ch-04 ignition and exhaust system

8/13/2019 Ch-04 Ignition and Exhaust System

1/54


2/54

An ignitionsystem is asystem forigniting a fuel-airmixture. It is bestknown in the

field of internalcombustionengines.


3/54

When a high voltage is appliedacross the electrode of a sparkplug it produces a spark across thegap. When such a spark isproduced to ignite a homogeneousair fuel mixture in the combustionchamber of an engine it is called

the spark ignition system.
http://en.wikipedia.org/wiki/Image:Sparkplug.jpg


4/54

IGNITION FUNCTION Produces30,000 volt spark across spark plug

Distributeshigh voltage spark to each spark plug

in correct sequence Timesthe spark so it occurs as piston is nearing

top dead center

Variesspark timing with load, speed, and other

conditions


5/54

It should provide a good spark between the electrodes

of the plugs at the correct timing .It should function efficiently over the entire range of

engine speed

It should be light and effective and reliable in service.

It should be compact and easy to maintain

It should be cheap and convenient to handle


6/54

BASIC IGNITION SYSTEM

COMPONENTS

BATTERY IGNITION SWITCH

IGNITION COIL

SWITCHING DEVICE

SPARK PLUG

IGNITION SYSTEM WIRES


7/54

Block diagram of the Ignition System


8/54

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 aslotted 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

Next >


9/54

Ignition Coil Operation

300turns 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 currentflows (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

Primarywinding

Soft iron

core

Secondary

winding

The collapsing magnetic

field induces an EMF in

the secondary winding.

Next >


10/54

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

Next >


11/54

Ignition Components - The Rotor Arm

The rotor arm fits onto the distributor

shaft, using a locating slot and aspring 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.

Next >


12/54

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 knownas ignition timing.

This action determines which

spark plug will receive a spark.

Rotor armOuterterminal

Centre

terminal

From

coil

To sparkplugs

Next >


13/54

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.

Next >


14/54

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.

Next >


15/54

Ignition System Circuits Primary Circuit

(Low Voltage)

Ignition Switch

Resistor

Coil Primary Winding

Ignition Module

Pick-up Assembly

Secondary Circuit (High Voltage)

Coil Secondary Winding

Coil Wire

Distributor Cap & Rotor

Plug Wires

Spark Plugs


16/54

The ignition systems are classified depending

upon how the primary energy for operating the

circuit is made available as:

Battery ignition systemMagneto ignition system


17/54

Most of the models spark ignition engine usebattery ignition system. in this system the energy

required for producing spark is obtained from 6 or12V battery, the construction of the battery isdepends upon the requirement of the engine.

Battery ignition system mainly used in

Passenger cars ,light trucks ,some motor cyclesand large stationary engines.


18/54

Ignition Circuits

PRIMARY CIRCUIT

Includes all the components

working on low voltage

(Battery,Alternator).

SECONDARY CIRCUIT

Consists of wires and points

between coil out-put and the

spark plug ground.


19/54

Essential components:

Battery

Ignition switch

Ballast resistor

Ignition coil

Contact breaker

Capacitor

DistributorSpark plug


20/54

The simplest form of spark ignition is that using a

magneto. The engine spins a magnet inside a coil,

and also operates a contact breaker, interrupting thecurrent and causing the voltage to be increased

sufficiently to jump a small gap. The spark plugs are

connected directly from the magneto output.

Magnetos were used on the small engine's ancestor,

the stationary "hit or miss" engine


21/54

IGNITION SYSTEMIGNITION SYSTEM

Magneto Operation

Coil

Soft Iron

Core

Secondary

Windings

PrimaryWindings

Engine

Driven Rotor

and Magnets


22/54

S N

IGNITION SYSTEMFaraday Law

S NS NS NS NS NS NS N

Principal -

Each time the magnetic field washes through wires

Volt

Meter

An electrical current is produced

Called an EMFElectro Motive Force

Coil

Windings


23/54

IGNITION SYSTEMIGNITION SYSTEM

Magneto Operation

The magnetic

field passes

through softiron core

EMF produced in

the coil windings


24/54

IGNITION SYSTEM

No magnetic

field in soft iron

core

No EMF produced

in the coil windings


25/54

IGNITION SYSTEM

The magnetic

field passes

through softiron core again

EMF produced in

the coil windings

again


26/54

IGNITION SYSTEMMagneto System

Ignition

Switch

Distribution

Contact

Breaker

Coil

Magneto

Condenser

PowerGeneration

Spark Generation

Magneto Unit Rotor Arm


27/54

COMPARISON BETWEEN BATTERY & MAGNETO

IGNITIONS SYSTEM

Magneto ignition system

Battery is necessary, difficultto start the engine whenbattery is discharged.

Maintenance problem ismore due to battery.

A good spark is available atthe spark plug even at low

speed . Occupies more space

Commonly employed in carsand light commercial vehicles

No battery is needed.

No maintenance problems.

During starting, quality ofspark in poor due to low

speed. Occupies less space.

Mainly used in racing carsand two wheelers.

Battery ignition system


28/54


29/54


30/54

Firing Order


31/54

Firing Order

1,3,4,2

1,2,5,4,3,2

1,5,6,3,4,2,7,8


32/54

Firing Order


33/54

In modern automobiles the following twoare coming into common use

Transistorized coil ignition system (TCI)

Capacitive discharge ignition system(CDI)

E h S


34/54

Exhaust Systems

exhaust systemsto remove the gases from the enginethat have been caused by combustion.

An exhaust system is essentially a length of tube thatruns to the back of the vehicle. It includes the catalyticconverter, which helps clean the gases and other parts.

There are 5 types of exhaust systems that arecommonly used on vehicles. Some are ideal for normalvehicles, while others are more suitable for vehiclesthat have high performance engines.


35/54

Exhaust Systems Exhaust silencers, or mufflers, are placed in engines'

exhaust systems to moderate the level of soundproduced by altering the direction and speed of theexhaust gas f low.

This has the effect of reducing noise, but can also

depress the performance of a vehicle.

Exhausts that have fewer silencers, or silencers that donot impede the flow of gas as much as others, will belouder, but can improve vehicle performance.Changing the exhaust silencing system that came witha car to a performance exhaust can increase your car'spower.


36/54

5 Different Types of Exhaust Systems

Single Exit PipeThe most common type of exhaust systems are thesingle exit type which youll typically find on cars andtrucks you buy from a dealer. As the name implies,

theres just one exhaust pipe. Youll usually find thesebecause theyre the cheapest to build and install. Thatdoesnt mean theyre necessarily the most efficientexhaust systems, but thats offset by the economy to

the manufacturers. The pipe will invariably have itsexit on the passenger side of the vehicle.


37/54

Single Exit Pipe, also well-known as single side exhaust, is a standard type of exhaust

system, used by auto manufacturers in vehicle production. As derived from the name,

the system has one exhaust pipe to release the exhaust gases away from the engine.

The tail pipe is commonly located behind the rear wheel on the passenger's side of a

car, truck or SUV. Single side exhaust is a cost effective system that comes factory-installed on most cars and trucks.


38/54

Dual Rear Exit

Dual rear exit exhaust systems are aimed at thesportier end of the market, or at least at those whowant their vehicles to look and sound sportier. It givesa deeper note to the exhaust so the carat least sounds

as if has a powerful engine. There are two exhaustpipes located on opposite sides of the vehicle underthe back bumper. Theyre more efficient at expellingthe gas than the single exit pipe exhaust systems.

Unlike some other system, the pipes dont bendaround the wheels.
http://www.doityourself.com/scat/carstrucksandboats/?lc=int_mb_1001http://www.doityourself.com/scat/carstrucksandboats/?lc=int_mb_1001


39/54

Dual Side Exhaust system has nearly the same design and location, as the single

pipe exhaust system. The one and major difference is in the quantity of exit pipes.

This type of exhaust systems is constructed with two pipes. Both pipes are located

near each other on the same side of the vehicle behind the rear passenger's side.

Depending on the diameter of the exit pipes the sound of system's performance

may vary. When the diameter is smaller, the deeper sound will be produced.


40/54

Opposite Dual Exhaust

Where dual rear exit exhaust systems dont

bend, opposite dual exhaust systems work

somewhat different.

They wrap around the wheel, using the bend toadd to the filtering process. You find them more

on vehicles designed to tow large loads.

Those hauling trailers or boats will use them asthey donttend to leave residue on the load thats

being towed. Opposite dual exhaust systems are

a variant on dual rear exhaust systems and can

be more efficient under specific circumstances.


41/54

Dual Rear Exit Exhaust is a popular exhaust system among those vehicles'

owners, who want their car, truck or SUV look sportier and sound more

aggressive. Like dual side exhaust system, this type has the same quantity of

pipes. The difference is in pipes location. Dual rear exit exhaust system comes

with two pipes that are fixed on the opposite sides under the rear bumper.

Contrary to some other types of exhaust systems, the pipes are not bent around

the vehicle's wheels. Comparing with the single exit pipe system, this type of

exhaust is more efficient. Moreover, a driver will experience deeper sound, giving

an impression of high-power engine under the hood.
http://www.carid.com/exhaust-systems.htmlhttp://www.carid.com/exhaust-systems.html


42/54

Dual Side Exhaust

The dual side exhaust is pretty much what it says,with two exhaust pipes next to each other on one

side of the vehicle.

Using two pipes to expel the gases is moreefficient. Often, the pipes are smaller than with

single exhausts so the sound is deeper.

They look and sound like high performance

systems and do offer some enhancement in

performance. They do it without the price tag

attached to high performance exhaust systems.


43/54

Opposite Dual Exhaust is also called extreme dual exit exhaust. It is a variationof the dual rear exhaust system. Opposite dual exhaust is mainly used on

vehicles that tow heavy cargo. In order to improve the filtering process, the

length of the pipes is increased and they are bent around the wheels. This

construction makes it possible to decrease the residue that is released on the

object that is towed. Besides the length and location of the pipes there is no

major difference towards the other exhaust systems.


44/54

High Performance

High performance exhaust systems are moreexpensive, but do a more efficient job of filtering out the

gases. Theyre not standard, but fitted as aftermarket

products.

In some cases they can make the car run more

efficiently and with increased performance. A wider

exhaust pipe can reduce pressure, which has the effect

of increasing engine performance. Few people are willing

to invest the money it costs to put in true highperformance exhaust systems, which involve changes to

the manifold. Most prefer systems that look and sound

good instead.


45/54

High Performance Exhaust is usually offered as an aftermarket add-on. The

system is custom-designed to fit the exact make and model. High performanceexhausts comparing to standard exhaust systems are more expensive though they

have more advantages. They can improve the performance of the engine, as well

as increase its efficiency. Moreover, this type of exhaust systems is a stylish option

which offers radically different sounds. Installation of the high performance

exhaust is one of the ways to customize the vehicle.


46/54

Types of Exhaust Silencers

Exhaust silencers, or mufflers, are placed in engines'

exhaust systems to moderate the level of sound

produced by altering the direction and speed of the

exhaust gas flow. This has the effect of reducing noise,

but can also depress the performance of a vehicle.Exhausts that have fewer silencers, or silencers that do

not impede the flow of gas as much as others, will be

louder, but can improve vehicle performance.


47/54

Multi-Chamber Exhaust Silencers

Multi-chamber exhaust silencers are usedin the majority of engines and control the

noise production of the engine while

creating reasonable back pressure levels

that do not affect performance of thevehicle unduly. These silencers are used

in naturally aspirated engines and in

supercharged engines. They are formedof several chambers into which the gas

flows sequentially before escaping.


48/54

Straight-Through Silencers

Straight-through silencers are used inturbocharged engines and some

naturally aspirated engines. They

pass gas through the center of thesilencer in a straight line, so the

exhaust gas is not impeded as much

as in a multi-chamber silencer. Theeffect of a rapid discharge of exhaust

gas improves the car's performance,

and still has an effect on noise levels.


49/54

Spark Arrestor Silencer

Spark-arresting silencers are fitted on engines that

are to be used in areas where there is a serious

risk of fire. This type of silencer both reduces noise

level and removes sparks from exhaust gasesbefore the gas is released. They contain a "spark

trap," along with regular silencing chambers. Spark

Arrestor Silencers can be added on to an existing

engine. They are used in construction equipment,military vehicles, electricity generators, propulsion

engines, oil rig equipment and gas compression

equipment.


50/54

Shapes of Exhaust Silencers

In order to fit a wide variety of equipment, silencers can

come in a number of shapes apart from the regular

straight-line exhaust silencer. For example, a silencer can

have exhaust gas entering from the top and exiting from

the side and vice versa, and gas entering from the top ofone end and exiting from the bottom of the other end.

Silencers can also have more than one inlet and outlet for

exhaust gas if required. Silencers that are used in

engines that are regularly handled, such as hospitalequipment, can also have outer insulation to prevent

burns from the exhaust heating the metal.


51/54


52/54

The Resonator

When a wave hits the hole, part of it continues

into the chamber and part of it is reflected. The

wave travels through the chamber, hits the back

wall of the muffler and bounces back out of thehole. The length of this chamber is calculated so

that this wave leaves the resonator chamber just

after the next wave reflects off the outside of the

chamber. Ideally, the high-pressure part of thewave that came from the chamber will line up

with the low-pressure part of the wave that was

reflected off the outside of the chamber wall,

and the two waves will cancel each other out.


53/54

Waves canceling inside a simplified muffler

In reality, the sound coming from the engine is a mixture of many different

frequencies of sound, and since many of those frequencies depend on the engine

speed, the sound is almost never at exactly the right frequency for this to happen.

The resonator is designed to work best in the frequency range where the engine

makes the most noise; but even if the frequency is not exactly what the resonator

was tuned for, it will still produce some destructive interference.

There are other features inside this muffler that help it reduce the sound level in

different ways. The body of the muffler is constructed in three layers: Two thin

layers of metal with a thicker, slightly insulated layer between them. This allows the

body of the muffler to absorb some of the pressure pulses. Also, the inlet and outlet

pipes going into the main chamber are perforated with holes. This allows

thousands of tiny pressure pulses to bounce around in the main chamber,canceling each other out to some extent in addition to being absorbed by the

muffler's housing.


54/54

ch-04 ignition and exhaust system

Documents