Fundamentals of Automotive Technology: Principles and Practice
Chapter 51: Emission Control
Chapter 51
Emission Control
NATEF Tasks
Engine Performance
General Engine Diagnosis
· Diagnose abnormal exhaust color, odor, and sound; determine necessary action. MAST, AST (pp 1798–1799)
Emission Control Systems
· Diagnose emissions and drivability concerns caused by the evaporative emission control system; determine necessary action. MAST (pp 1798–1799)
· Diagnose oil leaks, emissions, and drivability concerns caused by the PCV system; determine necessary action. MAST, AST (p 1799)
· Diagnose emissions and drivability concerns caused by the EGR system; determine necessary action. MAST, AST (pp 1799–1800)
· Diagnose emissions and drivability concerns caused by the secondary air injection and catalytic converter systems; determine necessary action. MAST (p 1800)
· Inspect and test catalytic converter efficiency. MAST, AST (pp 1802–1803)
· Inspect, test, and service positive crankcase ventilation (PCV) filter/breather cap, valve, tubes, orifices, and hoses; determine necessary action. MLR, MAST, AST (pp 1803–1805)
· Inspect, test, service, and replace components of the exhaust gas recirculation (EGR) system, including tubing, exhaust passages, vacuum/pressure controls, filters, and hoses; determine necessary action. MAST, AST (p 1805)
· Inspect and test electrical/electronic sensors, controls, and wiring of the EGR system; determine necessary action. MAST (p 1805)
· Inspect and test electrical/electronically operated components and circuits of air injection systems; determine necessary action. MAST, AST (p 1806)
· Inspect and test components and hoses of the evaporative emission control system; determine necessary action. MAST (pp 1806–1807)
Knowledge Objectives
1. Explain the composition of air in the atmosphere. (pp 1774–1775)
2. Describe the types of exhaust emissions released from the internal combustion engine. (pp 1776–1781)
3. Discuss how emissions can be reduced. (pp 1781–1785)
4. Define the term stoichiometric ratio. (p 1782)
5. List the types of emission control devices used. (pp 1785–1800)
6. Explain the process of emission testing an internal combustion engine. (pp 1800–1801)
7. Explain what is involved in the testing of individual emission control devices. (pp 1800–1807)
Skills Objectives
1. Use a five-gas analyzer. (pp 1801–1802)
2. Test a catalytic converter for efficiency. (pp 1802–1803)
3. Inspect and service the PCV system. (pp 1803–1805)
4. Inspect and service the EGR system and sensors. (p 1805)
5. Inspect and service the secondary air injection system. (p 1806)
6. Inspect and test electrical components of secondary air injection systems. (p 1806)
7. Inspect and service the hoses of the evaporative emission system. (pp 1806–1807)
Readings and Preparation
Review all instructional materials, including Chapter 51 of Fundamentals of Automotive Technology: Principles and Practice and all related presentation support materials.
Support Materials
• Lecture PowerPoint presentation
• Skill Drill PowerPoint presentations
Direct students to visit the companion website to Fundamentals of Automotive Technology: Principles and Practice at www.cdxauto.com/CW/Fundamentals.
Pre-Lecture
You are the Automotive Technician
“You are the Automotive Technician” is a progressive case study that encourages critical-thinking skills.
Instructor Directions
Direct students to read the “You are the Automotive Technician” scenario found at the beginning of Chapter 51.
• You may wish to assign students to a partner or a group. Direct them to review the discussion questions at the end of the scenario and prepare a response to each question. Facilitate a class dialogue centered on the discussion questions.
• You may also use this as an individual activity and ask students to turn in their comments on a separate piece of paper.
Lecture
I. Introduction
A. Emissions are substances released into the atmosphere.
1. Can occur naturally or be man-made
2. Auto emissions: by-product of combustion emitted from the exhaust system
3. Emissions can be managed by carefully designing the engine, accurately controlling the air to fuel ratio, or converting them to less harmful or nonharmful gases through the use of add-on emission control devices.
4. Today’s technology has reduced vehicles’ harmful emissions to almost zero.
II. Composition of Air
A. Air is composed primarily of two gases: nitrogen and oxygen.
1. Nitrogen is largest percentage: 78%.
a. Nitrogen is inert.
i. Does not react easily with other compounds
2. Oxygen is second largest percentage: 21%.
a. Oxygen is highly reactive.
i. Combines readily with almost all other elements
b. It reacts through combustion/oxidation.
3. The remaining 1% of air includes carbon dioxide and argon.
B. Oxygen is critical to humans.
1. The gases in our atmosphere provide a balanced environment for animal, plant, and human life.
a. Oxygen cycle
i. Humans breathe in oxygen and exhale carbon dioxide.
ii. Trees and plants take in carbon dioxide and give back oxygen.
b. Nitrogen cycle
i. Nitrogen from the atmosphere is converted to usable food for plants by bacteria in the ground.
c. Carbon cycle
i. Carbon fuels are burned and produce carbon dioxide in the air, which is converted to carbon and oxygen by plants.
ii. The carbon is used to grow the plant, while the oxygen is given back to the air.
2. The last 1% of air is made up of other gases.
a. Some are useful.
b. Some prevent oxidation while welding.
III. Sources of Emissions
A. Emission normally refers to the pollution produced by a light vehicle during operation or while sitting stationary.
1. All fuels produce pollution except pure hydrogen.
a. Emission control systems limit pollution caused by the storing and burning of various fuels.
b. Emissions from gasoline-fueled motor vehicles come from three sources: the fuel system, the crankcase, and the tailpipe.
2. Fuel tank evaporates liquid fuel into a gas.
a. If not controlled, those vapors can escape into the atmosphere and are called evaporative emissions.
b. Emissions are created when gasoline or other hydrocarbon fuel is burned in the combustion chamber along with oxygen and nitrogen from the air.
c. Some emissions are pollutants and are released from the exhaust system in the form of gases.
i. Tailpipe emissions
d. Some combustion gases leak past the combustion rings and cylinder walls and find their way into the crankcase.
i. These blow-by gases create pressure in the crankcase and if not controlled are vented into the atmosphere.
(a) Called crankcase emissions
3. Compression-ignition engine (diesel) creates emissions in combustion chamber the same way as they are created in spark ignition engines.
a. They escape into the atmosphere through the exhaust and crankcase breather.
b. Diesel fuel does not evaporate as easily as gasoline.
i. Emissions are not a major concern.
IV. Regulated Emissions
A. EPA requires manufacturers to control emissions produced by their vehicles.
1. Power trains must pass federal emission test before they can be sold in the US.
a. Federal test procedure (FTP) is designed to determine the emission output of that particular vehicle as classified by year, make, model, and drive train.
b. FPT uses a dynamometer that will duplicate normal driving pattern of the typical commuter.
i. Known as FTP drive cycle
c. Emission output is monitored in grams per mile (g/mi).
d. To pass, emissions must be under limits.
e. Other countries have other tests.
2. Vehicles must also be able to detect emission failure over their life, as they are being operated.
a. As of 1996, all vehicles must meet on-board diagnostics II (OBDII) standard.
i. OBDII is an automotive self-diagnostic system mandated by the EPA that requires a warning light to alert the driver of an emission system fault.
ii. The warning light must turn on and one or more specific diagnostic trouble codes must be set in memory when the vehicle’s emissions deviate from the FTP limit by 1.5 times.
3. Engine management system must be able to detect rich conditions.
a. Example: due to a leaking fuel injector
b. The engine control module (ECM) turns on MIL to warn the driver.
c. OBDII keeps vehicles emission-compliant and warns drivers if they are not.
4. Air pollutants can be divided into two groups.
a. Gases
i. Primary pollutant gases include hydrocarbons, carbon monoxide, oxides of nitrogen, and sulfur dioxide.
ii. These can have a damaging effect on people, atmosphere, and environment.
b. Particulates/particulate matter
i. Tiny particles of solid or liquid suspended in air
ii. Graded in size range from 10 nanometers to 100 micrometers in diameter
iii. Particulates less than 10 micrometers are dangerous to humans because they can easily become airborne and reach the lungs.
iv. Smaller particles tend to stay airborne longer than larger particles.
5. Many countries recognize global effects of pollutants in earth’s atmosphere.
a. These countries have developed emissions laws or follow international protocol.
b. Vehicle manufacturers must comply.
6. Manufacturers design emission control systems to monitor and control emissions.
a. Limit value is the maximum amount of emissions that a vehicle is allowed to emit.
i. Assigned to different classifications of vehicles
ii. They are normally given in grams per mile in the US and in grams per kilometer in Europe.
iii. These limits have become progressively more stringent as government regulations become tougher.
7. To meet tougher emissions standards, many manufacturers are turning to hybrid technologies, which couple two power sources (electric and gas).
a. Reduced emission output
b. Meet tougher fuel economy standards
c. Alternative fuels, such as compressed natural gas (CNG) and propane, are more frequently used to further reduce pollutions.
V. Types of Emissions
A. Internal combustion engines produce several emission gases as part of the conversion process of turning fuel into mechanical energy.
1. Three categories of emission gases
a. Nonharmful
i. Water (H20)
ii. Nitrogen (N2)
iii. Oxygen (O2)
b. Harmful
i. Carbon monoxide (CO)
ii. Oxides of nitrogen (NOX)
iii. Sulfur dioxide (SO2)
c. Debatable
i. Carbon dioxide (CO2)
B. Water
1. Natural by-product of complete combustion
2. Not harmful to the environment
3. Formed when two hydrogen molecules from the fuel are drawn into the combustion chamber and are combined with one oxygen molecule
4. By-product of completely burned hydrogen fuel
5. Burning 1 gallon of gasoline produces about 1 gallon of water
6. Formed in all internal combustion engines
7. Discharged along with all normal combustion gases through the exhaust system
C. Carbon Dioxide
1. By-product of complete combustion
2. Formed when one carbon molecule combines with two oxygen molecules
a. Completely burned carbon fuel
3. Not normally considered a poisonous gas
4. Some scientists think it is a serious contributor to global warming, and the EPA has labeled it as a pollutant.
5. Believed to act as a blanket, trapping heat
6. Since motor vehicles are a major source of carbon dioxide, governments are finding ways to regulate them.
7. Also formed inside catalytic converters
a. Completes combustion process by adding another oxygen molecule to carbon monoxide to produce carbon dioxide
8. Also produced by diesel, liquid petroleum gas (LPG), propane, CNG, and other carbon-based fuel.
D. Hydrocarbons
1. Gasoline, diesel, LPG, and natural gas are all hydrocarbon compounds
2. Hydrocarbons are created when raw fuel evaporates into atmosphere or when it does not burn at all in the combustion chamber and is exhausted out the tailpipe.
a. Hydrocarbon emissions are unburned fuel that escapes to the atmosphere.
3. Gasoline needs to evaporate easily to mix with air to burn properly in an internal combustion engine.
a. This also means it evaporates easily at ordinary temperatures and pressures.
i. Example: When a vehicle is being refueled, hydrocarbon vapors can escape from the filler neck into the atmosphere.
ii. Example: When the vehicle is left in the sun, the temperature of the fuel increases, and fuel can evaporate from the tank.
E. Carbon Monoxide
1. Carbon monoxide is a colorless, odorless, tasteless, flammable, and highly toxic gas.
2. Product of incomplete combustion of carbon and oxygen
a. Results from too much fuel (carbon) or not enough air (oxygen)
b. Carbon can only attach itself to one oxygen molecule.
3. Partially burned fuel
4. Other causes of high carbon monoxide emissions include improper ignition timing, low combustion temperature, or low compression of the engine.
5. Emissions have been reduced in modern vehicles by better engine designs, better fuel management, and the use of catalytic converters in the exhaust system.
6. Most engine fuels, except pure hydrogen, are carbon-based.
a. Unless the combustion process is perfect and complete, any internal combustion engine operating on a carbon-based fuel produces carbon monoxide emissions.
i. This is especially true when the engine temperature is low, such as during cold start.
(a) There is not enough oxygen present to completely burn the fuel.
(b) There is insufficient time in the combustion chamber for complete combustion.
7. Toxicity
a. Carbon monoxide is an extremely poisonous gas.
i. Inhaling it can be lethal.
ii. Because it comes from the exhaust system, it is important not to allow any engine to run inside a workshop without venting exhaust gases directly into outside air.
b. Victims of carbon monoxide poisoning can look healthy and pink-cheeked.
i. Concentrations of carbon monoxide give blood brighter red color.
ii. Brain is starved of oxygen when the hemoglobin becomes saturated with carbon monoxide and can no longer carry oxygen.
(a) When this happens, the victim becomes unconscious and can suffer brain damage or death.
iii. Early signs of carbon monoxide poisoning
(a) Headaches
(b) Nausea
(c) Weakness
(d) Irritability
c. Because it is absorbed easily by red blood cells, the following agencies set limits for permissible exposure limit (PEL) for the workplace:
i. OSHA PEL: 50 ppm per 8-hour shift
ii. National Institute for Occupational Safety and Health (NIOSH) PEL: 35 ppm per 8-hour shift with 200 ppm ceiling for any length of time
iii. American Conference of Governmental Industrial Hygienists (ACGIH) PEL: 25 ppm per 8-hour shift and 40-hour workweek
d. Understanding ppm
i. Exposure levels of 400 ppm may be fatal in as little as 3 hours.
ii. 6400 ppm fatal in 30 minutes
ii. 1% carbon monoxide = 10,000 ppm
e. Vehicles with an emission-related problem can run perfectly well and still have dangerously high carbon monoxide readings.
8. First aid
a. Recognize the signs of exposure.