Unit 1 automotive engine auxiliary systems

OAT551 AUTOMOTIVE SYSTEMS
UNIT - 1
P.HARIPRASAD
ASSISTANT PROFESSOR,
DEPARTMENT OF MECHANICAL
ENGINEERING,
KIT-KALAIGNAR KARUNANIDHI INSTITUTE
OF TECHNOLOGY, COIMABATORE - 641402

UNIT - 1-AUTOMOTIVE ENGINE
AUXILIARY SYSTEMS
• Automotive engines
• External combustion engines
• Internal combustion engines
• Classification of engines
• SI Engines
• CI Engines

UNIT - 1-AUTOMOTIVE ENGINE
AUXILIARY SYSTEMS
• Two stroke engines construction and working principles
• Four stroke engines construction and working
principles
• IC engine components‐ functions and materials
• Valve timing –port timing diagram
• Injection system ‐Unit injector system‐ Rotary
distributor type ‐ Electronically controlled injection
system for SI engines‐CI engines‐Ignition system ‐
Electronic ignition system ‐Transistorized ignition
system, capacitive discharge ignition system.

What is an engine ?
• An engine is an device which is use to
convert chemical energy into mechanical
energy or work.
Chemical energy -> mechanical energy

EXTERNAL COMBUSTION ENGINE
• An external combustion engine (EC engine) is
a heat engine where a working fluid,
contained internally, is heated by combustion
in an external source, through the engine wall
or a heat exchanger.
• The fluid then, by expanding and acting on
the mechanism of the engine, produces
motion and usable work.

EXTERNAL COMBUSTION ENGINE
• The fluid is then cooled, compressed and
reused (closed cycle), or dumped (open cycle).
In these types of engines, the combustion is
primarily used as a heat source, and the
engine can work equally well with other types
of heat sources.

INTERNAL COMBUSTION ENGINE
• An internal combustion engine (ICE) is a heat
engine in which the combustion of a fuel occurs
with an oxidizer (usually air) in a combustion
chamber that is an integral part of the working
fluid flow circuit.
• In an internal combustion engine, the expansion
of the high-temperature and high-pressure gases
produced by combustion applies direct force to
some component of the engine.

INTERNAL COMBUSTION ENGINE
• The force is applied typically
to pistons, turbine blades, rotor or a nozzle.
This force moves the component over a
distance, transforming chemical energy into
useful work.

Spark Ignition Engine
• An SI engine starts the combustion process
in each cycle by use of a spark plug. The
spark plug gives a high-voltage electrical
discharge between two electrodes which
ignites the air-fuel mixture in the
combustion chamber surrounding the plug.

Unit 1 automotive engine auxiliary systems

Combustion Ignition Engine
• The combustion process in a CI engine starts
when the air-fuel mixtures self-ignites due to
high temperature in the combustion chamber
caused by high compression.

FOUR STROKE ENGINE
• A 4 stroke petrol engine shown in figure.
• The valve operating the inlet is called inlet
valve and the valve operating the exhaust is
called exhaust valve. The spark plug fitted at
the top of cylinder head initiates the ignition
of the air fuel mixture.
• The piston performs four stroke to complete
one working cycle. The four different strokes
are;

FOUR STROKE ENGINE
• Suction stroke
• Compression stroke
• Power stroke
• Exhaust stroke

SUCTION STROKE
• During this stroke, inlet valve opens and
exhaust valve closed, the pressure in the
cylinder will be atmosphere .
• As the piston moves from the TDC To BDC ,
the volume in the cylinder increase , while
simultaneously pressure decreases.
• This create a pressure difference between the
atmosphere and inside of the cylinder. Due to
this pressure difference the petrol and air
mixture will enter into the cylinder through
carburettor.

• The crankshaft has now
made half rotation i.e. 180
degree of crank angle.
• At the end of this stroke,
the cylinder will filled
completely with petrol and
air mixture called charge
and inlet valve is closed.

COMPRESSION STROKE
• During this stroke both the inlet valve and
exhaust valve are closed, the piston moves from
BDC to TDC .
• As this stroke being performed ,the petrol and air
mixture contained in the cylinder will be
compressed , so pressure and temperature of
mixture increases. The process of compression is
shown in fig.

• Near the end of this
stroke , the petrol and
airmixture is ignited by
the electric spark given
out by the spark plug.
• The combustion of petrol
releases the hot gases
which will increases the
pressure at the constant
volume.

POWER STROKE
• During this stroke both the inlet valve and
exhaust valve are closed, the piston moves
from TDC to BDC.
• The high pressure and high temperature
burnt gases force the piston to perform this
stroke, called power stroke. This stroke is
also known as expansion or working stroke.
• The engine produces mechanical work or
power during this stroke.
• As the piston moves from TDC to BDC , the
pressure of hot gases gradually decreases
and volume increases.

• Near the end of this stroke,
the exhaust valve opens
which will release the
burnt gases to the
atmosphere.
• This will suddenly bring
the cylinder pressure to
the atmospheric pressure.

EXHAUST STROKE
• During this stroke, the
exhaust valve opens and the
inlet valve is closed .
• The piston moves from BDC
to TDC and during this
motion piston pushes the
exhaust gases (combustion
product) out of the cylinder
at constant pressure. Again
the inlet valve open and the
new cycle starts

TWO STROKE ENGINE
• As the name itself implies, all the processes in the
two stroke cycle engine are completed in two
strokes. These engine have 1 power stroke per
revolution of the crankshaft.
• In the two stroke engine there is a two opening
called ports are provided in place of valve of four
stroke engines.
• These ports are opened and closed by
reciprocating motion of the piston in the cylinder.

• One port known as a inlet port and another
port is known as a exhaust port.
• Two stroke engine consist of a cylinder with
one end fitted with a cylinder head and other
end fitted with a hermitically sealed
crankcase which enables it to function as a
pump in conjuction with the piston.

• At the beginning of the first stroke piston Is at
the TDC as shown in fig. A. Piston moves from
TDC to BDC.
• The electric spark ignites the compressed
charge . The combustion of the charge will
release the hot gases which increase the
temperature and pressure in cylinder. The
high pressure combustion engine to force
piston downward .
• The piston perform power stroke till it
uncovers the exhaust port As shown in fig. B.
The combustion gases which are at the
pressure slightly higher than atmosphere
pressure escape through exhaust port.

• The piston uncovers the transfer port the
fresh charge flow from the crankcase into
cylinder through transfer port as shown in fig.
B.
• Which enters the cylinder pushes the burnt
gases , so more amount of exhaust gases
come out through exhaust port as shown in
fog. B.
• This swiping out of exhaust gases by incoming
fresh charge is called scavenging.
• This will continue till the piston covers both
the transfer and exhaust port during next
upward stroke.

• In this stroke piston moves from BDC to TDC.
• When it covers the transfer port in fig. C. , the
supply of charge is stopped and then when it
moves further up it covers the exhaust port
completely in fig. D stop the scavenging.
• Further upward motion of the piston will
compressed the charge in the cylinder.
• After the piston reaches TDC the first stroke
repeats again.

Internal combustion Engine
Components:-
1. Engine Block : Body of the engine
containing cylinders, made of cast iron or
aluminium.

C
2. Cylinder: A cylinder is the central
working part of a reciprocating engine or
pump, the space in which a piston travels.

3. Head : The piece which closes the end of
the cylinders, usually containing part of the
clearance volume of the combustion
chamber.

4. Connecting Rod : In a reciprocating
piston engine , the connecting rod or
conrod connects the piston to the crank
or crankshaft.

Piston
5. Piston: The piston of an internal
combustion engine is acted upon by the
pressure of the expanding combustion
gases in the combustion chamber space at
the top of the cylinder.

6. Piston rings : A piston ring is a metal rings that
fit into circumferential grooves around the piston
and form a sliding surface against the cylinder
walls.

7. Crankshaft: Rotating shaft through
which engine work output is supplied
to external systems.

8. Camshaft : Rotating shaft used to
push open valves at the proper time
in the engine cycle, either directly or
through mechanical or hydraulic
linkage (push rods, rocker arms, tappets)
.

9. Intake manifold: Piping system which
deliver incoming air to the cylinders, usually
made of cast metal, plastic, or composite
material . In most SI engines, fuel is added
to the air in the intake manifold system
either by fuel injectors or with a carburetor.

10. Exhaust manifold : Piping
system which carries exhaust gases
away from the engine cylinders,
usually made of cast iron

11. Spark plug :
Electrical device
used to initiate
combustion in an
SI engine by
creating high
voltage discharge
across an
electrode gap

12. Flywheel :
Rotating mass with a large moment
of inertia connected to the crank
shaft of the engine. The purpose of
the flywheel is to store energy .

13. Fuel injector : A pressurized
nozzle that sprays fuel into the
incoming air (SI engines )or into the
cylinder (CI engines).

14. Combustion chamber: The end of the cylinder
between the head and the piston face where
combustion occurs . The size of combustion
chamber continuously changes from minimum
volume when the piston is at TDC to a maximum
volume when the piston at BDC.

Valve Timing Diagram
• A valve timing diagram is a graphical
representation of the opening and closing of the
intake and exhaust valve of the engine, The
opening and closing of the valves of the engine
depend upon the movement of piston from TDC
to BDC.
• This relation between piston and valves is
controlled by setting a graphical representation
between these two, which is known as valve
timing diagram.

Valve Timing Diagram
• The valve timing diagram comprises of a 360
degree figure which represents the movement of
the piston from TDC to BDC in all the strokes of
the engine cycle, Which is measured in degrees
and the opening and closing of the valves is
controlled according to these degrees.

Why do We Need Valve Timing
diagram?
• Synchronization between the steps of a cycle of
the engine from the intake of air-fuel ratio to the
exhaust of the combustion residual.
• Complete seizure of the combustion chamber at
the instant at which the combustion of air-fuel
mixture takes place as the leakage can cause
damage to the engine and can be hazardous.
• Provide engine with a mixed air and fuel or air in
case of diesel engine when required ( at the time
of suction) which is the necessity of the engine.

• Provide the exit for the combustion residual so
that the next cycle of the engine can take place.
• Ideal timing for the opening and closing of the
inlet and outlet valve which in turn protect the
engine from defects like knocking or detonation.
• A high compression ratio required to combust the
fuel especially in case of diesel engine by
overlapping the closing of the valve.
• The cleaning of engine cylinder which in turn
maintain the quality of combustion and
decreases wear and tear inside the cylinder.
• The study of the details of the combustion that is
required for the modification of the power of the
engine.

Valve Timing Diagram for 4-Stroke
Engine
• Suction Stroke- The engine cycle starts with this stroke,
Inlet valve opens as the piston which is at TDC starts
moving towards BDC and the air-fuel mixture in case of
petrol and fresh air in case of diesel engine starts
entering the cylinder,till the piston moves to BDC.
• Compression Stroke- After the suction stroke the
piston again starts moving from BDC to TDC in order to
compress the air-fuel (petrol engine) and fresh air
(diesel engine) which in turn raises the pressure inside
the cylinder which is essential for the combustion of
the fuel.
• The inlet valve closes during this operation to provide
seizure of the chamber for the compression of the fuel.

Valve Timing Diagram for 4-Stroke
Engine
• Expansion Stroke- After compressing the fuel,
The combustion of the fuel takes place which in
turn pushes the piston which is at TDC towards
BDC in order to release the pressure developed
by the combustion and output is obtained .
• Exhaust Stroke- After expansion stroke the piston
which is at BDC starts moving towards
TDC followed by the opening of exhaust valve for
the removal of the combustion residual.
• Exhaust valve closes after the piston reaches TDC.

Port Timing Diagram for 2-Stroke Engine
Expansion stroke-
At the beginning of the expansion stroke the
piston which is at TDC starts moving towards BDC due
to the combustion of compressed air-fuel (petrol
engine) and (diesel sprayed charge in diesel engine)
during compression stroke and the power output is
obtained.
• The air-fuel(petrol engine) and air (diesel diesel)
enters through the inlet port during the expansion
strokes as the piston moves from TDC to BDC
during this stroke.
• The expansion stroke continuous till the piston
reaches BDC.

Compression Stroke-
At the end of the expansion stroke, the piston
which is at BDC starts moving towards TDC and the
compression of air-fuel (petrol engine) and diesel sprayed
charge (diesel engine) starts along with the exhaust of
combustion residual through exhaust port due to the
movement of the piston from BDC to TDC.
• The piston closes both inlet port and exhaust port due
to its movement from BDC to TDC which in turn raises
the pressure inside the combustion chamber.
• At the end of the compression stroke i.e. when the
piston reaches TDC combustion of the air-fuel (petrol
engine) due to spark and diesel sprayed charge (diesel
engine) due to the high pressure takes place, And the
cycle repeats again.

Fuel Injection Systems
The Functions of Fuel Injection System,
• To enhance the engine
 Performance
 Fuel economy
• Initiating and controlling the combustion
process.
• Preparation of the combustible charge (Just
like carburettor).

Carburettor
Carburettor :
• Fuel is atomized by processes relying on the
air speed greater than fuel speed at the fuel
nozzle,
• The amount of fuel drawn into the engine
depends upon the air velocity in the venturi.

Types of Carburettor
• Simple Carburettor
• S.U Carburettor – Constant Vacuum type
• Zenith Carburettor – Compound jet with inner
main jet.
• Solex Carburettor – Down Draught type
• Carter Carburettor - Down Draught type

Fuel Injection System
Fuel Injection System
• The fuel speed at the point of delivery is
greater than the air speed to atomize the fuel.
• The amount of fuel delivered into the air
stream going to the engine is controlled by a
pump which forces the fuel under pressure.

Functional Requirements of An
Injection System
• Accurate metering of the fuel injected per
cycle.
• Timing the injection of the fuel correctly in the
cycle.
• Proper control of rate of injection Proper
atomization of fuel into very fine droplets.
• Proper spray pattern to ensure rapid mixing of
fuel and air

Functional Requirements of An
Injection System
• Uniform distribution of fuel droplets
throughout the combustion chamber.
• To supply equal quantities of metered fuel to
all cylinders case of multi cylinder Engines.
• No lag during beginning and end of Injection.

Classification of Injection Systems
• A fuel-injection system is required to inject
and atomize fuel in to the cylinder of CI
engines.
• For producing the required pressure for
atomizing the fuel either air or a mechanical
means is used.
• Thus the injection systems can be classified as:
– Air injection system
– Solid injection systems

Air injection system
• Fuel is forced into the cylinder by means of
compressed air.
• It has good mixing of fuel with the air with
resultant higher mean effective pressure.
• It has the ability to utilize high viscosity (less
expensive) fuels.
• The system is obsolete due to the requirement
of multistage air compressors.

Solid Injection System
• In this system the liquid fuel is injected
directly into the combustion chamber without
the aid of compressed air.
• Solid injection systems can be classified into
four types.
– Individual pump and nozzle system
– Unit injector system
– Common rail system
– Distributor system

Components of Fuel Injection System

• Fuel tank : To Store the fuel,
• Fuel filters: to prevent dust and abrasive particles
from entering the pump and injectors thereby
minimizing the wear and tear of the components
• Fuel feed pump: to supply fuel from the main fuel
tank to the injection system.
• Injection pump: to meter and pressurize the fuel for
injection,
• Governor: to ensure that the amount of fuel injected
is in accordance with variation in load,
• Injector: to take the fuel from the pump and
distribute it in the combustion chamber by atomizing
it into fine droplets,

Individual Pump and Nozzle System
• In this system, each cylinder is provided with
one pump and one injector.
• The pump may be placed close to the cylinder
or they be arranged in cluster
• The high pressure pump plunger is actuated
by a cam, and produces the fuel pressure
necessary to open the injector valve at the
correct time.

UNIT INJECTOR SYSTEM
• Unit Injector System is one in which the pump
and the Injector nozzle are combined with one
housing.
• Each cylinder is provided with one of these
unit injectors
• Fuel is brought up to the injector by low
pressure pump, where at the proper time, a
rocker arm actuates the plunger and thus
injects the fuel into the cylinder

Common Rail System
• A HP pump supplies fuel, under high pressure, to
a fuel header.
• High pressure in the header forces the fuel to
each of the nozzles located in the cylinders
• At the proper time mechanically operated valve
allows the fuel to enter the cylinder through the
nozzle.
• The amount of fuel entering the cylinder is
regulated by varying the length of the push rod
stroke

Distributor System
• In this system the pump which pressurizes the
fuel also meters and times it.
• Fuel pump after metering the required
amount of fuel supplies it to a rotating
distributor at the correct time for supply to
each cylinder.
• The number of injection strokes per cycle for
the pump is equal to the number of cylinders
• Since there is one metering element in each
pump, a uniform distribution is automatically
ensured.

Types of Injection system
• Single or Multi-point injection
• Indirect or Direct injection

Single point injection
• Injector located inside
throttle body.
• Injector sprays fuel from
above throttle valve.
• ECU control injector
openings.

Multi-point injection
• Multi point fuel injection (MPFI) is a newer
technology than the single point type.
Basically, this type is the same as the first
type but the number of injectors is adjusted
to the number of cylinders.
• This means that for a 4 cylinder engine using
4 injectors.
• Injector located below Throttle valve.
• Injector sprays fuel Directly to ports.
• ECU controls opening.

1 – Fuel supply,
2 – Air intake,
3 – Throttle,
4 – Intake manifold,
5 – Fuel injector (or
injectors),
6 – Engine

Direct Injection
• Injector is fixed to the
top of combustion
chamber.
• Fuel is injected above
Piston head.
• Smaller combustion
space, better thermal
efficiency.

Indirect Injection
• Indirect Injection
System has a small
swirl chamber above
the cylinder.
• Fuel is injected in swirl
chamber.
• Higher compression
ratio needed to aid
starting.

Electronic Fuel Injection System
• System Components
– Fuel tank
– Electric fuel pump
– Fuel filter
– Electronic control unit
– Common rail and Pressure sensor
– Electronic Injectors
– Fuel line

ELECTRONIC CONTROL UNIT
• In automotive electronics, electronic control unit (ECU)
is a generic term for any embedded system that
controls one or more of the electrical systems or
subsystems in a motor vehicle.
• An engine control unit (ECU), also known as power-
train control module (PCM), or engine control module
(ECM)
• It is a type of electronic control unit that determines
the amount of fuel, ignition timing and other
parameters an internal combustion engine needs to
keep running.
• It does this by reading values from multidimensional
maps which contain values calculated by sensor
devices monitoring the engine.

WORKING OF ECU
Control of fuel injection :
• If the throttle pedal is pressed further down, the ECU
will inject more fuel according to how much air is
passing into the engine.
• If the engine has not warmed up yet, more fuel will be
injected
Control of ignition timing:
• An ECU can adjust the exact timing of the spark (called
ignition timing) to provide better power and economy.

Control of idle speed :
• The engine RPM is monitored by the crankshaft
position sensor which plays a primary role in the
engine timing functions for fuel injection, spark events,
and valve timing.
• Idle speed is controlled by a programmable throttle
stop or an idle air bypass control stepper motor.

COMMON RAIL AND PRESSURE
SENSOR
• The term "common rail" refers to the fact that
all of the fuel injectors are supplied by a
common fuel rail which is nothing more than a
pressure accumulator where the fuel is stored
at high pressure. This accumulator supplies
multiple fuel injectors with high pressure fuel.

ELECTRONIC FUEL INJECTORS
• The injectors can survive the excessive
temperature and pressure of combustion by
using the fuel that passes through it as a coolant.
• The electronic fuel injector is normally closed,
and opens to inject pressurized fuel as long as
electricity is applied to the injector's solenoid
coil.
• When the injector is turned on. it opens. spraying
atomized fuel at the combustion chamber.
• Depending on engine operating conditions
injection quantity will vary.

FUEL LINE
• Fuel line hose carry gasoline from the tank to the
fuel pump, to the fuel filter, and to the fuel
injection system.
• While much of the fuel lines are rigid tube,
sections of it are made of rubber hose, which
absorb engine and road vibrations
• There are two basic types of fuel hose: Fuel and
oil hoses that meet the SAE 30R7 standard, and
fuel injection hose that meets the requirements
of SAE 30R9.

What is Ignition System ?
• The system in an internal-combustion engine
that produces the spark to ignite the mixture
of fuel and air: includes the battery, ignition
coil, distributor, spark plugs, and associated
switches and wiring.

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 centre.
• Varies spark timing with load, speed, and
other conditions.

BASIC IGNITION SYSTEM
COMPONENTS
• BATTERY
• IGNITION SWITCH
• IGNITION COIL
• SWITCHING DEVICE
• SPARK PLUG
• IGNITION SYSTEM WIRES

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

IGNITION COIL
• Transformer
• 2 sets of windings
– Primary windings
– Secondary windings
• Iron core
• Produces magnetic field

IGNITION SYSTEM TYPES
• Basically Convectional Ignition systems are of
2 types :
(a) Battery or Coil Ignition System, and
(b) Magneto Ignition System.
• Both these conventional, ignition systems
work on mutual electromagnetic induction
principle.

• Battery ignition system was generally used in 4-
wheelers, but now-a-days it is more commonly
used in 2-wheelers also (i.e. Button start, 2-
wheelers like Pulsar, Kinetic Honda; Honda-
Activa, Scooty, Fiero, etc.). In this case 6 V or 12
V batteries will supply necessary current in the
primary winding.
• Magneto ignition system is mainly used in 2-
wheelers, kick start engines. (Example, Bajaj
Scooters, Boxer, Victor, Splendor, Passion, etc.).
In this case magneto will produce and supply
current to the primary winding. So in magneto
ignition system magneto replaces the battery.

Battery or Coil Ignition System

Primary Circuit :
• It consists of 6 or 12 V battery, ammeter, ignition
switch, primary winding it has 200-300 turns of
20 SWG (Sharps Wire Gauge) gauge wire, contact
breaker, capacitor.
Secondary Circuit :
• It consists of secondary winding. Secondary
Ignition Systems winding consists of about 21000
turns of 40 (S WG) gauge wire.
• Bottom end of which is connected to bottom end
of primary and top end of secondary winding is
connected to centre of distributor rotor.
Distributor rotors rotate and make contacts with
contact points and are connected to spark plugs
which are fitted in cylinder heads (engine earth).

Working :
• When the ignition switch is closed and engine in
cranked, as soon as the contact breaker closes, a
low voltage current will flow through the primary
winding.
• It is also to be noted that the contact breaker cam
opens and closes the circuit 4-times (for 4
cylinders) in one revolution.
• When the contact breaker opens the contact, the
magnetic field begins to collapse.
• Because of this collapsing magnetic field, current
will be induced in the secondary winding.
• And because of more turns (@ 21000 turns) of
secondary, voltage goes into 28000-30000 volts.

Working :
• This high voltage current is brought to centre of
the distributor rotor. Distributor rotor rotates and
supplies this high voltage current to proper stark
plug depending upon the engine firing order.
• When the high voltage current jumps the spark
plug gap, it produces the spark and the charge is
ignited - combustion starts - products of
combustion expand and produce power.

Magneto Ignition System
• In this case magneto will produce and supply
the required current to the primary winding.
• In this case as shown, we can have rotating
magneto with fixed coil or rotating coil with
fixed magneto for producing and supplying
current to primary, remaining arrangement is
same as that of a battery ignition system.

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

TYPES OF ELECTRONIC IGNITION
SYSTEM
Electronic Ignition System is as follow :
(a) Capacitance Discharge Ignition system
(b) Transistorized system
(c) Piezo-electric Ignition system
(d) The Texaco Ignition system

DRAWBACKS OF
CONVENTIONAL IGNITION SYSTEMS
• Because of arcing, pitting of contact breaker point
and which will lead to regular maintenance
problems.
• Poor starting : After few thousands of kilometers
of running, the timing becomes inaccurate, which
results into poor starting (Starting trouble).
• At very high engine speed, performance is poor
because of inertia effects of the moving parts in
the system.
• Some times it is not possible to produce spark
properly in fouled spark plugs.

ADVANTAGES OF ELECTRONIC
IGNITION SYSTEM
• Moving parts are absent-so no maintenance.
• Contact breaker points are absent-so no arcing.
• Spark plug life increases by 50% and they can be
used for about 60000 km without any problem.
• Better combustion in combustion chamber, about
90-95% of air fuel mixture is burnt compared
with 70-75% with conventional ignition system.
• More power output.
• More fuel efficiency.

Capacitance Discharge Ignition System

• It mainly consists of 6-12 V battery, ignition switch, DC to
DC convertor, charging resistance, tank capacitor, Silicon
Controlled Rectifier (SCR),SCR-triggering device, step up
transformer, spark plugs.
• A 6-12 volt battery is connected to DC to DC converter i.e.
power circuit through the ignition switch, which is designed
to give or increase the voltage to 250-350 volts.
• This high voltage is used to charge the tank capacitor (or
condenser) to this voltage through the charging resistance.
• The charging resistance is also so designed that it controls
the required current in the SCR.

• Depending upon the engine firing order, whenever the SCR
triggering device, sends a pulse, then the current flowing
through the primary winding is stopped.
• And the magnetic field begins to collapse. This collapsing
magnetic field will induce or step up high voltage current in
the secondary, which while jumping the spark plug gap
produces the spark, and the charge of air fuel mixture is
ignited.

Transistorized Assisted Contact (TAC)
Ignition System

Ignition System
• When the engine is started, the crankshaft will
rotate the pick up coil so that the pick up coil
generates a low voltage current. This will cause
the transistor base to be active so that the
collector is connected to the emitter.
• In the ignition coil, the current from the battery
will flow in both coil in the ignition coil.
• As explained above, the pickup coil will generate
zig-zag electric current.

Ignition System
• Current from the pick up coil is then transmitted
to the base leg of the transistor.
• Induction in the ignition coil occurs when the
base foot does not get an electric current, but it
lasts for an instant, therefore in one cycle of the 4
cylinder engine can occur four times the
induction process.
• The induction produces high voltage which is
distributed to the distributor to be distributed to
each spark plug according to the firing order.

Piezo-electric Ignition System
• The development of synthetic piezo-electric
materials producing about 22 kV by mechanical
loading of a small crystal resulted in some
ignition systems for single cylinder engines.
• But due to difficulties of high mechanical loading
need of the order of 500 kg timely control and
ability to produce sufficient voltage, these
systems have not been able to come up.

Texaco Ignition System
• Due to the increased emphasis on exhaust emission
control, there has been a sudden interest in exhaust
gas recirculation systems and lean fuel-air mixtures.
• To avoid the problems of burning of lean mixtures, the
Texaco Ignition system has been developed.
• It provides a spark of controlled duration which means
that the spark duration in crank angle degrees can be
made constant at all engine speeds.
• It is a AC system. This system consists of three basic
units, a power unit, a control unit and a distributor
sensor.
• This system can give stable ignition up to A/F ratios as
high as 24 : 1.

FIRING ORDER
• The order or sequence in which the firing
takes place, in different cylinders of a
multicylinder engine is called Firing Order.
• In case of SI engines the distributor connects
the spark plugs of different cylinders
according to Engine Firing Order.

Unit 1 automotive engine auxiliary systems

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Unit 1 automotive engine auxiliary systems