AUR30405
CERTIFICATE III IN
AUTOMOTIVE
MECHANICAL
TECHNOLOGY
AURT304666A
Repair and replace emission control systems
LEARNER WORKBOOK
© Commonwealth of Australia 2011
ISBN: 978-1-876838-45-4
This document is available under a “Free for Education” licence for educational purposes – see
http://www.aesharenet.com.au/FfE2 for details.
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The views expressed in this publication do not necessarily represent the view of the Minister for Education or
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AURT304666A Repair and replace emission control systems
1
Elements ............................................................................................................ 1
About the workbook ....................................................................................... 1
Assessment ........................................................................................................ 3
Skills Recognition .............................................................................................. 4
Access and equity .......................................................................................... 4
Before you start ................................................................................................ 4
Personal safety
5
Activity 1 ........................................................................................................ 7
Types and causes of emissions
9
Emissions ............................................................................................................ 9
Forms of pollution............................................................................................. 9
Why do we need emission control systems? ............................................ 11
Normal combustion ...................................................................................... 12
Sources of emissions ...................................................................................... 13
Emissions from petrol engines ...................................................................... 14
Government legislation – light vehicles .................................................... 17
Emissions from diesel engines ...................................................................... 18
Government legislation – diesel vehicles.................................................. 20
Activity 2 ...................................................................................................... 21
Evaporative emission control systems
27
Components of the evaporative system .................................................. 28
Operation of the evaporative system ....................................................... 29
Activity 3 ...................................................................................................... 35
Activity 4 ...................................................................................................... 39
Activity 5 ...................................................................................................... 41
Crankcase emission controls
43
Crankcase ventilation system ..................................................................... 43
PCV valve ....................................................................................................... 45
Activity 6 ...................................................................................................... 49
Activity 7 ...................................................................................................... 53
Activity 8 ...................................................................................................... 55
Exhaust emission control systems
57
Combustion chamber design ..................................................................... 57
Activity 9 ...................................................................................................... 61
The Exhaust Gas Recirculation system (EGR) ........................................... 65
Activity 10 .................................................................................................... 71
Activity 11 .................................................................................................... 75
Catalytic converters ..................................................................................... 77
Activity 12 .................................................................................................... 81
Testing a catalytic converter ...................................................................... 85
Activity 13 .................................................................................................... 87
Particulate emissions in diesel engines ...................................................... 89
Activity 14 .................................................................................................... 91
Emission Control Information label ............................................................. 93
Activity 15 .................................................................................................... 95
Testing exhaust emissions ............................................................................. 97
Conducting an exhaust gas analyser test ................................................ 99
Activity 16 ..................................................................................................101
Glossary
103
1
AURT304666A Repair and replace emission
control systems
This unit covers the competence required to carry out repairs to emission control systems.
The unit includes identification and confirmation of work requirement, preparation for work, repair
of emission control systems and associated components and completion of work finalisation
processes, including clean-up and documentation.
Elements
1.
Prepare to undertake repair of emission control system
2.
Repair and replace emission control systems and/or associated components
3.
Prepare vehicle/ equipment for delivery to customer after repair is completed.
About the workbook
This workbook is designed to assist you in gaining underpinning knowledge and developing practical
skills to achieve the competency standard Repair and Replace Emission Control Systems.
This workbook contains:

information

questions

practical activities

directions to use additional resources.
The workbook is divided into stages. At the end of a stage, you will see an icon (picture with a
meaning) asking you to check your answers and/or practical activities with your trainer. This helps
the trainer to monitor your progress.
© Commonwealth of Australia 2011
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What do the icons mean?
An icon is a picture with a meaning. In the workbook, these icons tell you something about:

what to do next (activity, check your answers, watch a video clip) or

the text (this is a safety warning).
Complete an activity
Check your answers with your trainer
Watch this video clip
Safety warning
2
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Assessment
To meet the assessment requirements for this competency standard you must demonstrate the
following:
Knowledge of:

Emission system types and components.

Operation of emission control systems, sub-assemblies and components.

Motor vehicle emissions and their effect on the environment.

The relationship between system faults and symptoms.

Testing procedures.

Service, repair and adjustment principles.

OH&S and statutory legislation.
Practical ability to:

Access, interpret and apply technical information.

Use correct tools and equipment in a safe manner.

Remove and replace emission control system components.

Test, inspect and evaluate emission systems and components.

Repair and adjust emission control systems.

Maintain customer records.
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Skills Recognition
You may already have knowledge and skills for all (or part) of this competency standard. If you
believe you can demonstrate that you already have the skills and knowledge required, talk to your
trainer about applying for Skills Recognition.
This is also known as Recognition of Prior Learning (RPL), Recognition of Current competence (RCC),
or simply Recognition.
Skills Recognition is a process for gaining credit for those skills and knowledge gained through work
experience, formal training or other life experience.
Access and equity
In training, access and equity means ensuring that people with differing needs and abilities have the
same opportunities to successfully gain skills, knowledge and experience through education and
training. It is about removing barriers and providing the supports people need to access, participate
and achieve, irrespective of their age, disability, colour, race, gender, religion, sexuality, family
responsibilities or location.
For students with disabilities, training organisations may make adjustments to ensure equal
opportunity. Reasonable adjustments are designed to minimise the disadvantage experienced by
learners with a disability and can include administrative, physical or procedural modifications.
NOTE:
If you believe you could benefit from support to help
you overcome a barrier to participation, you should
speak to your trainer or the person in your RTO
responsible for access and equity.
Before you start
The purpose of this learning resource is to help you develop the knowledge and skills necessary to
carry out service and repairs to emission control systems and associated components.
Before you start this workbook, you should have a good understanding of the following:
4

Operating principles of two-stroke, four-stroke, spark ignition and compression ignition
engines.

Operating principles of carburettors, electronic fuel injection systems, diesel fuel
injection systems and engine management systems.

Operating principles of exhaust systems.
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Personal safety
Here are the key safety practices you should follow during this unit:

Wear safety clothing and Personal Protective Equipment (PPE) as required by OH&S
regulations.

Make sure the wheels are chocked and protective guard covers are used when you are
working on vehicles.

Keep clear of any hot and moving components.

Use safety stands which are positioned correctly when raising a vehicle for inspection or
repair.

If using a hoist, lift the vehicle correctly and use the safety catches.

Make sure there is enough ventilation when engines are running. Exhaust gas from a
running engine contains carbon monoxide and can be lethal in a confined space.
Figure 1: Ventilate work areas
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Activity 1
Question 1
What safety precautions should you take before you inspect or work on a vehicle?
________________________________________________________________________________
________________________________________________________________________________
Question 2
What safety precautions should you take when working near running engines?
________________________________________________________________________________
________________________________________________________________________________
Question 3
What safety precautions should you take when raising a vehicle for inspection?
________________________________________________________________________________
________________________________________________________________________________
Ask your trainer to check your results before proceeding.
Trainer Signature: ..............................................................
© Commonwealth of Australia 2011
Date: .......................
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Types and causes of emissions
Emissions
An emission is something that comes out.
Emissions from motor vehicles are the gases that come out of their engines when they burn fuel
and air. They are considered to be a major cause of air pollution.
For this reason, vehicle manufacturers are required to reduce emissions so that their vehicles meet
specified government standards. To achieve this, engines have been made more fuel efficient and
have various control devices fitted.
Forms of pollution
There are two general forms of pollution caused by motor vehicles:

pollution from evaporation

pollution from combustion.
Pollution from evaporation
Liquid fuel is an extremely volatile liquid. It takes only a little heat from the engine or from the
atmosphere to make it evaporate. The petrol vapour then floats into the air, polluting it.
Pollution from combustion
Combustion is when air and fuel combine and burn in the engine. The harmful chemicals left over
after the combustion process are then discharged through the exhaust into the atmosphere,
polluting the air.
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The main chemicals
FUEL
AIR
Oxygen (O) 20%
Nitrogen (N) 80%
+
A mixture of hydrogen
(H) and carbon (C) called
hydrocarbons (HC)
Figure 2: Mixing air and fuel
The air (oxygen & nitrogen) joins with the fuel (hydrocarbons) in the engine. The air and fuel is
burnt (combustion). A range of gases are produced called exhaust gases:

Carbon monoxide (CO)

Carbon dioxide (CO2)

Oxides of nitrogen oxygen (NOy)

Oxygen (O2)

Unburnt fuel (HCs).
Figure 3: Producing exhaust gases
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Why do we need emission control systems?
If combustion was a perfect process, there would be nothing left over afterwards, and we would
have less need for emission control systems.
The emissions would be water, carbon dioxide and heat.
Unfortunately this is not possible.
Figure 4: Perfect combustion
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Normal combustion
Normal combustion produces many more emissions and these must be controlled with emission
systems.
The emissions that must be controlled are:

Hydrocarbons HC

Oxides of nitrogen
NOx

Carbon monoxide
CO
Figure 5: Normal combustion
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Sources of emissions
Pollution or emissions from motor vehicles come from the following sources:
%?
System?
How?
60%
Exhaust
From combustion
30%.
Crankcase
From combustion and blow-by
10%
Fuel tanks and carburettors
By evaporation
Figure 6: Source of emissions
Watch this video: Source of emissions
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Emissions from petrol engines
Hydrocarbons (HC)
Hydrocarbon emissions can come from:
1. Unburnt fuel in exhaust gases
2. Evaporating fuel from the fuel tank and fuel system
3. Crankcase vapours or blow by gases.
Watch this video: Hydrocarbons via the exhaust
Unburnt fuel in exhaust gases can be a result of:
-
Cold combustion temperature
-
Mixture too rich in air or fuel
-
Mixture too lean
-
Cylinder misfiring or improper mixture burning
-
Worn or faulty injector – EFI or diesel
-
Worn or faulty diesel fuel injection pump
-
Severely blocked air filter element.
Evaporated fuel (HC) is emitted into the atmosphere from the fuel tank and carburettor vents
especially with:
-
A full tank of fuel and a vehicle left in the sun
-
Older vehicles with fuel tanks and carburettor vented to the atmosphere
-
An incorrect fuel tank cap fitted to newer vehicles
-
Fuel system leaks
-
Older vehicles with carburettor flooding problems.
Crankcase vapours or blow by gases are a mixture of combustion gases and fuel vapour.
These gases have leaked past worn piston rings and have escaped into the crankcase.
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Carbon monoxide (CO)
Carbon monoxide occurs during combustion when there is not enough oxygen (air), for complete
combustion.
Carbon monoxide levels increase as the air/fuel mixture is enriched.
Carbon monoxide levels decrease when a leaner air/fuel mixture is burnt.
Leaner air / fuel mixture
More air in the mixture
Good for combustion
Less carbon monoxide
Richer air / fuel mixture
More fuel in the mixture
Not enough air for
complete combustion
More carbon monoxide
Very lean air / fuel mixture
Too much air in the mixture
More unburnt fuel (HC)
Reduced power and throttle
response of engines
Watch this video: Carbon monoxide
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Oxides of nitrogen (NOx)
The air we use for burning fuel is made up of 50% nitrogen (N2) and 20% oxygen (O2). Oxygen burns,
but nitrogen does not burn.
When combustion temperatures get very hot (above 180°C), the nitrogen combines with oxygen to
form oxides of nitrogen (NOx).
Conditions which increase the formation of oxides of nitrogen (NOx) include:

moderate engine load

high combustion temperature.
High temperatures can be caused by:

increased compression ratios.

over advanced ignition timing.

severely retarded ignition timing

mixtures slightly leaner than ideal (14.7:1) during moderate load operation.
Watch this video: Oxides of nitrogen
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Government legislation – light vehicles
The main method used in Australia for reducing vehicle emissions has been the introduction of
tighter emission standards for new vehicles through the Australian Design Rules (ADRs). Australia
has had vehicle emission standards in place for petrol vehicles since the early 1970s and these have
been progressively (bit by bit) tightened over the past 30 years.
What are the ADRs?
The ADRs set the legal standards that each vehicle model is required to meet, prior to (before) their
first supply to the market. The ADRs set standards for emissions, noise and fuel consumption
labelling.
What are the emission ADRs?
The emission ADRs are performance standards which specify (state exactly) the maximum (highest)
levels of emissions permitted (allowed) under a specified test.
They do not require the use of particular technology, but from 1986 vehicle manufacturers had to
fit catalytic converters to light petrol vehicles in order to meet new emission limits.
How much have allowed emissions changed?
A summary of the emission standards which have applied to petrol engined cars since 1972 through
to 2010 can be viewed at.
http://www.infrastructure.gov.au/roads/environment/impact/emission.aspx
This table compares emissions allowed in 1976 with what is allowed from 2008.
YEAR
HC maximum
CO maximum
NOx maximum
1976
2.1 g/km
24.2 g/km
1.9 g/km
2008
0.1 g/km
1.0 g/km
0.08 g/km
The ADRs also give guidelines for 6 tests for petrol vehicles:
1. Exhaust emissions after a cold start
2. Carbon monoxide emission test at idling speed
3. Emissions of crankcase gases
4. Evaporative emissions from vehicles with positive-ignition engines
5. Endurance test for durability of pollution control devices
6. Average exhaust emissions of carbon monoxide and hydrocarbons after a cold start
at low ambient temperature.
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Emissions from diesel engines
A variety of different combustion deposits are formed when diesel fuel is burned.
The type of product formed depends on engine design, engine power output and working load. The
most complete combustion of the fuel leads to a major reduction in the formation of toxic
substances.
Complete combustion is supported by:

controlling the air/fuel mixture.

precision in the injection process

optimum air/fuel mixture turbulence.
Figure 7: Diesel vehicle
Diesel combustion produces water (H2O) and carbon dioxide (CO2).
The following substances are also produced in relatively low concentrations:

Carbon monoxide (CO).

Unburnt hydrocarbons (HC).

Oxides of nitrogen (nox).

Sulphur dioxide (SO2).

Sulphuric acid (H2SO4).

Soot particles (particulates).
When a diesel engine is cold, the exhaust gas emissions include unburnt hydrocarbons, which we
notice as white or blue smoke and the strong smell of aldehydes.
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Particulates
Particulates are solid or semi-solid particles of carbon in the exhaust gas and can sometimes be
seen as black smoke.
Carbon is formed due to:

incomplete combustion

slow cold engine operation

high engine oil consumption.
Particulate emission is considerably higher from diesel engines than from petrol engines.
Watch this video: Particulates
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Government legislation – diesel vehicles
There are also Australian Design Rules (ADRs) which control emissions from light duty and heavy
duty diesel engines.
These rules have applied since 1995. From 2006 the latest Euro 4 standards have applied. The ADR
sets out the emission limits, their timetable for adoption, and the tests which must be used to
check emissions.
The most recent version is the National Environment Protection Measure (Diesel Vehicle Emissions)
2001, amended (updated) in 2009.
How much have allowed emissions changed?
This table compares emissions allowed in 1996 with what is allowed in 2011.
YEAR
CO maximum
HC maximum
NOx maximum
Particulate matter
maximum
1996
4.5 g/kWh
1.1 g/kWh
8.0 g/kWh
0.36 g/kWh
2011
1.5 g/kWh
0.46 g/kWh
2.0 g/kWh
0.02 g/kWh
Figure 8: A page from the National Environment Protection Measure
(Diesel Vehicle Emissions) 2001
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Activity 2
Answer the following questions.
Question 1
Name the two general forms of air pollution caused by motor vehicles.
________________________________________________________________________________
________________________________________________________________________________
Question 2
What do these words mean?
Evaporation _____________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Combustion _____________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 3
Name the sources of emissions.
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
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Question 4
What are hydrocarbons (HC)?
________________________________________________________________________________
________________________________________________________________________________
Question 5
Name the three sources of hydrocarbon emissions.
1. _____________________________________________________________________________
2. _____________________________________________________________________________
3. _____________________________________________________________________________
Question 6
Name six causes of unburnt fuel in exhaust gases.
1. _____________________________________________________________________________
2. _____________________________________________________________________________
3. _____________________________________________________________________________
4. _____________________________________________________________________________
5. _____________________________________________________________________________
6. _____________________________________________________________________________
Question 7
Name five sources of evaporated fuel emissions.
1. _____________________________________________________________________________
2. _____________________________________________________________________________
3. _____________________________________________________________________________
4. _____________________________________________________________________________
5. _____________________________________________________________________________
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Question 8
How is carbon monoxide (CO) produced?
________________________________________________________________________________
________________________________________________________________________________
Question 9
a) What factors cause carbon monoxide levels to increase (go up)?
_________________________________________________________________________________
b) What factors cause carbon monoxide levels to decrease (go down)?
________________________________________________________________________________
Question 10
What effects will very lean mixtures have on emissions and engine power?
________________________________________________________________________________
________________________________________________________________________________
Question 11
How are oxides of nitrogen (NOx) produced?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 12
Name four conditions that will increase the formation of oxides of nitrogen (NOx).
1. _____________________________________________________________________________
2. _____________________________________________________________________________
3. _____________________________________________________________________________
4. _____________________________________________________________________________
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Question 13
Name the three requirements for complete combustion in a diesel engine.
1. _____________________________________________________________________________
2. _____________________________________________________________________________
3. _____________________________________________________________________________
Question 14
Name the eight substances produced in diesel engine exhaust emissions.
1. _____________________________________________________________________________
2. _____________________________________________________________________________
3. _____________________________________________________________________________
4. _____________________________________________________________________________
5. _____________________________________________________________________________
6. _____________________________________________________________________________
7. _____________________________________________________________________________
8. _____________________________________________________________________________
Question 15
What causes particulate emissions?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
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Question 16
Tick the correct answer
Particulate emission is considerably higher from diesel engines than from petrol engines?


True
False?
Question 18
In a diesel engine, how is complete combustion supported?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Ask your trainer to check your results before proceeding.
Trainer Signature ..............................................................
© Commonwealth of Australia 2011
Date .......................
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Evaporative emission control systems
There are three main types of emission control systems used:
1. Evaporative controls
Prevents fuel vapour (gas) from the fuel tank and fuel system escaping to the
atmosphere.
2. Crankcase ventilation
Prevents crankcase emissions escaping to the atmosphere.
3. Exhaust emission controls
Reduces the products of combustion before they are emitted (sent out) to the
atmosphere in exhaust gases.
The evaporative emission control system consists of:
 Fuel tank – provides vapour space at the top of tank.
 Fuel cap - with vacuum relief valve.
 Charcoal canister – stores the fuel vapours from the tank and carburettor when the
engine is stopped.
 Air vent solenoid valve – opens the vent between the carburettor float bowl and the
canister when the ignition switch is on.
 Purge valve no. 1 – located on the top of the charcoal canister, it opens and closes the
vapour passage (purge line) between the canister and the intake manifold.
 Purge valve no. 2 – also located on top of the canister, this valve is in the fuel tank vent
line. It opens and closes the vent according to fuel tank pressure.
 Liquid vapour separator.
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Components of the evaporative system
Figure 9: Carburettor evaporative system
Figure 10: Evaporative emission controls
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Operation of the evaporative system
To prevent evaporating fuel going to the atmosphere:

the fuel storage compartments (carburettors and fuel tanks) must be sealed

a temporary storage area for evaporated fuel must be provided

the temporary storage area must be flushed out regularly.
Faulty evaporative emission control systems can result in:

fuel odours

fuel leakage

fuel tank collapse (due to vacuum build up)

excess fuel tank pressure

rough engine idle (due to excess fuel vapours).
Watch this video: Hydrocarbons
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The charcoal canister
In warm weather, fuel evaporates from the carburettor (if fitted) and fuel tank in a vehicle. This is
vented or piped into the charcoal canister (also called the carbon canister).
The charcoal canister contains activated carbon (a special kind of charcoal). This temporarily
absorbs (soaks up like a sponge) the evaporating fuel vapour and prevents it from escaping into the
atmosphere.
Once the engine is operating above idle, throttle ported vacuum draws fresh air through the
canister which pushes the fuel vapour into the intake system where it is burnt in the combustion
chamber. This process is called purging (pushing out bad substances).
Figure 11: Charcoal canister
Watch this video: Charcoal canister
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Fuel tanks
Fuel tanks have room to store and condense the vapour rising from the fuel surface.
The tank has an overfill-limiting pipe. Once the fuel reaches the lower end of the pipe, air cannot
escape back up the filler neck. This stops more fuel being added, and provides the required vapour
space.
Figure 12: Overfill limiting pipe
Fuel tank vents can have more than one vent pipe. This depends on the location and shape of the
tank in the vehicle. These pipes are generally connected to a common vent, situated above the fuel
tank.
When there is more than one pipe, at least one of these pipes will be above the fuel level,
regardless of the vehicle position. This has 2 purposes:
4. Vents the tank
5. Prevents fuel from syphoning through the vent pipe.
Watch this video: Fuel tanks and lines
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Fuel tank cap
The fuel tank cap is fitted with a vacuum relief valve.
As fuel is consumed, a vacuum or negative pressure is created in the fuel tank. When the pressure
in the fuel tank falls below atmospheric pressure, this valve opens and allows air to enter the fuel
tank. This prevents the tank from buckling.
Figure 13: Fuel tank cap
Liquid vapour separator
Some systems have a ‘condense tank’ or a liquid vapour separator above the fuel tank. This acts as
a trap to prevent liquid fuel reaching the carbon canister. The canister will be damaged if liquid fuel
enters the canister.
Figure 14: Liquid vapour separator
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Electronic Fuel Injection (EFI) operation
The evaporative control system for EFI engines is similar to the system used on carburetted
engines, except that a solenoid-operated purge valve is used.
The purge valve is situated between the intake manifold and charcoal canister.
It is operated by the Electronic Control Unit (ECU), which controls all engine management
functions.
The ECU keeps the purge valve closed so that fuel vapour is not drawn into the intake manifold:

when the engine coolant temperature is low

during engine idle.
The ECU opens the purge valve so the canister is purged - the stored vapour enters the inlet
manifold and is burnt in the engine:

at normal engine operating temperature

during normal driving conditions.
Figure 15: Evaporative emission system
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Activity 3
Answer the following questions.
Question 1
How do evaporative emission controls reduce emissions?
________________________________________________________________________________
________________________________________________________________________________
Question 2
Label the diagram below to show the major components of the evaporative emission control
system.
Figure 16: Evaporative emission system
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Question 3
Which two system components will emit fuel vapour?
________________________________________________________________________________
________________________________________________________________________________
Question 4
Which system component is used to soak up fuel vapours?
________________________________________________________________________________
Question 5
Label the diagram below to show where the canister connections are fitted to on a vehicle.
Figure 17: Charcoal canister
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Question 6
Briefly describe how the charcoal canister works.
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 7
Describe how the fuel level is limited in the fuel tank.
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 8
State two functions of fuel tank vents.
________________________________________________________________________________
________________________________________________________________________________
Question 9
What is the function of a liquid vapour separator in a fuel tank?
________________________________________________________________________________
________________________________________________________________________________
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Question 10
Is liquid fuel allowed to reach the charcoal canister? Why?
________________________________________________________________________________
________________________________________________________________________________
Question 11
What is the function of the vacuum relief valve in the fuel tank cap?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 15
How is the purge valve operated on an EFI evaporative control system?
________________________________________________________________________________
Question 16
During which operating conditions will the purge valve be open on an EFI system?
________________________________________________________________________________
________________________________________________________________________________
Ask your trainer to check your results before proceeding.
Trainer Signature ..............................................................
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Date .......................
© Commonwealth of Australia 2011
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Activity 4
Step 1
Ask your trainer to nominate a vehicle/model relevant to your trade area.
Step 2
Obtain the relevant workshop manual, training material, resources for that vehicle/unit.
Step 3
Find the vehicle/model in the reference/resource material.
Locate all the components of the evaporative emission control system.
Study the operation of the evaporative emission control system and its components.
Step 4
When you feel you are ready, call your trainer and explain the operation of the evaporative
emission control system and its components on the vehicle.
Ask your trainer to check your results before proceeding.
Trainer Signature: ..............................................................
© Commonwealth of Australia 2011
Date: .......................
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Activity 5
For this activity, your teacher will select the charcoal canister and the type of test for you to
complete.
Step 1
Your trainer will nominate a charcoal canister and type of function test for you to complete.
Step 2
Obtain the relevant workshop manual, training material, resources for the charcoal canister
selected.
Step 3
Write down in point form below the manufacturer’s test procedure for this type of canister.
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
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Step 4
Fill in the table below after checking the charcoal canister and lines.
Component
Serviceable?
Comment
Defective fuel tank cap
Leaking charcoal canister
valves
Deteriorated or leaking
canister valves
Blocked filter pads
Fuel and vacuum leaks
Purge valve operation
Ask your trainer to check your results before proceeding.
Trainer Signature: ..............................................................
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Crankcase emission controls
Crankcase ventilation system
When the engine is operating, a small amount of gas escapes the piston rings and enters the
crankcase. These are called blow-by gases. These gases contain harmful pollutants (unburnt
hydrocarbons) that can cause contamination of the engine oil and contribute to air pollution.
The engine has to be ventilated for 2 reasons:

to remove blow-by gases from the crankcase

to prevent pressure from building up in the crankcase.
These blow-by gases are controlled by the PCV (Positive Crankcase Ventilation) system.
The PCV system supplies clean air to the crankcase and, at the same time, removes gases (HCs) that
are harmful to both the engine and the atmosphere.
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Operation of the PCV system

Filtered air is drawn into the rocker cover and into the engine where it mixes with the
blow-by gases.

The gases are drawn from the crankcase through the Positive Crankcase Ventilation
valve (PCV) and into the intake manifold.

The gases are now burnt as part of the normal combustion process.
Figure 18: PVC system for a carburetted system
Gases within the crankcase increase as the engine wears, and the pistons and rings allow more
blow-by to escape.
Similar systems are used both on carburettor and EFI engines.
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PCV valve
The PCV valve controls the flow of air and crankcase gases into the intake manifold, to ensure the
gases will not affect the engine operation.
PCV closed
The PCV valve is closed:

when the engine is not running to assist starting

it is forced closed during a backfire condition to reduce the chance of an explosion in the
crankcase.
Figure 19: PCV valve, closed position
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PCV restricted flow
During idle or deceleration, the high manifold vacuum pulls the PCV plunger inward, to restrict the
flow of crankcase gas drawn into the intake manifold. Only a small amount of flow is allowed to
enter the manifold as so that excess air will not affect the idle speed.
Figure 20: PCV valve, restricted position
PCV large flow
At cruising and high speed, the reduced manifold vacuum allows the plunger to be moved outwards
by the spring force. This allows a larger flow of air through the PCV valve.
Figure 21: PCV valve, large flow
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At high speed, the crankcase pressure forces the blow-by gases to reverse flow through the air
cleaner housing into the air inlet stream.
The crankcase emission system also reduces engine oil contamination during cold engine operation.
This helps extend engine oil quality between services.
Some small engines use a specially sized restrictor hole (orifice) in the intake manifold instead of a
PCV valve to control crankcase gas flow.
Checking a PVC valve
A faulty PCV system can cause:

Poor idling

Excessive crankcase pressure resulting in oil leaks.
There are several test procedures for PCV valves. Refer to manufacturer’s instructions if required.
To check a PCV valve:

Remove the valve

With the vacuum line still connected start the engine

Place finger over the end of the valve - a vacuum or a sucking should be felt.

If no vacuum or sucking is felt, valve or valve line is blocked or faulty.
Figure 22: Checking the PCV valve
Watch this video: Crankcase emission control
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Activity 6
Answer the following questions.
Question 1
What is the function of a crankcase ventilation system?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 2
Label the diagram below to show the major crankcase ventilation system components.
Figure 23: PVC system for a carburetted system
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Question 3
What are ‘blow-by gases’?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 4
Which harmful emission can be found in the crankcase?
________________________________________________________________________________
________________________________________________________________________________
Question 5
Where does the crankcase get ‘fresh air’ from?
________________________________________________________________________________
________________________________________________________________________________
Question 6
What substances are mixed with the fresh air and then drawn out of the crankcase?
________________________________________________________________________________
________________________________________________________________________________
Question 7
What happens to the pollutants after they leave the crankcase?
________________________________________________________________________________
________________________________________________________________________________
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Question 8
What position is the PCV valve in:

when the engine is not running
________________________________________________________________________________

during idle or deceleration
________________________________________________________________________________

at cruising and high speed
________________________________________________________________________________
Question 9
What happens if blow-by gases exceed the PCV valve flow rate?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 10
What can be used on small engines to control PCV valve flow other than a PCV valve?
________________________________________________________________________________
Ask your trainer to check your results before proceeding.
Trainer Signature: ..............................................................
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Date: .......................
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Activity 7
Step 1
Ask your trainer to nominate a vehicle.
Step 2
Obtain the relevant workshop manual, training material, resources for the vehicle/model
nominated.
Step 3
Find the vehicle/model in the references/resource material.
Locate all the components of the crankcase ventilation system.
Study the operation of the Crankcase Ventilation System and its components.
Step 4
When ready, call your trainer and explain the operation of the crankcase ventilation system and its
components.
Ask your trainer to check your results before proceeding.
Trainer Signature: ..............................................................
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Date: .......................
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Activity 8
Ask your trainer to nominate a vehicle.
Step 1
On a vehicle nominated by your teacher complete and inspection of PCV valve and related
components and complete this chart.
Components
Serviceable?
PCV valve
PCV valve vacuum hose
and clamps
PCV sealing thread and
grommets
Valve pass test
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Step 2
Write the manufacturer’s test procedure for the PCV valve for the vehicle nominated.
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Ask your trainer to check your results before proceeding.
Trainer Signature: ..............................................................
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Exhaust emission control systems
Emissions from the exhaust system account for approximately 60% of the total emissions from a
motor vehicle. Exhaust emissions are more complex than evaporative emissions.
If complete combustion occurred, the oxygen (O) in the air would combine with the hydrogen (H) in
the fuel to form water (H2O). The oxygen in the air would also combine with the carbon (C) in the
fuel to form carbon dioxide (CO2).
However, ideal complete combustion does not occur within the engine. Some hydrocarbons (HC)
remain after combustion and carbon monoxide (CO), a more harmful gas, is produced instead of
CO2.(carbon dioxide)
Manufacturers have changed engine designs to improve the combustion of the fuel/air mixture and
reduce exhaust emissions.
Combustion chamber design
The design of the combustion chamber can influence the amount of fuel that remains unburnt.
Burning of the air/fuel mixture starts at the spark plug and moves across the chamber, consuming
the air and fuel as it goes. Most fuel particles are completely burnt but some are not, and
contribute to pollution if not controlled.
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Wedge-shaped combustion chambers
In a wedge-shaped combustion chamber, burning starts at the spark plug at the side of the
combustion chamber and moves across the chamber.
This design has a large quench area which is a relatively cool section. This reduces the temperature
of the burning fuel and so prevents the chance of detonation.
Having the quench area is a disadvantage as far as emissions are concerned. The cooler area allows
particles of unburnt fuel to collect on its surface. These particles are exhausted as hydrocarbons
and increase the emissions of the engine.
Figure 24: A wedge-shaped combustion chamber
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Hemispherical combustion chambers
A hemispherical combustion chamber has the spark plug located in the centre. This enables burning
to occur in all directions. The benefits of this shape for emission output are:

There are no quench areas so the temperature of the burning fuel is higher and
combustions is more complete.

There is less surface area so fewer particles of unburnt fuel collect.

The hemispherical shape creates swirl during the intake stroke, so that the fuel remains
vaporised and burns more completely.
Figure 25: A hemispherical combustion chamber
Watch this video: Combustion chamber design
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Quench areas
The quench area is a zone in the combustion chamber where the piston top dead centre is very
close to the cylinder head. Because the piston and cylinder head is cooler than the unburned part
of the fuel – air mixture which is called end gas detonation is quenched or reduced. However, the
process does form unburned hydrocarbons
Engine cooling systems are designed to maintain uniform high operating temperatures of these
components, which improves combustion and reduces emissions that are produced by this action.
Valve overlap
Valve overlap is a certain period in which both the intake and exhaust are partially open. The intake
is starting to open while the exhaust is not yet closed.
It can be altered on some engines to reduce the scavenging effect of the intake charge. This causes
any unburnt hydrocarbons to remain in the combustion area where they are burnt rather than
being exhausted as HC fuel emissions
Ignition timing
Ignition timing is when the spark coming from the spark plugs ignites the air – fuel mixture at the
correct moment determined by the manufacturer of the engine. Often this is a few degrees before
top dead centre (BTDC).
Spark advance is required to obtain the maximum efficiency from the air/fuel charge. However
sometimes, at idle and slower speeds or when the engine is cold, a slightly retarded spark will
reduce emissions.
EFI and engine management systems (ECUs) are programmed to provide the optimum ignition
settings for all conditions.
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Activity 9
Answer the following questions.
Question 1
State two ways in which exhaust emissions can be reduced
1. _____________________________________________________________________________
________________________________________________________________________________
2. _____________________________________________________________________________
________________________________________________________________________________
Question 2
What is the advantage of wedge shape combustion chambers?
________________________________________________________________________________
________________________________________________________________________________
Question 3
What is the disadvantage of wedge shape combustion chambers?
________________________________________________________________________________
________________________________________________________________________________
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Question 4
What are the advantages of hemispherical combustion chambers?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 5
How do hemispherical combustion chambers help fuel vaporisation?
________________________________________________________________________________
________________________________________________________________________________
Question 6
What is a ‘quench area’ in a combustion chamber?
________________________________________________________________________________
________________________________________________________________________________
Question 7
What is the function of the cooling system in relation to quench areas?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
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Question 8
Why do some manufacturers alter valve overlap on their engines?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 11
Why is spark advance used?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 12
When and why would a slightly retarded spark be used?
________________________________________________________________________________
________________________________________________________________________________
Question 13
Describe how optimum ignition settings are achieved on EFI engines.
________________________________________________________________________________
________________________________________________________________________________
Ask your trainer to check your results before proceeding.
Trainer Signature: ..............................................................
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Date: .......................
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The Exhaust Gas Recirculation system (EGR)
An EGR system returns a controlled amount of exhaust gas into the intake manifold at cruising
speeds. This lowers the combustion temperature and reduces NOx emissions from the exhaust.
When the flow control valve (EGR valve) is opened, exhaust gas is carried into the intake manifold
by either a small external pipe or an internal port.
The vacuum port for EGR operation is situated above the throttle valve, so no EGR flow occurs at
idle. EGR is used to reduce combustion temperature, so it would cause rough running if used at idle
speed.
Figure 26: Exhaust gas system
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Operation of the EGR System
In a cold engine, combustion temperatures are too low for NOx formation. A thermal valve
prevents vacuum acting on the EGR valve until the engine reaches operating temperature
(approximately 55°C).
At warm or hot cruising speeds, the EGR valve is opened to allow exhaust gas into the intake
manifold. It provides up to 10% of non-combustible mixture, which dilutes the air/fuel mixture. This
reduces the heat during combustion and reduces NOx emissions.
During acceleration or heavy load operation, manifold vacuum is too low to operate the EGR valve
so it stays closed.
If EGR was used during heavy load conditions, it would dilute the air/fuel mixture, lower the
combustion temperature, and reduce engine power.
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Thermo Valve
The thermo valve in the cooling system prevents the EGR system from operating until the engine
reaches operating temperature.
The thermo valve is a bimetal (two metals) valve that acts like a vacuum switch.
Figure 27: Thermo valve
When the engine is cold, the thermo valve remains closed. It cuts off vacuum from the EGR valve
which in turn remains closed.
When coolant temperature reaches approximately 60°C, the thermo valve opens, allowing
vacuum from the throttle body port to pass through the thermo valve to reach the EGR valve
diaphragm.
Vacuum on the top side of the diaphragm will open the valve to allow some exhaust gases to pass
from the exhaust manifold to the inlet manifold and into the combustion chambers.
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Modulator control of EGR systems
Some EGR systems use a vacuum modulator unit to control the vacuum signal sent to the EGR
valve.
The vacuum modulator unit is sensitive to exhaust system back pressure. It bleeds out the EGR
vacuum supply until a specified exhaust back pressure is achieved (at moderate engine load).
During moderate load conditions, the exhaust system will build up enough back pressure so that
the internal bleed is closed off. The modulator then allows throttle ported vacuum to open the EGR
valve.
At light cruising load there is very little exhaust system back pressure. So when throttle ported
vacuum is applied to the modulator, the vacuum bleeds off to the atmosphere through the
modulator vent and the EGR valve remains closed.
By venting the modulator at differing throttle body ports, EGR operation can be controlled
depending on a combination of throttle valve opening angle and exhaust back pressure.
Some carburetted engines use an oxidation type catalytic converter which cannot reduce NOx
emissions. An EGR system is used to control NOx emissions but is only required during moderate
load conditions.
Electrical control of EGR systems
EGR valve operation can also be controlled by an emission control computer which is a part of the
engine management system.
The control computer or engine management system may:
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
operate a solenoid in the EGR vacuum line so that EGR operation only occurs during preprogrammed conditions

use an EGR valve position sensor to sense how far the EGR valve is opened, and supply
an input signal of the valve’s position to the ECU (Electronic Control Unit). The ECU then
uses this signal to pulse the EGR solenoid for the correct amount of exhaust gas
recirculation.
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Checking an EGR valve
The ERG valve can be tested for correct operation using a hand vacuum pump.
If accessible on the engine, it can be checked by feel. When the engine is at normal operating
temperature, the diaphragm should retract during acceleration, and return during deceleration.
However many EGR valves are not accessible and must be checked by the engine management
diagnostic procedure. If you need to conduct further testing of the EGR valve, refer to
manufacturer’s procedures.
Figure 28: EGR valve
Watch this video: Emission EGR
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Activity 10
Answer the following questions.
Question 1
What does the term ERG mean?
________________________________________________________________________________
Question 2
What is the function of an exhaust gas recirculation (EGR) system?
________________________________________________________________________________
________________________________________________________________________________
Question 3
Label the components in this diagram of the EGR system.
Figure 29: Exhaust gas system
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Question 4
Which harmful emission is reduced by using EGR action?
________________________________________________________________________________
Question 5
Why is the EGR valve not open at engine idle?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 6
Why is the EGR system not used during cold engine operation?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 7
Is the EGR vacuum port situated above or below the throttle valve?
________________________________________________________________________________
Question 8
How does the thermo valve operate?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
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Question 9
If the EGR system operated during acceleration or heavy load, what would be the effects on engine
performance?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 10
Vacuum modulators are fitted to some EGR systems. Briefly, how do they work?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Ask your trainer to check your results before proceeding.
Trainer Signature: ..............................................................
© Commonwealth of Australia 2011
Date: .......................
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Activity 11
Step 1
Ask your trainer to nominate a vehicle/model.
Step 2
Obtain the relevant workshop manual, training material, resources for the vehicle/model
nominated.
Step 3
Locate the vehicle/model in the references/resource material.

Identify the components of the EGR system.

Study the operation of the EGR system.
Step 4
When ready, call your trainer and:

Name all the components of the EGR system

Explain the operation of the EGR system.
Step 5
On a vehicle nominated by your teacher complete an inspection of the EGR valve and related
components and complete this chart.
Component
Serviceable?
EGR valve vacuum lines
& valves
EGR valve exhaust pipes
& gaskets
Electrical wires,
connectors & switches
Engine management or
scan tool test
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Step 6
For the vehicle nominated write the manufacturer’s test procedure here.
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Ask your trainer to check your results before proceeding.
Trainer Signature: ..............................................................
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Date: .......................
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Catalytic converters
Catalytic converters are fitted into the vehicle’s exhaust system.
They contains catalysts that promote a chemical reaction with the exhaust gases, which reduce the
amount of harmful pollutants that are emitted to the atmosphere (hydrocarbons, carbon
monoxide, and nitrous oxides).
Figure 30: Catalytic converter in the exhaust system
The catalytic converter consists of a stainless steel shell with a ceramic honeycomb core inside.
The cells of the honeycomb core have a coating of alumina, impregnated with special metals —
platinum, palladium, or rhodium. These metals provide the catalyst that produces the reaction with
the exhaust gases.
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Figure 31: Catalytic converter
The honeycomb core is used because:

it allows a free gas flow through the converter

It provides a large area of contact between the exhaust gas and the surface of the
catalyst, where the reaction occurs.
Catalytic converters can be TWO WAY or THREE WAY converters.
Two way converter
Two way, or oxidising, converters use palladium and platinum as a catalyst.
They convert hydrocarbons (HC) and carbon monoxide (CO) to water (H2O) and carbon dioxide
(CO2).,which are less harmful.
Figure 32: 2 way converter
Two way catalytic converters do not react with NOx, so the engine still requires an EGR system to
control NOx emissions.
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Three way converter
Three way converters use an extra catalyst of rhodium. It reacts with and reduces the NOx in the
exhaust gases.
The three way converter needs an ECU and fuel injection to accurately control the fuel air ratio so
the converter will operate efficiently
Figure 33: 3 way converter
In some EGR systems, air is injected into the exhaust system before the catalytic converter to
supply ‘secondary air’. The additional oxygen helps promote the reaction with NOx in the
converter.
Exhaust manifold catalytic converter
This type of converter is attached directly to the exhaust manifold, usually on smaller capacity
engines.
On some vehicles, this converter can be used with a second catalytic converter further along the
exhaust system.
Figure 34: Manifold catalytic converter
Watch this video: Catalytic converter
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Activity 12
Answer the following questions.
Question 1
What is the function of a catalytic converter?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 2
Fill in the labels on the diagram below.
Figure 35: Catalytic converter
Question 3
Describe the construction of a catalytic converter.
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
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Question 4
What is the advantage of using a honeycomb core in the catalytic converter?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 5
What are the catalyst chemicals used in a two way catalytic converter?
________________________________________________________________________________
________________________________________________________________________________
Question 6
Why might an EGR system be used in conjunction with a two way catalytic converter?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 7
How does a three-way catalytic converter controls NOx emissions.
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
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Question 8
Why do some EGR systems inject air into the exhaust system before the catalytic converter?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Ask your trainer to check your results before proceeding.
Trainer Signature: ..............................................................
© Commonwealth of Australia 2011
Date: .......................
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Testing a catalytic converter
Generally catalytic converters are trouble-free. The main reasons a converter will fail are:

physical damage e.g. hit a rock

partially or fully blocked - usually caused by excessive amounts of fuel entering the
catalytic converter. This extra fuel causes high internal temperatures that can melt the
converter core, leading to restricted (reduced) flow and performance.

contaminated core caused by:
-
coolant from leaking head gasket
-
excessive oil from worn engine piston rings coating converter core surface.
A converter failure is often the result of another fault i.e. excessive fuel. So when replacing a
damaged converter you also need to locate and repair the fault that caused the converter to fail.
There are a number of ways to test a converter. Vehicles with engine management systems can
diagnose a catalytic converter fault. Refer to manufacturer’s procedure for details.
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Temperature testing a catalytic converter
You can test converter operation by checking the temperature of the inlet and outlet of the
converter. If the converter is working correctly, the catalytic reaction will make the exhaust outlet
temperature higher than the inlet.
How to test the catalytic converter:

Warm the vehicle up to operating temperature

Run engine at 1500 rpm

Test the inlet and outlet temperatures of the converter with an infra red thermometer.
Remember - the converter and exhaust will be extremely hot.

The inlet temperature should be cooler than the outlet temperature by approximately
200-500C.
Figure 36: Temperature sensors
Catalytic converters operate at temperatures of 5000C and above.
Avoid touching hot exhaust components.
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Activity 13
Step 1
Ask your trainer to nominate a vehicle/model.
Step 2
Obtain the relevant workshop manual, training material, resources for the vehicle/model
nominated.
Step 3
Using the references/resource material:

Locate the catalytic converter

Identify the type of catalytic converter

Study the manufacturer’s test procedures for the converter.
Step 4
List the manufacturer’s test procedures for the catalytic converter you will test.
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
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Step 5
On a vehicle nominated by your teacher, complete an inspection of the catalytic converter and
related components.
Then complete this chart.
Component
Comment
Physical damage to converter
Rattle test
Engine management test results
Restricted exhaust gas flow
Converter temperature test
Input temp
Output temp
Ask your trainer to check your results before proceeding.
Trainer Signature: ..............................................................
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Particulate emissions in diesel engines
Diesel particulate filters (DPF)
Changes to new car emission legislation will make particulate filters on diesel engines much more
wide spread.
What are particulates in the exhaust?
Anything solid in the exhaust gas is called particulate matter (PM). It includes things such as carbon
soot.
Carbon soot is in the exhaust gas due to incomplete combustion of the fuel. Slow warm up and cold
engine conditions increase the particulate matter.
Figure 37 Diesel particulate filter
How do particulate filters work?
A diesel particulate filter (DPF) traps the carbon soot of the exhaust, a bit like the dustbag in a
vacuum cleaner.
However, instead of emptying or cleaning the filter, the diesel particulate filter operates at a very
high temperature and the carbon soot is burnt off.
This is called regeneration and it is either passive or active.
Particulate filters can be incorporated (included) into the catalytic converter. However, some
vehicles have the particulate filter separate from the catalytic converter.
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Passive regeneration
When the particulate filter reaches sufficient temperature (5600C) during normal operation, the
carbon soot is burnt off. This is called the passive regeneration cycle.
Active regeneration
In some driving conditions, the exhaust temperature may not reach a high enough temperature to
burn off the soot, so the ECU must control the process. This is called active regeneration.
The ECU directs small increases in fuel delivery or adjustments to fuel injection timing to raise the
exhaust gas temperatures. This rise in temperature will burn and clean out the accumulated carbon
soot.
If the particulate filter accumulates excessive carbon soot, a dashboard warning
light will illuminate and the vehicle will require attention by a dealer specialist.
Testing and maintenance
The diesel particulate filter needs to be serviced and maintained to a strict schedule. Generally a
fault with the filter will need to be repaired by the vehicle dealer or a specialist who has been
trained to do this task using specialist equipment.
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Activity 14
Answer the following questions
Question 1
What are diesel particulates?
________________________________________________________________________________
________________________________________________________________________________
Question 2
Where do diesel particulates come from?
________________________________________________________________________________
________________________________________________________________________________
Question 3
Where are diesel particulate filters located?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 4
How does a diesel particulate filter operate?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
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Question 5
When does the diesel particulate warning light operate?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 6
What is passive regeneration?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 7
What is active regeneration?
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Ask your trainer to check your results before proceeding.
Trainer Signature: ..............................................................
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Emission Control Information label
In 2005, the Australian Federal Government introduced regulations to control emissions called
Australian Design Rules (ADR) 79/02 Emission Control for Light Vehicles.
One of the things this required was for manufacturers to attach an Emission Control Information
Label in a visible position in the vehicle engine compartment.
The label must state engine specifications and adjustments including:

Idle speed

Ignition timing

Idle air/fuel mixture setting procedures and value

The transmission position during tune up

Any accessories which should be in operation (ADR 79/02).
Figure 38: Emission Control Information label
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Activity 15
Answer the following questions
Question 1
Where is the emission control information label located?
________________________________________________________________________________
Question 2
State the specifications given on the label in Figure 28 for service personnel.
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 3
State any recommendations given on the label in Figure 28 about adjusting the idle mixture (CO%).
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Question 4
On the nominated vehicle locate the emission control information label and state its exact location
below.
________________________________________________________________________________
Ask your trainer to check your results before proceeding.
Trainer Signature: ..............................................................
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Date: .......................
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Testing exhaust emissions
An exhaust gas analyser is used to measure the emissions of the vehicle exhaust before they enter
the catalytic converter. They can test between two and five different exhaust gas emissions.
The five exhaust gases that can be analysed are:1. Hydrocarbons (HC)
2. Carbon monoxide (CO)
3. Carbon dioxide (CO2)
4. Oxides of nitrogen (NOX)
5. Oxygen (O2).
Figure 39: Gas analyser
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Reasons for performing an exhaust gas test
There are two reasons for performing an exhaust gas test.
1. Engine performance
Exhaust gas measurement can be useful in diagnosing engine condition, engine management and
fuel injection faults etc.
Some typical exhaust readings are:
HC
200 ppm or less
CO
2% or less
O2
0%-2%
CO2
12%-15% or higher
NOX
less than 100 ppm
ppm = parts per million
2. Emission compliance
Exhaust gas measurement indicates if the engine and the emission devices are functioning correctly
for emission compliance.
Some typical exhaust readings are:
HC
30-50 ppm or less
CO
4% or less
O2
0%-2%
CO2
12%-15% or higher
NOX
less than 100 ppm
The test results can be compared with the vehicle manufacturer’s specifications and the
Environmental Protection Authority (EPA) standards to check that the exhaust outputs meet
emission standards.
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Conducting an exhaust gas analyser test
Following is a typical procedure for operating an analyser. However, there are many different types
of gas analysers available so you should always refer to manufacturer’s instructions.
STEP
DONE
1. Run the engine until it reaches operating temperature.
2. Connect the analyser to the proper voltage supply.
3. Allow the analyser to warm up and perform the calibration function.
4. Connect the analyser probe to the exhaust outlet.
5. Hold the engine speed at 2500 rpm (revolutions per minute), and record the
emissions readings.
6. Allow the engine to return to idle and record the emissions readings.
Compare the readings with manufacturer’s specifications and Environmental Protection Authority
(EPA) standards. See your workshop supervisor if the workshop does not have it available.
If the measured exhaust gases are outside the acceptable level, refer to the manufacturer’s
diagnosis procedure for further instructions.
Figure 40 Analyser measuring exhaust gases
Operating the engine in a confined space or without proper exhaust gas
extraction can cause death from breathing exhaust gases.
Do not carry out this test unless it is safe to do so.
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Activity 16
1. Your teacher will nominate a vehicle.
2. Locate the procedure and specifications for an exhaust emissions test in the gas
analyser operation instructions and the manufacturer’s manual.
3. Carry out an exhaust emissions test.
4. Fill in the chart below as you go.
IDLE
GASES
2500 RPM
Vehicle
Vehicle
Your results
Your results
specifications
specifications
COMMENTS
HC
(hydrocarbons)
CO
(carbon
monoxide)
CO2
(carbon
dioxide)
O2
(oxygen)
Ask your trainer to check your results before proceeding.
Trainer Signature: ..............................................................
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Date: .......................
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Glossary
WORD
MEANING
activated carbon
A special kind of charcoal
absorbed
Soaked up like a sponge
accumulated
Gathered, collected over some time
advanced
Moved forward
amended
updated
bimetal (say by-metal)
Made of two metals
buckling
Bending out of shape
canister
A container
compression
Pressing on something
concentration
How strong a mixture is
condense
When a gas turns back into a fluid
confined
Closed in, a small space
consumption
use
contamination
pollution
deceleration
Slowing down
deposits
Something left over
detonation
Explosion
emissions
What comes out of something
emitted
Sent out
evaporate
When surface liquid turns into vapour (a gas of
droplets)
hemispherical
A half globe shape
illuminate
Light up
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WORD
MEANING
incorporated
Included, built into
insufficient / sufficient
Not enough/ enough
internal
Inside
lethal
Deadly, can kill you
maximum
The most, the biggest, the highest
moderate
Medium
optimum
Close to perfect
orifice
Hole
particulates
A small piece of something, a particle. Can
sometimes be seen as black smoke in the exhaust
gas.
permitted
allowed
precautions
An action taken in advance to protect against
possible danger
pollution
Poisons in the air, water or earth
pollutants
Things which cause pollution
ported vacuum
Engine vacuum drawn from an opening (or port)
ahead of the throttle
prior to
before
progressively
bit by bit
purging
To remove impurities.
In this case, stored fuel vapour is the impurity and
it is pushed into the intake system where it is burnt
in the combustion chamber.
quench area
A cooler area
ratio
The amount of two things compared eg the ratio of
petrol to air in a fuel mixture
regeneration
Renew, make new again
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WORD
MEANING
restrict
Limit, make smaller
retarded
Slowed down
scavenging
Collecting and removing (exhaust gases)
situated
Placed, located
source
Where something comes from
specify
state exactly
specified government
standards
Standards set by government
sufficient/ insufficient
Enough/ not enough
swirl
Air or gas blowing around
temporarily
For a while, not forever
syphoning
Being sucked up
turbulence
Being thrown around or mixed up
vapour
gas
vented
Flows out of a hole in the container
ventilation
Fresh air
volatile
How easily a substance turns from liquid to
vapour/gas
wedge- shaped
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