The document discusses various components and systems of an engine's ignition system. It describes the purpose of each component as well as how they work together. The key components include the ignition coil, distributor, spark plugs, and wires. The ignition coil transforms low voltage from the battery into high voltage required for sparking. The distributor times the spark and directs it to the correct spark plug. Modern systems use sensors and electronic control units to adjust ignition timing based on factors like engine speed and load. The goal is to ignite the fuel-air mixture at the optimal time for combustion.

1. ENGINE SYSTEMS
& COMPONENTS

2.  Requirements of Ignition
system:-
1. Supply Minimum energy
2. Initiate the combustion
3. Establishment of Flame under
all operating.

3.  Produce high voltage (30,000V) spark across
spark plug
 Distribute high voltage spark to each spark
plug in correct sequence
 Time the spark so it occurs as piston is
nearing top dead center
 Vary spark timing with load, speed, and other
conditions

4. 1. Battery-Coil
2. Magneto
3. Electronic
a. Transistorized Coil Ignition(TCI)
b. Capacitor Discharge Ignition (CDI)

5.  BATTERY
 IGNITION SWITCH
 IGNITION COIL
 SWITCHING DEVICE
 SPARK PLUG
 IGNITION SYSTEM WIRES

6.  Battery supplies power to entire system
 Ignition Switch turns engine on or off
 Coil transforms voltage
 Switching device triggers ignition coil
 Spark Plug and wires distribute spark

9.  To make a spark inside the
engines cylinders which is
strong enough to ignite
the air/fuel mixture. In
normal atmospheric
conditions only about 600
Volts are needed to make
a spark, however in the
pressurised environment
of the engines cylinders,
8000 to 30,000 volts will
be required.
 To ensure the spark
happens at the right time
for each cylinder going
through the 4 Stroke Cycle
i.e. just at the end of the
compression stroke. The
ignition system also has to
change the time at which
the spark occurs (the
ignition timing) depending
on engine operating
conditions e.g. how fast
the engine is turning.

10.  The Battery provides the
electricity (12 Volts) for the
Low Tension LT or Primary
side of the ignition system.
 The Ignition Switch, this turns
the system on and off by
controlling the Low
Tension/Primary side of the
ignition system.
 The Ignition Coil, this
transforms or boosts the
Batteries 12 Volts up to a
voltage strong enough to
produce a spark in the engines
cylinders. The Coil is
connected to both the Low
Tension (12 Volts) and High
Tension HT (8000 to 30000
Volts) sides of the ignition
system.
 The High Tension HT leads,
these allow the spark from the
coil to travel to the spark
plugs
 Please note, the H.T Spark is
produced when the coils
primary windings are turned
off
 The Distributor, this sends the
HT spark form the ignition coil
to the correct cylinder . It may
also turn the coil on and off so
that the coil can produce the
HT spark at the correct time
when required by the engine
to start the air/fuel mixture
burning. Inside the distributor
in modern systems, a
electronic device, called a
‘pick up ’(pulse generator) and
‘control module’ turns the
coils primary winding on and
off. The distributor may also
change the ignition timing
depending on engine
requirements, it is driven by
the engine at half crankshaft
speed.
 The Spark Plugs, these screw
into the combustion chamber
and have two electrodes with a
set gap between them which
the spark has to jump to ignite
the air/fuel mixture.

11.  The ignition coil is switched off and by an electronic switch (pulse
generator) and control unit as shown. When the coil is switched
on,electricty(current) flows from the battery, through the ignition switch,
through the several hundred turns of the thick coil primary windings,
through the electronic switch and finally back to the battery. This sets up a
magnetic field in the coil itself. When the primary current is switched off
by the electronic switch, the magnetic field collapses through the several
thousand turns of the fine secondary windings, producing a very high
voltage (electrical pressure) in the form of a spark which is delivered by the
H.T. circuit to the spark plug.

13. Ignition Components - The Ignition Coil
Coil contains primary and
secondary windings, separated
by a ceramic insulator.
The windings are immersed
in oil and contained within a
slotted iron sheath.
The core is made from soft
iron laminations to produce a
strong magnetic field and
minimize losses.
The coil has 3 terminals
for circuit connection.
- terminal+ terminal
Secondary
terminal
Casing
Insulator
Primary
windings
Secondary
windings
Insulation
paper
Laminated
iron core

14. Ignition Coil Operation
300
turns 18000
turns
Spark plug
gap
‘Primary turned on, current
flows through primary winding,
building up strong magnetic
field, known as ‘Dwell Period’.
‘Primary turned off, no current
flows (suddenly stopped),
producing a BACK EMF in the
primary winding.
Secondary EMF
= turns ratio x primary BACK EMF
= 18000/300 x 200 = 12000V.
BACK EMF
= 200V
Control
unit
Battery
Primary
winding
Soft iron
core
Secondary
winding
The collapsing magnetic
field induces an EMF in
the secondary winding.

15. •It distributes the coils high voltage to the plugs
wires.
•Actuates the on/off cycle of current flow through the
ignition coil primary windings.

16. Ignition Components - The Distributor Cap
Made from hard plastic and
fabricated with locating lugs
or hollows to ensure
accurate placement.
The cap has moulded HT terminals,
which contain brass terminals for
electrical connections to the spark
plugs and the coil.
The terminals protrude inside the
cap, the centre terminal is a spring
loaded carbon button, the outer
terminals are small brass contacts.
Spark plug
HT
terminal
Coil HT
terminal
Brass
contact
Spring
loaded
contact
Securing /
Locating lug

17. Ignition Components - The Rotor Arm
The rotor arm fits onto the distributor
shaft, using a locating slot and a
spring to ensure correct fitment.
Distributes high voltage from the
centre button to each outer terminal.
The rotor arm should be periodically
replaced, as contacts wear and corrode.
Made from hard plastic and contains
brass contacts for voltage transferral.
End
contact
Centre
contact
Locating
slot and
spring
The centre contact may be spring loaded.

18. Distributor Operation
The distributor shaft turns the
rotor arm, transferring voltage
from the centre terminal in the
cap, to each outer terminal.
The distributor shaft cam rotates, a
signal is generated which is used
To switch on and off the primary
Ignition coil windings
A distributor contains vacuum and
centrifugal advance mechanisms to
change ignition timing.
This action determines when a
spark will occur and is known
as ignition timing.
This action determines which
spark plug will receive a spark.
Rotor arm
Outer
terminal
Centre
terminal
From
coil
To spark
plugs

19. Ignition Components - Spark Plug HT Leads
Leads carry voltage from
the distributor to each
spark plug, constructed
using a conductor and
an insulator.
The conductor is made
from carbon.
The conductor has an internal
resistance to reduce radio
frequency interference (RFI).
The terminals at the ends of the leads are protected
by rubber boots, which keep out moisture and dirt.
Rubber
boot
Terminal
Silicone
jacket
Distributor
end
Spark plug
end
The insulator is
made from silicone.

20.  It is cheap
 Provides better spark at low speeds
 Variation of ignition timing can be achieved
easily
 Maintenance is negligible except for battery
 Can be effectively used in cars and buses
Disadvantages
Heavy due to battery & Occupies more space
Provides weaker spark as speed increases as
primary vtg decreases
 The engine cannot be started if battery is
discharged
Maintenance Cost of battery is high

21. IGNITION SYSTEM – Magneto System
Ignition
Switch
Distribution
Contact
Breaker
Coil
Magneto
Condenser
Power
Generation
Spark Generation
Magneto Unit Rotor Arm

22. IGNITION SYSTEM – Dynamo/Alternator System
Dynamo/
Alternator
Distributor
Contact
Breaker
Coil
Ignition
Switch
Secondary
Windings
Primary
Windings
Condenser
Battery

23.  Less Maintenance
 Light in weight & occupies less space
 Provides High Intensity Spark at high speeds
 System is reliable
 Used in Two wheelers, racing cars, Aeroplane’s
Disadvantages
 Since wiring carry high voltage current there is
strong possibility of leakage causing misfiring.
 At low speeds it develops poor Quality of Spark
 Requires extensive shielding to prevent leakage of
high voltage current.

24. Ignition
Switch
Coil
Packs
IGNITION SYSTEM – Electronic Systems
Control Unit
Timing
SensorTiming
Disc
Engine Speed Sensing Unit
Alternator
Battery

26. Ignition Components - The Spark Plug
Centre electrode receives coil voltage.
Insulator prevents high voltages
from shorting to ground.
Terminal
Gap
Insulator
Gasket
Thread
Metal
shell
Hex
Centre
electrode
Side
electrode
Spark plug is located in the cylinder head,
it ignites the air and fuel mixture.
Has centre and side electrodes,
with an air gap between them.
High voltage jumps the
air gap, creating a spark.
Side electrode is grounded.

28.  Two or four stroke operation
 Compression Ratio
 Cylinder head design
 Location of spark
 Mix. Density
 Speed of engine
 Cooling arrangement
 Octane value of fuel

31. Ignition Timing
A spark has to occur at precisely the right moment in an engine
cycle, to ignite a pressurized mixture of air and fuel.
In theory, a spark should occur
just after TDC (top dead centre),
as a piston starts downward on
its power stroke.
Therefore, a spark has to occur
before a piston reaches top
dead centre (BTDC).
In practice, the air and fuel mixture
has to burn for a finite length of time.
This is known as ignition timing.
Ignition timing changes with engine
speed and load requirements.

32. Ignition Timing Change Due to Engine Speed
Ignition timing has to advance, because as an engine speeds up, the point
at which combustion occurs, comes around quicker.
An ignition
system must be
able to advance
and retard the
spark, with
regard to
engine speed.
Early DI systems use a centrifugal advance mechanism.
Electronic and distributor less ignition systems calculate spark advance from
sensor information.

33. Ignition Timing Change Due to Engine Load
Engine load and the mix of air and fuel affect burn time.
A long burn time is required
when the mixture is lean
and engine load is light.
A short burn time is required
when the mixture is rich and
engine load is heavy.
An ignition system must
be able to advance and
retard the spark, with
regard to engine load.
Early DI systems use a
vacuum advance mechanism.
Electronic and distributorless ignition systems
calculate spark advance from sensor information.

34. At low speed, the springs
hold the cam plate in base
ignition timing position.
Centrifugal Advance Mechanisms
Two springs, two flyweights
and a cam plate make up
the advance system.
Cam
Stop
Base
plate
Flyweight
Tension
spring
Cam plate
Rubbing block
Pivot
Assume distributor cam is
rotating counter-clockwise.
As speed increases, the
cam plate turns counter-
clockwise as the flyweights
overcome spring pressure.
The end stop limits cam plate travel.
The point at which the rubbing block
engages the cam has moved forward
(spark occurs earlier).
thrown out
Angle of
advance
meets cam
lobe earlier
at rest

35. Vacuum Advance Mechanisms
At idle speed, intake air and
the spring keep the diaphragm
in its ‘home’ position.
Advance
angle
Throttle plate at idle
Low load and speed
Assume distributor cam is rotating counter-clockwise.
The system consists of a diaphragm
and a spring inside a sealed housing,
with a link to the base plate.
At low speed, vacuum pulls the
diaphragm against the spring,
turning the base plate clockwise.
The pick up coil rotates clockwise
and timing is advanced.
The system does not function during low
vacuum conditions (acceleration or full load).
Vacuum
Intake
air
Base
plate
Diaphragm
Spring
Vacuum
port

36. •An electronic switch that turns the ignition coil primary current on/off
LOCATION
•Engine compartment
•On the side of distributor
•Inside the distributor
•Under vehicle dash

37. Electronic Advance Sensors input influences the ignition timing.
•Crank shaft Position Sensor (RPM)
•Cam Position Sensor (tells which
cylinder is on compression stroke)
•Manifold Absolute Pressure (MAP)
(engine vacuum and load)

38. Electronic Advance Sensors input influences the ignition timing.
•Intake Air Temperature Sensor
•Knock Sensor (Retards timing when pinging
or knocking is sensed)
•Throttle Position Sensor(TPS)
•Engine coolant Temperature

39. Primary Objectives:
 (i) To reduce friction between two moving
parts so that there is minimum power
loss.
 (ii) To minimize wear and tear of moving
parts.
 2. Secondary objectives:
 (i) To provide cooling effect.
 (ii) Act as sealing.
 (iii) Act as cleaning agent.

40.  Should Maintain required oil film
 Leave no carbon residue
 Prevent wear of bearings
 Low Cost
 Viscosity: It should ensure, hydrodynamic lubrication action
should take place.
 Chemical stability: It should be chemically stable under different
temperature conditions. Less tendency of oxidation.
 Resistance against corrosion : It should be good corrosion
resistance agent.
 occurred in the engine.
 Physical stability: It should be able to stable under different
condition of temperature.
 Flash point: It should be high to avoid flashing of oil vapors.
 Should contain no sulphur.
 Free from dirt & water.

41.  Solid Lubricants:-
 Solid Lubricants are used when film lubrication is not possible.
 Graphite,soap stone, molbdenum
 Powdered very finely & mixed with oil or Water
 Semi-Solid Lubricants:-
 Where retention of liquid lubricants is not possible and the mating parts are
subjected to very high pressure
 Greases made by mixing oils and thickening agents.
 Liquid Lubricants:-
 (a) Animal oils : These are generally obtained from animal fat. But they are not
good lubricants because they are easily oxidized and become gummy after
 some time of use.
 (b) Vegetables oils : These are generally obtained from vegetables like seeds,
plants and trees etc. It has same problem like animal oil but has very good
 lubricant proportion.
 (c) Mineral oil: It is generally derived from the petrochemical and it is most widely
used in automobile sector because of following properties.
 (i) Greater chemical stability at higher temperature. (ii) Less reactive with water.
 (iii) More plentiful and cheaper.
 (d) Synthetic lubricants : These are made from silicon fluids, polyglycol ethers and
aliphatic diester.

42.  The oil additives are added to the lubricating oil to reinforce some
properties
 which is not the natural properties of fluid or lubricating oil. These
additive are added according to the property of lubricants.
 e.g. Phenols, metal salts of thiophosphoric acid and suiphurized waxes
etc. Their important function are as follows:
 (i) Corrosion Inhilitors : Compounds such as metal salt of thiophasphoric
acid and suiphurized waxes act as anti agent in the formation of acid
which cause
 corrosion.
 (ii) Detergents These additions like polymers act as cleaning agent they
break the sludge particles into finely divided particles which are easily
scavenged through
 exhaust port.
 (iii) Viscosity index improvers These are the addition which prevent
minimising
 the decrease of oil viscosity with increase in temperature.

43.  Classification of lubricants is based on their
viscosity.
 SAE has assigned numbers for gradation
 Viscosity is measure of resistance of flow.
 Units are SUS (saybolt universal seconds) &
Centipoises
 Usually expressed at two temp:- (-18°C &
99°C)
 SAE 5W,10W, 20W,grades are defined in
terms of viscosity at -18°C
 SAE 20,30,40,50 grades are defined in terms
of viscosity at 99°C

44. Multi-grade
 The temperature range the oil is exposed to
in most vehicles can be wide, ranging from
cold temperatures in the winter before the
vehicle is started up, to hot operating
temperatures when the vehicle is fully
warmed up in hot summer weather. A specific
oil will have high viscosity when cold and a
lower viscosity at the engine's operating
temperature. The difference in viscosities for
most single-grade oil is too large between
the extremes of temperature.
 The SAE designation for multi-grade oils
includes two viscosity grades; for
example, 10W-30 designates a common
multi-grade oil with viscosity equal to that of
SAE 10W at -18°C & SAE 30 for 99°C

45.  Provides Ease of starting & short warming
period, Extends Battery life.
 Operates for wider range of temp
 Reduces oil comsumption
 Reduces carbon deposits

46.  Mist or Charge
 Wet Sump
1. Splash
2. Splash & Pressure
3. Fully Pressure
 Dry sump

51. Air cooling

52.  (a)Air cooled engines operate satisfactorily in both hot and cold climates.
(b) These engines can work at higher operating temperatures than their equivalent liquid-
cooled counterparts.
(c) The working temperature in these engines is attained rapidly from cold condition. id)
These engines are marginally lighter than liquid-cooledengines of same capacity. (e)
These engines do not encounter coolant-leakage or freezing problems.
 Cool circulating air comes in contact with the exposed and enlarged external surfaces of the
cylinder and head.
 Direct Air-cooled Engine System.
 Dis-advantages.
(a)The cooling fans require a relatively large amount of power to run.
(b) Due to the large quantities of intake air passing into the cooling system, the engine may
become noisy.
(c)The cooling fins can vibrate and amplify noise under certain conditions.
(d) For proper positioning of the fins between cylinders, the pitch between cylinder centres has
to be greater than in liquid-cooled engines.
(e) Each cylinder is required to be cast individually unlike liquid-cooled engines where a rigid
mono-block construction is used.
(/) To prevent overheating of the lubricant, the air-cooling is frequently supplemented by an
oil heat exchanger.
(g) The presence of the guide cowling and baffles around the cylinders may hinder
maintenance.
 Indirect Liquid-cooled Engine System.

55.  Advantages.
(a) Greater temperature-uniformity around the cylinders is achieved in
liquid-cooled engines causing less distortion compared with air-
cooledengines.
(b) The power consumption of the coolant pump and the fan together in
liquid-cooled engines is less than that of the fan in air-cooled engines.
(c) The liquid-cooled engine cylinders are much closer, providing a very
rigid and compact unit unlike the air-cooled engine.
(d) Both the coolant and the jackets dampen the mechanical noise from
the engine.
(e) Liquid-cooled units perform heavy-duty work more reliably than air-
cooled engines.
(f) Hot coolant can readily be circulated for interior heating of the
vehicle.
 Disadvantages.
(a)Liquid-coolant joints may develop leakage.
(b)Care must be taken to avoid freezing of the coolant.
(c) Liquid-cooled units require more time to warm up than the air-
cooled engines.
(d) The boiling point of liquid-coolant limits maximum
temperature of operation, whereas air-cooled engines can operate at
slightly higher temperatures.
(c) Formation of scale takes place in the coolant passages, and the hoses
and radiator tubes deteriorate with time.

56.  The advantages of thermo-syphon cooling are :
(a)Cheap as no water pump is required.
(b)Reliable as there are no moving parts.
(c)Circulation of water depends solely
on engine temperature. The hotter the engine, the greater
is the circulation.
 Disadvantages of thermo-syphon cooling
(a) In order to achieve efficient circulation, the radiator top
tank must be well above the engine. This needs a high
bonnet
(b) Cooled water enters the engine at the bottom of the
cylinder, where the engine normally runs fairly cool and it
heats up to maximum as it reaches the top of the
cylinders. Therefore, it has a reduced cooling effect on the
hottest part of the engine.
(c) Difficult to fit an interior heater successfully without a
water pump.
(d) Under conditions of very heavy load or in hot climates
the water may not circulate as quickly as required.
Incorporation of a water pump insures positive water
circulation and removes all the disadvantages of
the thermo-syphon cooling process.