DEFINATION,REQUIREMENT,TYPES,ADVANTAGE,DISADVANTAGE

1. Mr. MUBASSIR I. GHONIYA has satisfactorily
completed his PPT work on IGNITION SYSTEM OF
SI ENGINE in T.E-II course in mechanical
engineering department as per the GTU regulation.
Date :-
Guide External faculty H.O.D
Sign Sign Sign

2. A.Y.DADABHAI TECHNICAL INSTITUTE,
KOSAMBA
Subject:- IGNITION SYSTEM OF SI ENGINE
SUBMITTED BY
GHONIYA MUBASSIR AHMED IMTIYAZ AHMED
Enrolment No:- 136010319024
Guide BY:- Y.A.S

3. DEFINATION OF IGNITION
SYSTEM
 The system in an internal-combustion engine that
produces the spark to ignite the produces the
spark to ignite the mixture of fuel and air: includes
the battery , spark plugs, and associated switches
and wiring.
 It known as the ignition system

4. INFORMATION ABOUT IGNITION
SYSTEM IN SI ENGINE
 The term spark-ignition engine refers to internal
combustion engines generally, petrol engines.
 Where the combustion process of the air-fuel
mixture is ignited by a spark from a spark plug.
 Spark-ignition engines are commonly refer to as
“gasoline engines” in America ,and “petrol
engines” in Britain and the rest of the world .
 The working cycle of spark ignition engines may
be either two stock or four stroke
 A four stroke spark ignition engines is an Otto
cycle

5.  It consist following four stroke.
1. Suction stroke
2. Compression stroke
3. Power stroke
4. Exhaust stroke
 The combustion in spark ignition engine is
initiated by an electrical discharge across the
electrodes of a spark plug, which usually occurs
fro 100 to 300 before TDC depending upon the
chamber geometry and operating conditions.
 The ignition system provides a spark of
sufficient intensity to ignite the air fuel mixture at
the predetermined position in the engine cycle
under all speeds and load condition.

6. IGNITION SYTEM REQUIREMENT
 It should provide a good spark between the
electrodes of the plugs at the correct timing
 The duration of the spark must be long enough with
sufficient energy to ensure that ignition of the mixture
has a high chance of occurring
 The system must distribute this high voltage to each
of the spark plug at exact time in every cycle , i.e., i t
must have in it a distributing device
 It should function efficiently over the entire range of
engine speed
 It should be light, effective and reliable in service

7.  The development of high speed, high
compression internal combustion engine requires
reliable high-speed ignition speed ignition system.
This is met by a high-tension ignition system that
uses a spark plugs as the source of ignition. The
electrical energy to the spark plug is supplied by
one of the following systems and is termed
accordingly.

8. TYPES OF IGNITION SYSTEM
 COIL IGNITION SYSTEM
 MAGNETO IGNITION SYSTEM
 ELECTRONIC IGNITION SYSTEM

9. 1.COIL IGNITION SYSTEM

10.  The primary circuit consists of the battery, ammeter,
ignition switch, primary coil winding, capacitor, and
breaker points. The functions of these components
are:BATTERY PROVIDES THE POWER TO RUN THE SYSTEM
IGNITION
SYSTEM
ALLOWS THE DRIVER TO RUN TURN THE SYSTEM
ON AND OFF.
PRIMARY COIL PRODUCES THE MAGNETIC FIELD TO CREATE THE
HIGH VOLTAGE IN THE SECONDARY COIL.
BREAKER POINT A MECHANICAL SWICH THAT ACTS AS THE
TRIGGERING MECHANISM.
CAPACITOR PROTECS THE POINT FROM BURNING OUT

11.  The secondary circuit converts magnetic
induction into high voltage electricity to jump
across the sparkplug gap, firming the mixture at
the right time. The function of the

12. Secondary
Coil
Coil wire
: the part of the coil that creates the high
voltage
Electricity
A hire insulated wire to take high voltage to the
distributor cap
Distributor
cap
: a plastic cap which goes on top of the
distributor,
to hold the high tension wires in the right order
Rotor : spins around on the top of the distributor shaft,
and distributes the spark to the right spark plug
Spark plug
Leads
: another highly insulated wire that takes the
high
voltage from the cap to the plugs
Spark plugs : take the electricity from the wires, and give it
an

13.  The ignition switch provided, connects and
disconnects the ignition system from the
battery.hence the engine can be started or
stopped a will. When the ignition system is “ON
"the contact breaker points are closed.
 This allows the current to flow from the battery
trough primary winding of the ignition coil and
back to battery through earthlings .
 The magnetic field across the primary winding is
developed. This will induce back e.m.f. this will
oppose the battery current. With the result, the
current in the primary will slowly developed.
 This will delay the building up of magnetic field. A
voltage is induced in the secondary windings.
But the e.m.f.is too low to produce a spark at the
spark plug.

14.  The breaker point is opened by the distributor
arm when we want a spark in the engine. This
opens the primary circuit.
 The magnetic field in the primary field collapses.
The resulting induced current will flows in the
same directiopn as the battery current. It charge
the condenser. When the voltage of the battery
across the condenser plates, the flows of the
current is reversed.
 The magnetic field in the coil of the primary
winding reverses due to the quick reversal of the
current in the primary winding.
 This will cause a very high voltage to be induced
in the secondary winding.
 This depends upon the number of turns of the
secondary to primary wind.
 This induced voltage is of the order of 10 KV to

15.  When the contact breaker in the primary circuits
is opened, the distributor rotor connects with a
contact to the spark plug.
 This high induced voltage jumps across the air
gap of the spark plug.
 This will produce the spark for ignition system
battery of 6V to V used. The voltage induced is 6
V to 24 V used.
 The voltage induced is 6kV to 10kV.

16. ADVANTAGES OF THE COIL
IGNITION SYSTEM
1. At the time of starting and idling at low speed
good sparkling is available.
2. Initial expenditure is less . Hence, this system is
used in cars and commercial vehicles.
3. Maintenance cost is less.
4. Distributor drive is simple and non-complicated.
5. By adjusting spark-timing complete ignition
system is not adversely affected.

17. DISADVANTAGE OF COIL
IGNITION SYTEM
1. If the battery is discharged, then it is not
possible to start the engine.
2. Battery is to be checked regularly.
3. It occupies more space.
4. Its wiring is complicated.
5. The intensity of spark decreases with increase
in speed.

18. 2. Magneto ignition system
 The high powered, high speed spark ignition engines
like aircraft, sports and racing cars use magneto ignition
system. The basic components of a magneto ignition
system consist of a magneto, breaker points, capacitor,
ignition switch, distributor, spark plug leads, and
spark plugs.
 Magneto can either be rotating armature type or rotating
magneto type. In the former, the armature consisting of
the primary and secondary windings all rotate between
the poles of a stationary magneto, revolves and the
winding are kept stationary.

20. oElectric circuits
• Uses a changing
magnetic field to
generate current
in primary and
secondary
circuits

21. oMagnetic flux
• As magnet
approaches,
induces magnetic
flux in armature
• Breaker points close
and current
dissipates through
primary circuit

22. oSpark fires
• After magnet rotate past
armature flux reverses
direction, and the breaker
points open
• Change in magnetic
flux produces 170
volts in primary circuit
• Induces 10,000 volts
in secondary circuit,
firing spark plug

23. oBreaker points
• Crankshaft rotation causes
mechanical actuation of
breaker

24. ADVANTAGES OF MAGNETIC
IGNITION SYSTEM
 Since there is no battery or connecting table, the
system is more reliable.
 For medium and very high speed engines, the
system is more suitable.
 The space require is less, by using cobalt steel
and nickel aluminium magnet metals energy.
 This system in fairly reliable with resent
development.

25. DISADVANTAGES OF MAGNETO
IGNITION SYSTEM
 At low speed and during cranking the voltage is
very low. Suitable modifications are necessary in
the circuit to overcome this.
 Adjustment of the spark timing has determined
effect upon the spark voltage or energy.
 The burning of the electrodes will result with
powerful sparks at high engine speeds.
 More costly.
 Starting is troublesome.

26. 3. Electronic ignition system
 The disadvantage of the mechanical system is that it
requires regular adjustment to compensate for wear,
and the opening of the contact breakers, which is
responsible for spark timing, is subject to mechanical
variations.
 In addition, the spark voltage is also dependent on
contact effectiveness, and poor sparking may lower the
engine efficiency. Electronic ignition system has solved
these problems

27. .

28. • In this system, the contact breaker points are
replaced by an angular sensor of some kind - either
optical, where a vane rotor breaks a light beam, or
more commonly using a hall effect sensor, which
responds to a rotating magnet mounted on a suitable
shaft.
•The sensor output processed by a suitable circuitry is
then used to trigger a switching device such as a
thyristor, which switches a large flow of current through
the coil.
•The rest of the system remains the same as the
mechanical system. The lack of moving parts
compared with mechanical system leads to greater
reliability and longer service intervals. In some order
cars, it was usually possible to retrofit an electronic

29. • The spark plug ignites the air-
fuel mixture inside the cylinder.
This occurs when high voltage,
triggered at
precisely the right instant, bridges
the gap between the center and
the ground electrodes. It also
provides a secondary purpose of
helping to channel some heat
away from the cylinder.
oSpark plugs

30. Firing order
 Firing order indicates the sequence or order in
which the firing impulses occur in a multi-cylinder
spark ignition engine. It is chosen to give a uniform
torque, and hence a uniform distribution of firing per
revolution of the engine.
 This is naturally dictated by the engine design, the
cylinder arrangement and the crankshaft design. The
firing order be such that there must always be a
proper balance so as to minimize the engine
Vibration.