Electronic ignition system

SRI KRISHNA COLLEGE OF ENGINEERING AND TECHNOLOGY
DEPARTMENT OF MECHATRONICS ENGINEERING
Session: Electronic Ignition System
11/24/2020 16MT407 - Theory of Automobile Engineering 1
MODULE 1

SESSION OBJECTIVES
 On the completion of this session, the students might
be able to understand,
 How the electronic Ignition system works

Topics
 Function of Ignition system
 Types of Ignition system
 Types of Electronic Ignition system

FUNCTION OF IGNITION SYSTEM
Function of ignition system:
 To generate an electrical spark with
enough heat to ignite the air-fuel
mixture in the combustion chamber.
 To maintain the spark long enough to
allow for combustion of all the air & fuel
in the cylinder.
 To delivery the spark to each cylinder
 To properly time the spark so that the
combustion can be started at right time
during the combustion stroke of the each
cylinder

TYPES OF IGNITION SYSTEM
Types of Ignition system:
 Conventional Ignition system
 Battery Ignition system
 Magneto Ignition system
 Electronic Ignition system
 Transistorized Ignition system
 Capacitor discharge ignition system
 Fully electronic (i.e. Computer
controlled) direct ignition system.

Battery ignition system:
Components
 Battery
 Ignition switch
 Ammeter
 Ignition coil
 Contact breaker
 Condenser
 Distributor
 sparkplugs

Components
 Battery :
 Main source of electrical
energy
 Supplies current to primary
circuit
 One terminal is connected
with earth
 Other with Ignition switch,
Ammeter, Primary Coil of
high tension wire, contact
breaker points and then to
earth.

Components
 Ignition Switch :
 The ignition switch when
closed, allows the flow of
current from battery to the
primary circuit of the ignition
coil.

Components
 Ammeter:
 It is a gauge
 It indicates the flow of
electrical current through the
system.

Components
 Ignition coil:
 It is a type of induction coil
which steps up low voltage
current to high voltage
current.

Components
 Contact Breaker:
 It is the mechanism by
means of which make or
break of the contact is
affected in the primary circuit
of the ignition system for
obtaining high voltage
current.

Components
 Condenser:
 The condenser is connected
across the contact breaker.
 Prevents the arcing at the
contact breaker points at the
time of break in the primary
circuit

Components
 Distributor:
 The distributor is used to
distribute the high voltage
impulses to each of the spark
plug at regularly timed
intervals in the sequence of
the engine’s firing order.

Components
 Spark Plugs:
 The spark plugs are fitted in
the combustion chamber to
provide spark which cause
the compressed air-fuel
mixture to burn.
 Working :
 The induced voltage in the
secondary coil directly
proportional to the rate of
collapse of magnetic field

Pros & Cons of Battery Ignition system:
Advantages Disadvantages
1. Good spark is available at engine
start & Low speed
1. Engine speed increases means
battery energy gets reduced & more
time taken for building current
2.Auxiliary components utilized the
battery energy (Head light, Indicator
Light)
2. Mechanical & Electrical wear of
contact breaker leads to short interval
maintenance
3.Less cost 3.Not reliable at high speed

MAGNETO IGNITION SYSTEM: (ROTATING MAGNET TYPE)
 Magneto is basically an
electrical generator which
is turned to create a
periodic high voltage
pulse rather than
continuous current.
 An electrical generator is
the reverse of an
electromagnet.
 It is classified into two
types.
 Rotating magnet type
 Rotating Armature
type

MAGNETO IGNITION SYSTEM: (ROTATING ARMATURE TYPE)
Rotating Armature Type:
 In rotating armature type
magneto, the armature along with
the primary and secondary coils
revolves in the magnetic field set
up by the permanent magnets.

Pros & Cons of Magneto Ignition system:
Advantages Disadvantages
1. It is more useful at medium and
high speed
1.Starting problem because of Low
speed
2. No battery is required
2.Little more cost than the battery
ignition system
3. It requires less maintenance
3.Chances of miss fire, due voltage
leakage in the wire

Difference between Battery and Magneto Ignition system:
Battery Magneto
1. Battery supplies current to primary
circuit
1. Magneto generates current
2. Strong spark at starting & Low
speed of engine
2. Weak spark at starting & Low speed
3. Easy engine starting 3. The starting of engine is difficult
4. If battery dried out means, engine
never starts
4. No battery needed, no such kind of
difficulty in here
5. The spark strength decreases with
increase of speeds
5. The spark strength increases with
increase in speeds.
6.This system requires more space This system requires less space
7. The wiring is quite complicated The wiring is comparatively simple
8. This system is used in cars, heavy
vehicle likes buses & trucks
It is used in motor cycles, scooters and
racing cars

TYPES OF ELECTRONIC IGNITION SYSTEM
ELECTRONIC IGNITION SYSTEM:
 It overcomes the draw backs in the conventional ignition system.
 Easy control of ignition is possible
 Accurate ignition timing for all operating condition.
TYPES ELECTRONIC IGNITION SYSTEM:
 Transistorized Ignition system
 Capacitor discharge ignition system
 Computer controlled direct ignition system (Without distributor)

Transistorized ignition system:
 It improves the ignition performance
& reliability.
 No contact points required to open or
close the ignition primary circuit
 Therefore no possibility of point of
arc.
 Staring & Low speed characteristics
are improved
Transistorized ignition system:
Components
i.) Distributor,
ii.) Igniter
iii.) Ignition coil, iv.) Spark plug

Non Transistorized system:
 Ignition coil and spark plugs are
called non-transistorized ignition
system.
Transistorized system:
 Distributor & Igniters are called
transistorized systems.

Transistorized ignition
system:
Distributor:
 It consist solid state signal
generator & Spark plug
distributor.
 When the signal rotor is
rotates, an AC voltage is
induced in the pick up coil.
 The igniter is activated by
these AC signals,
 Which connects &
disconnects the primary
circuit.

system:
 Distributor advance
controllers are the same as
used in Non transistorized
system.
 Centrifugal governor advance
mechanism control the signal
rotor & causes to rotate
 Breaker plate rotate by
vacuum advance mechanism.
 The above two mechanism
helps the magnet & pick up
coil fitted

SPARK ADVANCE MECHANISM: NEED
 Ignition begins at the end of the
compression stroke in the combustion
chamber at an appropriate time –
Ignition Time
 If the spark occurs too early or too late
in the engine cycle, it results in
excessive vibration – Knocking
 Also affects engine power, Torque,
Fuel economy, Engine life
 So ignition should be occurs at exact
time in the cylinder.

SPARK ADVANCE MECHANISM: NEED
 At the end of compression stroke,
maximum pressure is developed inside
the combustion chamber.
 It results in Increasing engine speed.
So spark occurs need to be advanced
 Modern engine control rely on
electronics to control the timing
precisely & accurately.
 Earlier speed sensing mechanism are
used to control the spark timing
 Centrifugal Governor mechanism
 Vacuum advance mechanism

Centrifugal Governor
Advance Mechanism:
 It is used to regulate the
ignition timing in response to
the engine rpm.
 When the engine is running
the distributor shaft and
weight assembly rotate.
 As the engine speed
increases, the two weights
moves outwards from the
centrifugal force, turning the
breaker cam in advance
direction

Centrifugal Governor
Advance Mechanism:
 Under this condition, the
quantity of mixed air
entering the cylinder is
reduced.
 Set the air fuel mixture as
lean – Lean mixture
 This causes it to burn slowly
 So spark advance is required
for proper combustion

Centrifugal Governor Advance
Mechanism:
 This results in cam lobes on the breaker
cam to contact the rubbing block on the
contact set earlier. This will cause the
early spark on spark plug.
 The maximum advance can limit by
stopper pin
Stopper
Pin

Vacuum advance mechanism:
 During light load in Engine, The Air/Fuel Mixture
drawn inside combustion chamber is very small.
 So high vacuum is developed in the intake
manifold.
 It may be noted that inertia force of the
incoming gases to expel the burnt gases
becomes weak, allowing the mixture to diluted
with residual gas.
 It means mixes with reaming gas in the
combustion chamber
 Results in power combustion
 So the engine vacuum is used to provide earlier
ignition in combustion chamber.

Vacuum advance mechanism:
 Idle condition No vacuum at
Intake manifold.
 Partial open of Throttle:
Vacuum pressure at
Diaphragm shield chamber
 Wider & Full open no
vacuum pressure at intake
manifold
 So not suits for high engine
load

system:
Igniter :
 Detects the signal from
distributor pick up coil
output.
 It is a component to
amplify the signal &
switch on/off the current
in the primary circuit.
 It is Simply a transistor
unit

Transistorized ignition system: Function
 Enables the generation of high performance spark over all speed ranges from
high to low.
 The time control circuit controls the charging time to the ignition coil according
to engine speed.
 It will helps the electric power consumption at low speed.
 Prevent the secondary voltage drop at high speed.

1. Ignition Switch on:
 Pickup coil & signal rotor aligned, Therefore no magnetic flux change
 The base voltage of the transistor at point p becomes high.
 Base current flow happen, transistor state is gets on – While primary
current flows to the ignition coil.

2. Staring Engine:
 The AC current overlaps with the DC Voltage (i.e. Battery Voltage) at
point p and is applied in-between the transistor base & emitter
 When the applied AC current & DC voltage or on the plus side the
transistor is turned on and primary current flows to the ignition coil.

2. Staring Engine:
 However when the signal rotor rotates generating a minus voltage, this
voltage will reduce the DC voltage at Point P.
 Hence the electrical potential drops below the operational voltage of the
transistor, thus current will not flow to the base.

2. Staring Engine:
 This cause the transistor to turn off, cutting off the primary current while
the secondary coil generates high voltage.

Capacitor Discharge ignition system:
 Most of the vehicles follows inductive
ignition system
 Which depends on electric inductance of
the coil.
 Mean breaking the primary circuit &
trigger the secondary circuit
 In this method capacitor is used to store
the electrical energy, which is then
discharged into the primary coil when
required.
 The amount of stored energy depends on
the rating of capacitor & charging voltage
of the capacitor.

Capacitor Discharge ignition
system:
 Booster circuits converts 12V
from battery into 200 V by
the booster circuit.
 The pulse generator allows
the control circuit to send the
current to the thyristor to on.
 When the thyristor receives
the signal from the control
circuit, the current charged in
the capacitor flow to the
ignition coil and high voltage
is supplied to the spark plug.

system:
 Booster circuits converts 12V
from battery into 200 V by
the booster circuit.
 The pulse generator allows
the control circuit to send the
current to the thyristor to on.
 When the thyristor receives
the signal from the control
circuit, the current charged in
the capacitor flow to the
ignition coil and high voltage
is supplied to the spark plug.

system:
Advantage:
 Fast voltage rise.
 Short spark duration – Suits
high speed vehicle.
 Full burning of Rich mixture
Disadvantage :
 Insufficient energy for the
long spark duration.
 Not suits for lean mixture

HALL EFFECT SWITCH:
 Replace the signal generator.
(Signal rotor & Pick-up coil)
 According to hall effect, when
a thin semi – conductor chip
carrying current is cut by a
magnetic field at right angles
 A voltage is produced at the
edges of the switch.

HALL EFFECT SWITCH:
Advantage:
 High Accuracy
 Extremely precise which
results in optimum
performance.
 High fuel efficiency & Low
emissions.

Computer controlled direct
ignition system: (Distributor
less ignition system)
 Each spark plug has an
ignition coil built in the spark
plug cap.
 Ignition takes place when the
primary current is supplied
from the ignition control
module to each coil.
 By replace the distributor &
Wires reduce the power loss

Computer controlled direct
ignition system: (Distributor
less ignition system)
 Timing diagram of Distributor
less ignition system

Advantages of Electronic
Ignition system:
 No moving parts like previous
types
 No maintenance required
 Spark plug life is increased
 Combustion efficiency is
increased 90-95%
 More output power & More
fuel economy.

END

Electronic ignition system

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