The document discusses the ignition system of internal combustion engines. It begins by explaining the purpose of an ignition system, which is to generate sparks within the engine's cylinders strong enough to ignite the air-fuel mixture. It then describes the typical components of an ignition system, including the battery, ignition switch, ignition coil, distributor, and spark plugs. The document emphasizes that the ignition system must provide sparks at the right time and intensity to ensure proper combustion as the engine's speed and load changes.

1. INTRODUCTION
We know that in case of Internal Combustion (IC) engines,
combustion of air and fuel
takes place inside the engine cylinder and the products of
combustion expand to produce
reciprocating motion of the piston. This reciprocating motion of
the piston is in turn
converted into rotary motion of the crank shaft through
connecting rod and crank.
This rotary motion of the crank shaft is in turn used to drive
the generators for generating
power.
We also know that there are 4-cycles of operations viz.:
suction; compression; power
generation and exhaust.
These operations are performed either during the 2-strokes of
piston or during 4-strokes
of the piston and accordingly they are called as 2-stroke cycle
engines and 4-stroke cycle
engines.
In case of petrol engines during suction operation, charge of
air and petrol fuel will be
taken in. During compression this charge is compressed by
the upward moving piston.
And just before the end of compression, the charge of air and
petrol fuel will be ignited
by means of the spark produced by means of for spark plug.
And the ignition system
does the function of producing the spark in case of spark
ignition engines.

3. The Ignition System (Reasons for)
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

4. System Components
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
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

5. The Ignition Coil
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.

7. Block diagram of the Ignition
System

8. Ignition Components - The Spark
Plug
Centre electrode receives
coil voltage.
Side electrode is grounded.
Insulator prevents high
voltages from shorting to
ground.
Termi
nal
Gap
Insula
tor
Gask
et
Threa
d
Met
al
she
ll
Hex
Centre
electro
de
Side
electro
de
Spark plug is located in the
cylinder head, it ignites the air
and fuel mixture.
Has center and side
electrodes, with an air
gap between them.
High voltage
jumps the air gap,
creating a spark.
Next >

9. 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.
This is known as ignition
timing.
Ignition timing changes
with engine speed and
load requirements.
In theory, a spark
should occur just after
TDC (top dead center),
as a piston starts
downward on its power
stroke.
In practice, the air and fuel
mixture has to burn for a
finite length of time.
Therefore, a spark has
to occur before a piston
reaches top dead
center (BTDC).
Next >

10. Base Ignition Timing
Typically, a spark at idle speed will occur at 8
degrees BTDC.
This is known as base
ignition timing.
On contact breaker
ignition systems, base
timing is determined by
the position of the contact
breaker relative to the
distributor cam and is
affected by the gap
between the contacts.
On DI systems, the ICM
determines base timing from
speed sensor pulses.
On DIS / EI systems,
the ICM / ECU
determines base timing
from crankshaft pulses.
Exhaust Inlet
8°BTDC
TDC
Next >

11. 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.
Next >

12. 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 distributor less ignition
systems calculate spark advance from
sensor information. Next >

13. IGNITION FUNCTION
 Produces 30,000 volt spark across
spark plug
 Distributes high voltage spark to each
spark plug in correct sequence
 Times the spark so it occurs as piston
is nearing top dead center
 Varies spark timing with load, speed,
and other conditions

14. BASIC IGNITION
SYSTEM
 Battery supplies
power to entire
system
 Ignition Switch
turns engine on
or off
 Coil transforms
volts
 Switching device
triggers ignition
coil
 Spark Plug and
wires distribute
spark

15. PRIMARY CIRCUIT
 Consists of low
voltage wiring
and
components
 Uses
conventional
type
automotive
primary wires
 Controls when
ignition will
take place.
(When coil
fires)

16. SECONDARY CIRCUIT
 Distributes
current to
individual
cylinders to
jump spark
plug gap
 Must have
thicker, heavier
insulation on
wires
 Typical voltage
to jump gap -
10K Volts

17. Ignition Parts
BATTERY provides power for system.
IGNITION SWITCH allows driver to turn ignition on IGNITION COIL changes battery voltage to 30,000V normal operation and has a potential to produce up SWITCHING DEVICE mechanical or electronic switch Ignition coil(Pick-up coil, Crank sensor, Cam sensor).
SPARK PLUG uses high voltage from ignition coil in the combustion chamber.
IGNITION SYSTEM WIRES connect components.

18. Objectives
After studying this term paper, you should
be able to
Explain the function of ignition systems.
Differentiate between battery and
magneto ignition system
 Know the basic ignition system.
 You are able the component of ignition
system –spark plug
Appreciate the importance of ignition
timing .

19. • COMPARISON BETWEEN BATTERY AND
MAGNETO IGNITION SYSTEM
• Battery Ignition Magneto
Ignition
• Battery is a must. No battery needed.
• Battery supplies current Magneto produces the
required current
in primary circuit. for primary circuit.
• A good spark is available During starting the
quality of spark is poor
at low speed due to slow speed
• Occupies more space. Very much compact.
• Recharging is a must in No such arrangement
required
case battery gets discharged
• Mostly employed in car Used on motorcycles,
scooters, etc.
and bus for which it is
required to crank the engine
• Battery maintenance is required No battery
maintenance problems

20. References:
 http://www.google.co.in/url?sa=t&rct=j&q=ignition
%20system%20pdf&source=web&cd=1&cad=rja
&ved=0CCkQFjAA&url=http%3A%2F%2Fwww.ig
nou.ac.in%2Fupload%2Funit%25204.pdf&ei=N7
wTUufENsiXrAfn24EQ&usg=AFQjCNEqTMr1qLr
KhrtETcfCqS2Fh88vIQ&bvm=bv.50952593,d.bm
k
 http://en.wikipedia.org/wiki/Ignition_system#Mode
rn_ignition_systems
 I.C Engines By V.Ganesan ,TMH Punlication.