AURT3046666A REPAIR AND REPLACE EMISSION CONTROL SYSTEMS 1 © Commonwealth of Australia...

AURT3046666A REPAIR AND REPLACE EMISSION CONTROL SYSTEMS 1

© Commonwealth of Australia 2011 AURT3046666A Repair and replace emission control systems

AURT304666A

Repair and replace emission control

systems

AUR30405 CERTIFICATE III IN AUTOMOTIVE MECHANICAL TECHNOLOGY



Personal safety

• Use personal protective equipment (PPE).

• Use wheel chocks & guard covers.

• Keep clear of hot or moving components on engines.

• Lift vehicles correctly and safely.

• Plenty of ventilation when working on running engines.



Forms of pollution

Pollution from evaporation Pollution from combustion



Producing exhaust gases

Air enters the engine Fuel is injected into the engine

Combustion

Blow by

Exhaust gas exits the engine



Sources of emissions

Fuel tanks and carburettors10% by evaporation

Crankcase30% from combustion and blow by

Exhaust 60% from combustion



Emissions from petrol engines

Hydrocarbons (HC) come from:

•unburnt fuel

•evaporating fuel

•crankcase vapours or blow by gases




Carbon monoxide (CO) comes from:

•incomplete combustion due to a lack of oxygen(air) during combustion

•excessively rich fuel/air mixtures

•very lean fuel/air mixtures




Oxides of nitrogen (NOx) come from:

•overheating engine conditions

•increased compression ratios

•incorrect ignition timing

•lean fuel mixtures.



Guidelines for 6 tests:

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.

Government legislation

http://www.comlaw.gov.au/



Emissions from diesel engines

Particulates • carbon particles in the exhaust gas

• formed due to:

– incomplete combustion

– slow and cold engine operation

– high engine oil consumption.

Oxides of nitrogen (NOX)

• formed due to high combustion temperatures in diesel engines.



Government legislation

National Environment Protection Measure (Diesel Vehicle Emissions)2001, amended in 2009

www.nepc.gov.au



Types of emission control systems

3. Exhaust emission control Controls the products of combustion before they enter the atmosphere

2. Crankcase ventilationPrevents crankcase emissions escaping to the atmosphere

1. Evaporative control Prevents fuel vapour escaping to the atmosphere



Evaporative emission control system

Carburettor

Charcoal canisterVapour line to canister

Liquid/valve separator

Fuel tank

Petrol cap relief valveVapour vent

Fuel linePurge lineAir vent solenoid

valve



Evaporative emission control system

• Seals the fuel tank and carburettor.

• Temporarily stores the fuel vapour.

• Regularly flushes out the stored fuel vapour.

Stops fuel vapour escaping into the atmosphere:



Charcoal Canister

• Stores the evaporating fuel from the tank and carburettor (if fitted).

• When the engine starts the stored fuel vapour is sent to the engine.

Fuel vapour linefrom carburettor

CharcoalFilter

Filter

Air vent

Fuel vapour line from tank

Throttle ported vacuumLine to intake manifold



Fuel tank and cap

Stores the fuel. Prevents the fuel vapour from escaping to the atmosphere.

Fuel tank

Fuel filler cap

Liquid vapour separator



Crankcase ventilation system

PCV - Positive Crankcase Ventilation valve

• Prevents excessive pressure build up in the crankcase.

• Prevents unburnt fuel vapour from escaping to the atmosphere.

Fresh air inlet

Blowbygases

Crankcase vapours& blowby gases

PVC valve

Intake manifold

Air filter

Valve seatValve face

Valve spring

Shuttle valve

Retaining spring

Valve housingHose connection to inlet manifold



Exhaust emission control systems

Exhaust gases = more than 1/2 total emissions from vehicles.

Three ways to reduce or control exhaust emissions:

1.Engine design

2.Exhaust Gas Recirculating system (EGR)

3.Catalytic converter.



Engine design

Wedge shaped combustion chamber•large quench area •increased hydrocarbon emissions

Hemispherical combustion chamber•minimal quench area•less hydrocarbon emissions



Exhaust Gas Recirculating system (EGR)

• Returns some exhaust gas to intake manifold.

• Lowers combustion temperature.

• Reduces oxides of nitrogen (NOx) in exhaust gas.

Exhaust gas

Exhaust gasport

Thermo valve

ERG valve

Vacuum port



Catalytic ConverterFitted to the vehicle exhaust system

as close as possible to the engine.

Tailpipe

Muffler to tailpipe

Muffler

Pipe to mufflerCatalytic convertor

Engine pipe



Pollutants from engine

Catalytic Converter

To exhaust

HC - HydrocarbonsCO - Carbon monoxideNOx - Oxides of nitrogen

H2O - WaterCO2 - Carbon dioxideO2 - OxygenN - Nitrogen

Chemicals react with pollutants in exhaust gas



Diesel particulate filter

• Exhaust carrying particulate matter (PM) enters open channels.

• Ends of channels are blocked forces exhaust through walls.

• Pm is captured on the walls over time, pm burns away.

Exhaust in

Clean exhaustout

Soot and ash particles



Emission Control Information label

• 2005 ADR) 79/02 emission control regulations.

• Must be in a visible position in the vehicle engine compartment.

• Must state a range of engine specifications and adjustments.



Testing exhaust emissions

Measure pollutants in exhaust gases with an exhaust gas analyser

Good ventilation is critical when testing



© Commonwealth of Australia 2011ISBN: 978-1-876838-51-5

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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