.

The mechanic is often called upon to troubleshoot an engine problem relating to low power. There are many causes for this kind of complaint. This article will discuss one possibility that should be considered if this problem occurs after an engine has been overhauled or disassembled for other reasons.

First, let us consider the symptoms. In case of an engine fitted with a fixed pitch propeller, the static RPM may be several hundred RPM below what is specified for this engine/airframe combination. For an engine with constant speed propeller which has the governor and propeller blade angle set properly, it is possible that both static RPM and/or performance may be low. The cause of these symptoms in an engine that has recently been disassembled may be the result of improper timing between the crankshaft and the camshaft. Misalignment by one or two gear teeth may have occurred during engine assembly.

If these symptoms exist and if improper timing is suspected, it is not necessary to disassemble the engine to check the internal engine timing between crankshaft and camshaft. The procedure for accomplishing this check will be detailed below for those mechanics that have not been exposed to this method before.

First, insure that magneto and electrical switches are in the OFF position. Next, remove the cowling so that rocker box covers and spark plugs are accessible. Then rotate the engine so the piston in number one cylinder is positioned at top dead center on the compression stroke. The number one cylinder of Lycoming engines is the right front cylinder except for the 541 models that have number one cylinder at the left front position. For all Lycoming direct drive engine models, the top dead center position of number one piston can be verified by observing that the mark indicating the #1 TDC position on the rear side of the starter ring gear is exactly aligned with the split line of the crankcase at the top of the engine. As the last step of preparation, remove the rocker box cover from number two cylinder.

Engine timing is checked by first observing the number two cylinder valve rocker arms. Both valves should be closed or nearly closed. The next step is to move the propeller slightly in one direction. Rocker arm motion should be seen as one valve starts to open. STOP. Now rotate the engine back to the original position with the #1 TDC mark again aligned with the split in the crankshaft halves. Both valves should again be closed or nearly closed. Now move the propeller slightly in the direction opposite from the first movement. Rocker arm motion should again be seen as the other valve starts to open. If the two valves started to open as described with only a small amount of engine movement in each direction, the engine timing is correct.

For some individuals it may be simpler to rock the propeller slightly with a back and forth motion while observing that first one valve and then the other will start to open. If movement in either direction exceeds twenty degrees of engine rotation before motion of the rocker arm occurs, the crankshaft to camshaft timing is not correct.

If the observed rocker arm movement indicates that internal engine timing is correct, then this is not the cause of the low power being investigated. On the other hand, if both rocker arms do not move from engine rotation within the parameters discussed earlier, the internal engine timing is not correct. This indicates a probable error during engine assembly and it can only be corrected by opening the engine and realigning the crankshaft and camshaft gears.

The valve timing gear controls the feed of combustion mixture into the cylinders and waste gas exhausted into the atmosphere. The intake and the exhaust valves are not interchangeable. The camshaft rests on two bearings inside the engine crankcase. The front is a ball bearing and the rear one is a bronze blind bushing.

Correct valve timing is obtained by aligning the mark grooves on the timing gears. This must be carefully observed during disassembly and reassembly of the engine.

Valve adjustment. It is very important to adjust the valves properly. Valves are adjusted to provide the correct clearance with a cold engine. The clearance should be 0.05 mm/0.002 in. In service, it will change due to bedding-in of single parts.

It is important to readjust the clearances after grinding or partial disassembly of the valve mechanism. For this purpose, put a pan under the cylinder head, take off the head cap and drain off accumulated oil. Turn the crankshaft using the kick lever. Just when the intake valve begins to close, set the clearance for the exhaust valve and at the time the exhaust valve begins to open, set the clearance for the intake valve. Check the clearance between the larger end of the rocker arm and the valve stem. If the clearance happens to be larger or smaller than 0.05 mm/0.002 in, slacken off locknut and by turning the adjusting bolt in or out, set the required clearance with a feeler gauge. Lock the adjusting bolt with the locknut and check the clearance again.

Several runs were done with the engine timed at various full advance settings (full advance on this engine appears to occur at 6k RPM. The advance is controlled electronically by the ignition computer, but may be modified). In the case of the runs, we also took a new 'control' run – which is Run016. This was felt necessary since conditions (temperature of the shop, temperature and diameter of the tire) may have changed by this time (we had done a significant number of runs and these runs were actually taken after the runs for mixture that follow.)