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CONTROL TECHNIQUES
FOR CARBON MONOXIDE,
NITROGEN OXIDE,
AND HYDROCARBON EMISSIONS
FROM MOBILE SOURCES
U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Environmental Health Service
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CONTROL TECHNIQUES
FOR
CARBON MONOXIDE, NITROGEN OXIDE,
AND HYDROCARBON EMISSIONS
FROM
MOBILE SOURCES
U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Environmental Health Service
National Air Pollution Control Administration
Washington, D. C.
March 1970
For sale by the Superintendent of Documents, U.S. Government Printing Oflice, Washington, D.C., 20402 - Price $1.25
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National Air Pollution Control Administration Publication No. AP-66
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PREFACE
Throughout the development of Federal air
pollution legislation, the Congress has con-
sistently found that the States and local
governments have the primary responsibility
for preventing and controlling air pollution at
its source. Further, the Congress has con-
sistently declared that it is the responsibility
of the Federal government to provide tech-
nical and financial assistance to State and
local governments so that they can undertake
these responsibilities.
These principles were reiterated in the
1967 amendments to the Clean Air Act. A
key element of that Act directs the Secretary
of Health, Education, and Welfare to collect
and make available information on all aspects
of air pollution and its control. Under the
Act, the issuance of control techniques infor-
mation is a vital step in a program designed to
assist the States in taking responsible tech-
nological, social, and political action to pro-
tect the public from the adverse effects of air
pollution.
Briefly, the Act calls for the Secretary of
Health, Education, and Welfare to define the
broad atmospheric areas of the Nation in
which climate, meteorology, and topography,
all of which influence the capacity of air to
dilute and disperse pollution, are generally
homogeneous.
Further, the Act requires the Secretary to
define those geographical regions in the
country where air pollution is a problem
whether interstate or intrastate. These air
quality control regions are designated on the
basis of meteorological, social, and political
factors which suggest that a group of com-
munities should be treated as a unit for set-
ting limitations on concentrations of atmos-
pheric pollutants. Concurrently, the Secretary
is required to 'issue air quality criteria for
those pollutants he believes may be harmful
to health or welfare, and to publish related
information on the techniques which can be
employed to control the sources of those pol-
lutants.
Once these steps have been taken for any
region, and for any pollutant or combination
of pollutants, then the State or States re-
sponsible for the designated region are on
notice to develop ambient air quality stand-
ards applicable to the region for the pol-
lutants involved, and to develop plans of
action for meeting the standards.
The Department of Health, Education, and
Welfare will review, evaluate, and approve
these standards and plans and, once they are
approved, the States will be expected to take
action to control pollution sources in the
manner outlined in their plans.
At the direction of the Secretary, the
National Air Pollution Control Administra-
tion has established appropriate programs to
carry out the several Federal responsibilities
specified in the legislation.
Control Techniques for Carbon Monoxide,
Nitrogen Oxide, and Hydrocarbon Emissions
from Mobile Sources is one of a series of doc-
uments to be produced under the program
established to carry out the responsibility for
developing and distributing control tech-
nology information. Previously, on February
11, 1969, control technique information was
published for sulfur oxides and particulate
matter.
In accordance with the Clean Air Act, a
National Air Pollution Control Techniques
Advisory Committee was established, having a
membership broadly representative of indus-
try, universities, and all levels of government.
The committee, whose members are listed fol-
lowing this discussion, provided invaluable
advice in identifying the best possible meth-
ods for controlling the pollution sources,
111
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assisted in determining the costs involved, and
gave major assistance in drafting this docu-
ment.
As further required by the Act, appropriate
Federal departments and agencies, also listed
on the following pages, were consulted prior
to issuance of this document. A Federal con-
sultation committee, comprising members
designated by the heads of 17 departments
and agencies, reviewed the document, and
met with staff personnel of the National Air
Pollution Control Administration to discuss
its contents.
During 1967, at the initiation of the Secre-
tary of Health, Education, and Welfare, sev-
eral government-industry task groups were
formed to explore mutual problems relating
to air pollution control. One of these, a task
group on control technology research and
development, looked into ways that industry
representatives could participate in the review
of the control techniques reports. Accord-
ingly, several industrial representatives, listed
on the following pages, reviewed this docu-
ment and provided helpful comments and sug-
gestions. In addition, certain consultants to
the National Air Pollution Control Adminis-
tration also revised and assisted in preparing
portions of this document. These also are
listed on the following pages.
The Administration is pleased to acknowl-
edge efforts of each of the persons specifically
named, as well as those of the many not so
listed who contributed to the publication of
this volume. In the last analysis, however, the
National Air Pollution Control Administra-
tion is responsible for its content.
The control of air pollutant emissions is a
complex problem because of the variety of
sources and source characteristics. Technical
factors frequently make necessary the use of
different control procedures for different
types of sources. Many techniques are still in
the development stage, and prudent control
strategy may call for the use of interim meth-
ods until these techniques are perfected.
Thus, we can expect that we will continue to
improve, refine, and periodically revise the
control techniques information so that it will
continue to reflect the most up-to-date
knowledge available.
John T. Middleton,
Commissioner,
National Air Pollution
Control Administration.
IV
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NATIONAL AIR POLLUTION CONTROL TECHNIQUES ADVISORY
COMMITTEE
Chairman
Mr. Robert L. Harris, Jr., Director
Bureau of Abatement and Control
National Air Pollution Control Administration
MEMBER
Mr. Herbert J. Dunsmore
Assistant to Administrative
Vice President of Engineering
U. S. Steel Corporation
Pittsburgh, Pennsylvania
Mr. John L. Gilliland
Technical Director
Ideal Cement Company
Denver, Colorado
Dr. August T. Rossano
Department of Civil Engineering
Air Resource Program
University of Washington
Seattle, Washington
Mr. Jack A. Simon
Principal Geologist
Illinois State Geological Survey
Urbana, Illinois
Mr. Victor H. Sussman, Director
Division of Air Pollution Control
Pennsylvania Department of Health
Harrisburg, Pennsylvania
Dr. Harry J. White, Head
Department of Applied Science
Portland State College
Portland, Oregon
CONSULTANT
Mr. Robert L. Chass
Chief Deputy Air Pollution
Control Officer
Los Angeles County Air Pollution
Control District
Los Angeles, California
Mr. C. G. Cortelyou
Coordinator of Air & Water
Conservation
Mobil Oil Corporation
New York, New York
Mr. Charles M. Heinen
Assistant Chief Engineer
Chemical Engineering Division
Chrysler Corporation
Highland Park, Michigan
Mr. William Monroe
Chief, Air Pollution Control
Division of Clean Air & Water
State Department of Health
Trenton, New Jersey
Mr. William W. Moore
Vice President, and Manager of
Air Pollution Control Division
Research-Cottrell, Inc.
Bound Brook, New Jersey
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FEDERAL AGENCY LIAISON REPRESENTATIVES
Department of Agriculture
Dr. Theodore C. Byerly
Assistant Director of Science
and Education
Department of Commerce
Mr. Paul T. O'Day
Staff Assistant to the Secretary
Department of Defense
Mr. Thomas R. Casberg
Office of the Deputy Assistant Secretary
(Properties and Installations)
Department of Housing & Urban Development
Mr. Samuel C. Jackson
Assistant Secretary for Metropolitan
Development
Department of the Interior
Mr. Harry Perry
Mineral Resources Research Advisor
Department of Justice
Mr. Walter Kiechel, Jr.
Assistant Chief
General Litigation Section
Land and Natural Resources Division
Department of Labor
Dr. Leonard R. Linsenmayer
Deputy Director
Bureau of Labor Standards
Post Office Department
Mr. W. Norman Meyers
Chief, Utilities Division
Bureau of Research & Engineering
Department of Transportation
Mr. William H. Close
Assistant Director for Environmental Research
Office of Noise Abatement
Department of the Treasury
Mr. Gerard M. Brannon
Director
Office of Tax Analysis
Atomic Energy Commission
Dr. Martin B. Biles
Director
Division of Operational Safety
Federal Power Commission
Mr. F. Stewart Brown
Chief
Bureau of Power
General Services Administration
Mr. Thomas E. Crocker
Director
Repair and Improvement Division
Public Buildings Service
National Aeronautics and Space
Administration
Major General R. H. Curtin, USAF
(Ret.)
Director of Facilities
National Science Foundation
Dr. Eugene W. Bierly
Program Director for Meteorology
Division of Environmental Sciences
Tennessee Valley Authority
Dr. F. E. Gartrell
Assistant Director of Health
Veterans Administration
Mr. Gerald M. Hollander
Director of Architecture and Engi-
neering
Office of Construction
VI
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CONTRIBUTORS
Dr. William G. Agnew, Head
Fuels & Lubricants Department
Research Laboratories
General Motors Corporation
Warren, Michigan
Dr. A. D. Brandt
Manager, Environmental Quality Control
Bethlehem Steel Corporation
Bethlehem, Pennsylvania
Mr. John M. Depp, Director
Central Engineering Department
Monsanto Company
St. Louis, Missouri
Mr. Stewart S. Fritts
Operations Consultant
Lone Star Cement Corporation
New York, New York
Mr. J. C. Hamilton
Vice President for Administration
Director of Engineering
Owens-Illinois, Inc.
Toledo, Ohio
Mr. Richard B. Hampson
Manager, Technical Services
Freeman Coal Mining Corporation
Chicago, Illinois
Mr. C. William Hardell
Coordinator, Eastern Region
Air & Water Conservation
Atlantic Richfield Company
New York, New York
Mr. James F. Jonakin
Manager, Air Pollution Control Systems
Combustion Engineering, Inc.
Windsor, Connecticut
Mr. James R. Jones, Director
Coal Utilization Services
Peabody Coal Company
St. Louis, Missouri
Mr. John F. Knudsen
MMD-ED Industrial Hygiene Engineer
Kennecott Copper Corporation
Salt Lake City, Utah
Mr. Edward Largent
Manager, Environmental & Industrial
Hygiene, Medical Dept.
Reynolds Metals Company
Richmond, Virginia
Mr. Walter Lloyd
Director, Coal & Ore Services Dept.
Pennsylvania Railroad Company
Philadelphia, Pennsylvania
Mr. Michael Lorenzo
General Manager
Environmental Systems Department
Westinghouse Electric Corporation
Washington, D. C.
Mr. J. F. McLaughlin
Executive Assistant
Union Electric Company
St. Louis, Missouri
Mr. Robert Morrison
President, Marquette Cement Manufac-
turing Company
Chicago, Illinois
Dr. Clarence A. Neilson
Director of Laboratories & Manager
Of Technical Services
Laboratory Refining Dept.
Continental Oil Company
Ponca City, Oklahoma
Vll
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Mr. James L. Parsons
Consultant Manager
Environmental Control
E. I. duPont de Nemours & Co., Inc.
Wilmington, Delaware
Mr. James H. Rook
Director of Environmental Control
Systems
American Cyanamid Company
Wayne, New Jersey
Mr. K. J. Schatzlein
Chemical Engineer
Lehigh Portland Cement Company
Allentown, Pennsylvania
Mr. T. W. Schroeder
Manager of Power Supply
Illinois Power Company
Decatur, Illinois
Mr. Robert W. Scott
Coordinator for Conservation Technology
Esso Research & Engineering Company
Linden, New Jersey
Mr. Bruce H. Simpson
Executive Engineer, Emissions Planning
Ford Motor Company
Dearborn, Michigan
Mr. Samuel H. Thomas
Director of Environmental Control
Owens-Corning Fiberglas Corporation
Toledo, Ohio
Mr. A. J. VonFrank
Director, Air & Water Pollution Control
Allied Chemical Corporation
New York, New York
Mr. Earl Wilson, Jr.
Manager, Industrial Gas Cleaning Dept.
Koppers Company, Inc.
Baltimore, Maryland
Mr. Wayne Wingert
Environmental Improvement Engineer
The Detroit Edison Company
Detroit, Michigan
vui
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TABLE OF CONTENTS
Section Page
LIST OF FIGURES xii
LIST OF TABLES xiii
SUMMARY xv
1. INTRODUCTION 1-1
1.1 REFERENCE FOR SECTION 1 1-2
2. BACKGROUND INFORMATION 2-1
2.1 DEFINITIONS 2-1
2.2 TYPES AND NUMBERS OF MOBILE SOURCES 2-3
2.2.1 Growth History and Projections 2-4
2.2.2 Power Plants 2-5
2.2.2.1 Spark-Ignited Piston Engine 2-7
2.2.2.2 Diesel (Compression-Ignition) Engine 2-9
2.2.2.3 Aircraft Gas Turbine Engine 2-10
2.2.3 Emissions 2-11
2.2.3.1 Nature and Formation of Emissions 2-11
2.2.3.2 Emission Reactivity 2-15
2.2.3.3 Emission Quantities 2-15
2.3 REFERENCES FOR SECTION 2 2-16
3. FEDERAL EMISSION CONTROL PROGRAM 3-1
3.1 LEGISLATION 3-1
3.2 REGULATIONS 3-4
3.2.1 Emission Standards 3-4
3.2.1.1 General 3-4
3.2.1.2 Prospective: Conventional Gasoline Engine 3-5
3.2.1.3 Prospective: Diesel Engine 3-6
3.2.2 Compliance . 3-6
3.3 EFFECT ON EMISSION REDUCTIONS 3-10
3.3.1 New Vehicles 3-10
3.3.2 Durability and Surveillance 3-10
3.4 REFERENCES FOR SECTION 3 3-12
4. STATE EMISSION CONTROL OPTIONS 4-1
4.1 INTRODUCTION 4-1
4.2 PRESENT STATE PROGRAMS 4-2
4.2.1 California Program 4-3
4.2.2 New Jersey Program 4-3
4.3 LEGISLATION 4-4
4.4 OPTIONS ON INSPECTION AND/OR MAINTENANCE PROCEDURES . 4-6
4.4.1 Visual Inspection 4-6
4.4.2 Minor Tune-Up 4-7
4.4.3 Major Tune-Up 4-7
4.4.4 Exhaust Measurement at Idle 4-9
ix
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Section Page
4.4.5 Exhaust Measurement Under Load for Purpose of Identifying High
Emitters 4-9
4.4.6 Exhaust Measurement Under Load for Purpose of Diagnosis . 4-11
4.4.7 Crankcase Emission Control Device Inspection 4-11
4.4.8 Evaporative Emissions Control System Inspection 4-12
4.4.9 Oxides of Nitrogen Control System Inspection 4-12
4.5 OTHER OPTIONS RELATIVE TO VEHICLE EMISSIONS 4-12
4.5.1 Substitution of Public Transportation 4-12
4.5.1.1 Bus Systems 4-13
4.5.1.2 Rail Systems 4-13
4.5.2 Road Design and Traffic Control 4-13
4.5.3 Control of Older Vehicles 4-13
4.5.4 Long-Range Plans 4-14
4.5.4.1 Actions Under Emergency Situations 4-14
4.5.4.2 Other Vehicle Propulsion Systems 4-15
4.5.4.3 Certification of Maintenance Personnel 4-15
4.5.4.4 Driver Training 4-15
4.6 REFERENCES FOR SECTION 4 4-15
5. TYPES OF EMISSION CONTROL SYSTEMS 5-1
5.1 CURRENT SYSTEMS 5-1
5.1.1 Positive Crankcase Ventilation Systems 5-1
5.1.2 Exhaust Emission Control Systems 5-1
5.1.2.1 Engine Modification Systems 5-2
5.1.2.2 Air Injection Systems 5-7
5.2 PROSPECTIVE EMISSION CONTROL SYSTEMS 5-8
5.2.1 Evaporative Controls 5-8
5.2.1.1 General 5-9
5.2.1.2 Vapor-Recovery System 5-9
5.2.1.3 Adsorption-Regeneration System 5-9
5.2.2 Prospective Control System DevelopmentConventional Vehicles . 5-11
5.2.2.1 General 5-11
5.2.2.2 Automobiles and Other Four-Stroke-Cycle, Spark-Ignited
Engines , 5-11
5.2.2.3 Two-Stroke-Cycle, Spark-Ignited Engines 5-15
5.2.2.4 Diesel Engines 5-18
5.2.2.5 Aircraft 5-20
5.3 COSTS OF EMISSION CONTROL SYSTEMS 5-22
5.4 REFERENCES FOR SECTION 5 5-22
6. FUEL MODIFICATION AND SUBSTITUTION 6-1
6.1 EFFECTS OF FUEL MODIFICATION ON HYDROCARBON EMISSIONS 6-1
6.1.1 General 6-1
6.1.2 Gasoline Volatility Reduction 6-1
6.1.2.1 Effects of Volatility Reduction on Performance 6-2
6.1.2.2 Effects of Volatility Reduction on Emissions 6-2
6.1.2.3 Costs of Volatility Reduction 6-3
6.1.3 Removal of Highly Reactive Gasoline Constituents 6-3
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Section Page
6.1.3.1 Effects of Olefin Removal on Emissions 6-3
6.1.3.2 Costs of Olefin Removal 6-5
6.1.4 Effects of Lead on Emissions 6-5
6.1.5 Diesel Fuel Modification 6-5
6.2 EFFECTS OF FUEL MODIFICATION ON CO AND NOX EMISSIONS . . 6-6
6.2.1 Spark-Ignition Engines 6-6
6.2.2 Compression-Ignition Engines 6-6
6.3 FUEL SUBSTITUTION 6-6
6.4 REFERENCES FOR SECTION 6 6-7
7. POSSIBLE SUBSTITUTES FOR CURRENTLY USED MOTOR VEHICLE
ENGINES 7-1
7.1 AUTOMOTIVE GAS TURBINE 7-2
7.1.1 Principles 7-2
7.1.2 Historical 7-2
7.1.3 Emissions 7-3
7.1.4 Advantages and Disadvantages 7-4
7.1.5 Costs , 7-5
7.2 ROTARY COMBUSTION CHAMBER ENGINE 7-5
7.2.1 Principles 7-5
7.2.2 Historical 7-5
7.2.3 Emissions 7-5
7.2.4 Advantages and Disadvantages 7-5
7.2.5 Costs 7-6
7.3 STEAM ENGINE 7-6
7.3.1 Principles 7-6
7.3.2 Historical 7-7
7.3.3 Emissions 7-7
7.3.4 Advantages and Disadvantages 7-7
7.3.5 Costs 7-10
7.4 ELECTRIC DRIVES 7-10
7.4.1 Principles 7-10
7.4.2 Historical 7-11
7.4.3 Emissions 7-12
7.4.4 Advantages and Disadvantages 7-12
7.4.5 Costs 7-14
7.5 FREE-PISTON ENGINES 7-14
7.5.1 Principles 7-14
7.5.2 Historical 7-15
7.5.3 Emissions 7-15
7.5.4 Advantages and Disadvantages 7-1$
7.5.5 Costs 7-15
7.6 STIRLING ENGINE 7-15
7.6.1 Principles 7-15
7.6.2 Historical 7-15
7.6.3 Emissions 7-15
7.6.4 Advantages and Disadvantages 7-16
7.6.5 Costs 7-16
xi
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Section
7.7 STRATIFIED-CHARGE ENGINE ... 7-16
7.7.1 Principles 7"16
7.7.2 Historical 7"16
7.7.3 Emissions 7-16
7.7.4 Advantages and Disadvantages 7-16
7.7.5 Costs ... 7-18
7.8 REFERENCES FOR SECTION 7 7-18
8. REGIONAL EMISSION ESTIMATES AND EMISSION FACTORS FOR
MOBILE SOURCES 8-1
8.1 ESTIMATING REGIONAL VEHICULAR EMISSIONS 8-1
8.2 EMISSION FACTORS 8-3
8.3 REFERENCES FOR SECTION 8 8-3
9. VEHICLE EMISSIONS RESEARCH AND DEVELOPMENT 9-1
9.1 GOVERNMENTAL 9-1
9.2 INDUSTRIAL 9-1
9.2.1 Automobiles and Other Four-Stroke-Cycle, Spark-Ignited Engines. . 9-2
9.2.2 Motorcycles and Other Two-Stroke-Cycle, Spark-Ignited Engines . . 9-2
9.2.3 Diesel Engines 9-2
9.2.4 Aircraft 9-2
9.2.5 Heat Engines 9-2
9.2.6 Electric Power Systems 9-2
9.2.7 Hybrid Systems 9-3
9.2.8 Photochemical and Atmospheric Research 9-3
9.3 REFERENCES FOR SECTION 9 9-3
APPENDIX A A-l
APPENDIX B B-l
APPENDIX C C-l
SUBJECT INDEX H
LIST OF FIGURES
Figure
1-1. Effects of Air-Fuel Ratio on Exhaust Composition 1-1
2-1. Past and Projected United States Vehicle Miles 2-6
2-2. Composition of United States Air Carrier (Commercial) Fleet 2-6
2-3. Composition of United States General Aviation Fleet 2-6
2-4. Trends of American Passenger Car Engine Design 2-7
2-5. Schematic of Four-Stroke-Cycle Engine 2-7
2-6. Schematic of Two-Stroke-Cycle Engine 2-8
2-7. Effect of Air-Fuel Ratio on Power and Economy 2-9
2-8. Views of Three Types of Aircraft Gas Turbine Engines 2-11
2-9. Approximate Distribution of Emissions by Source for a Vehicle not
Equipped With any Emission Control Systems 2-12
2-10. Estimated CO Emissions from Gasoline-Powered Automobiles and Trucks
through 1990 if Federal Standards as of 1971 Remain Unchanged. Total
Urban and Rural Data Used 2-16
xii
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Figure Page
2-11. Estimated NOX Emissions from Gasoline-Powered Automobiles and Trucks
through 1990 if Federal Standards as of 1971 Remain Unchanged. Total
Urban and Rural Data Used 2-16
2-12. Estimated HC Emissions from Gasoline-Powered Automobiles and Trucks
through 1990 if Federal Standards as of 1971 Remain Unchanged. Total
Urban and Rural Data Used 2-16
3-1. Hydrocarbon Exhaust Emissions Versus Mileage 3-11
3-2. Carbon Monoxide Exhaust Emissions Versus Mileage 3-11
4-1. Frequency Distribution of Exhaust HC Emission Levels as Derived from
1655 Cold-Start Dynamometer Tests (Composite Cycle) on 1966 Model New
Cars in California (GM Quality Audit) 4-2
4-2. Frequency Distribution of Exhaust CO Emission Levels as Derived from
1655 Cold-Start Dynamometer Tests (Composite Cycle) on 1966 Model New
Cars in California (GM Quality Audit) 4-2
5-1. Closed Positive Crankcase Ventilation System 5-2
5-2. Ford IMCO Thermostatically Controlled Inlet Air Heater 5-3
5-3. Heated Air System for General Motors Controlled Combustion System.
Damper is shown with Cold Air Door in Open Position 5-4
5-4. Typical Methods Used to Limit Enrichment of Carburetor idle Mixture. . . 5-5
5-5. "Ported" Vacuum Source with Throttle Closed 5-6
5-6. Schematic View Showing Operation of Vacuum Switching Control Valve.
Valve is in Deceleration position 5-7
5-7. V-8 Engine with Air Injection Reaction Components Installed 5-8
5-8. Air Injection Tube in Exhaust Port 5-9
5-9. Adsorption-Regeneration Evaporative Emissions Control System 5-10
7-1. Vehicle Requirements and Motive Power Source Requirements 7-1
7-2. Schematic Diagram of Simple Gas-Turbine Engine 7-2
7-3. Schematic Diagram of Regenerative Free-Turbine Engine 7.3
7-4. Sequence of Wankel Rotary Engine Cycle Events 7.5
7-5. Schematic of Typical Rankine Cycle Steam Engine Components 7.7
7-6. Steam Engine Installation 7-g
7-7. Illustration of Lead-Acid Storage Battery 7-11
7-8. Illustration of a Simple Hydrogen-Oxygen Fuel Cell 7-12
7-9. Phantom View of General Motors XP-883 Experimental Hybrid Car 7-13
7-10. Schematic of Free-Piston Engine Serving as a Gasifier to Drive a Power
Turbine 7-14
7-11. Schematic Drawing of Stirling Thermal Engine 7-17
LIST OF TABLES
Table
2-1. Population of Mobile Sources of Emissions in Use in the United States. . . . 2-4
2-2. 1968 U.S. Motor Vehicle Registrations, by States as of the End of the
Registration Year 2-5
2-3. 1968 Nationwide Emission Estimates 2-15
3-1. Sequence of California and Federal Gasoline-Powered Vehicle Emission
Standards for CO, NOX, and HC 3-5
xiii
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Figure Page
3-2. Allowable Emission Rates Under 1968 Federal Standards 3'6
3-3. Light-Duty Vehicle Emissions 3-8
4-1. Effects of Maladjustment on CO and HC emissions 4-2
4-2. Cost and effectiveness for Several Tune-Up Inspection and/or Maintenance
Approaches 4-8
4-3. Cost and Effectiveness for Several Tune-Up Inspection and Maintenance
Approaches Using Dynamometers 4-10
4-4. Effect of Vehicle Mode on Emissions 4-14
5-1. Summary of Opinion of Proposed Technical Approaches to Control Emis-
sions from Automobiles and Other Four-Stroke-Cycle, Spark-Ignited Engines. 5-15
5-2. Evaluation of Proposed Technical Approaches to Control Emissions from
Automobiles and Other Four-Stroke-Cycle, Spark-Ignited Engines 5-17
5-3. Evaluation of Proposed Technical Approaches for CO and HC Control for
Two-Stroke-Cycle, Spark-Ignited Engines 5-19
5-4. Summary of Opinion of Proposed Technical Approaches to Control NOX
Emissions from Diesel Engines 5-20
5-5. Evaluation of Proposed Technical Approaches to Control NOX Emissions
from Diesel Engines 5-21
5-6. Average Initial Cost Ranges of Emission Control Systems (Nonincremental)
to Consumer 5-22
7.1. Emission Data for Chrysler Turbine Car - Cold-Start, Composite-Cycle,
Dynamometer Tests 7-4
7-2. Data on Several Automotive Steam Engines Either Built or Studied
Since 1950 7-9
7-3. Emission Data for External Combustors Associated with Stirling Engines and
Steam Engines 7-10
8-1. Average On-the-Road Emission Rates for Gasoline-Powered Motor Vehicles. . 8-2
8-2. Factors for Estimating Vehicle Miles of Travel 8-2
8-3. Emission Factors for Aircraft Below 3,500 Feet 8-3
8-4. Emission Factors for Diesel Engines 8-3
xiv
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SUMMARY
This document considers the techniques for
the control and prevention of the emission of
carbon monoxide (CO), nitrogen oxides
(NOX), and hydrocarbons (HC) from all types
of vehicles. This approach has been pursued
because measures taken to reduce emissions
of one contaminant may affect emissions of
another. Although these mobile sources emit
other contaminants, the discussion in this
document is restricted to those cited above.
Transportation in general is a major source
of CO, NOX, and HC. In 1968 estimated emis-
sions from vehicles in the United States were
64 million tons of CO, 8 million tons of NOX,
and 17 million tons of hydrocarbons. The pri-
mary mobile source of these emissions is the
gasoline-powered motor vehicle. Other signifi-
cant sources are diesel-powered vehicles and
aircraft. Lesser sources are vessels and boats
operating on inland waterways, off-road util-
ity and recreational vehicles, construction
equipment, motorcycles, power lawn mowers,
and other utility tools.
Emissions from a gasoline-powered vehicle
without any emission control systems origi-
nate from the fuel tank, carburetor, crank-
case, and engine exhaust. The exhaust is the
source of almost all CO and NOX and more
than half of the HC. Formation of the three
in the combustion chamber is influenced by
such factors as air-fuel ratio, ignition timing
and quality, intake-manifold vacuum, engine
compression ratio, engine speed and load, fuel
distribution between cylinders and within a
cylinder, coolant temperature, and combus-
tion chamber configuration and deposits.
Emission constituents can react chemically
after release into the atmosphere. Several
reactivity indexes &ave been proposed and are
used to evaluate and quantify the tendency of
certain HC to react photochemically.
LEGISLATIVE PROGRESS
The Clean Air Act, as amended, is the legis-
lative basis for the Federal air pollution con-
trol program for new motor vehicles; how-
ever, California pioneered with legislation in
this area in 1947. Initial legislation by the
Federal Government was in 1955 with the
enactment of the Air Pollution Control Act.
Subsequent legislation resulted in mandatory
installation of crankcase controls on all new
cars sold in California beginning in 1963, and
on new cars sold nationwide beginning with
the 1968 models. The automobile manu-
facturers, however, had voluntarily installed
these devices on all new cars sold in California
beginning with the 1961 models and on new
cars sold nationwide beginning with the 1963
models. Exhaust emission standards for HC
and CO, applicable to new cars sold in Cali-
fornia, became effective with the 1966 model
year. Federal regulations prescribed the same
standards for new light-duty vehicles sold
nationally beginning with the 1968 models,
and more stringent standards beginning with
the 1970 models. Federal regulations also pre-
scribe standards for evaporative HC emissions
beginning with the 1971 models.
Federal standards for new vehicles will
cause a decrease in HC and CO emissions be-
yond 1980 in spite of the increase in vehicle
population. Nitrogen oxide emissions, how-
ever, will continue to increase at a rate aug-
mented by efforts to control CO and HC
emissions, unless NOX emissions are specifi-
cally controlled. Prior to 1970, exhaust emis-
sion regulations for light-duty vehicles were
expressed in terms of concentrations, but be-
ginning with the 1970 standards, mass units,
considered to be more equitable for various
vehicle sizes, are being used.
xv
-------
Although the Federal Government has
specifically preempted the authority to set
emission standards for new vehicles, a special
waiver provision permits the State of Cali-
fornia to establish and enforce more restric-
tive standards and procedures than the nation-
al standards. California has already established
standards for NOX beginning with 1971
models, becoming more stringent in 1972,
and still more stringent in 1974. The Cali-
fornia standards for HC in 1972 are also more
strict than existing Federal standards. Sta'te
standards for evaporative emissions became
effective in California beginning with 1970
models.
Automobile manufacturers may request
that prototype new vehicles be certified as
complying with established emission stand-
ards, before production vehicles of substan-
tially the same construction are sold. The
National Air Pollution Control Administra-
tion (NAPCA) maintains its principal labor-
atory for this purpose in Ypsilanti, Michigan,
where prototype new vehicles can be certified
and vehicles in public use are checked to de-
termine the durability or continued effective-
ness of control devices and systems in service.
A surveillance program conducted by the
State of California indicates that the effective-
ness of control systems for HC and CO de-
creases in service, but that they are becoming
generally more effective with succeeding years
(although not significantly for HC in 1968
and 1969) even though applicable CO and HC
emission standards have not changed for the
vehicles surveyed.
STATE EMISSION CONTROL PROGRAMS
Federal authority for the control of vehicu-
lar emissions ends with the sale of new
vehicles. States should be encouraged to take
action to ensure the continued operation and
efficiency of emission control systems and
other automotive systems that affect emis-
sions. Reduced effectiveness of control sys-
tems after they leave the manufacturer may
be due to a number of causes, including gross
malfunction, improper adjustment, and delib-
erate removal or inactivation.
A state may determine that its air quality
in certain areas is such that a state control
program for vehicle emissions is necessary to
augment the degree of control provided by
the Federal standards for new cars sold since
1968. Options available to the states, such as
inspection and maintenance programs may re-
duce CO and HC exhaust emissions.
Other methods are available to check
crankcase control devices and may be consid-
ered in addition to exhaust inspection. Future
vehicles will be equipped with evaporative
control systems. Inspection and maintenance
of these may be desirable, but little informa-
tion on possible programs is currently avail-
able.
States should select methods for reducing
vehicular emissions for both the control of
existing air pollution and the prevention of
future air pollution. Many practical difficul-
ties may arise in implementing a statewide in-
spection and a maintenance system, but
experience now being obtained by several
states should be of assistance.
Five programs of the Coordinating Re-
search Council, which are concerned with sur-
veillance, maintenance, and inspection, are of
particular significance to this document, even
though the bulk of information generated by
them will not be available until 1971 or 1972.
These are Cooperative Air Pollution Engineer-
ing (CAPE) Projects 14 through 18.
Although it has been shown that various
inspection and maintenance programs can re-
duce emissions of CO and HC, additional data
are needed to demonstrate the cost and
cost-effectiveness of such programs in prac-
tice.
In addition to inspection and maintenance
of vehicles, other actions that may assist in
reducing emissions from motor vehicles in-
clude the following:
1. Substitution of public transporta-
tion, in part, for the private auto-
mobile in urban areas.
2. Application of exhaust emission con-
trol devices (which, reportedly, will
xvi
-------
be available soon) to pre-1968 (pre-
exhaust-controlled) light-duty ve-
hicles.
3. Planning of freeways and traffic con-
trol systems to minimize stop- and
go-driving and thus affect emissions.
States may wish to consider long-range
planning with respect to vehicle emissions.
Some options of this type are listed below:
1. Planning for emergency actions to re-
duce vehicular emissions during peri-
ods when unfavorable weather condi-
tions create an air pollution emer-
gency.
2. Planning for governmental certifica-
tion of maintenance and inspection
personnel to protect the public from
mechanics who inadvertently cause
an increase in vehicular emissions
through maladjustment or improper
maintenance of engine components.
As an aid in estimating the quantity of
vehicle emissions in a certain region, a pro-
cedure developed by the National Air Pollu-
tion Control Administration is available for
use by states or communities. It requires only
information concerning vehicle registrations
or vehicle miles to arrive at estimated emis-
sions.
EMISSION CONTROL SYSTEMS
Emission control systems in use on cur-
rent-model motor vehicles include positive
crankcase ventilation systems (in which
vapors are routed to the fuel induction sys-
tem) and exhaust emission control systems
(and evaporative controls in California begin-
ning with 1970 models). The exhaust controls
are of two general types and reduce emissions
either by oxidizing CO and unburned HC in
the exhaust system or by minimizing their
quantities emanating from the engine cylin-
ders. The air injection system was used on
some 1968 and 1969 domestic models and
consists of employment of an air pump to
inject air into the exhaust manifold at each
exhaust valve. The second commonly used
approach for controlling exhaust CO and HC
is currently more prevalent and consists of
engine modifications to minimize formation
of contaminants in the cylinders. This ap-
proach consists of designing engines with
improved air-fuel mixing and distribution
systems and tailoring ignition characteristics
for optimum emission control.
Evaporative controls, required on new cars
in California beginning with 1970 models and
nationally in 1971, collect vapors from the
fuel tank and carburetor and vent them either
to the crankcase or to an activated-carbon
canister. In either case, the collected vapors
are eventually returned to the fuel induction
system and burned in the engine.
Control systems for NOX emissions are
under development. Some of the technical
approaches being considered are exhaust gas
recirculation and catalytic reduction. Since
systems incorporating these approaches have
not been produced in large numbers, accurate
data on costs are not available.
FUEL MODIFICATION
It is sometimes possible to alter emissions
of CO, NOX, and HC by modifying the volatil-
ity of the fuel, its constituent hydrocarbon
types, or its additive content.
The use of liquefied petroleum gas (LPG),
liquefied natural gas (LNG), and compressed
natural gas (CNG) as fuels for conventional
vehicle engines is being considered and
appears promising. Use of these fuels, how-
ever, involves problems of fuel distribution
and fuel storage and fairly high installation
and engine modification costs. Supplies of
these fuels are also very limited compared to
currently used vehicle fuels.
State governments may wish to encourage
use of specific mobile power sources known
for their low emissions. These include the
automotive gas turbine, the steam engine,
electric drives, the free-piston engine, the
Stirling engine, and the stratified-charge
engine.
xvii
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CONTROL TECHNIQUES FOR CARBON
MONOXIDE, NITROGEN OXIDE, AND HYDROCARBON
EMISSIONS FROM MOBILE SOURCES
1. INTRODUCTION
Pursuant to authority delegated to the
Commissioner of the National Air Pollution
Control Administration, Control Techniques
for Carbon Monoxide, Nitrogen Oxide, and
Hydrocarbon Emissions from Mobile Sources
is issued in accordance with Section 107(c) of
the Clean Air Act as amended (42 U.S.C.
1857-18571).
The predominant source of carbon
monoxide (CO), nitrogen oxide (NOX), and
hydrocarbon (HC) from mobile combustion
sources is the exhaust gas from gasoline-fueled
engines. An example of the difficulties
involved in eliminating exhaust emissions is
portrayed in Figure 1-1. This graph illustrates,
u
i-
8°:
CO
Zco
O LLJ
u
05
u
i
? STOICHIOMETRIC
r
NOV
10 12 14 16 18
AIR-FUEL RATIO
20
22
Figure 1-1. Effects of air-fuel ratio on
exhaust composition."'
for a typical range, that exhaust CO and HC
emissions could be reduced by increasing the
ratio of air to fuel to the point where more air
is present than is required for complete
combustion of the fuel to carbon dioxide and
water (i.e., an air-fuel ratio greater than the
stoichiometric ratio). Maximum emissions of
NOX, however, would occur under such
conditions. At very low air-fuel ratios, the
NOX emissions could be reduced, but high
concentrations of CO and HC would be
produced. At the extremely high air-fuel
ratios where all three emissions could, theo-
retically, be low, operating difficulties such as
misfire and stalling would be encountered
with most commercially available, gasoline-
fueled, internal combustion engines, causing
poor performance and high emissions of CO
and HC.
Various approaches and devices have been
developed, and others are under development
for controlling emissions of CO, NOX, and HC
from mobile sources. These encompass
various principles of operation, degrees of ef-
fectiveness, complexity, and cost. It is the
purpose of this document to present a review
of these control methods and to summarize
Federal and state emission control programs
as they relate to emissions of CO, NOX, and
HC from mobile sources.
The principal mobile sources that generate
CO, NOX, and HC emissions are described
individually. Various techniques to control
such emissions from these sources are review-
ed. Technical considerations of the more
prominent and feasible design modifications,
alternative power sources, fuel modifications,
auxiliary devices, and alternative trans-
portation modes are presented. Sections on
1-1
-------
source evaluation, equipment costs, cost ef-
fectiveness analysis, and current research and
development also are included. Pertinent
references are presented at the end of each
section.
While some data are presented herein on
quantities of CO, NOX, and HC emitted to the
atmosphere from mobile sources, the subject
of the effects of these substances on health
and welfare is considered in the companion
documents listed below:
1. AP-62, Air Quality Criteria for Carbon
Monoxide
2. AP-63, Air Quality Criteria for Photo-
chemical Oxidants
3. AP-64, Air Quality Criteria for Hydro-
carbons
4.Air Quality Criteria for Nitrogen
Oxides*
1. REFERENCE FOR SECTION 1
1. Trayser, D. A. et al. A Study of the Influence of
Fuel Atomization, Vaporization, and Mixing
Processes on Pollutant Emissions from Motor-
Vehicle Power Plants. Battelle Memorial Insti-
tute. Columbus, Ohio. April 30, 1969. p. 16.
*To be issued at a later date.
1-2
-------
2. BACKGROUND INFORMATION
2.1 DEFINITIONS
The following definitions apply to terms
used in this document:
1. "Air carrier fleet" includes all civil-
ian aircraft transporting persons or
property for hire.
2. "Bottom dead center" or "bottom
center" refers to the position of a
piston in an internal combustion en-
gine when it has reached the bottom
(or end) of its travel in the cylinder
during the intake or power strokes.
3. "Blowby" means the leakage of the
air-fuel charge or the combustion
gases past the piston rings and into
the crankcase during the compres-
sion or power strokes in an internal
combustion engine.
4. "Closed-cycle engines" are engines in
which the working fluid is not ex-
hausted to the atmosphere but is
used over and over again.
5. "Combustion chamber" means a
volume inside an internal combus-
tion engine bounded by the cylinder
head, the top surface of the piston,
and the cylinder wall. Within this
volume, the air-fuel mixture is
ignited and burns.
6. "Condenser" is the device in which
vapor is cooled sufficiently to cause
it to change to a liquid phase.
7. "Day" means one 24-hour period of
time.
8. "Diesel Engine" is a compression-
ignition, internal-combustion engine,
which operates on the limited-
pressure thermodynamic cycle and
generally uses a hydrocarbon fuel.
9. "Diurnal breathing losses" means
fuel evaporative emissions as a result
of the fluctuations in temperature to
which the fuel system is exposed
during one day.
10. "Exhaust emission" means sub-
stances emitted to the atmosphere
from any opening downstream from
the exhaust port of a motor vehicle
engine.
11. "External-combustion engine" is an
engine in which the working fluid
(such as steam) is separated from the
products of combustion by a wall or
barrier through which heat must
pass.
12. "Fuel evaporative emissions" means
vaporized fuel emitted into the
atmosphere from the fuel system of
a motor vehicle.
13. "Fuel percolation" refers to the
movement of fuel from the passages
in the carburetor to the carburetor
bore and into the intake manifold as
a result of fuel vaporization, especial-
ly during the hot soak period.
14. "Fuel system" means the combina-
tion of fuel tank, fuel pump, fuel
lines, and carburetor or fuel injection
components, and includes all vents
and fuel evaporative emission control
systems or devices.
15. "General aviation fleet" is a broad
category consisting of all civilian air-
craft except those of the air carrier
fleet.
16. "Heavy-duty vehicle" means a motor
vehicle weighing more than 6,000
pounds gross vehicle weight.
2-1
-------
17. "Hot soak" means the transfer of
heat from hot components of an en-
gine to cooler components such as
the carburetor. The "hot soak"
period begins immediately after the
engine is stopped.
18. "Inspection" is meant to cover a
visual check for the presence of emis-
sion control devices or measurement
of emissions on vehicles, and implies
that adjustment, maintenance, certi-
fication, or some other subsequent
action will be taken if the inspection
shows it to be necessary or appropri-
ate.
19. "Internal-combustion engine" is an
engine in which the products of com-
bustion are the working fluid and
come into direct contact with the ex-
pander (piston or turbine blade).
20. "Lean air-fuel ratio" describes a mix-
ture of air and fuel in which the ratio
of mass of air to mass of fuel is high
compared to a stocihiometric mix-
ture. This term often causes confu-
sion because a high A/F (air to fuel)
ratio indicates a lean mixture.
21. "Lean surge" refers to the tendency
for the power output of an engine to
pulsate or surge because of a lean
air-fuel ratio.
22. "Light-duty vehicle" means a motor
vehicle designed for transportation
of persons or property on a street or
highway and weighing 6,000 pounds
gross vehicle weight or less.
23. "light ends" refers to the more vola-
tile portion of a petroleum fraction,
the material that evaporates first.
24. "Maximum rated horsepower"
means the maximum brake horse-
power output of an engine as stated
by the manufacturer in his sales and
service literature.
25. "Misfire" means that the air-fuel
charge in a cylinder did not ignite
and, therefore, did not supply any
power during the cycle in which the
misfire occurred.
26. "Open-cycle engines" are engines m
which the working medium or fluid
is exhausted to the atmosphere, such
as in noncondensing steam engines
and internal-combustion engines.
27. "Reactivity" is a measure of the
tendency of certain substances to
enter into atmospheric reactions in
the presence of nitrogen oxides and
ultraviolet radiation (sunlight).
28. "Recuperator and Regenerator" are
heat exchangers. They may be used
to preheat combustion air or to heat
or cool working fluids.
29. "Reid vapor pressure" (RVP) is a
composite, empirical value which re-
flects the cumulative effect of the in-
dividual vapor pressures of the dif-
ferent motor fuel fractions. It
provides both a measure of how
readily a fuel can be vaporized to
provide a combustible mixture at
low temperatures, and an indicator
of the tendency of the fuel to vapor-
ize and cause vapor lock at high
temperatures. Determinations of
RVP are made at 100° F with a vapor
to liquid volume ratio of 4 to 1.
30. "Rich air-fuel ratio" describes a mix-
ture of air and fuel in which the ratio
of mass of air to mass of fuel is lower
than would be required to burn the
fuel completely (i.e., lower than that
of a stoichiometric mixture). This
term often causes confusion because
a low A/F (air to fuel) ratio indicates
a rich mixture.
31. "Spark-ignition engine" is an intern-
al-combustion engine, which oper-
ates on the Otto thermodynamic
cycle, in which gasoline fuel is gen-
erally used, the fuel-air mixture
being ignited by an electric arc.
32. "Specific fuel consumption" is a
measure of engine fuel consumption
per unit time at a specified power
level. The units of this expression
2-2
-------
generally used in United States en-
gineering practice are pounds of fuel
per horsepower-hour (Ib fuel/hp-hr).
33. "Stalling" refers to the loss of power
from an engine, either momentarily
or completely, because of some mal-
function or misuse.
34. "Stoichiometric mixture" is a term
used to define an air-fuel mixture
which is theoretically of the correct
ratio to obtain complete combustion
without excess oxygen.
35. "Surveillance" is meant to include
measurement of emissions, on ve-
hicles which supposedly represent
the entire population of vehicles in
an area, possibly on a random spot-
check basis. It is usually used to eval-
uate emissions in the area and/or per-
formance characteristics of vehicles.
36. "System or device" includes any
motor vehicle equipment or engine
modification which controls or
causes the reduction of substances
emitted from motor vehicles or
motor vehicle engines to the atmos-
phere.
37. "Top dead center" or "top center"
refers to the position of a piston in
an internal combustion engine when
it has reached the top (or end) of its
travel in the cylinder during the com-
pression or exhaust strokes.
38. "Working fluid" is the fluid that is
heated either directly or indirectly
and which produces work in the en-
gine expander.
2.2 TYPES AND NUMBERS OF
MOBILE SOURCES
Gasoline-powered motor vehicles constitute
the major mobile sources of CO, NOX, and
HC emissions in the United States. To a far
lesser extent, diesel-powered motor vehicles,
aircraft, railroad locomotives, vessels and
boats operating on inland waterways, off-road
utility and recreational vehicles, heavy con-
struction equipment, motorcycles, power
lawnmowers, and similar utility tools also
contribute. Populations of various vehicles as
of the latest date for which information is
available are contained in Tables 2-1 and 2-2.
The relative contributions of mobile sources
by major categories are included in a table at
the end of Section 2.
Emission characteristics of the gasoline-
powered, light-duty motor vehicle have been
the subject of intensive study with respect to
both the nature and extent of emissions, and
numbers of vehicles and emission character-
istics are well documented. Methods of
controlling emissions from diesel-powered
motor vehicles have been studied, with
particular emphasis on smoke and odorous
emissions. Populations of diesels are fairly
well documented, and standards for CO, NOX,
and hydrocarbon emissions are to be
proposed in California in 1971.
Little has been done toward determining
emission characteristics of locomotive diesel
engines. Numbers of units in service and total
locomotive miles are available from the U. S.
Interstate Commerce Commission.
Characteristics of emissions from outboard
engines are not well documented. Essentially
all, however, are two-stroke-cycle engines, in-
dicating high hydrocarbon concentrations in
the exhaust relative to four-stroke-cycle
engines. Most are run at high power levels
resulting in large exhaust flow rates, since
power output is increased as mass flow rate
through the engine increases. Complete data
on larger commercial vessels that operate on
inland waterways as to types of power-plants
are not available.
Off-road utility t vehicles such as four-
wheel-drive, dune buggies, etc., are compara-
tively few in number and usually powered by
conventional gasoline engines. Heavy con-
struction equipment is powered principally by
diesel engines, but a count of equipment
actually in use is not obtainable. Motorcycle
engines are now predominantly two-stroke-
cycle and, reportedly, are high hydrocarbon
emitters in terms of concentrations and flow
rates for the same reasons that outboard
motors are believed to be. Although the
frontal area of a motorcycle with a rider is
2-3
-------
Table 2-1. POPULATION OF MOBILE SOURCES OF EMISSIONS
IN USE IN THE UNITED STATES
(as of 1968, except as noted)
Vehicle
Passenger cars
Trucks (total)
Trucks
Buses (total)
Buses
Motorcycles
Off-highway wheel type tractors
(contractors)
Wheel type tractors
(except contractors)
Tracklaying tractors
Aircraft (non-military)
Aircraft (non-military)
Aircraft (military)
Locomotives
Ships
Outboard motors
Boats (registered, pleasure)
Boats (registered, pleasure)
Utility tools
Power plant
Gasoline
Gasoline and diesel
Diesel
Gasoline and diesel
Diesel
Gasoline
Gasoline and diesel
Gasoline and diesel
Gasoline and diesel
Gas turbine
Piston engine
Predominantly gas turbine
Diesel
Diesel
Gasoline
Outboard
Inboard
Gasoline
Number in use
83,698,100
16,998,546
416,454(1967)
351,804
65,742(1967)
1,753,000(1966)
21,647a
2,128,914a
245,595a
2,577(1967)
151,111 (1967)
33,749(1967)
27,045
Not available
6,988,000
3,965,502
543,216
Not available
Reference
1
1
2
1
2
3
4
4
4
5
5
5
6
7
8
8
aTotal units manufactured 1959 through first 9 months of 1968 are given.
not large compared to that of an automobile,
the drag coefficient involved is greater than
that for a streamlined vehicle. Thus, fairly
high power levels and associated high mass
flow rates through the engine are required to
maintain high speeds.
2.2.1 Growth History and Projections
Because of their relative importance in the
United States, numbers of motor vehicles and
aircraft in use are well documented. The
numbers of the majority of other mobile
sources are not. Table 2-2 presents data for
1968 populations ,of passenger cars, trucks,
and buses for each of the 50 states. Projec-
tions of vehicle miles are also studied ex-
tensively, and totals for the period from 1960
to 1990 are indicated in Figure 2-1. The total
miles for diesel vehicles are assumed to be
12.1 percent of the total truck and bus miles.
(Total miles minus passenger car miles times
12.1 percent equals diesel miles.)
Example, for 1975:
(1210 x 109-990x 109) 12.1%
= 27 x 109 diesel miles
Numbers of vehicles and vehicle miles are
related in that the average passenger car can
be considered to be driven 9,400 miles per
year. Therefore, dividing total passenger car
miles by 9,400 gives an indication of the
number of cars registered in that year.
Numbers of aircraft in the U.S. air carrier
fleet, by type of power source, for 1960 to
1967, and estimated for 1968 to 1979, are
indicated graphically in Figure 2-2, and
similarly for the U.S. general aviation fleet in
Figure 2-3.
2-4
-------
Table 2-2. 1968 U.S. MOTOR VEHICLE REGISTRATIONS, BY STATES
AS OF THE END OF THE REGISTRATION YEAR5
As of the End of the Registration Year
data do not include publicly-owned vehicles with trie exception of school buses. Publicly-owned
fthicles art estimated to be approximately 1.4 million in 1969.
STATE
Passenger
Ctrl'
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
DisLolCol.
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetta
Michijan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
NewYork
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Totals
1,397,860
80.871
717.376
699,877
9,245 913
987,724
1,322,852
237,177
225,863
3.24S.080
1,895,924
309.730
409,876
4.345. 857
2,190,091
1.328,976
1.000,500
1.333,300
. .. 1.311.154
375.955
1.453.991
2.0S2.000
3.841.135
1.672,214
831,662
1,798,000
311.893
791.794
225.000
272.000
2,956,630
411.218
5.571.921
2,021.021
260. 288
4.714,450
1.173.955
1.088.797
4.828.372
397,448
976.065
2S3.678
1. 748,111
4.752,000
498,608
170,408
1.718,114
1.479.775
610.649
1.731,037
146,103
83.543.093
Truck!
318.404
31.819
204.627
300,060
1.515.613
286,407
132,238
42,491
16,615
435.062
397,000
39,095
70.058
581.130
487.835
329.039
455,000
341,100
336.610
(5,965
203.548
209.000
577.156
379,846
267,536
490.700
154.739
250.829
66,000
41.000
307,932
156,344
597,900
476.145
140.678
538,978
433.996
78.769
663.113
47.347
209,119
122.943
351,223
1.300.425
169.628
27,602
300.816
419.600
153.700
299.523
73,746
19,928.049
Buses*
2.235
442
2.035
4. ICO
5.953
(«)
4.054
9.873
2.315
(')
1,557
14,717
10.612
6.603
6,191
240
6.411
7.550
9,176
3.780
Y.393
5.425
2.094
13.900
20,000
37
7.891
684
l.SOS
22,047
425
7.424
884
2.717
20.717
228
96
4.877
4.600
4.800
11.151
780
241.436
Total Motor
Vehicle)
1.718.499
112.932
924.038
1,004.097
10.761.526
1.274.131
1.461.043
279.668
246.532
3.693.015
2,295,239
344,825
481.491
4,941,704
2,688.538
1,653.015
1.515.500
1.681.003
1,653.955
472,160
1.663,950
2,298,550
4,418.291
2.058,414
1.103.374
2.292,480
466.832
1.047.018
291.000
313.000
3.269.987
569,656
6,183,721
2,517.168
401.003
5,261.319
1.608.835
1,187,374
5,513,532
445,220
1,192.608
407.505
2.102.051
6.079,142
668,464
198,106
2,023,807
1.903.975
769,149
2.041.911
220,629
99,710,578
Taxlcab)'
2.266
278
221
624
4.954
(')
650
()
10.150
7.442
1,750
675
1.545
(»)
'"366
4.623
169
68.300
3,363
1.357
I0>97
1.225
fi49
23t.851
cycles
25.745
5,702
25.220
16.025
362,715
28,594
23,424
3,631
2,613
72,895
29,000
9.632
22.537
89,131
69,031
41,824
35.000
28,200
24.977
6,345
22,119
32,000
120,084
60,516
11,279
39,250
17.175
21.603
13,000
7,000
38.502
14,939
71,700
32.448
9.358
121.248
34.598
31.981
113.612
6,455
12.143
9.663
32.848
96.000
16.575
5,263
25.517
50.950
18.000
76.209
6.820
2,091,096
Trailer) and Semi-trailer) -
Tourist* Commercial
21.350
11.814
67,177
49,420
63,161
150,267
95.000
8,655
60.230
96.101
144,115
29.836
19,000
19.400
92.400
77.895
255.625
28.450
91.996
8.800
64.453
24,208
7.755
98,749
37,352
95,147
47.922
11,862
2,010
55.000
52.72;
127.250
27,000
20.470
14.398
2.077.195
43.6S3
2.277
66,651
77,896
15,471
'iiess
306.095
31,000
890
40,717
241,670
53.576
140.993
110.000
16.800
44.560
480,235
66.276
14.099
844
21.000
53.935
26.592
1.127
274.011
27.028
21.192
107,764
16.621
23.555
500,000
3,084.420
Total
65.033
14.091
133.828
85,132
1,099.330
127.316
78.632
20.334
1,685
456.382
126,000
9,545
100.947
337.771
197,691
170,829
129,000
36.200
136.960
131.475
74.457
158.000
558.130
322,101
42,549
175,700
48,185
92,840
29,800
35,000
118,388
50,800
314,400
224,697
6.882
372,760
64.380
116.339
155,686
27,076
28,483
43,785
25,565
555.000
33,963
22.271
112,952
240,075
41,000
57,285
46.710
7,683.103
1Includes Uxieabs. *Includes school buses whether fee or non fee. sTnr-ludcd with passenger car?, but shown separately for your convenience. lucludes house or
c*mp trailer and light 2-whecl trailers pulled by ear or utility truck. 'Included with passenger cars. Included with truvks.
NOTE: In the above tabulation we (Automotive Industries Magazine) have endeavored to make as accurate a count as existing
conditions permit. This census is compiled from material secured direct from the state motor vehicle commissioners. Wherever
possible duplications occasioned by transfers and non-resident registrations have been eliminated. Data are for the registration year,
even though this necessitates partial estimates. In the case of those states whose registration year ends February or March of the
following year, or whose data are not compiled by the time we go to press. (Courtesy of Automotive Industries Magazine.)
2.2.2 Power Plants
The most common power plant in this
country for mobile use is the four-stroke-
cycle spark-ignited internal-combustion en-
gine. It is used to a large extent in ground
vehicles. Its largest application is in passenger
cars and light-duty trucks. Figure 2-4 shows
trends in United States passenger car engine
design. The next most common power plant is
the four- and two-stroke-cycle, compression-
ignition, internal-combustion engine, which is
frequently referred to as the diesel. It is used
to propel large trucks, buses, locomotives,
ships, and heavy construction equipment.
The third type of power plant commonly
used is the aircraft gas-turbine engine. This
engine is rapidly replacing the spark-ignition
engine on large commercial and military air-
craft, although the latter engine is still the
primary power source for light aircraft. The
gas turbine is used to a very limited extent in
experimental or test installations on railroad
locomotives in passenger service only. Use of
the gas turbine to power large truck-tractors
2-5
-------
2.000
y
i
UJ
1,500
1,000
500
PASSENGER CARS, TRUCKS, AND
BUSES; GASOLINE- AND
DIESEL-POWERED
PASSENGER CARS
1960
1970
1980
1990
YEAR
Figure 2-1. Past and projected United States vehicle miles.9 (Curve-fitted data for medium
estimates in Reference 9)
4.UUU
3,000
1-
<
o:
u
a:
<
>i 2,000
LJ_ *
0
o:
CD
^
13
Z
1,000
0
II.-
~ .x
x .-*
.«
~ X*'*' ~
REPORT DATE ^ V ****** X*** ~~
/* f
S / s
.' / /
/ '
//
\ : t ---TOTAL AIRCRAFT
_ ^^^ / / TOTAL TURBINE- _
^N / / ENGINE AIRCRAFT
~ N/ / TURBOJET AND ~~
..Aj/ TURBOFAN
_ ,S / \ '"TURBOPROP _
...-" / S PISTON-ENGINE
.'** X ^i AIRCRAFT
? I I I
1960 1965 1970 1975 1980
YEAR
Figure 2-2. Composition of United States
air carrier (commercial) fleet.4
-o
c
o
o
-£
en
LL
o
Qi
too
50
I
-TOTAL AIRCRAFT
SINGLE-ENGINE ,
PISTON X
MULTI-ENGINE x*
PISTON
TURBINE .'
/X
* .*
X ..*
-^*^ .»
X*
1960
1965
1970
YEAR
1975
1980
Figure 2-3. Composition of United States
general aviation fleet.4
2-6
-------
-------
which drives the car through a suitable drive
train.
The four strokes of the four-stroke-cycle
engine are:
1. Intake Descending piston draws
charge through open inlet valve filling
cylinder space.
2. Compression Rising piston compres-
ses charge against closed valves, spark
plug fires, starting combustion.
3. Expansion Burning mixture expands,
forcing the piston down. This is the
one stroke of the four that deliveres
power.
4. Exhaust With the exhaust valve
open, the rising piston forces products
of combustion out of cylinder.
Two-stroke-cycle engine operation is in-
dicated by Figure 2-6. The poppet valves are
usually replaced by ports, especially on small
engines, which are opened and closed by the
movement of the piston, although two-
stroke-cycle engines sometimes use valves to
open and close the exhaust ports. Two-
stroke-cycle engines are not used on any pas-
senger cars manufactured in the United
States; they are, however, commonly used for
motorcycles and motor scooters, small gaso-
line utility engines, and outboard motors. The
phases of the two-stroke cycle are:
1. Intake - With transfer and exhaust
ports open, air under slight pressure in
crankcase flows into engine cylinder.
2. Compression - Rising piston covers
ports, compresses charge in cylinder,
creates vacuum in crankcase. Spark
plug fires.
3. Expansion - Burning fuel expands,
pushing piston down. Air flows into
crankcase, to be compressed as the
piston descends.
4. Exhaust - Descending piston uncovers
exhaust port. Slight pressure builds up
in crankcase, enough to move air into
cylinder.
Some two-stroke-cycle engines are fitted
with an air-box that serves the same purpose
as the crankcase in the preceding discussion.
The carburetor used on current four-stroke-
cycle, light-duty vehicles, provides the cor-
rect air-fuel ratios for best performance and
fuel consumption across the vehicle speed and
load range. The air-fuel mixture in the engine
must be within a rather narrow band of ratios
TRANSFER IP
PORT FROM tyi
TH CRANKCASE /
/'t\ TO CYLINDER /*
W\\ /»
Si
PHASE 1.
INLET PORT Jj^
TO CRANK-*^%T;
CASE FROM M
OUTSIDE //>
EXHAUST
PORT
PHASE 2.
PHASE 3.
PHASE 4.
2-8
Figure 2-6. Schematic of two-stroke-cycle engine.
-------
in order to be combustible. This band general-
ly encompasses air-fuel ratios of between
about 9 and 17 pounds of air per pound of
fuel. Best fuel economy is obtained when all
cylinders receive a ratio slightly leaner than
stoichiometric, but best power output is
obtained at ratios that are slightly fuel-rich.
(Figure 2-7).
LU
O
Q_
1 1 1
MAXIMUM
^^
&
^
f
' *- POWER
/ P'
* ^
&.
M
tt-
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*« CD
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1 1 1
1 1 1
d POWER
*^ -^
s
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LU
H
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CO
FUEL
CONSUMPTION
*^
BEST ECC
1 1 1
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to
10 11 12 13 14 15
AIR-FUEL RATIO
16
17
Figure 2-7. Effect of air-fuel ratio on power
and economy.13
It is desirable to be able to change the air-
fuel ratio to suit specific driving require-
ments. When power is needed, as in ac-
celeration, a richer mixture is desired than
during steady-state cruise, where a leaner
mixture can be used to achieve greater
economy. At open-throttle conditions during
low speed acceleration, the maximum octane
requirement of an engine can be lowered by
enriching (reducing) the air-fuel ratio. This is
a phenomenon that is considered in
carburetor and engine design.
The ignition system is designed to ignite
the air-fuel mixture at the precise instant at
which conditions are optimum for best
power. As engine speed increases, the time of
ignition must be advanced to a point on the
compression stroke before top dead center
(i.e., earlier). Again, a compromise must be
made under high-load conditions to reduce
octane number requirement. To accomplish
this, the spark is retarded slightly (i.e., later in
the compression stroke) from best power.
The distributor shaft has centrifugal
weights attached to it that advance the spark
as engine speed increases. A pressure
diaphragm, subjected to carburetor bore
vacuum, senses engine air-flow and advances
the spark as air-flow increases. Through these
systems, the distributor senses engine speed
and load and provides the proper spark
advance for various driving conditions.
The exhaust system of the engine is made
up of a manifold connected to each cylinder
exhaust port, and piping to carry the gases to
the rear of the vehicle, where they are dis-
charged to the atmosphere. At some point be-
tween the manifold and the discharge, a muf-
fler is used to quiet the exhaust noises.
2.2.2.2 Dz'ese/ (Compression-Ignition)
Engine
Diesel (or compression-ignition) engines use
either the two- or the four-stroke cycle, as
described for the spark-ignition gasoline
engines. The method of ignition and the fuel
systems differ for the diesel engine, however.
The fuel does not enter the cylinder as a
mixture with air, but is injected under high
pressure into the chamber in precise quanti-
ties through precision nozzles. As the piston
nears the top of the cylinder on the compres-
sion stroke, the air charge is compressed to a
high pressure and a high temperature. Fuel
injected into this high temperature air ignites
without the aid of a spark. Ignition timing is
controlled by timing the injection of the fuel.
Unlike the gasoline engine, in which power
output is regulated by airflow control, power
output of the diesel engine is controlled by
the amount of fuel injected for each cycle.
2-9
-------
When the engine is operating within its
normal design limits (maximum rated power
or less), the overall air-fuel mixture is much
leaner than for a spark-ignition engine. Air is
always delivered to the cylinders in excess of
quantities necessary for complete combustion
of the fuel. Because of this excess air, and the
high temperature in the combustion chamber,
the diesel engine is inherently low in CO emis-
sions.
The advantages of the diesel engine, i.e.,
relatively low emissions of CO and relatively
good fuel economy, are offset by other
factors that have discouraged its use in pas-
senger cars. These include:
1. High weight-to-power ratio The high
compression ratio necessary to achieve
compression ignition requires more
rugged construction for the diesel
than for the spark-ignition engine.
2. Noise High rates of pressure-rise
during combustion make the diesel
noisy relative to a spark-ignition
engine.
3. Large size for comparable power - The
maximum speed of diesel engines is
generally lower than that of gasoline
engines because of the difficulty in
getting efficient combustion at high
speeds. Thus, a larger diesel engine is
required to produce the same amount
of power that could be obtained from
a smaller, higher-speed, spark-ignition
engine.
4. Cost - The requirement for rugged
engine construction and precision
fuel-injection equipment causes the
diesel to be more expensive to
manufacture than the spark-ignition
engine.
5. Odor and smoke - Exhaust odor and
smoke from diesel engines are general-
ly considered more objectionable than
those from spark-ignition engines.
2.2.2.3 Aircraft Gas Turbine Engine
Fundamentally, a gas turbine engine may
be considered as consisting of four main
sections: (1) a compressor, (2) a burner, (3) a
2-10
turbine, and (4) a tailpipe (possibly having a
jet nozzle). A conventional turbojet engine is
illustrated diagrammatically in Figure 2-8a.
The air entry section is fitted with a diffuser,
and supplies air to a rotary compressor of the
centrifugal or axial type, in which the air is
compressed and delivered at a higher pressure
and a higher temperature to one or more com-
bustion chambers. There fuel is added and
burned in primary combustion air, increasing
the gas temperature to a maximum value. Sec-
ondary air is added to cool the gases, which
then expand through a turbine wheel, con-
verting some portion of the available energy
of the gases into work. The work produced by
the turbine must be sufficient to drive the
compressor at the desired speed of rotation in
order to produce the required air-flow for the
thrust required. The energy available in the
combustion gases far exceeds the work re-
quirement of the compressor. The gases leave
the turbine wheel with a large proportion of
energy still available, and the gas pressure is
still well above atmospheric. A suitably-
designed exit nozzle releases the gases at high
velocity, their momentum providing engine
thrust.
Turboprop engines (Figure 2-8b) function
in a similar manner, except that the jet thrust
is held to a minimum. These relatively large
turbines are designed to extract all of the
power possible from the expanding gases to
rotate the propeller and produce thrust.
The turbofan engine (Figure 2-8c) is much
the same as the turboprop except that the
propeller is replaced by a duct-enclosed,
axial-flow fan. Engine thrust is developed by
both the spinning fan and the jet thrust of the
exhaust gases.
Turbojet engine performance is best at high
altitude and high speed; fuel consumption is
high at low airspeeds. The turboprop develops
high thrust at low altitude, and has lower fuel
consumption than the turbojet for com-
parable thrust. The turbofan lies between the
two for low altitude thrust and fuel consump-
tion, and is quieter than the turbojet.
-------
TURBOFAN
Figure 2-8. Views of three types of aircraft
gas-turbine engines.14
2.2.3 Emissions
Contaminant emissions from a motor vehi-
cle without emission controls originate from
four sources: (1) the carburetor, (2) the fuel
tank, (3) the crankcase, and (4) the engine
exhaust. Hydrocarbon emission from the first
source is the result of fuel vaporization during
"hot soak" after shutdown. Vaporization
from the tank occurs primarily when the fuel
temperature in the tank increases. Crankcase
emissions are the result of blowby past the
piston rings. These emissions, unless control-
led, escape to the atmosphere through the
road draft tube or the crankcase ventilation
cap. Hydrocarbons and CO appear in the ex-
haust gas as products of incomplete com-
bustion. Oxides of nitrogen result from the
reaction of the nitrogen and oxygen contain-
ed in the combustion air at the high tem-
perature prevailing during combustion.
Figure 2-9 shows the approximate distri-
bution of the emissions from a motor vehicle
without any emission control devices.15
2.2.3.1 Nature and Formation of Emissions
When a hydrocarbon fuel is burned with
the amount of air containing enough oxygen
2-11
-------
I
FUEL TANK AND
CARBURETOR EVAPORATION
HC 20%
CRANKCASE
BLOWBY
HC 20%
Figure 2-9. Approximate distribution of emissions by source for a vehicle not equipped with
any emission control systems.15
to oxidize it completely, the following basic
reaction might be assumed to occur:
1.00 CHj 85 + 1.460 O2 + 5.50 N2 ->
0.925 H2O + 1.00 CO2 +5.50 N2
This reaction incorporates the following as-
sumptions:
1. Most hydrocarbon fuels are accurately
represented as consisting of 1.85
hydrogen atoms per carbon atom
(CHL85).
2. The volume ratio of nitrogen (N2) to
oxygen (O2) in the air is 3.76:1.
3. The fuel is burned completely to
water (H2O) and carbon dioxide
(C02).
4. Nitrogen is inert and does not react
with any other substances in the com-
bustion chamber.
2-12
Assumptions 1. and 2. are quite true in
practice. The formation of CO, NOX, and HC
in the combustion process indicates that as-
sumptions 3. and 4. are not wholly correct.
2.2.3.1.1 CO and hydrocarbons. Combus-
tion of the carbon in the fuel proceeds
(simplified) through the following steps:
2C + O2 -» 2 CO
2 CO + O2 -» 2 CO2
The first reaction proceeds at a much greater
rate than the second. Hydrogen in the fuel is
oxidized to H2O quite easily, provided suf-
ficient oxygen is available locally for com-
bustion. Poor distribution and mixing of fuel
and air (which is likely to occur to some
extent when fuel droplets rather than fuel
vapor are present) can result in incomplete
combustion, and produce CO that is emitted
-------
in the exhaust gases. Although the overall air-
fuel mixture may be stoichiometric, local con-
ditions at a particular point in a combustion
chamber may be far from stoichiometric.
Such conditions of poor distribution are also
conducive to increased hydrocarbon emis-
sions.
Obviously, a fuel-rich (low air-fuel ratio)
mixture introduces more fuel into the com-
bustion chamber than can be completely
burned, increasing emissions of CO and
hydrocarbons. Also, an air-rich (high air-fuel
ratio) mixture would provide excess air to
partially offset the increased emissions that
result from poor distribution and vapor-
ization. The relatively large amount of excess
air used in the diesel and gas turbine engines is
the dominent reason for their relatively low
emissions of CO and hydrocarbons.
Other factors may also contribute to in-
creased emissions. One of these is the quench-
ing of the flame at the relatively cool com-
bustion chamber boundaries. Quenching can
occur even if the fuel is perfectly vaporized
and distributed throughout the chamber and
is well established as the most significant
mechanism leading to exhaust hydrocarbon
emissions in properly designed spark-ignition
engines.16
Gross malfunction of the ignition or fuel
induction systems can increase emissions of
CO and hydrocarbons from spark-ignition
engines. A misfire allows an entire air-fuel
charge to be emitted. An automatic choke
sticking closed or a very dirty air cleaner
element can reduce air-fuel ratio, generally in-
creasing emissions of CO and hydrocarbons.
Chemical equilibrium phenomena should
be considered in a discussion of the formation
of CO and hydrocarbons. Combustion reac-
tions are somewhat reversible at high tempera-
tures, indicating that products and reactants
can exist in equilibrium at high temperatures.
This partial reversal of combustion reactions
at high temperature is known as dissociation.
If the equilibrium mixture is cooled rapidly
(as it is by rapid expansion), it may be
"frozen", meaning that its composition is
unable to change, even though equilibrium
considerations indicate that dissociation
should be greatly reduced as the temperature
is reduced. The rapid lowering of temperature
and the accompanying decrease in the rate at
which the mixture approaches the new low-
temperature equilibrium, are responsible for
the freezing of the composition of the mix-
ture.
2.2.3.1.2 NOX. Equilibrium consider-
ations are very important in the discussion of
the formation of NOX. The reaction
N2 + O2 ^ 2 NO
indicates that nitrogen may be oxidized to
nitric oxide (NO) and exist in equilibrium with
N2 and ©2- The concentration of NO which
may exist (theoretically) is significant only at
high temperatures. This means that N2 and
O2 do not unite to form a significant con-
centration of NO at low temperatures. Rapid
cooling (as discussed in Section 2.2.3.1.1) can
occur, however, and "freeze" the mixture
with a relatively high concentration of NO.
Generally, the higher the flame temperature
to which air is exposed, the higher will be the
resulting NO concentration after rapid
cooling. The rate of reaction of NO back to
N2 and ©2 is very low at low temperatures,
even though equilibrium considerations favor
the reaction.
It is essential to understand the difference
between chemical kinetics, which involve the
rate at which chemical reactions proceed
(which is influenced by temperature), and
chemical equilibrium, which involves theoret-
ical concentrations of products and reactants
as a function of temperature (and pressure for
some reactions), without any consideration of
the time which may be required to achieve
equilibrium as conditions of temperature (and
pressure) change.
From the preceeding discussion, it is ap-
parent that NOX emissions could be mini-
mized by:
1. Reducing the flame temperature
during combustion of air-fuel mix-
tures.
2-13
-------
2. Providing insufficient oxygen to
oxidize N2-
3. Expanding (cooling) the mixture of
combustion products at a slow rate
which would allow NO to reform N2
and O2-
One of the most effective methods for
reducing both flame temperature and the
amount of oxygen available is to reduce the
air-fuel ratio. A fuel-rich mixture burns at a
lower temperature than a stoichiometric mix-
ture because heat that could otherwise be
used to heat the gases in the combustion
chamber must be used to heat excess fuel.
Since oxidation of carbon to CO occurs at
a greater rate than oxidation of CO to CO2,
and because combustion of a mole (specific
number of molecules) of carbon to CO
releases less heat than combustion of a mole
of CO to CO2, burning of a fuel-rich mixture
results in a lower heat release than burning of
a stoichiometric mixture. The overabundance
of fuel leaves little oxygen available to react
with nitrogen. This rich-mixture approach
would minimize NOX emissions at the
expense of greatly increased emissions of CO
and hydrocarbons unless further measures
were taken to control them specifically.
When a high air-fuel ratio charge is burned,
much oxygen is available for oxidation of N2,
but the effect of low-flame temperature^
resulting from the heating of excess air that
does not enter into the combustion reactions-
predominates, and reduces NOX emissions.
Presently available spark-ignited, gasoline-
fueled engines exhibit poor performance
under such conditions, however, probably be-
cause of the low velocity of flame prop-
agation through a fuel-lean mixture, resulting
in reduction of thermal efficiency. Operation
at fuel-lean conditions can damage exhaust
valves, and may cause backfiring through the
carburetor at very high air-fuel ratios.
Other engine variables influencing the NOX
concentration in spark-ignited engine exhaust
gas are:! 7 l 9
1. Spark timing Advancing the spark
usually increases the oxides of
2-14
nitrogen by increasing peak com-
bustion temperature.
2. Engine speed Increasing speed while
advancing the spark and at constant
or increasing torque (decreasing
manifold vacuum) promotes NOX
formation with either lean or rich
mixtures by allowing less time for
the products of combustion to
expand and approach equilibrium at
a lower temperature. Increasing
engine speed, however, while main-
taining constant power and
decreasing torque may tend to
decrease NOX formation by depres-
sing combustion pressure and tem-
perature. The fact that power is
proportional to the product of
torque and speed suggests that it
may be possible to "optimize" the
engine characteristics for the lowest
NOX emissions at a given power
level.
3. Compression ratio Higher compres-
sion ratios, which increase peak
combustion pressure and tempera-
ture, favor formation of NOX, parti-
cularly under lean-mixture con-
ditions.
4. Fuel distribution - NOX concentra-
tion for a particular cylinder depends
on the air-fuel ratio in the cylinder.
Poor mixture distribution resulting
in a near stoichiometric mixture in
only a few cylinders of an engine
causes a relatively large increase of
NOX for the entire engine.
5. Coolant temperature Raising the
coolant temperature tends to
increase NOX concentration.
6. Combustion chamber deposits - A
greater deposit accumulation may
increase NOX concentration.
The high compression ratio of the compres-
sion-ignition (diesel) engine results in a high
combustion temperature conducive to NO
emissions. The gas turbine may prove to have
-------
the inherent capability for low NOX emis-
sions.20 Combustion at fuel-lean conditions
in the primary zone, followed by dilution of
combustion gases with secondary air at an
optimum rate in a long combustion chamber
to approach equilibrium at the turbine inlet
temperature, may greatly reduce NOX emis-
sions. The cooling of gases at an optimum rate
in a reciprocating-piston, internal-combustion
engine is difficult to achieve because engine
speed inherently sets the rate of expansion.
2.2.3.2 Emission Reactivity
A discussion of emissions from mobile
sources would not be complete without some
reference to the concept of reactivity. This
term describes the tendency of organic sub-
stances of certain chemical formulas and
molecular structures to enter into chemical
reactions in the presence of NOX and
ultraviolet radiation (sunlight) in the
atmosphere more readily than substances of
other formulas and structures.
Although rigid criteria of reactivity or the
assignment of precise indexes of reactivity are
not offered for the various organic substances
at this time, several relative chemical reactivi-
ty scales have been suggested.21"30 While
these scales vary somewhat in detail, general
trends are similar. In general, paraffinic
hydrocarbons and acetylene exhibit the
lowest reactivity. At the opposite extreme,
olefinic hydrocarbons represent the most
reactive class of hydrocarbons. References to
hydrocarbon or organic emissions in this
document refer to total emissions rather than
reactive emissions, unless otherwise noted.
2.2.3.3 Emission Quantities
Estimates of nationwide emissions of CO,
NOX, and HC for the year 1968 are presented
in Table 2-3. All major sources are included to
Table 2-3. 1968 NATIONWIDE EMISSION ESTIMATES15
[106 tons/year]
Category
Transportation
Motor vehicles
Gasoline
Diesel
Aircraft
Railroads
Vessels
Nonhighway use of motor fuels
Fuel combustion in stationary sources
Coal
Fuel oil8
Natural gas"
Wood
Solid waste disposal
Industrial processes
Miscellaneous
Total
HC
15.2
0.4
0.3
0.3
0.1
0.3
0.2
0.1
n
0.4
1.6
4.6
8.5c'd
32.0
CO
59.0
0.2
2.4
0.1
0.3
1.8
0.8
0.1
n
1.0
7.8
9.7
16.9C
100.1
NOX
6.6
0.6
n
0.4
0.3
0.3
4.0
1.1
4.7
0.2
0.6
0.2
1.7C
20.7
alncludes kerosene.
^Includes natural gas processing plants and transmission facilities, and liquefied
petroleum gas (LPG).
clncludes emissions from agricultural burning, forest fires, structural fires, and
coal refuse fires,
"Includes organic solvent evaporation and gasoline marketing.
n - negligible.
2-15
-------
indicate the contribution of transportation
relative to other sources. It is obvious that
mobile sources are responsible for major
portions of emissions of concern in this doc-
ument. Estimated total tonnages for the three
emissions from gasoline-powered passenger
cars and trucks as a function of year are
shown graphically in Figures 2-10 through
2-12. The effects on the quantity of a single
emission by imposition of a constant emission
standard, assimilation of vehicles with emis-
sion control systems into the composite vehi-
cle population, and vehicle population growth
are illustrated by the curves for CO and
hydrocarbons. Increases in emissions from 1960
to 1967, due to increase in vehicle pop-
ulation, are arrested and turned down during
the period of 1967 to about 1980 by the
increase in numbers of vehicles equipped with
emission control systems and withdrawal of
older cars from the vehicle population. Emis-
sion increases resume in the early 1980's, to
again achieve rates of increase corresponding
to growth of the vehicle population. National
emissions of NOX will continue to rise (having
65
60
55
50
45
40
o
a 35
Z-o
o
Q
UJ
25
20
10
T
T
T
T
T
J L
1960 196.5 1970 1975 1980 1985 1990
YEAR
Figure 2-10. Estimated CO emissions from
gasoline-powered automobiles and trucks
through 1990 if Federal standards as of 1971
remain unchanged. Total urban and rural
data used.15
2-16
24
20
16
0-12
UJ
I-
< Z 8
Pr
1960 1965
1970 1975 1980
YEAR
1985 1990
Figure 2-11. Estimated NOX emissions from
gasoline-powered automobiles and trucks
through 1990 if Federal standards as of 1971
remain unchanged. Total urban and rural
data used.15
o .
I- o
Q
LLJ
18
16
14
12
10
8
6
4
2
J I I I
1960 1965
1970 1975
YEAR
1980 1985 1990
Figure 2-12. Estimated HC emissions from
gasoline-powered automobiles and trucks
through 1990 if Federal standards as of 1971
remain unchanged. Total urban and rural
data used. 15
increased with efforts to control CO and
hydrocarbons) with increasing vehicle miles,
unless they are specifically controlled.
2.3 REFERENCES FOR SECTION 2
1. Vehicles in U.S. Top 100 Million. Automotive
News. June 9, 1969. p. 26.
2. Motor Truck Facts, 1968. Detroit, Automobile
Manufacturers Association, Inc. 1968. p. 16.
3. 1968 Automobile Facts and Figures. Detroit,
Automobile Manufacturers Association, Inc
1968. p. 48.
-------
4. 51st Annual Engineering Specifications &
Statistical Issue. Automotive Industries.
140(6): 1-332. March 15, 1969.
5. Nature and Control of Aircraft Engine Exhaust
Emissions. Northern Research and Engineering
Corp. Cambridge, Mass. Report Number 1134-1.
Nov. 1968. 388 p.
6. Annual Summary of Locomotive Ownership and
Conditions Reports. Association of the American
Railroads. Washington, D.C. Report Number
608. January 1, 1969. 10 p.
7. Boating 1968. Chicago, Boating Industries As-
sociation.
8. Boating Statistics-1968 (CG-357). U.S. Coast
Guard. Washington, D.C. May 1, 1969. p. 22-25.
9. Landsberg, H.H., L.F. Frischman, and J.L.
Fisher. Resources in America's Future, Patterns
of Requirements and Availabilities 1960-2000.
Baltimore, John Hopkins Press, 1963. 1017 p.
10. Brief Passenger Car Data 1969. New York, Ethyl
Corp. 1969. p. 9.
11. The Automobile and Air Pollution: A Program
for Progress, Part II. Subpanel Reports to the
Panel on Electrically Powered Vehicles. U.S.
Dept. of Commerce. Washington, D.C. U.S.
Government Printing Office. December 1967.
160 p.
12. Turbine Power for Astro 95 Tractor. Automotive
Industries. 740(12):35-36, June 15, 1969.
13. Motor Vehicles, Air Pollution, and Health. A
Report of the Surgeon General to the U.S.
Congress in Compliance with Public Law 89-493,
the Schenck Act. U.S. Dept. of Health, Educa-
tion, and Welfare, Public Health Service, Division
of Air Pollution. Washington, D.C. U.S. Govern-
ment Printing Office. House Document No. 489,
87th Congress, 2nd Session. 1962. 459 p.
14. The Aircraft Gas Turbine Engine and Its Opera-
tion. PWA Operating Instruction 200. Pratt and
Whitney Aircraft. Hartford, Conn. Second Ed.
1963. p. 18.
15. National Air Pollution Control Administration.
Determination of Air Pollutant Emissions from
Gasoline-Powered Motor Vehicles. U.S. DHEW,
PHS, EHS. Durham, North Carolina. (Scheduled
for publication in 1970.)
16. Scheffler, C.E. Combustion Chamber Surface
Area, A Key to Exhaust Hydrocarbons. (S.A.E.
Paper No. 660111.) S.A.E. Transactions. Vol. 75.
New York, Society of Automotive Engineers,
Inc. 1967.
17. Nebel, G.J. and M.W. Jackson. Some Factors
Affecting the Concentration of Oxides of Nitro-
gen in Exhaust Gases from Spark Ignition En-
gines. J. Air Pollution Control Assoc.
S(3):213-219, November 1958.
18. Huls, T.A. and H.A. Nickol. Engine Variables In-
fluence Nitric Oxide Concentrations in Exhaust
Gas. S.A.E. Journal. 76:40-45, August 1969.
19. Spindt, R.S., C.L. Wolfe, and D.R. Stevens.
Nitrogen Oxides, Combustion, and Engine
Deposits. S.A.E. Transactions. 64:797-811,
1956.
20. Korth, M.W. and A.H. Rose, Jr. Emissions from a
Gas Turbine Automobile. (S.A.E. Paper No.
680402.) New York, Society of Automotive En-
gineers, Inc. 1968.
21. Altshuller, A.P. Reactivity of Organic Substances
in Atmospheric Photooxidation Reactions.
Division of Air Pollution. Cincinnati, Ohio. PHS
Publication Number 999-AP-14. July 1965. 29 p.
22. Altshuller, A.P. Application of Reactivity
Concepts to Emissions from Device Equipped
and Unequipped Automobiles. U.S. Dept. of
Health, Education, and Welfare, Division of Air
Pollution. Cincinnati, Ohio. June 1968. 19 p.
23. Caplan, J.D. Smog Chemistry Points the Way to
Rational Vehicle Emission Control (SAE Paper
No. 650641). In: Vehicle Emissions, Part II, Vol.
12. New York, Society of Automotive Engineers,
Inc., 1966. p. 20-31.
24. Ebersole, G.D. and L.A. McReynolds. An
Evaluation of Automobile Total Hydrocarbon
Emissions (SAE Paper No. 660408). In: Vehicle
Emissions, Part II, Vol. 12. New York, Society of
Automotive Engineers, Inc., 1966. p. 413-428.
25. Maga, J.A. and J.R. Kinosian. Motor Vehicle
Emission Standards Present and Future (SAE
Paper No. 660104). In: Vehicle Emissions, Part
II, Vol. 12. New York, Society of Automotive
Engineers, Inc., 1966. p. 297-306.
26. McReynolds, L.A., H.E. Alquist, and D.B.
Wimmer. Hydrocarbon Emissions and Reactivity
as Functions of Fuel and Engine Variables (SAE
Paper No. 650525). In: Vehicle Emissions, Part
II, Vol. 12. New York, Society of Automotive
Engineers, Inc., 1966. p. 10-19.
27. Stephens, E. R. and W. E. Scott. Relative Reac-
tivity of Various Hydrocarbons in Polluted
Atmospheres. Proc. Am. Petroleum Inst., Sect.
111.42:665-670, 1962.
28. Tuesday, C. S. The Atmospheric Photooxidation
of OlefinsThe Effect of Nitrogen Oxides. Arch.
Environ. Health. 7(2): 188-201, August 1963.
29. Altshuller, A. P. et al. Photochemical Reactivities
of n-Butane and Other Paraffinic Hydrocarbons.
Journal of the Air Pollution Control Association.
7P(10):787-790. Oct. 1969.
2-17
-------
3. FEDERAL EMISSION CONTROL PROGRAM
3.1 LEGISLATION
Title II of the Clean Air Act, as amended,1
is the legislative basis for the Federal air
pollution control program for new motor
vehicles. Federal Government action was
preceded, however, by acts of the State of
California.
Because of the early occurrence and
intensity of its air pollution problem, Cali-
fornia has pioneered in legislation and activi-
ties associated with control of vehicle emis-
sions. The basic legislation for air pollution
control in the State was enacted in 1947, in
the form of enabling legislation to permit
local jurisdictions to cope with specific pol-
lution control problems.2'3 The occurrence
of air pollution in other areas of the United
States emphasized the need for action on a
nationwide scale.4 In 1955 the Air Pollution
Control Act5 was enacted by the U.S.
Congress to authorize a program for research
and technical - assistance for control and
abatement of air pollution by the Secretary of
Health, Education, and Welfare and the
Surgeon General of the Public Health Service.
The act recognized the primary responsi-
bilities and rights of the states, local govern-
ments, and other public agencies in control-
ling air pollution, but provided grants to those
agencies concerned with air pollution control
for assisting them in the formulation and
execution of their abatement research pro-
grams.
Emphasis on vehicular air pollution
emerged with legislation in California from
1957 to 1960, and, nationally, in 1960. In
19593,6,7 the State Legislature required the
Department of Public Health to develop and
publish before February 1, 1960, standards
for the quality of air and emission of exhaust
contaminants from motor vehicles. The emis-
sion standards were based on a "rollback"8
technique that was intended to reduce hydro-
carbon emissions from the total vehicle pop-
ulation to the levels emitted by the total vehi-
cle population in California in 1940. In 1960
the California Motor Vehicle Pollution
Control Act was enacted; it created the Motor
Vehicle Pollution Control Board (MVPCB) to
implement the emissions standards adopted in
19592,3,6,7 The Act made the Board re-
sponsible for issuing certificates of approval
for motor vehicle pollution control devices,
and stipulated that 1 year from the date on
which two or more control devices were
certified, all new cars registered in the State
would be equipped with such devices. The
Department of Health also adopted blowby
standards.
The Schenck Act9, enacted by the U.S.
Congress in 1960, directed the Surgeon
General of the Public Health Service to make
a study and report to Congress within 2 years
on the discharge of substances into the
atmosphere from the exhaust of motor vehi-
cles.
In 1961 the MVPCB approved a number of
blowby control devices, and these controls
thus became mandatory for new cars sold in
California beginning with the 1963 model
year.7 The U.S. auto manufacturers, however,
installed them voluntarily on new cars sold in
California beginning with the 1961 models.
Also in 1961, an exhaust emission-control
test procedure was developed and adopted,
using 7- and 11-mode driving cycles, and re-
quiring satisfactory operation of emission
control systems for 12,000 miles.10 During
3-1
-------
the period 1961 to 1963, the Board invoked
an odor criterion pertaining to vehicle emis-
sions which stimulated development of
closed-crankcase emission-control systems.
Garages and mechanics were licensed to install
and service the open-crankcase emission
control system in use at that time.11
In July 1962 the report of the Surgeon
General to the Congress, directed by the
Schenck Act, was approved by joint
resolution of the U.S. House of Representa-
tives and the Senate.12 Its content is divided
into three parts:
Part I summarizes then-current information
and theories of the nature of air pollution
resulting from emissions from motor vehi-
cles, and examines approaches to the
reduction of such pollution and some of
the problems associated with control
measures.
Part II reviews information that had been
reported concerning the influence of air
pollution on health, with particular
reference to the effects of pollution arising
from operation of motor vehicles.
Part III describes how motor vehicle opera-
tion relates to emissions of contaminants,
the magnitude of the pollution problem,
the nature of chemical reactions in the
atmosphere, factors affecting concentra-
tions, methods for reducing pollution, and
the subject of ambient air quality and emis-
sion standards.
Late in 1963, the 88th Congress passed the
Clean Air Act,1 3 which replaced the 1955 Air
Pollution Control Act. Among the provisions
of this Act, a section on "Automotive Vehicle
and Fuel Pollution" was particularly in-
dicative of the continued and increasing
concern for the problem of motor-vehi-
cle-related air pollution. This section pertain-
ed to continued efforts by the automotive
and fuel industries to control motor vehicle
emissions. To encourage such efforts, the Sec-
retary of Health, Education, and Welfare was
directed to appoint a technical advisory com-
mittee composed of representatives of
industry and the Department of Health,
Education, and Welfare, to meet as directed
3-2
by the Secretary, and to evaluate progress and
recommend research toward devices and fuels
to control automotive vehicle emissions. The
Secretary was further directed to report semi-
annually to Congress on measures taken
toward resolution of the vehicle exhaust emis-
sions problem, including:
1. Occurrence of pollution as a result
of the discharge of contaminants
from automotive exhausts.
2. Progress of research into develop-
ment of devices and fuels to reduce
emissions from exhausts of automo-
tive vehicles.
3. Criteria on effects of contaminant
matter discharged from automotive
exhausts.
4. Efforts to improve fuels so as to
reduce emissions of exhaust contam-
inants.
5. Recommendations for additional
legislation, if necessary, to regulate
the discharge of contaminants from
automotive exhausts.
In 1964 the California MVPCB approved
exhaust emission control devices for new
automobiles, which became effective with the
1966 model year cars.7 It also adopted more
stringent HC and CO exhaust standards for
1970 model cars; adopted standards for
crankcase, fuel tank, and carburetor emis-
sions; and issued a policy statement that
standards for NOX were needed and that the
Board would consider in 1965 adoption of an
exhaust standard for nitrogen oxide.
In 1965 the California requirement for
installation of crankcase emission control
devices on 1950 to 1960 model cars was
relaxed in favor of Senate Bill 317, which re-
quired installation of such devices on only
1955 to 1960 models in certain counties
when the vehicle is sold and reregistered.6
The MVPCB specified reestablishment of
deterioration factors based on 50,000 miles
instead of 12,000, and required certification
of each size engine instead of permitting
averaging of all sizes of one make.14
-------
Also in 1965 Congress amended the Clean
Air Act to include a section known as the
Motor Vehicle Air Pollution Control Act,15
which directed the Secretary of Health,
Education, and Welfare to prescribe standards
applicable to exhaust emissions from new
motor vehicles or new motor vehicle engines,
and to issue certificates of conformity for
vehicles and engines conforming with those
standards. The Act also directed the Secretary
to conduct and accelerate programs relative to
hydrocarbon evaporative losses and NOX and
aldehydes from gasoline-powered or diesel-
powered vehicles, and provided for con-
structing, equipping, and staffing facilities
necessary to carry out the authorized actions.
In 1966 U.S. standards for crankcase emis-
sions and hydrocarbon and CO exhaust emis-
sions, and procedures for determining
compliance with such standards, were publish-
ed; they applied to all 1968 model auto-
mobiles.16 U.S. auto manufacturers, however,
had installed crankcase devices voluntarily
throughout the country beginning with the
1963 models. The standards for the 1968 and
subsequent models required the use of a
"closed" crankcase ventilation system in place
of the open system which had been employed
on a voluntary basis. (See Section 5.1.1 for a
discussion of open and closed systems.)
In 1967 California adopted test procedures
for emission control systems for mobile
internal combustion engines used inside build-
ings,1 7 and passed the Pure Air Act of 1967,
to become effective in November 1968.18
Features of the Act included:
1. Provisions for adoption of low emis-
sion standards for new state vehicles
more stringent than the approved
test standards for public vehicles.
2. Adoption of test procedures for the
approval of new motor vehicles
based upon emission standards spec-
ified in the Act, bringing the Cali-
fornia procedures into conformance
with the Federal.
3. Adoption of regulations for the ap-
proval of devices for used motor
vehicles, based upon their emissions.
4. Adoption of regulations specifying
the manner in which motor vehicles
on factory assembly lines are to be
emission tested.
5. Adoption of exhaust emission
standards for hydrocarbons, CO, and
NOX for new diesel-powered vehicles
no later than January 1, 1971, ap-
plicable no later than January 1,
1973.
6. Adoption of emission standards for
motor vehicles not now covered.
7. Requirement that manufacturers of
vehicles report their work relative to
control of oxides of nitrogen for
their vehicles.
8. Establishment of exhaust emission
standards and effective dates for
those standards, beginning in 1970,
for hydrocarbon, CO, and NOX for
gasoline-powered cars, trucks,
truck-tractors, and buses; diesel-
powered vehicles, and for fuel evap-
orative losses from gasoline-powered
vehicles.
Late in 1967, Congress enacted Public Law
90-148, an amendment to the Clean Air Act
of 1963. In addition to continuing all major
activities which the Department of Health,
Education, and Welfare was authorized to
conduct, it provided the basis for systematic
control activities on a regional scale, hinging
on state action to deal with air pollution
problems within air quality regions designated
by the Department. The states are responsible
for setting air quality standards for such
regions and for developing plans to meet
those standards. The Department of Health,
Education, and Welfare assists the states by
publishing air quality criteria and information
on the status and cost of recommended
techniques for preventing and controlling air
pollution, including cost-effectiveness of
alternative methods.
The Act explicitly provides for preemption
by the Federal Government concerning estab-
lishment of standards for emissions from new
motor vehicles and engines. It provides, how-
ever, that this preemption may be waived
3-3
-------
upon application by any state which has
adopted standards other than crankcase emis-
sion standards prior to March 30, 1966.
Practically, this stipulation limits application
for waiver to the State of California. The Act
further provides that any state or political
subdivision has the right to otherwise control,
regulate, or restrict, the use, operation, or
movement of registered or licensed vehicles.
State maintenance and/or inspection pro-
grams may be assisted by grants to state air
pollution control agencies for up to two-
thirds of the cost of developing uniform
motor vehicle emission device inspection and
emission testing programs. Any such grant can
be made only if the Secretary of Transpor-
tation certifies that the program is consistent
with any highway safety program established
pursuant to the Highway Safety Act.
Standards for exhaust emissions, fuel evap-
orative emissions, evaporative losses, and
smoke emissions, applicable to 1970 and later
vehicles and engines, were published in the
Federal Register.19
In 1968, the California Pure Air Act of
1968 became effective, but waiver of Federal
preemption by the Secretary of Health,
Education, and Welfare was necessary before
the more stringent California emission
standards could be adopted. In response to
California's application, a waiver was
granted20 in May 1969.
In December 1969, The Federal Register19
notice applicable to 1970 and later vehicles
and engines was amended21 to include
labeling by the manufacturer of each gaso-
line-powered, light-duty vehicle as conforming
to U.S. DHEW regulations for new motor ve-
hicles. This provision is effective February 10,
1970 and requires also that engine tune-up
specifications be included on the label (see
Section 3.2.2).
3.2 REGULATIONS
3.2.1 Emission Standards
3.2.1.1 General
Table 3-1 represents the sequence in which
California and Federal emission standards for
34
motor vehicles became effective, or are to
become effective, through provision of
devices and systems to control emissions in
compliance with these standards. In general,
the tabular data represent standards for those
gasoline-powered motor vehicles and motor
vehicle engines constituting a majority of the
vehicle population. (Standards for diesel en-
gines are to be adopted in California by
January 1, 1971, and are to become effective
by January 1, 1973.) Footnotes cover some
of the additional information necessary to
portray the standards adequately, and refer-
ences provide more detail. The data suggest
the manner in which control effectiveness in
California preceded the national program for
vehicular emission control, but do not indi-
cate the extent to which development of
California standards led Federal regulation.
Exhaust emission standards applicable to
1966 model motor vehicles sold in California,
for example, were adopted in 1959, whereas
comparable Federal standards applicable to
1968 models were published in 1966. In this
and other instances, the time lapse between
adoption of standards and compliance with
them in California has been influenced by the
regulation which made installation of a
system mandatory 1 year after two or more
such systems or devices have been certified as
complying with an emission standard.
Applicability to specific types of vehicles
and engines varies between California22 and
Federal16'19 hydrocarbon and CO emission
standards. Both, however, currently apply to
gasoline-powered motor vehicles and motor
vehicle engines. Neither applies to engines of
less than 50 cubic inches (810 cc) displace-
ment, nor to such vehicles as motorcycles,
motor scooters, marine craft, aircraft, loco-
motives, lawntending equipment, and con-
struction machinery. With certain exceptions,
depending on model year and vehicle type,
notably pre-1966 models, California regula-
tions with respect to crankcase and exhaust
emissions apply to every passenger vehicle,
except motorcycles. In addition, they apply
to trucks, truck-tractors, and buses, provided
they are not diesel-powered. Federal
-------
Table 3-1. SEQUENCE OF CALIFORNIA AND FEDERAL GASOLINE-POWERED VEHICLE EMISSION
STANDARDS FOR CO, NOX, AND HC1'12-17'20
Emission
California
Crankcase
exhaust
HC
CO
NOX as NO2
Evaporative
Federal
Crankcase
exhaust
HC
CO
NOX as NO2
Evaporative
Standards according to date of compliance
1963
0.1 5%a
1966
0.1 0%a
275 ppm
1.5%
1968
0.0%
275 ppmc
1.5%c
1970
2.2 g/mib
(180 ppm)
23 g/mib
(1.0%)
6g/test
2.2 g/mid
23 g/mid
1971
4.0 g/mib
6 g/teste
1972
1.5g/mib
3 g/mib
1974
1.3g/mib
aEmission is stated as a percent of fuel supplied.
bFor vehicles less than 6001-lb gr wt. Standards for heavier vehicles are:
Year
1970
HC 275 ppm
CO 1.5%
cFor engines over 140 cu in. For smaller engines, standards are:
Displacement
HC
CO
50 to lOOcuin.
1972
180 ppm
1.0%
101 to 140cuin.
410 ppm 350 ppm
2.3% 2.0%
"For light-duty vehicles. For heavy-duty gasoline engines, standards are HC, 275 ppm; CO, 1.5 percent.
eDoes not apply to off-the-road utility vehicles until 1972.
standards apply only to 1968 and later mode!
motor vehicles and motor vehicle engines. For
1968 and 1969 model years, the regulations
apply to all new vehicles and vehicle engines
(except commercial vehicles over ^-ton and
motorcycles, and their respective engines).
Beginning with 1970 models, applicability is
differentiated between "light-duty vehicles"
(6,000 Ib gross weight or less) and engines for
"heavy-duty vehicles" (over 6,000 Jb gross
weight).
Beginning with 1970 standards, vehicle
exhaust emissions from light-duty vehicles are
expressed in mass terms (grams per mile)
rather than in terms of concentration
(fraction of total exhaust). Exhaust emis-
sions from heavy-duty vehicles continue to
be expressed in terms of concentration. A
single, median concentration standard may
give no credit to the small motor vehicle en-
gine, or may falsely credit the large engine
insofar as total mass emissions are concerned.
Pre-1970 standards attempted to avoid this
inequity by allowing higher emission con-
centrations for smaller engines as shown in
Table 3-2.
3.2.1.1 Prospective: Conventional Gasoline
Engine
As the greatest single contributor to
production of CO, NOX, and hydrocarbons
3-5
-------
Table 3-2. ALLOWABLE EMISSION RATES UNDER 1968 FEDERAL STANDARDS16
Engine displacement,
cu in.
0-49
50-100
101-140
141 and over
Average maximum allowable
emissions
CO, %
No limit
2.3
2.0
1.5
Hydrocarbons, ppm
No limit
410
350
275
from mobile sources the conventional
gasoline-powered motor vehicle is receiving
the greatest share of the effort toward emis-
sion control.
3.2.1.2.1 Hydrocarbons. Initially,
crankcase emission standards in California
permitted hydrocarbon emissions equivalent
to 0.15 percent of supplied fuel. This was
later reduced to 0.10 percent. The 1968
Federal standards allow no crankcase emis-
sions. Maximum average exhaust hydrocarbon
emission was initially specified as 275 ppm,*
or 3.4 grams per mile (g/mile), and later
reduced for 1970 model vehicles to 2.2 g/mile
(or 180 ppm). The California standard to
become effective in 1972 is 1.5 g/mile (120
ppm). Concentrations as low as 50 ppm (0.61
g/mile) are considered commercially feasible
by 1975, and ultimately as low as 25 ppm
(0.31 g/mile).23 Control of evaporative losses
is required in California with standards for
1970 models and nationally with standards
for 1971 models.
3.2.1.2.2 CO. Carbon monoxide
standards, as a part of vehicle emission
standards for 1966 model cars in California
and 1968 models nationally, permitted a
maximum average concentration of 1.5
percent by volume of total exhaust, equiv-
alent to 35 g/mile. With the 1970 models, the
Federal and California standards become 23
g/mile (1.0 percent). A concentration as low
as 0.5 percent (12.5 g/mile) is considered
*1968 Federal standards were expressed in terms of
concentration; 1970 Federal standards are expressed
in terms of grams per mile. Both are presented here
for ease of comparison.
3-6
commercially feasible, and 0.25 percent (6.3
g/mile) is considered ultimately feasible.2 3
3.2.1.2.3 NOX. Standards for exhaust
emissions of NOX become effective for the
first time with the California standard of 4.0
g/mile in 1971 for vehicles under 6,001
pounds of gross weight, with successive
reductions to 3.0 g/mile for the 1972 model
year and 1.3 g/mile for the 1974 model year.
Mass emission levels of NOX for a vehicle with
no emission controls are about 5 g/mile (see
Table 3-3). With some control systems for
exhaust HC and CO, however, NOX emissions
may tend to increase as CO and HC emissions
decrease.
3.2.1.3 Prospective: Diesel Engine
By comparison with the effort expended
with respect to the gasoline engine, very little
has been done regarding control of hydrocar-
bon, CO, and NOX emissions from diesel
engines. California legislation22 provides for
adoption of standards for diesel engines in
1971, to become effective in 1973. Crankcase
and evaporative emissions are extremely low
for the diesel, its exhaust being essentially the
only emission source.
3.2.2 Compliance
Testing for compliance with established
standards is a prerequisite to the sale of new
motor vehicles. California procedures for ap-
proving devices for emission control were
established early in its vehicle emission
control program, and have been developed
further as requirements have become more
stringent. Federal procedures are similar to
those of California for 1966 models, and were
first published in 1966 to be effective with
-------
1968 models.16 Federal procedures published
in 1968 for 1970 models were expanded and
amplified.19
To obtain Federal certification,19'24
manufacturers must furnish data showing that
the vehicles they intend to offer for sale
comply with the Federal standards. They
must also provide representative vehicles for
confirmatory testing in Federal laboratories.
The National Air Pollution Control Admin-
istration has its principal motor-vehicle test
laboratory in Ypsilanti, Michigan.
To qualify for certificates of conformity,
manufacturers must submit applications
containing data pertaining to crankcase and
exhaust emissions, and, for 1971 models,
evaporative emissions. Data supplied must
cover both phases of a two-part test program.
The first phase of testing provides data that
indicate the performance of the emission con-
trol equipment after the engine has been
broken in, but before substantial mileage has
been accumulated. These data are obtained, as
nearly as possible, during the first 4,000 miles
of operation, using one fleet of cars. The sec-
ond phase of the test program, using a second
fleet of cars, provides data on the durability
of the emission control systems.
To complete the requirements of the first
phase of the test program, four prototype
vehicles are generally selected from each en-
gine class in accordance with representative-
ness of annual sales. The four vehicles, each
powered by the same size engine, are usually
selected from the most popular models. These
four vehicles make up one segment of the
4,000-mile emission-data fleet. The remainder
of the 4,000-mile emission-data fleet consists
of similarly selected vehicles (in sets of four)
for each engine displacement to be produced.
Test results for each vehicle of the emission-
data fleet are submitted with the application
for certification to Federal automotive en-
gineers for evaluation. These data and con-
firmatory test data subsequently obtained by
testing these vehicles in the Federal
laboratory in Michigan are used to determine
the representative low-mileage emission level
for each engine displacement.
The second phase of required testing pro-
vides durability data indicative of perform-
ance of control systems or devices over ex-
tended mileage. Durability testing is conduct-
ed on a second fleet of automobiles
comprising a minimum of 4 and a maximum
of 10 vehicles under procedures for 1968-69
models, and 12 vehicles under procedures for
1970 models. Each is operated for 50,000
miles under actual driving conditions. During
this period of mileage accumulation, emission
measurements are made every 4,000 miles in
the manufacturer's laboratory. For vehicles
equipped with evaporative control systems,
evaporative emissions are measured through
not less than 12,000 miles for 1970 models,
and not less than 50,000 miles for subsequent
models. The data thus obtained provide a
basis for evaluation of probable emissions
over the life of a typical vehicle (defined as
100,000 miles).
Compliance with the Federal standards is
ascertained for each class of engine by aver-
aging the 4,000-mile emission data for each
engine displacement and adjusting these data
on the basis of data from the durability fleet
to lifetime emissions for 100,000 miles. The
resultant figures are then compared with the
standards. If the engine class meets the stand-
ards, a certificate of conformity is issued for
each model powered by that engine. By law,
all vehicles or engines sold that are "in all
material respects substantially the same con-
struction as the test vehicles or engines for
which a certificate of conformity has been
issued . . . (are). . . deemed to be in conform-
ity with the regulations . . . ."
Federal regulations specify emission meas-
urement equipment and techniques, and com-
pliance with Federal standards is based on the
results obtained in accordance with those
specifications. For crankcase emissions, the
regulations provide only that the manufac-
turer shall test the vehicle in accordance with
good engineering practice to ascertain that the
vehicle, equipped and maintained in accord-
ance with the manufacturer's recommenda-
tions, can be expected to meet requirements
3-7
-------
oo
Table 3-3. LIGHT-DUTY VEHICLE3 EMISSIONS24
Exhaust:
Hydrocarbons
Carbon monoxide
Oxides of nitrogen
(as N02)
Crankcase blowby:
Hydrocarbons
Evaporation:
Hydrocarbons
Total:
Hydrocarbons
Carbon monoxide
Oxides of nitrogen
Oxides of nitrogen
(as NO2)
Uncontrolled vehicles, pre-1968
1963b'c model
year car, grams/
vehicle mile-
dynamometer
cycle
10.20
76.89
5.38
3.15'
2.77
16.12f
76.89
5.38
1963c'd model
year car,
grams/vehicle
mile on the
road
8.87
44.47
5.26
s.isf
2.77
14.79f
44.47
5.26
Estimatedd>e
emissions
pounds/ car/
year on the
road
270
1,370
160
100f
80
450f
1,370
160
National standards, 1968
1968b'c model
year car, grams/
vehicle mile-
dynamometer
cycle
3.43
35.10
6.76
0.0
2.77
6.20
35.10
6.76
1968c'd model
year car,
grams/vehicle
mile on the
road
2.98
20.30
6.60
0.0
2.77
5.75
20.30
6.60
Estimatedd'e
emissions
pounds/car/
year on the
road
90.0
630.0
200.0
0.0
80.0
170.0
630.0
200.0
~
Percent reduc-
tion for 1968
model year
car on the
road
67.0
54.0
-268
100.0
0.0
62.0
54.0
-26.08
-------
Table 3-3(continued). LIGHT-DUTY VEHICLE3 EMISSIONS24
Exhaust:
Hydrocarbons
Carbon monoxide
Oxides of nitrogen
(as NO2)
Crankcase blowby:
Hydrocarbons
Evaporation:
Hydrocarbons
Total:
Hydrocarbons
Carbon monoxide
Oxides of nitrogen
(as NO2)
National standards, 1970
1970b'c model
year car, grams/
vehicle mile-
dynamometer
cycle
2.20
23.00
6.76
0.00
2.77
4.97
23.00
6.76
1970c'd model
year car,
grams/vehicle
mile on the
road
1.91
13.30
6.60
0.00
2.77
4.67
13.30
6.60
Estimated*1'6
emissions
pounds/ car/
year-on the
road
60
410
200
0
80
140
410
200
Percent reduc-
tion for 1970
model year
car on the
road
78
70
-268
100
0
69
70
-268
National standards, 1971
1971b>c model
year car, grams/
vehicle mile-
dynamometer
cycle
2.20
23.00
6.76
0.00
0.49
2.69
23.00
6.76
1 97 lc'd model
year car,
grams/vehicle
mile on the
road
1.91
13.30
6.60
0.00
0.49
2.40
13.30
6.60
Estimated*1'6
emissions
pounds/car/
year on the
road
60.00
410.00
200.00
0.00
15.00
75.00
410.00
200.00
Percent reduc-
tion for 1971
model year
car on the
road
78
70
-268
100 .
81h
83
70
-268
aVehicles with a gross vehicle weight of 6,000 pounds or less.
"Tested according to Federal LDV test procedures.
8At 2,000 miles (odometer reading).
^Assumes 50 percent urban and 50 percent rural driving for the vehicle.
eAverage first year emission rates.
fApplies only to pre-1963 cars.
8Estimates range from -15 percent to -50 percent reduction (or a 15 to 50 percent increase).
"Recent test data indicate that this is over 90 percent.
-------
for not less than 1 year. Exhaust and evapora-
tive emissions are measured during prescribed
sequences of vehicle operating conditions.
Exhaust emissions are measured through use
of nondispersive infrared analyzers while the
vehicle is operating on a chassis dynamom-
eter. Evaporative emissions are determined as
the weight of fuel collected in an activated-
carbon trap connected to possible raw-fuel
vapor-emission points of the vehicle fuel
system. The test procedure consists of collect-
ing emitted fuel vapor during three modes (1)
diurnal breathing, (2) running, and (3) hot
soak.
The issue of the Federal Register19 con-
taining emission standards and certification
procedures for 1970 and later model gasoline-
powered motor vehicles has been amended21
to include labeling of each vehicle by the
manufacturer stating that it "... conforms
to U.S. Department of Health, Education, and
Welfare regulations applicable to (appropriate
year) model-year new motor vehicles." This
provision was effective February 10, 1970, and
requires that the label be permanently
attached in a readily visible position in the
engine compartment so that it cannot be
removed without destroying or defacing the
label. In addition to the statement of con-
formity, the label must contain the following
information:
1. The label heading: Vehicle Emission
Control Information.
2. Full corporate name and trademark of
manufacturer.
3. Engine size (in cubic inches).
4. Engine tuneup specifications and adjust-
ments, as recommended by the manufac-
turer, including recommended idle
speed, ignition timing, and air-fuel mix-
ture setting and/or idle carbon monoxide
setting. These specifications should
indicate the proper transmission position
during tuneups and what accessories
(e.g., air-conditioner), if any, should be
in operation.
3-10
3.3 EFFECT ON EMISSION REDUCTIONS
3.3.1 New Vehicles
Table 3-3 presents vehicle emission data
based on the national standards effective with
1968 and later models, and includes emission
data for an uncontrolled vehicle for com-
parison as a base. Data are applicable to new
cars (during only their first year of use for
those with exhaust emission controls), and are
estimated in terms of:
1. Typical emissions, grams per vehicle
mile, both on the composite dynamom-
eter cycle and actual on-the-road emis-
sions.
2. Estimated emissions, pounds per car per
year, for HC, CO, and NOX by source,
including an allowance for deterioration
of control system effectiveness during
the first year. Mileage for the first year is
assumed to be 13,200 miles.24
3. Percent reduction in emissions referred
to the uncontrolled car, according to
controls in effect as of the date of par-
ticular standard.
Table 3-3 does not attempt to indicate the
extent of total emissions nationally, which is
influenced by the continual entrance of new
cars into the vehicle population and by attri-
tion of older cars.
3.3.2 Durability and Surveillance
Data on the effectiveness of emission con-
trol systems are obtained during a 50,000-
mile "lifetime" of driving over a prescribed
course at speeds and under driving modes
intended to simulate urban driving. The pro-
cedure does not stipulate whether mileage
may be accumulated continuously by the
manufacturer, but time requirements would
almost dictate continuous driving for at least
considerable portions of the mileage. Results
obtained through this procedure and corre-
sponding use of emission measurements may
not truly indicate the effectiveness of a device
or system after 50,000 miles have been
accumulated on a vehicle, nor be indicative
of performance of a device or system in
public use.
-------
To investigate the durability and continued
effectiveness of emission controls, the Federal
Government laboratory at Ypsilanti obtains
data from a fleet of vehicles in daily use by its
staff, and from vehicles operated by auto
rental agencies. The auto manufacturers are
400
calling in individually owned cars in public
use for continuing surveillance, and California
has a program for measuing emissions of
hydrocarbon and CO from 1966 and later
model vehicles in public use.26 Figures
3-1 and 3-2 represent data obtained in
Q.
O.
O
1-
<
u
z
O
u
z
O
CD
300
200
K 100
275 STANDARD
._. 1966
-~ 1967
1968
1969
HYDROCARBONS
CORRECTED TO
COLD START
COMPOSITE CYCLE
10
20 30
THOUSANDS OF MILES
40
50
Figure 3-1. Hydrocarbon exhaust emissions versus mileage.
26
2.0
1.5
1.0
0.5
o
a.
O
X
O
CO
on
u
1.5 STANDARD
1966
1967
1968
1969
CARBON MONOXIDE
CORRECTED TO
COLD START
COMPOSITE CYCLE
10
20 30
THOUSANDS OF MILES
40
50
Figure 3-2. Carbon monoxide exhaust emissions versus mileage.26
3-11
-------
this program. For both HC and CO, the data
indicate a gradual decrease in effectiveness to
50,000 miles, which is possibly a plateau of
effectiveness. These figures are based on
4,921 tests on California vehicles and are
weighted as vehicle types and makes are
actually distributed. It should be noted that
not many high-mileage, late-model cars are
available yet; thus, curves for 1968 and,
especially, 1969 models may change as more
data become available.
3.4 REFERENCES FOR SECTION 3
1. Air Quality Act of 1967, Public Law 90-148,
90th Congress, 1st Session, November 21, 1967.
In: U.S. Statutes at Large. 81: 485-507, 1968.
2. Middleton, J.T. Control of Environment-Ec-
onomic and Technological Prospects. In: Envi-
ronmental Improvement (Air, Water, and Soil),
Marquis, R.W. (ed.). Washington, D.C., The Grad-
uate School, U.S. Dept of Agriculture, 1966. p.
53-71.
3. Hass, G.C. The California Motor Vehicle Emis-
sion Standards (Paper No. 210A, presented at the
SAE National West Coast Meeting, August 1960).
In: Vehicle Emissions, Vol. 6. New York, Society
of Automotive Engineers, Inc., 1964. p. 39-44.
4. Kennedy, H.W. and M.E. Weekes. Control of
Automobile Emissions-California Experience and
the Federal Legislation. In: Air Pollution Con-
trol, Havighurst, C.C. (ed.). Dobbs Ferry, Oceana
Publications, Inc., 1969. p. 101-118.
5. An Act to Provide Research and Technical Assist-
ance Relating to Air Pollution Control, Public
Law 159, 84th Congress, 1st Session, July 14,
1955. In: U.S. Statutes at Large. 69: 322-323,
1955.
6. Smog, The Silent Enemy. California Motor Vehi-
cle Pollution Control Board. Los Angeles, Calif.
Fourth Biennial Report for 1965-66. January
1967. 32 p.
7. Mills, K.D. Current and Future Developments in
the Control of Motor Vehicle Emissions. Pre-
sented at the Society of Automotive Engineers
Meeting. Philadelphia, Pennsylvania, March 10,
1965.
8. Technical Report of California Standards for
Ambient Air Quality and Motor Vehicle Exhaust.
California Dept. of Public Health. Berkeley,
Calif. [1960] 136 p.
9. Automotive Air Pollution. A Report of the
Secretary of Health, Education, and Welfare to
the U.S. Congress Pursuant to Public Law
88-206, the Clean Air Act. U.S. Dept. of Health,
Education, and Welfare. Washington, D.C., U.S.
3-12
Government Printing Office. Senate Document
No. 7. 89th Congress, 1st Session. January 15,
1965. 22 p.
10. California Test Procedure and Criteria for Motor
Vehicle Exhaust Emission Control. California
Motor Vehicle Pollution Control Board. Los
Angeles, Calif. January 23, 1964.
11. Brubacher, M.L. and J.C. Raymond. A Status
Report: California Vehicle Exhaust Control. J.
Air Pollution Control Assoc. 19: 224-229, April
1969.
12. Motor Vehicles, Air Pollution, and Health, A
Report of the Surgeon General to the U.S.
Congress in Compliance with Public Law 89-493,
the Schenck Act. U.S. Dept. of Health, Educa-
tion, and Welfare, Public Health Service, Division
of Air Pollution. Washington, D.C., U.S. Govern-
ment Printing Office, House Document No. 489,
87th Congress, 2nd Session. 1962. 459 p.
13. Clean Air Act, Public Law 88-206, 88th Con-
gress, 1st Session, December 17, 1963. In: U.S.
Statutes at Large. 77: 392-401, 1964.
14. Motor Vehicle Pollution Control Board Bulletin.
California Motor Pollution Control Board (Los
Angeles). 4: 1-4, October 1965.
15. Motor Vehicle Air Pollution Control Act, Public
Law 89-272, 89th Congress, 1st Session, October
20, 1965. In: U.S. Statutes at Large. 79:
992-1001, 1966.
16. Control of Air Pollution from New Motor Vehi-
cles and New Motor Vehicle Engines. Federal
Register (Washington) Part II. 31(61):
5170-5238, March 30, 1966.
17. Test Procedure for Portable and Mobile Internal
Combustion Engines Used Inside Buildings. Part
IX. California Air Resources Board. September
13,1967.
18. Motor Vehicle Pollution Control Board Bulletin.
California Motor Pollution Control Board (Los
Angeles). 6, August 1967.
19. Control of Air Pollution from New Motor Vehi-
cles and New Motor Vehicle Engines. Federal
Register (Washington) Part II. 33(108):
8303-8324, June 4, 1968.
20. California Air Resources Board Bulletin. Cali-
fornia Air Resources Board (Sacramento). 1(13):
1-4, March-April 1969.
21. Control of Air Pollution from New Motor Vehi-
cles and Motor Vehicle Engines. Federal Register
(Washington) Part LXXXV. 34(236): 19506.
December 10, 1969.
22. California Legislature Assembly Bill No. 357,
July 25, 1968. In: Statutes and Amendments to
the Codes. 1: 1463-1486, 1968.
23. The Automobile and Air Pollution: A Program
for Progress, Part II. Subpanel Reports to the
Panel on Electrically Powered Vehicles. U.S.
Dept. of Commerce. Washington, D.C., U.S.
-------
Government Printing Office, December 1967.
160 p.
24. Federal Motor Vehicle Certification Data, 1968
and 1969. U.S. Dept. of Health, Education, and
Welfare, Public Health Service, Consumer Protec-
tion and Environmental Health Service.
25. National Air Pollution Control Administration.
Determination of Air Pollutant Emissions from
Gasoline-Powered Motor Vehicles. U.S. DHEW,
PHS, EHS. Durham, North Carolina. (Scheduled
for publication in 1970.)
26. Hocker, A.J. Exhaust Emissions from Privately
Owned 1966-1969 California Automobiles: A
Statistical Evaluation of Surveillance Data. Cali-
fornia Air Resources Laboratory. Los Angeles,
Calif. Supplement to Progress Report Number
16. November?, 1969. p. 7.
3-13
-------
4. STATE EMISSION CONTROL OPTIONS
4.1 INTRODUCTION
As discussed previously in this document,
Federal legislation empowered the Secretary
of Health, Education, and Welfare to establish
standards for the control of automobile
exhaust emissions from new gasoline-powered
motor vehicles and engines offered for sale in
interstate commerce, beginning with the 1968
model year. The Federal law also specified
penalties that can be imposed on anyone who
removes or inactivates an exhaust control
system prior to delivery of a new vehicle to
the purchaser.
At this point, however, Federal authority
ends. Any actions to control existing air
pollution or prevent future air pollution from
mobile sources are left to the individual states
under current legislation. There is, therefore,
a need for appropriate state action to
augment the Federal program if air quality in
a region indicates that such measures are, or
will be necessary. This section discusses and
identifies various optional plans for considera-
tion by the states. Methods of inspection
and/or maintenance are effective in reducing
emissions of CO and HC from vehicles both
equipped and unequipped with emission con-
trol systems. Indirect methods of control
presented in this section may substantially
reduce emissions from the entire vehicle
population in an area. Fuel modification, a
state option, is considered in Section 6, Fuel
Modification and Substitution.
To be fully effective, a state program must
minimize emissions from all vehicles or make
it possible to identify individual vehicles that
are emitting greater amounts of contaminants
than originally certified as acceptable, and
provide a mechanism whereby these emissions
can be reduced. Such high emissions from a
population or an individual vehicle may occur
for any of several reasons, some of which are
discussed below.
Since present control systems for CO and
HC depend, for the most part, on achieving
substantially complete combustion in the
engine, adjustment of all operating conditions
that influence combustion is important. Since
these adjustments may change over a period
of time, proper maintenance is also very
important if emissions are to be kept at a
satisfactory level. Tests have shown that
minor maladjustments that might not be
detected by most drivers can increase exhaust
emissions far above design level.1 Thus,
engine adjustment and maintenance are ex-
tremely important in limiting exhaust emis-
sions. Table 4-1 shows the effects of several
maladjustments on CO and HC emissions.
With modern methods of mass production,
some variation is inevitable among engines in
the dimensions of critical parts and in their
assembly and adjustment. These manufac-
turing tolerances will inevitably result in dif-
ferent emission rates for different vehicles.
Within a large group of vehicles, these varia-
tions will most likely be characterized by a
normal distribution. Inevitably, a proportion
of the total vehicle population will emit
greater amounts of contaminants than the
average for the entire group, even though all
are similar in design and construction (Figures
4-1,4-2).
A percentage of vehicle owners will delib-
erately attempt to remove or in some way
inactivate the control system. This might be
done by someone interested in obtaining high
acceleration rates, which, generally, will also
increase exhaust emissions.
One approach to controlling vehicular emis-
sions is to attempt to minimize emissions
from all vehicles. Another is to identify indi-
vidual high-emitters for subsequent corrective
4-1
-------
Table 4-1. EFFECTS OF MALADJUSTMENT3
ON CO AND HC EMISSIONS1
Maladjustment
Intermittent miss
Low idle speed
Rich idle
Plugged PCV
Choke too rich
Advanced spark timing
Air injection belt off
Air injection system
HC, ppm
570
260
230
280
270
280
520
CO, %
1.20
1.25
1.80
1.55
1.35
1.20
3.25
Engine modification
HC, ppm
650
280
230
280
250
290
-
CO, %
1.20
1.20
1.80
1.55
1.80
1.20
aComposite values of typical emission control car properly adjusted
after 4,000 miles are 230 ppm HC and 1.2 percent CO for this study.
E
0.
Z
O
s
LJU
Z
o
CO
CK
HYDROC/
300
200
100
0
I I I
HYDROCARBONS
275 STANDARD
AVERAGE 222 ppm ^L
~*~''*~~' "
X*"*
I I I
I '
/
/-
i~^
^~"
I
20 40 60 80
PERCENT OF CARS TESTED
100
Figure 4-1. Frequency distribution of exhaust
HC emission levels as derived from 1655 cold-
start dynamometer tests (composite cycle) on
1966 model new cars in California (GM quality
audit).1
o 3-u
t/>
oo
LLJ
UJ 2.0
Q £
x 8
0 J;
Z Q.
O
s 1.0
o
CO
Of.
U 0
1 1 1
CARBON MONOXIDE
-
1.5 STANDARD
AVERAGE 1.17 PERCENT ~^Lf
~ «*-^*"
-»-*^"
y^
'III
1 |
;
f
/-
s
.****
1
0 20 40 60 80 100
PERCENT OF CARS TESTED
Figure 4-2. Frequency distribution of exhaust
CO emission levels as derived from 1655 cold-
start dynamometer tests (composite cycle) on
1966 model new cars in California (GM quality
audit).1
action. The remainder of this section discusses
various factors involved in implementing such
programs.
4.2 PRESENT STATE PROGRAMS
In considering the problems faced by the
states in establishing active control programs,
it is helpful to examine some of the efforts
that have already been made. A number of
states are presently planning or initiating
active programs for surveillance, maintenance
4-2
and/or inspection, and other activities neces-
sary to evaluate the problems that exist and
to aid in achieving the necessary degree of
control. At present, however, no state is
operating a program to ensure continued
compliance with Federal emission standards.
California and New Jersey have made major
contributions to the knowledge that now
exists concerning the methods of control for,
mobile sources that can be used. Selecting
these two states for detailed discussion does
-------
not in any way minimize the progress made in
other states; the work in these two provides
information useful in evaluating the various
control options that exist.
4.2.1 California Program
California has taken several steps relating to
periodic inspection of vehicles. At the present
time, when a vehicle is resold, the new owner
(if he is a resident of a county that is in an air
pollution control district) must obtain a cer-
tificate of compliance from a certified inspec-
tion station. This requires that the vehicle be
equipped with a crankcase control system.
In addition, the State Highway Patrol is
authorized to give tickets for vehicles that
emit excessive visible smoke; this provides a
partial degree of control by forcing owners of
vehicles that are grossly maladjusted or in
need of repair to obtain maintenance work.
California uses a random spot-check system
for safety inspections; inspection teams move
from one location to another and check vehi-
cles without prior warning. In addition to
safety checks, these teams also check for the
presence of emission control systems on those
vehicles required to be so equipped.
Diesel trucks are being checked on an ex-
perimental basis for smoke emissions. At a
truck weighing station, readings are obtained
with a "smokemeter" instrument while the
truck is running under heavy load on a dyna-
mometer.
Investigations are in progress to identify
other inspection procedures that might be
used to advantage. Since past experience
indicates that the present control systems are
partially effective without inspection of all
vehicles, however, a concerted effort is being
made to evaluate the cost/benefit aspects of
various inspection methods. Since the costs of
some types of inspection are considerable,
this work should provide valuable information
on the incremental reduction of emissions
that can be achieved with various inspection
methods. The following methods are under
study as possible inspection and/or mainte-
nance procedures that might be required:
1. Inspection for the presence of evapora-
tive control devices (starting with 1970
models) and crankcase control devices,
plus measurement of exhaust emissions
including CO, NOX, and HC on a com-
plete driving cycle.
2. Exhaust gas measurements at idle condi-
tions only.
3. Tune-up type inspection and mainte-
nance to set engine adjustments to
manufacturers' specifications.
4. Checks for the presence of the necessary
control system components.
5. A "quick-cycle" dynamometer test and
exhaust gas measurement.
4.2.2 New Jersey Program
The State of New Jersey has adopted legis-
lation that, in essence, requires that each
motor vehicle manufactured under the
Federal emission control standards must pass
a test each year to show satisfactory perform-
ance of the emission control system and other
engine systems. It also requires vehicles manu-
factured prior to the adoption of Federal
standards to pass a test to show that the
engine is functioning properly and that emis-
sions are not excessive for a vehicle not
equipped with a control system. For con-
trolled vehicles, this will probably have the
effect of requiring the vehicle owner to main-
tain the control system and other engine
systems so that they operate according to the
manufacturers' specifications on engine
adjustment. For uncontrolled vehicles, this
will probably have the effect of requiring a
tune-up or other maintenance work to elim-
inate excessive emissions due to gross mal-
functions of some vehicles.
To implement this legislation, the State
Health Department is developing a rapid test
method for use in an annual inspection pro-
gram, and is now obtaining data to see what
emission levels are proper for both uncon-
trolled and controlled vehicles so that "pass-
fail" limits can be established for inspection
purposes. Limits are also being set on the
4-3
-------
emission of smoke from diesel-powered vehi-
cles, and a rapid-test method is being devel-
oped to enforce this provision.
Several hundred vehicles have been tested
at a State-operated inspection station, using a
dynamometer. A simplified four-mode driving
cycle is used. Analytical equipment measures
unburned HC, CO, and CO2 in the exhaust.
To assist in this work and to provide informa-
tion potentially useful to all of the states, the
National Air Pollution Control Administra-
tion has financed a portion of this investiga-
tion through a Federal grant. While many
problems still remain, this project has
achieved a substantial degree of progress in
development of an exhaust-measurement type
of inspection procedure for mass inspection
purposes.
Briefly, the accomplishments to date can
be summarized as follows:
1. The simple four-mode test cycle (ACID
for accelerate, cruise, idle, and deceler-
ate) has been developed, and test data
indicate that there appears to be some
correlation with test results obtained
with the longer and more expensive
seven-mode test cycle.
2. Different methods of measuring HC have
been evaluated. It was concluded that
results of analysis with the infrared tech-
nique are influenced by fuel composition
to some degree and that flame-ionization
detectors would be more suitable for
New Jersey's purposes. Thus, the present
method utilizes flame-ionization detec-
tors to measure HC emissions. Carbon
monoxide and CC>2 are measured with
infrared detectors.
3. Information has been developed on a
semidiagnostic readout, to assist the
motorist in securing proper maintenance
for vehicles that do not pass the test.
4. Available instruments and data process-
ing methods have been evaluated, and
some improvement in the present state
of the art has been brought about
through the adaptation and use of these
instruments.
4-4
One factor that has facilitated this work is
that New Jersey has State-owned and-
operated inspection lanes in which annual
safety inspection of all vehicles is performed.
Thus, both the experimental program and the
later implementation of a complete inspection
procedure can be facilitated through closer
control than could be achieved in other states
in which safety inspections are performed by
private garages and service stations. Progress
to date indicates that these lanes can be
equipped for exhaust measurement at a cost
in the range of $15,000 per inspection lane.
Included at this price would be a dyna-
mometer, analytical instrumentation, engi-
neering, and installation costs, since the
equipment is to be incorporated into existing
safety inspection lanes. This is a preliminary
estimate subject to confirmation as more
experience is gained in such installations.
Testing of some 250 cars per day in a single
lane appears to be possible. The vehicle would
pass or fail this inspection, and diagnostic
information could be given to the owner of
the vehicle that does not pass. At the present
time, data handling is the major bottleneck in
processing cars rapidly, but there is some indi-
cation that this can be improved through fur-
ther development.
4.3 LEGISLATION
Several states have already passed legisla-
tion that establishes a legal requirement for
the control of emissions from motor vehicles.
In some cases, this has been by an act of the
state legislature; in other cases, official action
has been taken by an air pollution control
board, commission, or other state agency.
Either method is acceptable, depending on
the legal requirements of individual states, so
long as a firm legal authority is established
under which necessary action can be taken.
Most of these laws and regulations include
two provisions. The first is a legal requirement
that the owner or operator of a motor vehicle
should not deliberately remove or inactivate
the control system. The second establishes a
system of inspection and/or maintenance.
-------
To illustrate, reference is made to a portion
of a suggested state air pollution control act
drawn up by the Council of State Govern-
ments, Committee of State Officials on Sug-
gested State Legislation.2 Although the exact
language may need to be modified to meet
legal requirements or special situations in the
various states, this law illustrates the provi-
sions that should be incorporated in the
legislation. This excerpt is taken from a sug-
gested state air pollution control law which is
comprehensive in nature, covering all sources
of air pollution, and establishing legal author-
ity and a state agency to conduct a complete
program. In this case, the "appropriate state
agency" referred to in the draft is similar in
nature to the existing air pollution control
boards or commissions in many of the states.
The "state motor vehicle agency" referred to
has, in many states, the legal responsibility for
conducting periodic safety inspections of
motor vehicles.
"SECTION 16. MOTOR VEHICLE POLLU-
TION
"(a) As the state of knowledge and tech-
nology relating to the control of emissions
from motor vehicles may permit or make
appropriate, and in furtherance of the pur-
poses of this Act, the (appropriate state
agency) may provide by rules and regulations
for the control of emissions from motor vehi-
cles. Such rules and regulations may prescribe
requirements for the installation and use of
equipment designed to reduce or eliminate
emissions and for the proper maintenance of
such equipment and of vehicles. Any rules or
regulations pursuant to this Section shall be
consistent with provisions of federal law, if
any, relating to control of emissions from the
vehicles concerned. The (appropriate state
agency) shall not require, as a condition pre-
cedent to the initial sale of a vehicle or vehic-
ular equipment, the inspection, certification
or other approval of any feature or equipment
designed for the control of emissions from
motor vehicles, if such feature or equipment
has been certified, approved or otherwise
authorized pursuant to federal law.
"(b) Except as permitted or authorized by
law, no person shall fail to maintain in good
working order or remove, dismantle or other-
wise cause to be inoperative any equipment or
feature constituting an operational element of
the air pollution control system or mechanism
of a motor vehicle and required by rules or
regulations of the (appropriate state agency)
to be maintained in or on the vehicle. Any
such failure to maintain in good working
order or removal, dismantling or causing of
inoperability shall subject the owner or oper-
ator to suspension or cancellation of the
registration for the vehicle by the (state
motor vehicle agency). The vehicle shall not
thereafter be eligible for registration until all
parts and equipment constituting operational
elements of the motor vehicle have been
restored, replaced or repaired and are in good
working order.
"(c) The (appropriate state agency) shall con-
sult with the (state motor vehicle agency) and
furnish it with technical information, includ-
ing testing techniques, standards and instruc-
tions for emission control features and equip-
ment.
"(d) When the (appropriate state agency) has
issued rules and regulations requiring the
maintenance of features or equipment in or
on motor vehicles for the purpose of con-
trolling emissions therefrom, no motor vehicle
shall be issued an inspection sticker as
required pursuant to (cite appropriate section
of motor vehicle inspection law), unless all
such required features or equipment have
been inspected in accordance with the stand-
ards, testing techniques and instructions fur-
nished by the (appropriate state agency)
pursuant to subsection (b) hereof and has
been found to meet those standards."
In addition, a law should establish some
sort of legal remedy and penalty to apply in
cases of violation. Also, depending on what
other legislation may be in existence, defini-
tion of the term "motor vehicle" and of other
terms used in the act may be necessary. With
this type of legislation or regulation, it is
possible to establish a legal framework within
4-5
-------
which an active state program can be
conducted.
4.4 OPTIONS ON INSPECTION AND/OR
MAINTENANCE PROCEDURES
Many different inspection procedures have
been suggested to identify vehicles with unac-
ceptably high exhaust emission rates or to
reduce emissions from an entire vehicle popu-
lation. Several of these are being evaluated at
the present time, and it is anticipated that
much more information will be available in
the near future. This document outlines only
the known advantages and limitations of each
of these methods so that state agencies can
evaluate them and make their own selection.
It is emphasized here that a choice of
inspection and/or maintenance methods and
other details of an automotive emission con-
trol program may properly vary from state to
state. Each state agency should evaluate the
relative importance of automotive emissions
as a present and future source of air pollution
in comparison with industrial, municipal, and
other sources, and it should establish prior-
ities accordingly for automobile emission
control.
Some essentially rural states may attach a
lower priority to motor vehicle emissions at
this time. Favorable climatological conditions
for more rapid dispersion of contaminants
may reduce the immediate need for an aggres-
sive program to control vehicular emissions in
some localities. Vehicle emission control pro-
grams, however, may be needed to maintain
acceptable air quality (prevent air pollution)
in these states in the future.
In evaluating different inspection and/or
maintenance procedures that might be used to
prevent and control CO and HC emissions, it
is important to point out that the control
systems being installed on new vehicles are
inherently quite dependable and will achieve a
fair degree of reliability, even in the absence
of any inspection and/or maintenance pro-
cedure. This has been demonstrated in Cali-
fornia, where approximately 4 years of
experience has been accumulated.
4-6
The following inspection and/or mainte-
nance procedures for control of CO and HC
exhaust emissions1 -3'1 2 have been suggested:
1. Visual inspection for the presence of
control devices or systems.
2. Requirement of a minor tune-up at some
time interval.
3. Requirement of a major tune-up at some
time interval.
4. Exhaust measurement at idle to identify
high emitters for subsequent corrective
action.
5. Exhaust measurement under load on a
dynamometer to identify high emitters
for corrective action.
6. Exhaust measurement under load on a
dynamometer to diagnose reasons for
high emissions and to indicate what cor-
rective action should be taken.
Some of the known advantages and limita-
tions of each method are included in the
following discussion. Various inspection and/
or maintenance procedures have reduced
emissions of CO and HC; additional data are
needed to demonstrate the cost and cost-
effectiveness of such programs in practice.
4.4.1 Visual Inspection
It is difficult to estimate how many vehi-
cles, which were equipped with emission
control systems at the factory, have had these
systems removed or inactivated. Most studies
of deterioration of the effectiveness of con-
trol devices have involved cars that the
owners have voluntarily made available to the
study group. It would seem that owners who
volunteer their cars for such a study would
not be likely to have disconnected or inacti-
vated the control system. There are indica-
tions, however, that a sizeable percentage of
motorists do deliberately remove or inactivate
their emission control systems.
Legislation, of the type discussed in Sec-
tion 4.3, coupled with a visual inspection for
the presence of emission control systems,
could be an effective way to prevent most of
this deliberate removal and inactivation.
There would be some difficulty in enforce-
ment because some "devices" are engine
modifications and adjustments of operating
-------
parameters. Alterations of these might be
difficult to perceive. A stipulated fine and
inspection, on a random spot-check basis or
incorporated into a state vehicle-safety inspec-
tion program, might be sufficient to stop most
deliberate removal and inactivation of control
systems; however, such a program would
require that inspectors be familiar with at
least the types of systems and equipment
provided for emission control on the most
popular vehicles.
4.4.2 Minor Tune-Up
The minor tune-up type inspection and
maintenance program consists of checking
adjustments of idle speed, idle air-fuel ratio,
spark advance at idle, and possibly other
engine operating parameters and resetting
them to manufacturers' specifications if
necessary. This procedure can usually be
accomplished with fairly simple equipment,
which is generally available in most garages,
service stations, and dealerships. If air-fuel
ratio is to be measured directly, some expen-
sive instrumentation will necessarily be in-
volved. A tachometer, which measures engine
speed, can often be used to set the idle air-
fuel ratio approximately.3
Cost and effectiveness of the tune-up type
inspection and maintenance program, done on
an annual basis, are shown in Table 4-2. Some
difficulties associated with this type of pro-
gram should be pointed out. Mechanics at
service stations, independent garages, and
even automobile dealerships, in most areas of
the country, are not accustomed to tuning
cars so as to reduce emissions. Their principal
concern is generally to improve performance
or operating economy; therefore, it would be
desirable for personnel involved in a tune-up
type inspection and maintenance program to
undergo fairly extensive training. Attempting
to train the large number of auto service per-
sonnel (with associated high turnover rates)
throughout a state would probably be a
tremendous undertaking in most cases. The
general type of minor tune-up inspection and
maintenance described herein is recom-
mended by the Automobile Manufacturers
Association.4
Although several sources of data 3 7 indi-
cate that emissions of CO and hydrocarbons
can be reduced through this type of minor
tune-up program, it is likely that oxides of
nitrogen emissions would be increased. The
effects of minor tune-up on NOX emissions3
in one study were:
Number of test vehicles .... 15
Average emissions of NOX
(as NC>2) as received 1,777 ppm*
Average emissions of NOX
(as NC<2) after adjust-
ment of idle speed and
idle air-fuel ratio 1,890 ppm*
Increase 6.3%
Modification of the basic minor tune-
up type of approach to include an oscillo-
scope diagnosis of the ignition system tends
to increase control effectiveness and cost as
shown in Table 4-2.
4.4.3 Major Tune-Up
Major tune-up generally includes replace-
ment of spark plugs and breaker points, and
possibly other parts of the engine. This is
done on the basis of the expected life of these
parts, and generally no diagnosis is involved.
It may include the adjustments made as part
of the minor tune-up program.
The length of time required to perform a
major tune-up is such that it is unlikely that a
state can provide facilities and personnel at an
early date to tune up all registered vehicles on
an annual basis. Implementation of a major
tune-up program would, therefore, invariably
involve the private sector. Since mechanics are
generally unaccustomed to tuning cars to
reduce emissions, the magnitude of the train-
ing program required is again apparent. Since
automobile dealerships do only about 25
percent of the total auto service in the coun-
try, a training program sponsored by the auto-
mobile industry would probably not reach the
majority of people performing auto service.
The cost of a tune-up can not be strictly
considered as an expenditure only for emis-
sion control, because cars are also tuned for
*Bag-sampling, 10-mode dynamometer cycle, hot-
start tests.
4-7
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oo
Table 4-2. COST AND EFFECTIVENESS FOR SEVERAL TUNE-UP INSPECTION
AND/OR MAINTENANCE APPROACHES3
Type of inspection
and/or maintenance
Minor tune-up - adjustment of idle
speed and air-fuel ratio
Minor tune-up - adjustment of idle
speed and air-fuel ratio, and
ignition timing
Minor tune-up with oscilloscope
diagnosis of ignition system
Major tune-up (approximate figures)
Major tune-up by commercial
garages - no specific instructions
to garages
Major tune-up by commercial
garages - specific instructions
written by AMA
Major tune-up including replacement
of air filters and some wiring - idle
set 50 rpm over manufacturers' speci-
fications - spark retarded 5 degrees
Reference
3a
12b
12b
id
6e
6e
6e
Average total annual,
out-of-pocket cost
per car,
including repairs
$3.00
$6.70C
$15.00
$20 - 30.00
$23.45f
$29.25f
$36.88f
Immediately after
service
HC
reduction
(exhaust),%
10
18
24
10
5
6
27
CO
reduction
(exhaust), %
16
29
27
20
9
8
21
Cost-benefit ratios
$ per car/
% HC removed
0.30
0.37
0.62
2.00-3.00
4.69
4.88
1.37
$ per car/
% CO removed
0.19
0.23
0.55
1.0-1.50
2.61
3.66
1.76
aBased on 53% equipped, 47% not equipped with exhaust emission control systems.
°Based on 22% equipped, 78% not equipped with exhaust emission control systems.
cReference 12 indicates that this could be reduced to $1.60 per car on a large-scale, full-utilization basis.
"AH vehicles studied equipped with exhaust control systems.
eNone equipped with exhaust control systems.
'Reference 6 indicates that these costs .should be reduced by $8.80 to account for gasoline savings resulting from tune-up, and by $7.81 to account for what
owners normally spend voluntarily on major tune-ups. Since all other methods of inspection and/or maintenance have some uncertain dollar value (other than
emission control), average, total, annual, out-of-pocket costs are reported for the years in which studies were done.
-------
reasons of performance and economy.6 Since
it is very difficult to assess the benefit derived
from a tune-up in terms of dollars saved on
gasoline, the value of better performance, or
the possible prevention of more expensive
maintenance in the future, the costs quoted in
Table 4-2 are total out-of-pocket costs for the
years in which the studies were conducted.
It is interesting to note the effect climate
has on the frequency of tune-up in a given
area. Since well-tuned cars start more reliably
in very cold weather, motorists in cold cli-
mates probably have their cars tuned more
often than do owners in warm climates. For
this reason, many vehicles in warm climates,
which need a tune-up from an emissions point
of view, continue to start and perform
adequately, and their owners are not induced
to have them tuned up.
4.4.4 Exhaust Measurement at Idle
One type of inspection has been proposed
in which exhaust emissions at idle are meas-
ured, and, thus, vehicles that emit large
amounts of CO and hydrocarbons can be
identified.8 Since automobiles are used pri-
marily under conditions other than idle, it
may be debated whether a test of emissions at
idle adequately reflects emissions during other
operating modes. One study has shown that
there is some correlation between high emis-
sions at idle and high emissions during other
modes of operation.8
Any inspection system concerned with
measurement of the concentration of CO and
hydrocarbons in the exhaust gas involves
fairly expensive and sophisticated equipment.
Although an idle test may indicate which
vehicles have abnormally high emissions, it
provides very little diagnostic aid as to what
specific type of malfunction or maladjust-
ment produces the high emissions. It should
also be pointed out that many engines that
are not well tuned may perform adequately at
idle, but poorly under load. A measurement
of exhaust emissions at idle might not indi-
cate that such an engine needs a tune-up.
4.4.5 Exhaust Measurement Under Load
For Purpose of Identifying High
Emitters
To measure exhaust under load conditions,
an inspection procedure utilizing a dynamom-
eter to simulate driving conditions has been
proposed. Emissions as determined on the
ACID cycle (Accelerate, Cruise, Idle, and
Decelerate) or other load-test cycle would be
compared with standards for the maximum
allowable emission rates for CO and HC for a
given vehicle on the cycle. It would be the
owner's responsibility to have his car repaired
if it did not pass, and then to return so that it
could be retested.
In a large group of vehicles, a few of them
could not meet any reasonable emission limit,
no matter how much they were repaired or
tuned up. This is due to the variability of
emissions of both controlled or uncontrolled
vehicles. The selection of test standards for
this type of program is, therefore, a very diffi-
cult task.
Just as there would be some vehicles with
very high emissions, there would be some
with very low emissions, which might increase
because of poor maintenance or maladjust-
ment. As long as the emissions from these
vehicles stayed below maximum limits, no
corrective action would be taken. There is no
question, however, that this type of program
identifies vehicles that are high emitters.9 For
this reason, it can reduce emissions of CO and
hydrocarbons from vehicles, as shown in
Table 4-3.
This system does provide some diagnostic
data to assist the owner in obtaining necessary
repair work if his car is rejected. Installation
cost, for one of the many lanes which would
be required for such a program on a statewide
basis, is approximately $15,000 per lane, if
the dynamometer and exhaust measurement
equipment can be incorporated into an exist-
ing safety-inspection lane. If, however, facili-
ties were built only to determine vehicle
emissions, costs for a building, dynamometer,
instrumentation, fire protection system,
4-9
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Table 4-3. COST AND EFFECTIVENESS FOR SEVERAL TUNE-UP INSPECTION
AND MAINTENANCE APPROACHES USING DYNAMOMETERS
Type of inspection
and maintenance
New Jersey - ACID identifies high
emitters, corrective action taken
Clayton - Key Mode diagnosis,
corrective action taken
ACID type cycle used for diagnosis-
indicated adjustments and repairs
made
Dynamometer and oscilloscope used
for diagnosis - indicated adjustments
and repairs made - all carburetors
rebuilt or replaced - idle set 75 rpm
above manufacturers' specifications
Reference
12a
12a
5C
6d
Average total annual,
out-of-pocket cost
per car,
including repairs
$4-7.50b
$13.85b
$10.30
$50-60.00e
Immediately after
service
Exhaust
HC
reduction ,
%
13-19
24
6
28.9
Exhaust
CO
reduction,
%
7-14
23
13
13.4
Cost-benefit ratios
$ per car/
% HC removed
0.31 -0.39
0.58
1.72
1.73 -2.08
$ per car/
% CO removed
0.57-0.54
0.60
0.79
3.73 -4.48
aBased on 22% equipped, 78% not equipped with exhaust control systems.
Estimated - large-scale, full-utilization basis.
CA11 vehicles studied equipped with exhaust control systems.
"None equipped with exhaust control systems.
eReference 6 indicates that these costs should be reduced by $8.80 to account for gasoline savings resulting from tune-up, and by $7.81 to account for wha
owners normally spend voluntarily on major tune-ups. Since all other methods of maintenance and/or inspection have some uncertain dollar value (other thar
emission control) average, total, annual, out-of-pocket costs are reported for the years in which studies were done.
-------
exhaust removal system, and other necessities,
would be very much higher.
Since the capital costs of this or any other
program involving the use of dynamometers
and exhaust measurement instrumentation are
quite high, states may find that only a few
auto service establishments are willing or able
to make the investment required to partici-
pate on a franchise basis. It is likely, then,
that if a state adopted this or any other pro-
gram involving such expensive apparatus on a
full-scale basis, it would have to be prepared
to invest in equipment and training of per-
sonnel.
4.4.6 Exhaust Measurement Under Load for
Purpose of Diagnosis
The primary aim of this approach is to
diagnose all cars in a state so that they can be
tuned, if necessary, to reduce emissions of
hydrocarbons and CO.
Since there is no absolute maximum
emission limit involved, all cars would even-
tually be able to pass, provided their owners
had taken all indicated steps to reduce emis-
sions. Diagnostic data accumulated for all cars
would tend to indicate the kind of adjust-
ments or repairs needed to reduce emis-
sions.10 Cost and effectiveness for this kind
of system are shown in Table 4-3. Installation
cost for the necessary equipment for one
inspection lane, when incorporated in a vehi-
cle safety inspection lane, is about
$10,000.J1
As indicated in Section 4.4.5, costs for
independent facilities designed only to deter-
mine vehicle emissions would be much higher.
Remarks in Section 4.4.5 with regard to
capital investment by states are equally
applicable to this section.
4.4.7 Crankcase Emission Control Device
Inspection
Several options may be considered for
crankcase control inspection. One is a crank-
case vacuum check with a gage to determine
that the control valve on the device is oper-
ating properly.13 This is relatively simple to
perform and could be added to an exhaust
inspection procedure at little added cost.
Another option is merely to check for the
physical presence of the control valve and
tubing which constitute a crankcase control
device. This will detect deliberate circum-
vention but will not detect the occasional
engine which might be subject to malfunction
of the positive crankcase ventilation (PCV)
valve. Although malfunction of the valve in a
complete, closed positive crankcase ventila-
tion system will not cause emissions of
blowby directly, it may cause an increase in
exhaust emissions of both CO and HC.1
Options for rapidly determining whether
the valve is working properly include the
following:
1. With the engine running at a high idle
speed (1200 to 1500 rpm) and the oil
filler cap off, place a sheet of paper or
cardboard over the open oil filler pipe
and thus check for vacuum in the crank-
case. If a vacuum is perceived, the valve
is open. If it is stuck open, the engine
will idle roughly at low rpm (500 to
700) or will be unable to run at all at
low idle speed.
2. With the engine idling at low speed (500
to 700 rpm), clamp and release the
crankcase ventilation hose between the
PCV valve and the intake manifold. If
the valve is working properly, a "click"
will be heard each time the hose is
clamped and released.
3. With the engine idling at low speed (500
to 700 rpm), and the oil filler cap
removed, some traces of visible emissions
may vent from the crankcase. If the PCV
valve is functioning properly, these emis-
sions will cease and even appear to
change direction of flow as the engine
speed is increased to a high idle (1200 to
1500 rpm).
The principles of operation of both "open"
and "closed" crankcase ventilation systems
are discussed in Section 5.1.1. As indicated
therein, it is desirable from the standpoints of
both emission control and engine life and
4-11
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operation that defective or clogged PCV
valves be replaced or repaired.
4.4.8 Evaporative Emissions Control System
Inspection
Starting with the 1971 models (1970
models in California), evaporative control
devices will be required on new cars by Fed-
eral law, and their inspection could be
included in any vehicle emission control plan.
Two types are described in Section 5.2.1,
Evaporative Controls.
Most of these devices are relatively simple
in operation, and an inspection to determine
that the equipment is on the vehicle would
probably suffice. Further information will be
available on these devices when they are
introduced on more production vehicles, and
more detailed information on various inspec-
tion and/or maintenance procedures, and on
their advantages and limitations may be avail-
able at that time.
4.4.9 Oxides of Nitrogen Control System
Inspection
No specific guidelines can be established at
this time for inspection of systems to reduce
emissions of nitrogen oxides, since such sys-
tems have not yet been applied to production
vehicles. Several are under development and
are described in Section 5.2.2, Prospective
Control System Development.
4.5 OTHER OPTIONS RELATIVE TO
VEHICLE EMISSIONS
In addition to the various controls dis-
cussed earlier, other actions can be taken by
state and local governments to reduce CO,
NOX, and HC emissions from automobiles.
These actions, however, are not directly re-
lated to control systems or maintenance pro-
cedures. These other measures are additional
options that should be considered because
they may make an overall state program more
effective. One or a combination of the follow-
ing objectives may be accomplished:
4-12
1. A decrease in emission levels of individ-
ual vehicles.
2. A decrease in use of individual vehicles.
3. A decrease in number of vehicles.
4. A reduction in traffic congestion to
minimize stop-and-go driving and to
maintain slow-cruise conditions and
thereby affect vehicular emissions.
4.5.1 Substitution of Public Transportation
"Substitution" of public transportation is
suggested as a method of reducing the number
of automobiles in urban areas. If there is a
good transit system, private ownership of
automobiles becomes less practical or desira-
ble in some very densely populated cities
because of the availability of good public
transportation and because of costs and
inconveniences incidental to private owner-
ship. Most of the work to investigate and
encourage development of public transporta-
tion has been focused on expediting move-
ment of masses of people rather, and rightly
so, than reduction of vehicle emissions.
Generally, however, a result of substitution of
public transportation is lower emissions per
passenger mile. A determination of the rela-
tive merit, from an emission-reduction point
of view, of a particular public transportation
system is meaningful only when the percent
reduction in vehicle-miles traveled caused by
the system can be established.
Increase in capacity, reduction of travel
time, or combinations of the two are em-
ployed to achieve prime objectives in upgrad-
ing public transportation. Improvement of
bus and rail systems has yielded gratifying
results, but route inflexibility remains a prob-
lem, solutions for which are being investi-
gated.14 It should be remembered that the
success of a particular public transportation
system is related to the population density
and the average distance that separates the
points between which people wish to travel in
the area. Generally, the higher the population
density, and the closer the points to be con-
nected, the more applicable is public trans-
portation to a particular area.
-------
4.5.1.1 Bus Systems
Use of bus systems may be expanded by
increasing carrying capacity by means of
articulated buses or double-deck buses, either
of which can reduce operating costs since
two-thirds of present costs represent driver
wages and fringe benefits.14 Maximum legal
speeds are apparently reached without diffi-
culty by current equipment. A dual mode bus
capable of operating on either streets or rails
has been investigated experimentally, but
requires additional work.14
4.5.1.2 Rail Systems
Rail systems include commuter railroads,
rapid transit (subways), street cars, and
monorails. As a means for conveying passen-
gers, they are concentrated in, around, and
between large cities. Their main advantage is
their ability to provide rapid transportation
for large numbers of passengers.14 They also
have a significant effect on reducing emissions
in urban areas. A once-abandoned rail system
(the Skokie Swift Project), a demonstration
study by the Chicago Transit Authority, for
example, reportedly reduced hydrocarbons 13
percent over a 40-square-mile area because of
a decrease of 2000 automobile trips per
day.1 s Prior to enactment of the Urban Mass
Transportation Act of 1964, such rail sys-
tems and associated facilities had seen only
limited upgrading. From that time through
Fiscal year 1969, however, the Act has
authorized financial assistance totalling $150
million.14 The San Francisco BART system is
still under construction, but will have a trans-
port capacity of 30,000 seated passengers per
hour and a maximum speed of 80 mph.14
4.5.2 Road Design and Traffic Control
Traffic routing is a function of right-of-way
and roadway planning. Reduction of vehicle
emissions may be induced through these
aspects of road design primarily as they
reduce travel distances and permit sustained
moderate speeds.
Table 4-4 shows the effect of vehicle oper-
ating mode on emissions of CO, NOX, and
HC, and points out the advantages of traffic
flow at low-speed cruise conditions in urban
areas.16 It has also been reported17 that the
logarithms of both CO and HC emissions
decrease proportionally as the logarithm of
route speed increases. While freeways are not
always feasible, the value of the establishment
or designation of continuous traffic arteries
featuring minimum flow interruption is illus-
trated. The effectiveness of such arteries in
both traffic handling and emission reduction
will also benefit from entrances and exits so
designed as to avoid traffic bottlenecks and
significant variations in mass traffic flow.
Clear, direct, and uniform marking of exits
and destinations in order to minimize driver
indecision at traffic diversion points would
also be effective.
Objectives of freeways and other traffic
arteries may be furthered by controls con-
ducive to the elimination or reduction of
traffic congestion peaks and by abnormal
flow interruptions. Staggered working hours
have been used where employee concentra-
tion is high, largely to facilitate traffic flow.
This method is not limited to traffic arteries,
but is also generally applicable to metro-
politan areas.
Traffic speed may be controlled by auto-
matic sensors and controllers.18 Optical
devices, treadles, or buried loops sense traffic
flows and speeds, and modulate mass flow by
such devices as traffic lights. Several complex
automatic systems are in operation.1 4
Regulations to limit .the numbers or use of
vehicles may take the form of fuel rationing,
limited registration of second or third cars in
metropolitan areas, banning or limiting the
use of internal combustion engines in affected
areas at critical times, and reducing the avail-
ability of all-day parking in affected areas.
The net effect of some of these measures is
the encouragement of car pools.
4.5.3 Control of Older Vehicles
The present Federal regulations for emis-
sion control apply to new vehicles as they are
manufactured. Because of the normal rate of
4-13
-------
Table 4-4. EFFECT OF VEHICLE MODE ON EMISSIONS16
Condition
Vehicle
Idle
Cruise
Low speed
High speed
Acceleration
Moderate
Heavy
Deceleration
Soak
Hot
Diurnal
Engine
Operating
Stopped
Exhaust
Flow
Very low
Low
High
High
Very high
Very low
None
None
Concentration
HC
High
Low
Very low
Low
Moderate
Very high
-
CO
High
Low
Very low
Low
High
High
-
NOX
Very low
Low
Moderate
High
Moderate
Very low
-
Blowby3
flowb
Low
Moderate
High
Moderate
Very high
Very low
None
None
Fuel system0
flowb-HC
Tank
Average
to
Moderate
High
Moderate
Carburetor
Moderate
Small
Nil
Nil
Nil
Moderate
High
Very low
Concentration of HC is high, CO low, and NOX very low.
bplows are at least one order of magnitude lower than the exhaust flow.
cFor a vehicle not equipped with an evaporative emission control system.
obsolescence, however, several years must
elapse before most of the entire vehicle popu-
lation in any metropolitan area will be con-
trolled. This suggests the possibility that
present vehicles not equipped with control
systems might be controlled to accelerate the
rate of progress in the reduction of automo-
tive emissions.
The difficulties involved in such a program
are formidable, since it is much more difficult
and expensive to install a control system on
an existing vehicle than to install a system on
a vehicle at the time of manufacture. Since
the value of a used car is usually less, the
control system will thus cost much more in
proportion to the value of the car than for the
equipping of a new vehicle.
Exhaust control systems capable of being
installed on used cars were tested by the Cali-
fornia Motor Vefiicle Pollution Control Board
in 1963 and 1964, but were never required
for used vehicles because of excessive cost.
The State of California is still interested in
cheaper devices for use on older vehicles, but
so far systems have not been certified that
4-14
cost less than the maximum of $65 estab-
lished by the legislature to equip a used vehi-
cle.19 One domestic manufacturer, however,
may provide a kit to reduce CO and HC
exhaust emissions from pre-1968 cars pro-
duced by that company for about $50.20
This idea was proposed by the automobile
industry as early as 1962.2 1
California has been requiring the installa-
tion of crankcase control devices on used
vehicles since 1964. California requires that
such a device be installed (in most cases)
when a used car is sold or traded. The diffi-
culties encountered in equipping used cars in
California illustrate probable obstacles in
attempting this in other jurisdictions.
4.5.4 Long-Range Plans
The states may wish to consider planning
for future reductions in vehicular emissions.
Some options of this type are listed below.
4.5.4.1 Actions Under Emergency Situations
Planning for emergencies may invite consid-
eration of means to reduce vehicle use. Any
-------
locality can expect a few days per year when
conditions of the atmosphere will produce a
higher degree of air pollution than at other
times. Some cities have investigated the pos-
sibility of establishing emergency plans for
use on such days to limit to the maximum
extent possible all sources of air pollution.
Limitation of automobile traffic would
decrease the amount of vehicular emissions.
There can be difficulties with such a program,
however, since transportation by automobile
is an integral part of our society in most
urban areas, and a reduction in automobile
traffic would seriously overload public trans-
portation facilities. Some means of legal
enforcement would be required. No state or
local governments have instituted a wide-
spread plan in the past, although on some
occasions appeals have been made for volun-
tary cooperation by the public in limiting use
of automobiles.
4.5.4.2 Other Vehicle Propulsion Systems
Research efforts have been expended
within the past few years to develop other
systems of propulsion for vehicular use,
including gas turbines, steam engines, electric
drives, and others. Some of the most promi-
nent are treated briefly in Section 7, Possible
Substitutes for Currently Used Motor Vehicle
Engines. A major justification advanced for
this effort is the relatively low emissions of
some such sources. Realistic evaluation should
consider these possibilities over a rather long
time interval. At present stages of develop-
ment, practical systems employing these
concepts in mass production are unlikely
within less than 10 years. Several more years
will be required before vehicles employing
these low-emission power sources dominate
the vehicle population. Thus, significant
reductions of CO, NOX, and HC emissions by
other vehicle propulsion systems are many
years away.
4.5.4.3 Certification of Maintenance
Personnel
The State of California has established a
program of certification for mechanics and
inspection stations authorized to grant a
certificate of compliance for vehicles at the
time of resale. Since proper maintenance of
exhaust control systems and other engine sys-
tems affecting emissions requires considerable
knowledge and skill by a mechanic, a me-
chanic certification program might aid in
reducing maladjustment and malfunction of
systems. This suggests the possibility that a
state or local certification program might be
considered. At the present time, no feasible
plan has been found, except in California,
where the resale of the vehicle can be used as
a mechanism to aid enforcement.
4.5.4.4 Driver Training
Suggestions have been made that some
emphasis in driver education on the effects of
driving practices upon vehicle emissions may
yield benefits.18 Such an effort might take
the form of incorporation in public and pri-
vate driver instruction programs preparatory
to driver license examination, coordination
with a vehicle fleet safe-driving instruction
program, etc. The effects of driving practices
on both concentration and mass of vehicle
emissions are recognized in the seven-mode
driving cycle specified for Federal certifica-
tion compliance testing of new vehicles.
Accelerations and decelerations, particularly
at high rates, result in considerable increase in
emissions. No concerted effort in this direc-
tion is known, although during wartime peri-
ods of gasoline rationing, significant reduc-
tions in gasoline consumption per vehicle for
commercial fleet operations resulted from
concentrated educational and promotional
campaigns coordinated with some form of
individual merit recognition.
4.6 REFERENCES FOR SECTION 4
1. Roensch, M. M. Exhaust Emission Control-
Maintenance vs. Inspection. Presented at 61st
Meeting Air Pollution Control Association. St.
Paul, Minnesota. June 1968.
2. Degler, S. E. Appendix B. Model State Air Pollu-
tion Control Act. In: State Air Pollution Control
Laws. Washington, D.C., Bureau of National
Affairs, Inc., 1969. p. 68-86.
4-15
-------
3. Dickinson, G. W., H. M. Ildvad, and R. J. Bergin.
Tune-up Inspection, A Continuing Emission
Control (General Motors Corp., SAE Paper No.
690141) Presented at Automotive Engineering
Congress and Exposition, 1969 Annual Meeting.
Detroit. January 13-17, 1969. 23 p.
4. Bowditch, F. W. Automobile Manufacturers
Association Statement Before the President's
Environmental Quality Council. San Clemente,
Calif. August 26, 1969.
5. Brubacher, M. L. and J. C. Raymond. Reduction
of Vehicle Emissions by a Commercial Garage.
Presented at the 7th Technical Meeting, West
Coast Section, Air Pollution Control Association.
October 20, 1967.
6. Brubacher, M. L. and D. R. Olson. Smog Tune-up
for Older Cars (SAE Paper No. S403) Presented
at SAE Southern California Section, April 1964.
In: Vehicle EmissionsPart II, VoK 12, New
York, Society of Automotive Engineers, Inc.,
1966. p. 268-290.
7. Sweeney, M. P. and M. L. Brubacher. Exhaust
Hydrocarbon Measurement for Tuneup Diagnosis
(SAE Paper No. 660105). In: Vehicle
EmissionsPart II, Vol. 12. New York, Society
of Automotive Engineers, Inc., 1966. p. 307-316.
8. Chew, M. F. Auto Smog Inspection at Idle Only.
(SAE Paper No. 690505). May 1969.
9. Pattison, J. N. et al. New Jersey's Rapid Inspec-
tion Procedures for Vehicular Emissions (SAE
Paper No. 680111). New Jersey State Dept. of
Health. Presented at Automotive Engineering
Congress and Exposition, 1968 Annual Meeting.
Detroit. January 8-12, 1968. 13 p.
10. Cline, E. L. and L. Tinkham. A Realistic Vehicle
Emission Inspection System. J. Air Pollution
Control Assoc. 19:230-235, April 1969.
11. Merritt, W. O. et al. A Study to Determine the
Feasibility of Instituting a Periodic Motor Vehi-
cle Inspection Program for the State of Wiscon-
sin. Clayton Manufacturing Company. El Monte,
California. March 6, 1969. 53 p.
12. A Study of Selected Hydrocarbon Emission Con-
trols. National Air Pollution Control Administra-
tion. Raleigh, N.C. July 1969.
13. Glenn, H. T. Automotive Smog Control Manual.
New York, Cowles Education Corp., 1968. 147
P-
14. Tomorrow's Transportation: New Systems for
the Urban Future. U.S. Dept. of Housing and
Urban Development, Washington, D.C., U.S.
Government Printing Office, 1968. 100 p.
15. U.S. Congress. Senate. Committees on Commerce
and Public Works. Electric Vehicles and Other
Alternatives to the Internal Combustion Engine.
Joint Hearings Before the Committee on Com-
merce and the Subcommittee on Air and Water
Pollution of the Committee on Public Works,
90th Congress, 1st Session on S. 451 and S. 453,
March 14-17 and April 10, 1967. Washington,
D.C., U.S. Government Printing Office, 1967.
550 p.
16. Brehob, W. M. Control of Mobile Sources. Pur-
due University. Presented at the 8th Conference
on Air Pollution Control. Lafayette, Indiana.
October 14-15, 1969.
17. Rose, A. H., Jr. et al. Comparison of Auto
Exhaust Emissions in Two Major Cities. Journal
of the Air Pollution Control Association.
75(8):362-366. August 1965.
18. Duckstein, L., M. Tom, and L. L. Beard. Human
and Traffic Control Factors in Automotive
Exhaust Emission (SAE Paper No. 680398).
Arizona University. Presented at SAE Mid-Year
Meeting. Detroit. May 20-24, 1968. 9 p.
19. Annual Report to Governor Ronald Reagan and
the Legislature. Air Resources Board. State of
California. January 1969.
20. Irvin, R. Number One Auto ProblemFord
Fights Pollution. Detroit News. December 11,
1969. p. 1.
21. Heiner, C. M. Using the Engine for Exhaust Con-
trol. Presented at the Los Angeles Section of the
Society of Automotive Engineers. November 19,
1962.p. 11.
4-16
-------
5. TYPES OF EMISSION CONTROL SYSTEMS
5.1 CURRENT SYSTEMS
Emission control systems presently in use
on new cars nationwide include a closed
positive crankcase ventilation system, de-
signed to prevent gases that blow by the
piston rings from escaping into the atmos-
phere, and exhaust emission control systems,
designed to reduce CO and HC emissions in
the exhaust gas.
5.1.1 Positive Crankcase Ventilation
Systems
These systems provide the means of circu-
lating air through the crankcase and drawing
the circulated air and blowby gases into the
intake manifold, where they are carried on to
the combustion chambers.
Typically, ventilation air is drawn either
directly from the engine compartment (open
system), or through the engine air cleaner
through a hose (closed system), into a rocker
arm compartment, down into the crankcase,
across and up into the opposite rocker arm
compartment, up through a ventilator valve
and hose, and into the intake manifold. In-
take manifold vacuum draws gases from the
crankcase into the intake manifold.
When airflow through the carburetor is
high, additional air from the positive crank-
case ventilating system has no noticeable
effect on engine operation; but at idle speed,
airflow through the carburetor is so low that
an excessive amount added by the ventilating
system would upset the air-fuel mixture and
cause rough idle. For this reason, a flow con-
trol valve is used to restrict the ventilating
system flow whenever intake manifold
vacuum is high. At idle, if abnormally high
volumes of blowby gases occur, they are con-
ducted to the air cleaner through the intake
air hose in the closed system, or are vented to
the engine compartment through the crank-
case "breather cap" in the open system, since
it does not include a hose from the air cleaner
to the crankcase. Figure 5-1 illustrates six-
and eight-cylinder engine installations of a
typical closed crankcase ventilation system.
After a period of operation, the ventilator
valve may become clogged with deposits, re-
ducing and perhaps finally stopping all crank-
case ventilation. An engine operated without
any crankcase ventilation can be damaged
seriously; therefore, manufacturers recom-
mend cleaning or replacing the ventilator
valve periodically.
5.1.2 Exhaust Emission Control Systems
The amount of combustibles exhausted
from motor vehicles can be reduced by either
of two broad approaches, oxidizing CO and
unburned HC in the exhaust system or mini-
mizing the mass of these contaminants re-
leased from the cylinders.
For the 1966 models sold in California,
American Motors, Ford, and General Motors
adopted the first approach, injecting addi-
tional air into the exhaust ports to further
burn the hydrocarbons and CO and, thus,
forming additional water and CO2- Chrysler
adopted the approach of establishing engine
operating conditions that minimize emission
of unburned hydrocarbons and CO from the
combustion chambers. Beginning with the
1968 model year, American Motors, Ford,
and General Motors adopted the engine modi-
fication system for most of their models. For
1969 and later models, the air injection
approach is generally used only on vehicles
equipped with manual transmissions.
5-1
-------
CLOSED OIL
FILLER CAP
AIR CLEANER HOSE
r
VENTILATOR VALVE HOSE
CYLINDER
HEAD
COVER
VENTILATOR VALVE
HOSE
AIR CLEANER HOSE
VCLOSED OIL
.FILLER CAP
CYLINDER HEAD
COVER
VENTILATOR VALVE
ASSEMBLY
SIX-CYLINDER ENGINES
V-8 ENGINES
Figure 5-1. Closed positive crankcase ventilation systemJ (Courtesy of Chrysler Corporation)
The engine modification approach includes
designing engines with very good fuel distri-
bution characteristics so that they can operate
at quite lean air-fuel ratios. Spark advance
characteristics are also tailored for optimum
emission control.
5.1.2.1 Engine Modification Systems
The engine modification approach is used
on most of the 1969 model cars produced in
the United States. Among the various manu-
facturers, the approach is known as the
Cleaner Air Package (CAP) for Chrysler-
produced cars, Improved Combustion (IMCO)
system for Ford, Controlled Combustion
System (CCS) for General Motors, and
"Engine-Mod" for American Motors. Al-
though the systems used by the various manu-
facturers have a number of features in com-
mon, there are some important differences,
both among manufacturers and among models
within one company.
Features shared by essentially all versions
of the engine modification system include
calibrated carburetors that provide (1) rela-
tively lean air-fuel mixtures for idle and cruise
operation and (2) higher engine idle speeds.
Refined control of spark timing is also used,
and, in some cases, retarded spark timing at
idle is employed. In addition, many engines
5-2
are fitted with special air cleaners and ducting
designed to supply heated air at nearly con-
stant temperature to the carburetor, to permit
even leaner mixture settings. Most versions
also incorporate high-temperature radiator
thermostats to raise coolant temperatures and
thus improve mixture distribution and pro-
mote complete combustion. In some cases,
higher-capacity cooling systems are used to
handle the additional cooling load at idle that
results from wider throttle openings and re-
tarded ignition timing during this operating
condition. In addition, combustion chamber
design attempts to avoid flame quenching
zones where combustion might otherwise be
incomplete, and result in high hydrocarbon
emissions.
Hydrocarbon and CO emissions are reduced
by adjusting the carburetor to a fuel-lean mix-
ture during part throttle and idle operation.
"Lean surge" during cruise has been largely
overcome through improvement in manifold-
ing (better mixture distribution), better car-
buretor fuel-metering characteristics, higher
coolant temperatures, increased heating of the
air-fuel mixture, and, in some cases, provision
for heating the incoming air to the carburetor
(Figures 5-2 and 5-3).
Exhaust emissions of CO and HC are partic-
ularly difficult to control during engine idle
-------
THERMOSTAT
TO AIR
CLEANER
COLD AIR
UAMirni n VACUUM
VArFmu OVERRIDE
VACUUM MQTOR
HOT AIR
(PRE-HEATED
BY EXHAUST
MANIFOLD)
A. This drawing shows the thermostatically controlled
air cleaner with the hot-air plate open. This action
takes place during the warm-up period of operation
HOT AIR
"LOW OR NO VACUUM
B. As the engine warms up, the thermostat allows under-
hood air to enter through the partially opened valve
plate. This action occurs during the time that the
plate is opened halfway.
<£=, <=»
<£=, COLD AIR
HOT AIR
C. After the engine reaches operating temperature and the
underhood air is 105° F. or higher, the heat valve is
closed by the thermostat and only underhood air enters
the carburetor air intake.
Figure 5-2. Ford IMCO thermostatically
controlled inlet air heater.2
(Courtesy of Cowles Book Company)
5-3
-------
AIR CLEANER
ASSEMBLY
TEMPERATURE
SENSING SPRING
AIR BLEED VALVE
HOSES AND PIPES
AIR BLEED
VALVE OPEN
CONTROL DAMPER
ASSEMBLY
DIAPHRAGM SPRING
SNORKEL TUBE
VACUUM CHAMBER
CONTROL DAMPER
ASSEMBLY
HOT AIR
PIPE
Figure 5-3. Heated air system for General Motors controlled combustion system. Damper is
ShOWn With COld air dOOr in Open position.3 (Courtesy of Buick Chassis Service Manual)
5-4
-------
IDLE-MIXTURE SCREW
CARBURETOR THROTTLE BODY
A. Fixed-orifice control of idle mixture
IDLE-MIXTURE
SCREWS
B. Fixed stops on idle-mixture screws limit rich
setting
IDLE-LIMITER
NEEDLE
IDLE-MIXTURE
SCREW
C. Factory-sealed internal limiter needle with
conventional idle-mixture adjustment
Figure 5-4. Typical methods used to limit
enrichment of carburetor idle mixture.4
(Courtesy of Ethyl Corporation)
and closed-throttle operation (deceleration).
Considerable effort has gone into designing
carburetor idle systems that will provide a
lean air-fuel mixture and minimize emissions
during these periods. To ensure that idle air-
fuel mixture cannot be adjusted to be too rich
(which would tend to increase CO and HC
emissions appreciably), some means of limit-
ing idle-mixture adjustment is used on most
carburetors. Such devices allow idle mixture
to be adjusted leaner than a predetermined
value, but not richer. Typical forms of idle-
mixture limiters are shown in Figure 5-4. With
the fixed-orifice type shown in Figure 5-4A, a
conventional idle-mixture screw is used, but
maximum mixture richness is controlled by
the size of the fixed orifice. Other types of
carburetors incorporate fixed stops on the
head of the idle-mixture screws to limit the
rich setting to a predetermined value (Figure
5-4B). A third type of limiter system (Figure
5-4C) uses a factory adjusted and sealed in-
ternal limiter needle in conjunction with a
conventional mixture-adjusting screw.
Along with carburetor design changes,
altered ignition timing also plays an important
part in the reduction of emissions of CO and
HC. A number of cars use one or more
vacuum-switching control mechanisms to pro-
vide refined control of vacuum advance
characteristics. Most of these employ some
means of retarding the spark timing at idle
(and possibly advancing or retarding it during
deceleration), while maintaining normal spark
advance for acceleration and cruising.
Retarding ignition timing at idle tends to
reduce exhaust emissions in two ways. With
retarded timing, exhaust gas temperatures are
higher, thereby promoting additional burning
of the hydrocarbons in the exhaust manifold.
More importantly, retarded timing requires a
slightly larger throttle opening (increased fuel
and airflow) to obtain the desired idle speed.
The larger throttle opening not only results in
better charge mixing and combustion at idle,
but also reduces emission concentrations
appreciably during closed-throttle decelera-
tion, as a result of better charge mixing and
higher charge density. To further increase the
5-5
-------
benefits of larger throttle openings, somewhat
higher than normal idle speeds are specified
for most engines using the engine modifica-
tion approach to emission control. The use of
this technique is restricted since lower concen-
trations are accompanied by higher exhaust
volume flow rates.
Techniques used to retard timing for opti-
mum emission control vary from manu-
facturer to manufacturer and even between
certain engine-transmission combinations. In
one of the simpler configurations, a "ported"
vacuum source (Figure 5-5) is used with a dis-
tributor having conventional vacuum and
CARBURETOR THROTTLE BODY
Figure 5-5. "Ported" vacuum source
with throttle closed.4
(Courtesy of Ethyl Corporation)
centrifugal advance mechanisms. Since the
vacuum source is above the throttle plate
when the throttle is closed, no vacuum ad-
vance occurs during idle or closed-throttle
deceleration, and basic spark setting plus
centrifugal advance controls timing under
these conditions.
With some engine-transmission combina-
tions, driveability and emission control are
optimized by spark retarding at idle, and full
vacuum advance (instead of retard) during the
early part of a 'deceleration. To attain the de-
sired distributor action in such cases, two al-
ternate vacuum sourcesa carburetor port
and a manifold portare used, with the
appropriate source selected by means of a
vacuum-switching control valve (Figure 5-6)
5-6
inserted between the sources and the distri-
butor advance mechanism. During all types of
operation, except deceleration, the carburetor
port controls vacuum advance as before.
During deceleration, however, the carburetor
port is closed by the throttle plate and the
control valve switches temporarily to the
manifold port, thereby providing full vacuum
advance until manifold vacuum decreases to a
level close to idle vacuum. At this point, the
control valve switches back and the carburet-
or port again takes over providing either no
vacuum advance (if the throttle remains
closed) or normal vacuum advance (if the
throttle is opened for cruising or accelera-
tion).
With the two vacuum control systems just
described, maximum ignition retard is limited
by the basic timing setting of the engine.
Engines using these systems frequently have
basic settings retarded from those usually con-
sidered normal for standard engines
sometimes as much as 5 degrees ATC (after
top center). Centrifugal advance curves are
then usually tailored with a sharp-rise initial
advance characteristic to provide close to nor-
mal ignition timing in the middle to high
speed range. Since proper ignition timing con-
stitutes a vital link in effective emission con-
trol, basic timing should not be advanced
beyond specifications. To do so will not only
increase exhaust emissions, but may also lead
to harmful engine knock or knock-induced
preignition.
In addition to the spark-advance control
devices already described, a number of cars
are using a new type of distributor vacuum
advance mechanism to retard ignition during
closed-throttle operation. With this device,
the usual distributor vacuum advance unit is
replaced by one incorporating both vacuum
"retard" and "advance" action. Two varia-
tions of the concept are found: a dual-acting
vacuum advance unit and a dual-diaphragm
vacuum advance unit.
Both the dual-acting and dual-diaphragm
vacuum advance units take care of closed-
throttle retard entirely by control of distri-
butor vacuum. Basic ignition timing and
-------
TDC
STRONG VACUUM AT MANIFOLD
PORT OVERCOMES SENSING
VALVE SPRING
ADVANCE
RETARD
DISTRIBUTOR TIMING
MOVES TO MAXIMUM
ADVANCE
Figure 5-6. Schematic view showing operation of vacuum switching control valve. Valve
is in deceleration position.2 (Courtesy of cowies Book Company)
centrifugal advance curves are similar to those
for conventional engines. These features allow
the engine to be started at near-normal spark
advance.
Although cooling systems with the various
engine modification control systems are sized
to handle the greater heat rejection resulting
from retarded ignition timing at idle, some
engines may tend to overheat during periods
of prolonged idle or in slow-moving traffic.
To prevent overheating under these condi-
tions, many engines are equipped with an
auxiliary thermovacuum switching valve that
automatically provides some timing advance if
coolant temperature exceeds a predetermined
limit. Such valves have a temperature-sensing
element installed in a coolant passage of the
engine. When coolant temperatures are nor-
mal, the control valve allows the various
vacuum retard mechanisms to operate in their
normal fashion. If overheating occurs, the
valve responds by connecting the vacuum
advance mechanism to an alternate vacuum
source that temporarily advances idle timing
(and hence raises the idle speed) until coolant
temperature returns to normal.
5.1.2.2 Air Injection Systems
New cars not employing engine modifica-
tion use an air injection system to control
emissions. Devices of this type are used pri-
marily in cars with standard transmissions and
in one make of luxury-type automobile manu-
factured in the United States. Among the
various manufacturers, the air injection sys-
tem is called "Air Guard" by American
Motors, "Thermactor" by Ford, and "Air In-
jection Reactor (AIR)" by General Motors.
Air injection has not been used on Chrysler
Corporation cars.
Air injection systems decrease exhaust CO
and HC emissions by injecting air at a con-
trolled rate and at low pressure into each
exhaust port. Here, the oxygen in the air re-
acts with the hot exhaust gases, resulting in
further combustion of the unburned hydro-
carbons and CO that would otherwise be ex-
hausted to the atmosphere. Optimum reduc-
tion of emissions by this method depends on
proper air injection rates over a wide range of
engine operating conditions, carefully tailored
air-fuel mixture ratios and spark advance
characteristics, and, in some cases, the use of
5-7
-------
heated carburetor air. Some engines also pro-
vide for retarded ignition timing during
closed-throttle operation. Basic components
of the air injection system are shown in
Figure 5-7.
All air injection systems use essentially the
same basic air pump, a positive displacement
rotary-vane type.
To guard against excessive temperature and
back pressure in the exhaust system resulting
from high air delivery rates at full throttle and
high speeds, a pressure-relief valve is installed
in the pump housing. The valve opens to
bleed off some of the pump flow at a prede-
termined pressure setting.
Output from the air pump is directed
through hoses and an air distribution mani-
fold (or two manifoldsone for each bank on
V-8 engines) to the air injection tubes located
in each exhaust port. Figure 5-8 shows a typi-
cal tube in an exhaust port. A check valve
between the air distribution manifold and the
air pump prevents reverse flow of hot exhaust
gases in the event that pump output is inter-
rupted.
BACKFIRE-SUPPRESSOR VALVE
I II I II
VACUUM SENSING LINE
A vacuum-controlled antibackfire valve is
used to prevent flow of air to the exhaust
ports during the initial stage of closed-throttle
deceleration. The high vacuum that occurs
during deceleration causes rapid evaporation
of liquid fuel from the intake manifold walls.
The resulting rich mixture creates a poten-
tially explosive vapor in the exhaust manifold
if injected air is present.
As with engine modification systems, most
air injection systems also employ spark retard
during idle or idle and deceleration through
use of "ported" vacuum sources or dual-
diaphragm distributor-vacuum-advance mech-
anisms.
5.2 PROSPECTIVE EMISSION CONTROL
SYSTEMS
5.2.1 Evaporative Controls
Fuel evaporative emission standards appli-
cable to 1971 models (1970 models in Cali-
fornia) require that fuel systems be equipped
or designed to limit HC evaporative emissions.
CHECK VALVE
AIR MANIFOLD
AIR FILTER
AIR SUPPLY PUMP
Figure 5-7. V-8 engine with air injection reaction components installed.2
(Courtesy of Cowles Book Company)
5-8
-------
AIR-INJECTION,
Figure 5-8. Air injection tube in exhaust
POrt.4 (Courtesy of Ethyl Corporation)
5.2.1.1 General
Gasoline tanks and carburetors are pres-
ently vented to the atmosphere. Losses at the
carburetor occur almost entirely during the
hot soak period after shutting off a hot en-
gine.5 The residual heat causes the temper-
ature of the fuel bowl to rise to 150° to
200° F, resulting in substantial boiling and
vaporization of the fuel. Losses vary because
of many factors, but may be as much as 28
grams of fuel per soak period without evap-
orative controls.
Two evaporative control methods are pres-
ently under development. They are the
vapor-recovery and the adsorption-
regeneration systems. The latter system has
been developed to the extent that it was avail-
able for one vehicle model6 introduced at
midyear in 1969. Evaporative emissions are a
function of fuel vapor pressure and ambient
temperature. Current evaporative emission
control systems are designed to be used with
fuels of 9 pounds or less Reid vapor pressure.
5.2.1.2 Vapor-Recovery System
In the vapor-recovery system, the crankcase
is used as a storage volume for vapors from the
fuel tank and carburetor. During the hot soak
period after engine shutdown, the declining
temperature in the crankcase causes a reduc-
tion in crankcase pressure sufficient to induct
vapors. During this period, vapors emanating
from the carburetor are drawn into the crank-
case. Vapor formed in the fuel tank is carried
to a condenser and liquid-vapor separator; the
condensate returns to the fuel tank, and re-
maining vapors are drawn into the crankcase.
When the engine is started, the crankcase is
purged of vapors by the action of the positive
crankcase ventilation system.
A sealed fuel tank with a fill-limiting device
is required to ensure that enough air is present
in the tank at all times to allow for thermal
expansion of the fuel. A vacuum-relief gas-
tank cap is used to admit air to the tank as
fuel is used.7
5.2.1.3 Adsorption-Regeneration System
In the adsorption-regeneration system, a
canister of activated carbon traps the vapors
and holds them until such time as they can be
fed back into the induction system for burn-
ing in the combustion chamber.7 >8 During a
hot soak period, vapor from the fuel tank is
routed to a condenser and separator, and
liquid fuel is returned to the tank. The re-
maining vapor, along with fuel vapor from the
carburetor, is vented through a canister filled
with activated carbon, which traps the fuel
vapor.
When the engine is started, fresh purge air
drawn through the canister strips the acti-
vated carbon of the trapped fuel vapor and
carries it to the combustion chambers. A
purge control valve (if used) allows a flow of
air over the hydrocarbon-laden carbon in the
canister to strip it of the trapped vapors only
at engine speeds above idle. The vapors are
then carried to the combustion chamber dur-
ing periods of engine operation other than
idle. The liquid-vapor separator may consist
of a small tank mounted high enough to pre-
vent liquid from entering the line to the canis-
ter. A float valve, which stops liquid but
allows vapor to enter the line, is an alternative
design. A sealed fuel tank with air trapping
space that cannot be filled with fuel is also
required. A vacuum- and pressure-relief gas-
tank cap is used with these systems.
5-9
-------
VAPOR SEPARATOR
SEALED
CAP
PURGE OUTLET
TO AIR CLEANER
THREE-WAY
CHECK VALVE
FUEL TANK
VAPOR INLET
PURGE AIR
INLET
ACTIVATED
CARBON BED
CARBON CANISTER STORAGE
Figure 5-9. Adsorption-regeneration evaporative emissions control system.
(Courtesy of Ford Motor Company Engineering Staff)
-------
With some systems a three-way valve is
used with a nonventing filler cap to accom-
plish three major functions:
1. In conjunction with a fill-limiting-type
filler pipe, the three-way valve provides
a liquid expansion volume in the tank
by closing during tank filling, thereby
creating a dead air space in the top of
the tank. Under pressure, however, the
valve opens to permit vapor to pass into
the vapor line leading to storage.
2. It vents to the atmosphere to prevent
excessive pressure in the fuel tank in
the event of an obstruction in the vapor
line.
3. It permits air to enter the fuel tank to
compensate for consumed fuel or for
fuel and air volume loss induced by
declining temperatures.
Figure 5-9 shows a typical adsorption-regen-
eration evaporative emission control system
employing a three-way check valve.9
5.2.2 Prospective Control System
DevelopmentConventional Vehicles
5.2.2.1 General
Although the states may assume only indi-
rect authority to encourage the use or devel-
opment of emission control systems, it is well
that they have some acquaintance with the
types of systems that may be used in the
future. A research survey was conducted by
the National Air Pollution Control Adminis-
tration to determine prospective control
systems for meeting specified emission-reduc-
tion research goals.10 This survey dealt with
research goals for four-stroke and two-stroke
spark-ignition engines, diesel engines, and air-
craft spark ignition and gas turbine engines.
The opinions of many research experts in
the Government and private sector were used
to evaluate these approaches and are sum-
marized under the discussion of each type of
engine. These experts estimated the research
time and cost as well as the probability of
achieving the research goals.
Based on these opinions, the study staff
evaluated each technical approach for (1)
technological feasibility and (2) absolute de-
sirability as a control measure, regardless of
feasibility. Technological feasibility takes into
account research cost, time, and probability
of success. The desirability rating is an order-
ing of the technical approach alternatives, i.e.,
number 1 is the best alternative, number 2,
second best, etc. The desirability rating takes
into account fixed and operating costs to the
consumer, the number of emissions con-
trolled, and the increased vehicle maintenance
costs.
5.2.2.2 Automobiles and Other Four-Stroke-
Cycle, Spark-Ignited Engines
The two programs discussed in this section
are: (1) hydrocarbon and CO control in
vehicle exhaust and (2) NOX control in
vehicle exhaust. For each program the goals
are first listed. The technical approaches to
those goals are then discussed, by generic type
of control, where applicable. Then opinions
of several governmental and private experts1 °
regarding the time and cost required to imple-
ment these approaches are presented in a
table. Finally, evaluations1 ° with respect to
technical feasibility and order of desirability
are presented in another table.
5.2.2.2.1. Hydrocarbon and CO control in
vehicle exhaust. The research goals for this
program are:
1. First level: Reduce emissions of hydro-
carbons to 1.25 g/mile and CO to 17.25
g/mile.
2. Second level: Reduce emissions of
hydrocarbons to 0.60 g/mile and CO to
11.50 g/mile.
3. Third level: Reduce emissions of
hydrocarbons to 0.25 g/mile and CO to
4.70 g/mile.
Eleven technical approaches initially con-
sidered as having potential for control of CO
and HC in the exhaust were evaluated as
future research and development projects.
Secondary Combustion-Technical approaches:
Exhaust manifold reactor
Exhaust manifold reactor with exhaust
recirculation
5-11
-------
Exhaust system reaction with exhaust
recirculation
In the exhaust manifold reactor system a
fuel-rich mixture is burned in the engine, and
secondary air is added in the exhaust mani-
fold to promote oxidation of HC and CO. The
fuel-rich mixture in the combustion chamber
inhibits NOX formation for the reasons stated
in Section 2.2.3.1.2. Therefore, exhaust gas
recirculation, a control approach for NOX,
may not be needed with the exhaust manifold
reactor system.
Technically, the high-temperature exhaust
manifold reactor approach offers high poten-
tial for HC and CO control. It has good to
excellent technical potential for meeting both
the first and second level research emission
goals. Two types of reactors are being devel-
oped to meet the severe temperature prob-
lems associated with this control approach:
(1) the use of high-temperature-resistant
materials and (2) the use of temperature-
sensing controllers to limit combustion air or
to activate an exhaust gas bypass as a tem-
perature control.
From the design standpoint, the high-
temperature-resistant-material approach is
thought to be preferable if the materials can be
developed at reasonable prices. For both
systems a major problem, aside from the
high-temperature problem, is the compatibil-
ity of the combustor design with the temper-
ature-control technique to be employed.
A somewhat less effective approach to
secondary exhaust combustion employs lean
engine operation under maximum heat con-
servation and utilization to promote oxida-
tion in the exhaust system (exhaust system
reaction). Such a system has a lower technical
probability of success than the manifold
reactor system. The low probability of success
is due, in part, to the greater complexity of
the system and, in part, to the problem areas
yet to be resolved. Two basic problems re-
main unsolved: (1) a carburetion induction
system for optimum lean air-fuel operation
under all speed and power conditions with the
necessary engine timing sensors and controls
and (2) the technique and equipment neces-
sary for the maximum conservation and use
of engine exhaust heat with adequate durabil-
ity and economic feasibility. Several advan-
tages result; i.e., the system gives improved
fuel economy in contrast to the fuel penalty
of the exhaust manifold reactor system. No
secondary air supply is required, and material
requirements are relatively moderate. On this
basis, this technical approach seems to have a
good capability of controlling HC and CO to
the levels of both the first- and second-level
research emission goals.
Engine FactorsTechnical approaches:
Lean engine operation
Engine refinement
In lean engine operation the air-fuel ratio is
increased through a systems approach in
which the carburetor and intake manifold are
considered a single operating system. Fuel is
pressurized and/or heated to improve atom-
ization. Manifold geometry is also designed to
improve distribution.
Overall engine refinement is based on con-
tinuing detailed investigations of the effects
of engine and fuel parameters on emissions.
Basic consideration for control is directed
toward lean engine operation under condi-
tions of high heat conservation and utiliza-
tion. Engine parameters indicating small emis-
sion gains will be combined with other con-
trol techniques.
Both of the engine factor approaches consid-
ered indicate a good capability of meeting the
first level of the research emission goals, but a
poor capability of reaching the second- and
third-level goals. There are theoretical and
practical limits on HC and CO reduction by
these approaches. Both lean engine operation
and engine refinement can control NOX
moderately. These two systems rate the
highest in desirability because of their simplic-
ity and the optimum convenience to the user.
On this basis, the overall rating is considered
to be good.
5-12
-------
Catalytic Oxidation-Technical approaches:
Oxidizing catalytic system: unleaded
fuels
Dual catalytic system: oxidizing, reduc-
ing
Dual catalytic system: reducing agent
Oxidizing catalytic system: leaded fuels
Catalytic oxidation occurs when exhaust
gases pass through a bed of active catalyst
material. Oxidation of HC and CO starts at
some minimum temperature that depends on
the catalyst. Rich-mixture exhaust containing
CO with a secondary air supply maintains
operating temperatures more readily than lean
mixture exhaust which contains oxygen but
lacks CO. Material requirements or temper-
ature protection considerations are similar to
those for exhaust reactors; they are more
severe for the rich mixture with the secondary
air system.
Generally, the four catalytic oxidation
approaches considered for exhaust HC and
CO reduction are not now thought to have
more than a fair technical potential for suc-
cess. The principal deterrents to the use of
catalytic oxidation as a control approach arise
from the lack of a catalyst with a 50,000-mile
durability potential under the normal oxidiz-
ing temperatures occurring in the exhaust.
The technical feasibility of catalytic oxidation
as a control approach is higher with non-
leaded fuels.
The system desirability factors, considering
annual cost, simplicity of technical approach,
and convenience, indicate that the overall
potential for the development of a satisfac-
tory control approach using a catalytic system
can only be considered as fair. It is conceiv-
able that a catalytic converter might be used
to further reduce emissions from a well-
controlled engine in order to attain the lower
research goals. If the engine operated on
leaner than stoichiometric air-fuel ratios, sec-
ondary air supply would not be required, and
material requirements would be less severe.
Ignition and Fuel Control-Technical ap-
proaches:
Fuel modifications, additives, or alterna-
tive fuels
Ignition system modification
Fuel modification as a control approach
has limited potential beyond the first research
emissions goal. It has the unique advantage,
however, of immediate applicability to both
new and used motor vehicles. See Section 6,
Fuel Modification and Substitution for a
more complete discussion.
The remaining approach, ignition modifica-
tion, is, in general, considered to have such
low technical potential that Government-
funded work in this area would not be pro-
ductive at this time. The potential for im-
provement through modified ignition systems
has been systematically investigated by spark
plug and ignition system manufacturers with
negative results.
5.2.2.2.2. NOX control in vehicle exhaust.
The research goals of this program are:
1. First level: Reduce emissions of NOX to
1.35 g/mile
2. Second level: Reduce emissions of NOX
to 0.95 g/mile
3. Third level: Reduce emissions of NOX
to 0.40 g/mile
where NOX is expressed as NO2 equivalent.
Nine technical approaches initially were con-
sidered as having potential for exhaust NOX
control.
Eight of the nine approaches were devel-
oped as combined approaches with exhaust
HC and CO control. Four demonstrate both
high technical feasibility and high system de-
sirability for the control of NOX, HC, and CO.
Significantly, no approach to date, either
under consideration or under test, has indi-
cated a technical potential sufficient to reach
beyond the first level of the research goals set
for NOX.
Exhaust Gas RecirculationTechnical ap-
proaches:
Exhaust recirculation
5-13
-------
Exhaust manifold reactor with exhaust
recirculation
Exhaust system reaction with exhaust
recirculation
Exhaust gas recirculation either as a single
approach or combined with a control ap-
proach for HC and CO offers the highest
potential for NOX control. The problem of
principal concern is the compatibility of ex-
haust gas recirculation approach with one of
the technical control approaches for exhaust
HC and CO. Preliminary studies indicate that
the exhaust gas recirculation approach has
some adverse interaction with many of the sec-
ondary combustion approaches used for ex-
haust HC and CO control. It is considered to
be difficult to use with any of the engine
modification approaches used for HC and CO
control. Despite this limitation, exhaust re-
circulation is considered, from a technical
standpoint, to be the most effective control
approach for NOX.
A secondary problem still requiring a final
solution relates to the technique by which the
exhaust gas is introduced into the intake
system of the vehicle, i.e., the "dirtying" of
the carburetor, with its subsequent variation
in air-fuel ratio. Another problem lies in ex-
haust recirculation flow control to meet all
power and speed conditions. A combination
of technical control approaches using exhaust
recirculation with secondary combustion is
somewhat lower in technical potential than
exhaust recirculation alone. The desirability
of a combination system, in terms of simplic-
ity, annual cost, and convenience to the user,
can be classed only as good; however, the
overall rating of the combined system is con-
sidered to have the greatest overall potential
for success.
Engine Air-Fuel Ratio Factors-Technical
approaches:
Lean engine operation
Exhaust manifold reactor: fuel rich
Two technical approaches employing de-
partures from the normal engine air-fuel ratio
5-14
operation range are considered as possible
NOX control techniques. Two technical ap-
proaches are under development: The first
operates at a very lean air-fuel ratio and pro-
vides exhaust HC and CO control as well as
NOX control; the second operates at rich ait-
fuel ratios for NOX control with an exhaust
manifold reactor for control of the HC and
CO emissions. Both of these approaches have
a good probability of meeting the first level of
the research emission goals, but not the more
severe levels. In system desirability both ap-
proaches rate as the highest of NOX alterna-
tives because of system simplicity and con-
venience to the user. On this basis the overall
rating of these approaches is considered good.
Catalytic Reduction-Technical approaches:
Dual catalytic systems: oxidizing, reduc-
ing
Dual catalytic systems: reducing agents
One dual catalytic system involves the use
of a reducing catalyst with relatively fuel-rich
engine operation followed by an oxidizing
catalyst with secondary air injection. It could
be used more effectively with nonleaded fuels.
The other dual catalytic system uses a
selective reactant (possibly ammonia) for
reducing NOX under conditions that generally
favor the oxidation of CO and HC.
The two reducing catalytic approaches con-
sidered for exhaust NOX control are not
thought to have more than a fair to poor tech-
nical potential for success. In general, the
same basic problems must be resolved for the
reducing catalytic approach as for the oxidiz-
ing catalytic approaches. In particular, there is
a lack of potential catalysts with a
50,000-mile durability under (1) the normal
operating temperature occurring in the ex-
haust and (2) existing fuel lead conditions.
Further, the system desirability factors, con-
sidering annual cost, simplicity of technical
approach, and convenience, indicate that the
overall rating of the potential for satisfactory
control can at best be considered only fair to
poor.
-------
Fuel Modification and Engine Refinement-
Technical approaches:
Fuel modifications, additives, or alterna-
tive fuels
Engine refinement.
The two remaining approaches considered
for NOX exhaust control, fuel modification
and engine refinement, are believed to be of
low technical potential. See Section 6.2 for
further discussion of the fuel modification
approach.
Tables 5-1 and 5-2 summarize the opinions
and evaluations of these approaches.
5.2.2 3 Two-Stroke-Cycle, Spark-Ignited
Engines
Two-stroke-cycle engines account for a
very small percentage of vehicle emissions and
therefore have only recently come under con-
sideration for control. The possible control
alternatives are more tentative and speculative
than automobile controls, since there has
been almost no research to support opinions.
Hydrocarbon and CO control is the only
program that has been proposed for this type
engine. The research goals for this program
are:
1. First level: Reduce emissions of hydro-
carbon to 1.25 g/mile and CO to 17.25
g/mile.
2. Second level: Reduce emissions of
hydrocarbon to 0.60 g/mile and CO to
11.50 g/mile.
3. Third level: Reduce emissions of hydro-
carbon to 0.25 g/mile and CO to 4.70
g/mile.
The following information is little more
than a description of possible control ap-
proaches. Expert opinions on the approaches
were sought, but no soundly based opinions
could be given. The study team's evaluations
of the approaches are presented in a table.
Two-stroke-cycle engines have application
where requirements call for simplicity, low
cost, and a high horsepower-to-weight ratio.
Lubricating oil is mixed with gasoline in ratios
varying from 1/16 to 1/50; 1/100 is being
considered. The system of loop scavenging, in
which the slightly compressed air-fuel mixture
flows into the cylinder through an intake port
while the exhaust gases exit through exhaust
ports on the opposite side, results in some loss
of mixture through the exhaust products.
This loss, together with relatively rich mix-
tures required for smooth operation and good
response in the two-stroke-cycle engine, re-
sults in high HC and CO content in the ex-
haust gases. Essentially no background is
available, and R/D studies have only recently
begun to try to determine emissions from
Table 5-1. SUMMARY OF OPINION OF PROPOSED TECHNICAL APPROACHES TO
CONTROL EMISSIONS FROM AUTOMOBILES AND OTHER
FOUR-STROKE-CYCLE, SPARK-IGNITED ENGINES10
Technical approach
HC and CO control in vehicle exhaust
Secondary combustion
1 . Exhaust manifold reactor -
fuel rich
2. Exhaust manifold reactor
with exhaust recirculation
3. Exhaust system reaction
with exhaust recirculation
Research
Cost, $
millions
5-10
15
2-4
Time,
years
2-6
3-6
3-6
Probability of achieving
research goal level, %
1
50-100
80-90
30-75
2
50-100
80-90
30-75
3
0
80-90
Annual cost
per car, $
40-50
45
15
5-15
-------
Table 5-1 (continued). SUMMARY OF OPINION OF PROPOSED TECHNICAL APPROACHES TO
CONTROL EMISSIONS FROM AUTOMOBILES AND OTHER
FOUR-STROKE-CYCLE, SPARK-IGNITED ENGINES10
Technical approach
Engine factors
4. Lean engine operation
5. Engine refinement
Catalytic oxidation
6. Oxidizing catalytic system,
nonleaded fuels
7. Dual catalytic system:
oxidizing, reducing
8. Dual catalytic system:
reducing agent
9. Oxidizing catalytic system,
leaded fuels
Ignition and fuel control
1 0. Fuel modifications, additives
or alternate fuels
1 1. Ignition system modification
NOX control in vehicle exhaust
Exhaust gas recirculation
1 . Exhaust recirculation
2. Exhaust manifold reactor
with exhaust recirculation
3. Exhaust system reaction
with exhaust recirculation
Engine air-fuel ratio factors
4. Lean engine operation
5. Exhaust manifold
reactor - fuel rich
Catalytic reduction
6. Dual catalytic system:
reducing, oxidizing
(nonleaded fuels)
7. Dual catalytic system:
reducing agents
Fuel modification and engine
refinement
8. Fuel modifications, addi-
tives, or alternate fuels
9. Engine refinement
Research
Cost, $
millions
2.5-10
5-30
3-10
3-5
5
2
1.5-3
N/A
2-5
15
3
2.5
2-12
3-5
5
Time,
years
5
Continuous
4-5
5-6
5
3
3-5
N/A
2-3
3-6
6
5
3-5
6
5
Probability of achieving
research goal level, %
1
50-90
50-80
20-80
20-75
25
0-90
10-90
0
0-90
80-90
20
50
0-100
20-75
25
2
0
0
20-80
20-75
25
0-80
0
0
0
0
0
0
20-75
25
No data developed; fuel additives may be i
3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Jossible
approach to NOX control.
N/A N/A | 0
0
0
Annual cost
per car, $
0
5
40
45
35
20
15
7.5
45
15
0
0-40
40
35
5
5-16
-------
Table 5-2. EVALUATION OF PROPOSED TECHNICAL APPROACHES TO
CONTROL EMISSIONS FROM AUTOMOBILES AND OTHER
FOUR-STROKE-CYCLE, SPARK-IGNITED ENGINES10
Technical approach
Hydrocarbon or CO control in vehicle exhaust
Secondary combustion
1 . Exhaust manifold reactor, fuel rich
2. Exhaust manifold reactor with exhaust recirculation
3. Exhaust system reaction with exhaust recirculation
Engine factors
4. Lean engine operation
5. Engine refinement
Catalytic oxidation
6. Oxidizing catalytic system, nonleaded fuels
7. Dual catalytic system: oxidizing, reducing
8. Dual catalytic system: reducing agent
9. Oxidizing catalytic system, leaded fuels
Ignition and fuel control
10. Fuel modifications, additives, or alternate fuels
1 1 . Ignition system modification
NOX control in vehicle exhaust
Exhaust gas recirculation
1 . Exhaust recirculation
2. Exhaust manifold reactor with exhaust recirculation
3. Exhaust system reaction with exhaust recirculation
Engine air-fuel ratio factors
4. Lean engine operation
5. Exhaust manifold reactor - fuel rich
Catalytic reduction
6. Dual catalytic system: reducing, oxidizing
7. Dual catalytic system: reducing agents
Fuel modification and engine refinement
8. Fuel modifications, additives, or alternate fuels
9. Engine refinement
Technical
feasibility
goal level3
1
E-G
E-G
G
G
G
G-F
G-F
F
F-P
F
P
E
E-G
G-F
G-F
G
F-P
F-P
2
E-G
E-G
G-F
P
P
G-F
G-F
F
P
P
P
P
P
P
P
P
F-P
F-P
3
F-P
F-P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
Order of
desirability13
3
3
3
1
1
4
4
5
3
2
2
3
2
1
2
4
5
No data developed ; fuel additives
may be possible approach to NOX
control.
P
P
P
1
aE - excellent, G - good, F - fair, P - poor.
b 1 - most desirable, 2 - second most desirable, etc.
5-17
-------
two-stroke-cycle gasoline engines and possible
approaches to their reduction.
Two-stroke-cycle engines used in road vehi-
cles mostly motorcycles, scooters, and
powered minibikes - are subjected to speed
and load variations typical of passenger cars.
Outboard motors, snowmobiles, and small
utility motors (lawn mowers) normally
operate about 10 percent of the time at idle
and 90 percent at full throttle. These opera-
tional differences pose some variation in the
application of control approaches.
5.2.2.3.1. Conventional engine redesign.
Complete engine redesign with emissions as a
major parameter would result in improvement
in HC and CO emissions. There was wide
difference, however, in forecasting the degree
of improvement that could be expected. One
approach considered the use of fuel injection,
using air alone to scavenge the engine until
the exhaust port was closed. This method
would also require the use of an engine lubri-
cation system in place of the fuel oil mixtures
now used. Although the engine redesign
system seems to be the most desirable control
alternative if it could be successfully devel-
oped, it is obvious that the complexity and
cost of the small two-stroke-cycle engine
would rise.
5.2.2.3.2. Exhaust reactor with secondary
air supply. Experience with manifold reactor
development in four-stroke-cycle automotive
engines indicates that it should be possible to
develop a reactor for oxidizing HC and CO in
two-stroke-cycle engine exhaust. The rich
mixtures burned would require a supply of
secondary air to permit the oxidation process.
As is true in the development of exhaust
reactors for automobiles, it probably would
be necessary to have high-temperature-resist-
ant materials or to have a temperature-sensing
control for limiting air or bypassing the ex-
haust gas. The probability of attaining the
first-level research goal appears better for the
exhaust reactor than for the conventional en-
gine redesign approach. In complexity and
cost the exhaust reactor approach is about as
desirable as the engine redesign.
5-18
5.2.2.3.3. Advanced engine design Wankel
engine. As a backup to fill the requirements
of the two-stroke-cycle engine in the event it
is not possible to feasibly reduce its emissions,
consideration has been given to the use of the
Wankel type engine, which has been under
intensive development in many countries for
several years. The Wankel engine, which
operates on the four-stroke-cycle principle,
also has a high horsepower-to-weight ratio and
is very compact. Experience indicates that its
combustion chamber configuration would
result in high HC emissions. It is known, how-
ever, that this engine can burn lean air-fuel
ratios in the exhaust reactor without a sec-
ondary air supply. It is estimated that this
approach could reach the first-level and
possibly the second-level goals and would be
a desirable system if the problems associated
with the durability of the Wankel engine can
be successfully solved.
5.2.2.3.4. Catalytic converter. The same
principles that apply to catalytic conversion
of exhaust gases in automobile engines would
probably also be effective for two-stroke-
cycle engine exhaust. Both the need for sec-
ondary air supply and the space required for a
catalytic converter tend to reduce the desir-
ability of this approach for small two-stroke-
cycle engines. The probability of attaining the
first-level research goal was rated only fair,
possibly because of the unknown effect on
the catalyst of oil mixed with the gasoline.
5.2.2.3.5. Fuel studies. Changes in the
gasoline-oil ratio should change the composi-
tion of the exhaust gas. The technical feasi-
bility of emission reduction by ratio changes
for the first-level goal is considered only fair,
however.
Table 5-3 presents the highly speculative
evaluation of these approaches.
5.2.2.4 Diesel Engines
Diesel engines are used chiefly in trucks,
buses, off-road vehicles, and other heavy-duty
applications. Because diesel engines generally
exhibit fairly complete combustion, their HC
and CO emissions are relatively low. One of
the principal emissions from diesel engines,
-------
Table 5-3. EVALUATION OF PROPOSED TECHNICAL APPROACHES10
FOR CO AND HC CONTROL FOR TWO-STROKE-CYCLE,
SPARK-IGNITED ENGINES
Technical approach
1 . Conventional engine
redesign
2. Exhaust reactor with
secondary air
3. Advanced engine design -
Wankel engine
4. Catalytic converter
5. Fuel studies
Technical
feasibility
goal level3
1
F
G-F
G
F
F
2
P
F-P
F
P
P
3
P
P
P
P
P
Order
of
desirability t>
1
1
2
3
1
G - good, F - fair, P - poor.
1 most desirable, etc.
and one with which this document is con-
cerned, is NOX. Current emissions range from
about 4 to 10 grams NOX per mile.
The research goals for this program are:
1. First level: Reduce emissions of NOX to
1.35 g/mile.
Second level: Reduce emissions of NOY
2.
to 0.95 g/mile.
3. Third level: Reduce emissions of NOX
to 0.40 g/mile.
Four technical approaches to NOX control in
diesel exhaust have been proposed. These
approaches, which are engine and fuel modifi-
cations and control techniques, are described
below. Opinions of experts in industry and
research were sought on the feasibility and
desirability of each of the alternatives. These
opinions are summarized in a table. The evalua-
tion of the technical approaches, based on the
opinions obtained and the knowledge of the
study group, are presented in another table.
Technology for the reduction of NOX emis-
sions in diesel engine exhaust is limited. Since
the known need for control is relatively
recent, the industry has had little time to
carry out engine research and development
with NOX reduction as a design parameter.
Few approaches are currently being con-
sidered, and half of those being considered are
not much past the conception stage. Of the
four technical approaches considered, two are
under active investigation by engine builders
and research laboratories, and only one engine
refinement shows both a reasonable proba-
bility that the first-level goal will be reached
and good desirability for the method of con-
trol.
5.2.2.4.1. Engine refinement. Since the
enrichment of the air-fuel ratio is not practi-
cal in the diesel engine, all other variables of
engine operation are being systematically
investigated for effect on NOX reduction and
interaction with other engine and emission
characteristics. This technical approach
appears to be the best method for controlling
NOX emissions with the potential to reach the
first- level goal, although it is recognized that
compromises may be required. The trade-offs
may include derating of engine output and
changes in engine variables such as lowering
5-19
-------
the compression ratio and modifying valve
and/or injection timing. These changes may
reduce efficiency and increase fuel consump-
tion. At present no agency forecasts even a
low probability of achieving the second- or
third-level goals.
5.2.2.4.2. Fuel additives. Some researchers
believe that prevention of NOX formation
could be a more feasible control approach
than dissociating the compound after it has
formed. A possible approach would be an
inhibitor to NOX formation that could be
introduced into the combustion process
through a fuel additive. It is not known how
this approach can be carried out, but one
leading additive supplier is interested in
exploring the possibility. Again, the proba-
bility of success appears low, but this
approach appears more attractive to some
researchers than catalytic converters.
5.2.2.4.3. Catalytic converter. The chem-
ical reduction of NOX in the exhaust stream
appears difficult, if not impossible, because of
the oxygen-rich character and the relatively
low temperature of diesel exhaust. The use of
a CO generator has been proposed as a source
for a catalytic converter, but this compli-
cation would obviously be undesirable. Cata-
lyst manufacturers, however, are aware of the
opportunity of a catalytic approach, and at
least one has expressed an interest in studying
this approach. Still, the probability of success
must be considered low at this time.
5.2.2.4.4. Peak combustion temperature
reduction. Reduction of peak combustion
temperature by means of induction of an
inert material such as exhaust gas or water is
an approach that could be effective for NOX
reduction. It is, however, more complex than
the derating approach mentioned in the
discussion of engine refinements. Injection of
inert material amounts to a form of derating,
since air normally available for combustion is
displaced by nonreactive material.
Tables 5-4 and 5-5 are summaries of the
opinions and evaluations of these technical
approaches.
5.2.2.5 Aircraft
The basic need for aircraft emission control
research and development is to determine the
nature and extent of emissions. As further
research results in the identification of con-
trol needs, the development of appropriate
control measures may proceed upon more
clearly defined lines.
Specific areas for further investigation are:
1. Emissions for aircraft piston engines
and the effects of natural afterburning
on emissions.
Table 5-4. SUMMARY OF OPINION OF PROPOSED TECHNICAL APPROACHES
TO CONTROL NOX EMISSIONS FROM DIESEL ENGINES10
Technical approach
Engine and fuel modification
1 . Engine refinement
2. Fuel additive
Control techniques
3. Catalytic converter
4. Peak combustion
temperature reduction
Research
Cost,
$ millions
4
1
0.5
0.75
Time,
years
5
4
5
4
Probability
of achieving
research goal
level, %
1
60
7
8
7
2
0
0
0
0
3
0
0
0
0
Comments
Trade-offs involved
Technology unknown
Technology not developed
5-20
-------
Table 5-5. EVALUATION OF PROPOSED TECHNICAL APPROACHES
TO CONTROL NOX EMISSIONS FROM DIESEL ENGINES10
Technical approach
Engine and fuel modification
1 . Engine refinement
2. Fuel additive
Control techniques
3. Catalytic converter
4. Peak combustion temperature reduction
Technical
feasibility
goal level3
1
G-F
P
P
P
1
P
P
P
P
3
P
P
P
P
Order of desirability1*
1
2
3
3
1G - good, F - fair, P - poor.
1 most desirable, etc.
2. Effectiveness of exhaust gas treatment
systems as applied to aircraft piston
engines.
3. The relationships between turbine en-
gine emission rates and design param-
eters.
4. Sampling and analysis techniques for
characterizing organic emissions from
aircraft turbine engines.
5. Emissions from aircraft during ground
operations at major air terminals.
Several technical approaches to the reduc-
tion of emissions from aircraft are briefly
described.10
5.2.2.5.1 Piston engine aircraft. Reduc-
tion of CO and hydrocarbon emissions from
piston engine aircraft can be accomplished by
replacing these aircraft with turbine engine
aircraft. This practice is progressing rapidly
for the commercial carrier fleet.
Improved carburetors and engine induction
systems, accompanied by spark adjustment
can be used for operation at lean mixture
ratios. Control systems for hydrocarbon and
CO emissions may be applied. Auxiliary
devices may augment the natural afterburning
associated with piston aircraft engines.
Systems to reduce CO and HC emissions
include the following:
A. Exhaust port air injection.
B. Exhaust manifold reactors.
C. Direct flame afterburners.
D. Catalytic converters.
5.2.2.5.2 Turbine engine aircraft. More
complete fuel combustion and, therefore,
reduction of CO and hydrocarbon emissions
may be achieved by a reduction of cooling air
required to maintain the mechanical integrity
of the combustor walls. Use of redesigned fuel
spray nozzles to reduce penetration of fuel
toward turbine engine combustor walls during
idling could reduce air cooling requirements
and decrease CO and hydrocarbon emissions.
Reduction of NOX .emissions can be
achieved through reduction of maximum tem-
perature in the primary zone of the com-
bustor. Decreased air-fuel ratio may reduce
combustor chamber temperature and thereby
reduce NOX emissions.
5.2.2.5.3 Piston and turbine engine air-
craft. Emissions of NOX from piston and
turbine engine aircraft, and of CO and hydro-
carbons from piston aircraft are reduced in
direct proportion to reduction in holding time
in the air near airports. Reduction of emis-
sions through reduction of ground operations
in the taxi and idle modes is possible. Auxil-
iary vehicles could tow aircraft to the termi-
5-21
-------
nal or transport passengers to aircraft in order
to reduce idling time in the waiting line at the
takeoff runway.
Since no emission reduction goals have
been set, the probability and cost of reaching
them are meaningless, and evaluations of tech-
nical feasibility and desirability have not been
undertaken at this time.
5.3 COSTS OF EMISSION CONTROL
SYSTEMS
Table 5-6 shows initial cost ranges from
available sticker prices and several industrial
sources for systems designed to reduce emis-
sions of CO and HC. They are reported on a
nonincremental basis. The cost ranges re-
ported indicate approximately the average
total consumer expenditures required per car
for the systems listed on a large volume pro-
duction basis.
The Bureau of Labor Statistics (BLS) of
the U.S. Department of Labor has pub-
lished1 1 -12 average retail values (which have
been used for BLS price index purposes) of
exhaust emission control systems for the
1968 and 1970 model new motor vehicles.
These are weighted average retail values per
car, based on distribution of the various sys-
tems used for control of the exhaust emis-
sions. They are based on cost and engineering
evaluations of the control systems by the
Bureau of Labor Statistics. These estimates of
retail values of $16.00 and $21.50 for the
1968 and 1970 exhaust control devices, re-
spectively, are included in footnote b in Table
5-6.
Table 5-6. AVERAGE INITIAL COST RANGES OF EMISSION CONTROL
SYSTEMS3 (NONINCREMENTAL) TO CONSUMER
System
Initial cost
Positive crankcase ventilation system (open)
Positive crankcase ventilation system (closed)
Air injection exhaust control system
Engine modification for 1968-69 exhaust control
Engine modification for 1970 exhaust control
Evaporative emission control systems for 1971
$ 5-8.00
$12-15.00
$45-50.00b
$18-25.00b
$36-45.00b
$36-50.00
"Based on available sticker prices and estimates of automobile industry
personnel.
bU.S. Department of Labor, Bureau of Labor Statistics estimates of the
weighted average retail values of exhaust emission control systems as
used for price index purposes are (nonincremental):
$16.00 for the 1968 models1' and
$21.50 for the 1970 models.12
5.4 REFERENCES FOR SECTION 5
1. Plymouth Service Manual. Detroit, Chrysler
Corp., 1969. p. 1-16.
2. Glenn, H. T. Automotive Smog Control Manual.
New York, Cowles Education Corp., 1968. 147 p.
3. 1969 Buick Chassis Service Manual. Detroit, Gen-
eral Motors'Corp., 1969. p. 67-75.
4. Controlling Exhaust Emissions. Ethyl Technical
Notes - PCDTN 268, Detroit, Ethyl Corp., 1968.
5. Martens, S. W. and K. W. Thurston. Measurement
of Total Vehicle Emissions (SAE Paper No.
5-22
680125). General Motors Corp. Presented at
Automotive Engineering Congress and Exposi-
tion, 1968 Annual Meeting. Detroit. January
8-12, 1968. 13 p.
Naughton, J. Maverick: A Stacked Deck. Auto-
motive Industries. ;40(9):55-58, 114, May 1,
1969.
Back to the Engine for Evaporative Emissions.
S.A.E. Journal. 77:46-48, October 1969.
Clarke, P. J. et al. An Adsorption-Regeneration
Approach to the Problem of Evaporative Control
(SAE Paper No. 670127). S.A.E. Transactions.
76:824-842, 1968.
-------
Pnrri IT M' Contro1 of Mobile Sources. 10. National Air Pollution Control Administration.
T lim,7rsity- Presented at 8th Conference Federal Research and Development Plan for
1(0n
on ,
October 14 ?1(?La0ntrOL Lafayette' Indiana. Mobile Sources Pollution Control - Fiscal Years
15> I969' 1970-1975. U.S. DREW, PHS, EHS. Arlington,
Virginia. (Scheduled for publication in 1970.)
5-23
-------
6. FUEL MODIFICATION AND SUBSTITUTION
Sometimes emissions of CO, NOX, or HC
from mobile sources can be changed by alter-
ing those characteristics of fuel subject to
modification. Fuel characteristics of this type
include volatility, hydrocarbon type, and
additive content.
Emissions from mobile sources normally
originate from:
1. Combustion exhaust gases.
2. Fuel evaporation.
3. Blowby gases (crankcase emissions).
The relative importance of these origins
varies among types of mobile sources and
depends upon prevailing approaches to emis-
sion control being employed. For example,
use of certain emission control systems may
eliminate, or decrease, the need for fuel modi-
fications aimed at reducing emissions. Gener-
alizations with regard to the influences of fuel
modifications on emissions must be qualified.
For example, if vehicles are equipped with
evaporative emission control systems, reduc-
tion in fuel volatility will provide less overall
reduction in HC emissions than if vehicles are
not equipped with evaporative emission con-
trol systems. Some effect, however, is realized
immediately with fuel modification. This
effect is maximal at the time of initial applica-
tion and gradually decreases as vehicles with
controls replace those without.
6.1 EFFECTS OF FUEL MODIFICATION
ON HYDROCARBON EMISSIONS
6.1.1 General
Fuel tanks are a source of evaporative HC
emissions. Evaporative emissions occur con-
tinuously and increase with increasing tem-
perature. When a gas tank is being filled, the
incoming liquid forces the fuel vapor out of
the tank and into the atmosphere.
Other nonexhaust HC emissions include
carburetor "hot soak" emissions and crank-
case emissions. Carburetor emissions may
represent light end losses through the air filter
or through vents and leaks in the system
during hot soak, or may stem from subse-
quent overrich startup following percolation
or slugging of fuel from the carburetor into
the intake manifold during hot soak. Crank-
case emissions represent composite mixtures
of the gases passing the piston rings into the
crankcase during various portions of the
engine cycle. Consequently, the blowby-gas
components range from unaltered fuel
through preflame reaction products, to ex-
haust gas constituents. Lubricant deteriora-
tion, resulting from extreme operation, could
produce volatile products that would contri-
bute to crankcase emissions.
6.1.2 Gasoline Volatility Reduction
The term "volatility" refers to the tend-
ency of fuel constituents to vaporize and
thereby escape from the liquid phase. As such
vaporization occurs in a vented system, the
resulting fuel vapors simply escape through
the vent. In a closed system, however, the
vaporized fuel constituents cause the system
pressure to increase until no further vaporiza-
tion occurs. This stable pressure is the vapor
pressure of the fuel, and it becomes greater as
the system temperature is increased. In the
case of complex mixtures of hydrocarbons
such as gasoline, the light ends (i.e., the
lowest-molecular-weight molecules) have the
greatest vaporizing tendency and thereby
contribute more to the vapor pressure than do
the higher-molecular-weight constituents
(higher-boiling-point hydrocarbons). As the
fuel is depleted of light constituents (low-
6-1
-------
boiling-point) by evaporation, the fuel vapor
pressure decreases. The measured vapor
pressure of gasoline, consequently, depends
upon the extent of vaporization during a
measurement test. The Reid vapor pressure
(RVP) determination is a standardized test in
which the final ratio of vapor volume to
liquid volume is constant (4:1) so that the
extent of vaporization is always the same.
Hence, the thus-measured vapor pressure (at
100°F) for various fuels provides meaningful
and comparative volatility data.
Fuel modification aimed at reducing the
quantity of evaporative emissions is relatively
straightforward; it entails adjustment of the
fuel composition to reduce volatility. Such
changes in fuel composition are not without
complications, however. For example, present
fuel volatility characteristics are dictated
largely by climatic conditions, operating
characteristics of current motor vehicles, and
economics of fuel manufacture. Excessive
reduction in fuel volatility could lead to
operating problems such as startup and warm-
up difficulties. Moreover, significant reduc-
tion in fuel volatility in some cases may cause
an increase in the quantity of reactivity of
exhaust HC.
6.1.2.1 Effects of Volatility Reduction on
Performance
The following examples illustrate possible
effects of extreme reductions in fuel vola-
tility. Gasoline having a Reid vapor pressure
of 10 pounds reportedly gave no startup diffi-
culties in a particular group of automobiles at
ambient temperature above 15° F, whereas
reduction of Reid vapor pressure to 5 pounds
resulted in startup problems at temperatures
below 30° F. Also, to prevent warmup stalls
or hesitations in these automobiles, the
minimum ambient temperature had to be
increased from about 60° to 80° F when the
Reid vapor pressure was reduced from 10 to 5
pounds.1 Such extreme reductions in fuel
volatility would not normally be considered
in most climates. A test of a fuel with sub-
stantially reduced volatility was conducted in
Los Angeles in 1968 during March and April
when the ambient temperature varied through
the relatively narrow range of 55° and 70° F.
This 1,800-car survey demonstrated that sub-
stantial reduction in fuel volatility is accept-
able.2 '3
6.1.2.2 Effects of Volatility Reduction
on Emissions
The effects of gasoline volatility reduction
on emissions have been studied.4>s One
study4 draws the following general conclu-
sions:
1. Total (sum of exhaust and evaporative)
HC emissions and reactive HC equiva-
lents (based on the reactivity scale
selected for this study) are both reduced
by approximately 25 percent by lower-
ing fuel volatility from 9 to 6 pounds
RVP when the ambient temperature is
95° F. When the ambient temperature is
70° F, these HC emissions are reduced
by 5 to 10 percent.
2. In spite of the overall reduction, exhaust
HC emission quantities and reactivity
equivalents showed respective increases
of 5 to 10 percent and 10 to 12 percent
in the range of temperatures considered.
3. Exhaust emissions of CO showed a slight
increase with decreasing fuel volatility,
but NOX emissions appeared to be inde-
pendent of fuel volatility changes in the
range considered.
Another investigation,5 which is applicable
only to Los Angeles County because of
special conditions of temperature, driving
patterns, fuel consumption, and existing fuel
composition, to name only a few, resulted in
the following conclusions with respect to fuel
volatility reduction in Los Angeles County:
1. A reduction in fuel volatility from about
8.5 to 6.0 RVP in Los Angeles County in
1968 would have reduced total organic
emissions from gasoline-associated
sources about 9 percent. It would also
have produced an increase in the quan-
tity of aromatics in emissions associated
with gasoline and from all sources; a
marked decrease in paraffins in the
evaporative emissions and in the total
6-2
-------
emissions just cited; a marked decrease
in olefins in the evaporative emissions;
an increase in the olefins in exhaust
emissions; and a modest decrease or no
change in the quantity of olefin emis-
sions from other types of emissions or
their totals. The overall change in reac-
tivity of HC emissions from all sources
that would have resulted from such a
change in volatility would be a reduction
of about 3 or 0 percent, depending upon
the reactivity scale used (based on the
reactivity scales selected for this study).
2. In spite of the overall reduction of HC
emissions, exhaust HC emissions would
have been increased somewhat.
3. Carbon monoxide emissions from motor
vehicles would have been increased by
about 7 percent.
4. Because the total emissions remaining
uncontrolled are expected to decrease
rapidly in the years ahead, benefits in
terms of both total HC emissions and
reactive equivalents prevented from
entering the atmosphere would decrease
each year until about 1985, starting in
1970, because of installation of evapora-
tive control devices on all new cars sold
in California. During this period, an illu-
sory increase in percent reductions in
both total HC emissions and reactive
equivalents would occur.
6.1.2.3 Costs of Volatility Reduction
A study6 parallel to the one discussed
immediately above5 was conducted to deter-
mine the costs of gasoline modification in Los
Angeles County. It, too, is applicable only to
Los Angeles County. The reported estimated
cost to the producer for reducing RVP from
about 9 to 6 pounds would be approximately
1.33 cents per gallon for large refineries and
approximately 2.13 cents per gallon for small
refineries. Total capital investments needed to
achieve this change were estimated at $56 mil-
lion for the large refineries and $4.2 million
for the small refineries.
A similar study7 reported estimated aver-
age costs to the producer, on a nationwide
basis, for reducing the percent of gasoline
evaporated at 160° F from 30 to 20 percent,
and to 10 percent (generally considered as
being approximately indicative of reductions
in currently used gasoline RVP from 10 to
7.5, and to 5 pounds4'7) as 0.7 cents per
gallon and 1.6 cents per gallon, respectively.
It should be stressed that all these costs are
quoted as costs to the producer rather than to
the consumer.
Estimated capital investments were also
reported in this study.7 Investments would be
approximately $680 million for achieving the
20 percent evaporated at 160° F gasoline and
$1.83 billion for the 10 percent evaporated at
160° F on a nationwide basis.
6.1.3 Removal of Highly Reactive
Gasoline Constituents
In some cases, alteration of fuel composi-
tion to reduce the reactivity of evaporative
HC emissions may be more effective than
adjustment of fuel volatility. For example,
substitution of saturated hydrocarbons for
more reactive hydrocarbons, such as volatile
olefins, may be employed to reduce the re-
activity of the evaporative emissions without
affecting fuel volatility.8 >9
6.1.3.1 Effects of Olefin Removal on
Emissions
The effects of removal of olefins from gaso-
line on emissions have been studied.4'5 One
study4 draws the following general conclu-
sions:
1. Modifying a gasoline of average volatility
by replacing the 4 and C5 olefins with
corresponding paraffins (and no accom-
panying change in fuel volatility) has no
effect on gross HC emissions, but re-
duces the reactivity equivalent approxi-
mately 30 percent at 95° F and 20
percent at 70° F (based on the reactivity
scale selected for this study).
2. Extending the C^-C^ olefin replacement
to include all olefins boiling below 220°
F gives only a small additional reduction
in reactivity equivalent (e.g., from 30 to
37 percent at 95° F).
6-3
-------
3. The reactivity equivalent of the exhaust
HC emissions is unaffected by light-
olefm replacement. Thus, the benefit of
this fuel modification is reflected only in
the evaporative losses.
4. Emissions of CO and NOX are relatively
unaffected by olefin removal.
Another investigation,5 that is applicable
only to Los Angeles County because of
special conditions of temperature, driving
patterns, fuel consumption, and existing fuel
composition to name only a few, resulted in
the following conclusions with respect to the
removal of olefins from gasolines in Los
Angeles County.
1. A change during 1968 from the base fuel
to one which had about the same RVP,
but in which the C^ and C5 olefins had
been replaced with comparable saturates,
would have produced a reduction of less
than 1 percent in the quantity of HC
emissions from vehicles. It would also
have produced a moderate reduction in
olefins emitted from evaporation and in
the total emissions of olefins from all
sources. There would have been small
changes in emissions of paraffins and
aroma tics from individual types of
sources and in their totals. The net effect
on the reactivity of HC emissions from
all sources would have been a net reduc-
tion of about 5 to 6 percent, using either
of the two reactivity scales selected for
this study. Reactivity of emissions from
gasoline-associated sources would have
been reduced approximately 6 to 7 per-
cent by either reactivity scale (based on
the reactivity scales selected for this
study).
2. Exhaust emissions of CO would have
been increased approximately 7 percent
(per vehicle), but NOX emissions would
not have been affected appreciably.
3. Benefits in terms of total reactive equiv-
alents prevented from entering the
atmosphere would decrease each year
until about 1985, when essentially all
cars will be equipped with evaporative
emission controls as well as exhaust and
crankcase emission control systems.
Percent reductions of reactive equiv-
alents, however, would increase every
year until then, but only because the
total quantity of HC emissions and reac-
tivity equivalents are expected to
decrease rapidly in the years ahead.
Reactivity of fuel constituents should be
considered in a discussion of engine exhaust
HC emissions. Engine exhaust gases represent
the largest source of HC emissions. Their oc-
currence is due to insufficient combustion air,
incomplete mixing of fuel and air prior to
combustion, and/or quenching of the air-fuel
mixture adjacent to the walls of the com-
bustion chamber. Quenching is well estab-
lished as the most significant mechanism lead-
ing to exhaust HC emissions in properly
designed spark-ignition engines.1 °
The presence of a flame-quench zone adja-
cent to solid surfaces is substantiated by basic
combustion theory and many experimental
observations.11 The thickness of the quench
zone varies with other combustion parameters
such as pressure, gas flow velocity past the
surface, turbulence, and air-fuel ratio.
The following is cited to illustrate the signi-
ficance of the quench zone relative to engine
exhaust HC emissions.12 This information
was obtained by sampling the quench zone in
a single-cylinder, spark-ignition engine oper-
ating on propane-air mixtures. Depending
upon operating conditions, the exhaust HC
emissions contained from 16 to 98 percent
unaltered fuel. The maximum concentrations
of this fuel occurred at the quench surface,
and the maximum concentrations of fuel
hydrocarbon derivatives occurred a short dis-
tance from the surface. The composition of
these gases continued to change after combus-
tion as the unaltered fuel continued to react
in the hot cylinder and exhaust system during
blowdown. These results clearly demonstrated
that the exhaust HC emissions can be largely
explained on the basis of the quench-zone
gases.
In view of the foregoing, it is apparent that
only those fuel modifications that affect the
quench zone and the subsequent reactions of
-------
the quench-zone gases should appreciably af-
fect exhaust HC emissions from currently
used spark-ignition engines. As in the case of
evaporative emissions, not only the quantity
of emissions, but the reactivity of the emis-
sions, must be considered. Fuels containing
substantial concentrations of highly reactive
hydrocarbons have been observed to produce
substantial increases in exhaust HC reactivity
relative to that of less reactive fuels. In such
cases, those fuels containing the largest
concentrations of reactive olefins13'14
produced the most reactive exhaust HC emis-
sions. On the other hand, other experimental
data have indicated little or no effect on ex-
haust HC emission reactivity when olefin and
aromatic concentrations were varied through
ranges typical of commercial practice.15
Reductions in exhaust olefins resulting from
reductions in fuel olefin reach a limiting value
because of "cracking" of paraffins and
formation of olefins during combustion.
6.1.3.2 Costs of Olefin Removal
A parallel study6 to the one concerning
gasoline modification in Los Angeles County5
was conducted to determine the costs of such
modification. It, too, is applicable only to Los
Angeles County. Reported costs to the
producer for removing C^ and C5 olefins
would be approximately 1.04 cents per gallon
for large refineries, and 0.24 cent per gallon
for small refineries. The lower cost for small
refineries may be due to their ability to use
processes for olefin saturation that larger
refineries could not use. A similar study7
reported estimated costs to the producer of
0.25 cent per gallon for C$ and lighter olefin
removal, and 0.7 cent per gallon for Cj and
lighter olefin removal on a nationwide basis.
It should be stressed that all these costs are
quoted as costs to the producer rather than to
the consumer.
Estimated capital investments for the Los
Angeles area study6 were reported to be
$66.5 million for the large refineries and
$525,000 for the small refineries. Estimated
capital investments were reported7 as
approximately $410 million for C^ and light-
er olefin removal, and approximately $1.13
billion for C-j and lighter olefin removal on a
nationwide basis.
6.1.4 Effects of Lead on Emissions
Published data1 6~1 8 indicate that the quan-
tity and/or reactivity of exhaust HC emissions
may increase as deposits accumulate in the
combustion chamber. Analysis has shown that
these deposits consist substantially of lead. It
has also been shown that leaded gasoline
causes increased difficulty in oxidizing CO and
HC in the engine exhaust by the use of a
catalyst.19 For these reasons, some con-
sideration has been given to the use of non-
leaded fuels in gasoline engines. A study
concerned with the economics of leaded and
nonleaded gasoline production2 ° reports that
the added cost for producing conventional
octane-number gasoline without the use of
lead alkyl additives would be 2.15 cents per
gallon.
6.1.5 Diesel Fuel Modification
With compression-ignition (diesel) engines,
the relatively low-volatility fuels do not lead
to significant evaporative losses, and the wall-
quench zone does not present as serious a
problem as it does in conventional spark-
ignition engines. This is because of the inher-
ently different fuel delivery systems and igni-
tion characteristics in these two types of en-
gines. A major cause of HC emissions from
diesel engines is incomplete combustion of
the dispersed fuel droplets, sometimes mani-
fested as white smoke. Although barium-
containing fuel additives are known to sup-
press diesel-engine black smoke (particulate
carbon), they do not appreciably influence
white smoke emissions.2 !
The only fuel characteristic that is known
to be related to diesel white smoke is the
cetane number, with smoke decreasing with
increasing cetane number. The addition of
cetane improvers, such as isopropyl nitrate,
exerts a strong white smoke suppression
effect, particularly during warmup
periods.22-23 This probably reflects more
6-5
-------
complete fuel droplet evaporation and com-
bustion because of the reduced ignition delay
(reflected by the higher cetane number) in the
fuel vapor surrounding each droplet.
6.2 EFFECTS OF FUEL MODIFICATION
ON CO AND NOX EMISSIONS
Fuel modifications to reduce emissions of
CO and NOX would involve changes in fuel
characteristics in order to permit combustion
to occur under conditions that are not con-
ducive to formation of these substances.
6.2.1 Spark-Ignition Engines
Experimental evidence indicates that a
decrease in the volatility of conventional
spark-ignition fuels may slightly increase CO
exhaust emissions.4-s Also, an increased
octane number, which will allow spark-timing
advance, may lead to increased emissions of
NOX for fuel-lean operating conditions; for
stoichiometric and fuel-rich conditions, NOX
emissions may be decreased, particularly at
the most advanced spark-timings.24 Never-
theless, for all practical purposes, it is general-
ly accepted that emissions of CO and
NOX are relatively insensitive to modifications
of conventional spark-ignition fuels.15
Formation of NOX during combustion of
gasoline fuels can be diminished significantly
by water injection into the intake man-
ifold.25 Although this technique is not fuel
modification directly, it is a modification of
the composition and temperature of the
inducted charge, and appears to be effective
in reducing NOX emissions. The introduction
of water vapor into the combustion chamber
decreases the maximum cycle temperature be-
cause of its dilution effect. Intake-manifold
water injection has a further advantage in that
its evaporation cools the gases in the
induction system. This increased gas density
results in higher mass flows through the en-
gine and thereby provides higher maximum
power levels. Disadvantages of water injection
are the possible formation of sludge in the
engine crankcase and the acceleration of en-
gine wear.
6-6
6.2.2 Compression-Ignition Engines
It has been shown that reasonable changes
in volatility or cetane number do no ap-
preciably influence either CO or NOX in diesel
exhaust.22'26 Recent experimental evidence,
however, indicates that control of combustion
temperatures in diesel engines by use of
cetane improvers may eventually lead to
reductions in NOX emissions.2 3
6.3 FUEL SUBSTITUTION
Although investigations of chemical modifi-
cations of fuel have included the use of ethyl
alcohol or ammonia as fuel or fuel additives,
no significant developments have resulted
from such investigations.2 7 ~3 °
The substitution of normally gaseous
hydrocarbons for normally liquid gasoline
fuels has been investigated extensively. Such
substitute fuels are liquefied petroleum gas
(LPG), liquefied natural gas (LNG), and com-
pressed natural gas (CNG).
LPG products are mixtures containing
primarily propane and butane, with vapor
pressures ranging from about 100 to 300
pounds per square inch (psi) at normal
ground-level atmospheric temperatures. The
utilization of LPG fuel in mobile engines
necessitates a pressurized fuel tank and a
vaporizer-regulator LP-gas carburetion system.
In other respects, the engine and its operation
are comparable to gasoline-fueled engines. In
fact much of the reported information on
LPG engine operation was obtained by run-
ning modified conventional spark-ignition en-
gines.
For various combinations of operating
conditions with LPG-fueled engines, signifi-
cant improvements in economy and emission
reductions have been reported.31'32 It has
been shown that fuel-lean operations effect
significant reductions in HC and CO emis-
sions, but sometimes at the expense of in-
creased emissions of NOX for near-
stoichiometric mixtures.32 Operation at very
fuel-lean (high) air-fuel ratios, however, may
tend to reduce combustion temperatures and,
therefore, decrease NOX emissions. On the
other hand, operation with fuel-rich air-LPG
-------
mixtures, while using a catalytic muffler,
produces low emissions of NOX and HC, with
somewhat higher CO concentrations' (but
lower than 1968 Federal standards).32
The predominant hydrocarbon in natural
gas used for LNG or CNG applications is
methane. This, the lowest-molecular-weight,
and hence most volatile, hydrocarbon, boils at
-259° F. Thus the successful storage of LNG
requires very low (cryogenic) temperatures
and extremely efficient thermal insulation
materials. Even then, periodic venting is re-
quired to prevent pressure buildup. On the
other hand, significant amounts of methane
can be stored at ordinary temperatures by
compressing it to high pressures (CNG). Such
fuel requires heavy-wall, high-pressure
containers in order that a significant quantity
of natural gas can be stored in a reasonable
volume (e.g., at pressures of 1,000 to 2,000
psi).
The use of LNG or CNG as fuel for con-
ventional spark-ignition engines is being in-
vestigated extensively. Results indicate that
the use of such fuels could lead to substantial
reductions in emissions.14'33 Tests in Cali-
fornia34 showed that emissions of CO, NOX,
and HC from spark-ignition vehicles fueled
with natural gas were well below any
standards currently in effect or scheduled to
go into effect. (See Table 3-1, Section 3, for a
summary of these standards.) Of the six vehi-
cles tested, only one emitted more NOX than
the 1974 California standard of 1.3 grams per
mile. It should be pointed out that HC emis-
sions were reported as hydrocarbons other
than methane. This was done because of the
very low value of relative reactivity assigned
to methane on most reactivity scales.
Before serious consideration can be given
to substituting LPG, LNG, or CNG for con-
ventional motor fuels, reserves, logistics, and
economics of sucty fuels must also be con-
sidered. The technologies and capital invest-
ments currently related to the utilization of
conventional motor fuels have developed
along with the automotive industry, and the
supply, consumption, and investment related
to such fuels are enormous in comparison
with those of LPG, LNG, and CNG.
Maintaining cleanliness of the induction
system (i.e., carburetor, intake manifold, and
intake port area) of currently used, spark-
ignition engines may reduce the tendency for
CO and HC emissions to increase as mileage is
accumulated.35 One major domestic fuel
manufacturer is now marketing a gasoline
containing an organic additive package that
not only prevents formation of induction
system deposits, but may also remove pre-
existing induction system deposits.35 This
additive reportedly has no significant effect
on combustion chamber deposits, and will not
increase the price of the fuel in which it will
be available.
6.4 REFERENCES FOR SECTION 6
1. Gerrard, J.E. and P.J. Clarke. The Effect of Fuel
Volatility Variations on the Performance of
Automobiles Over a Range of Temperatures.
Esso Research Engineering Co. Linden, N.J. April
2, 1968.
2. Nelson, E.E. Hydrocarbon Control for Los
Angeles by Reducing Gasoline Volatility (SAE
Paper No. 690087). General Motors Corp.
Presented at Automotive Engineering Congress
and Exposition, 1969 Annual Meeting. Detroit.
January 13-17, 1969. 24 p.
3. Wilson, H.I. et al. Automotive Starting and
Warmup Respond to Gasoline Volatility (SAE
Paper No. 680434). 1968.
4. Stone, R.K. and B.H. Eccleston. Vehicle Emis-
sions vs Fuel Composition, Part II, Proc. Amer.
Petrol. Inst. Ref. 49: 651-690, May 1969.
5. Gasoline Modification Its Potential as an Air
Pollution Control Measure in Los Angeles
County. Joint Project of: California Air Re-
sources Board, Los Angeles County Air Pollution
Control District, Western Oil and Gas As-
sociation. Final Report. November 1969.
6. Statement on Cost of Changing Fuel Composi-
tion. Joint Project of: California Air Resources
Board, Los Angeles County Air Pollution Control
District, Western Oil and Gas Assoc. November
10,1969.
7. Hendrickson, D.L. et al. Effect of Changing Gas
Volatility on Refining Costs. Chem. Eng. Progr.
65:51-58, February 1969.
8. Ebersole, G.D. Hydrocarbon Reactivities of
Motor Fuel Evaporation Losses (SAE Paper No.
690089). Phillips Petroleum Co. New York,
Society of Automotive Engineers, Inc. 1969.
6-7
-------
9. Jackson, M.W. and R.L. Everett. Effect of Fuel
Composition on the Amount and Reactivity of
Evaporative Emissions (SAE Paper No. 690008).
General Motors Corp. New York, Society of
Automotive Engineers, Inc.. 1969.
10. Scheffler, C. E. Combustion Chamber Surface
Area, a Key to Exhaust Hydrocarbons (SAE
Paper No. 660111). In: Vehicle Emissions, Part
II, Vol. 12. New York, Society of Automotive
Engineers, Inc. 1966. p. 60-70.
11. Lewis, B. and G. von Elbe. Combustion, Flames
and Explosions of Gases. New York, Academic
Press, Inc., 1961. 731 p.
12. Daniel, W.A. Engine Variable Effects on Exhaust
Hydrocarbon Composition (A Single-Cylinder
Engine Study with Propane as the Fuel) (SAE
Paper No. 670124). S.A.E. Transactions.
7(5:774-795, 1968.
13. Caplan, J.D. Smog Chemistry Points the Way to
Rational Vehicle Emission Control (SAE Paper
No. 650641). In: Vehicle Emissions, Part II, Vol.
12. New York, Society of Automotive Engineers,
Inc. 1966. p. 20-31.
14. Hum, R.W., B. Dimitriades, and R.D. Fleming.
Effect of Hydrocarbon Type on Reactivity of Ex-
haust Gases (SAE Paper No. 650524). In: Vehi-
cle Emissions, Part II, Vol. 12. New York,
Society of Automotive Engineers, Inc., 1966. p.
1-9.
15. Dishart, K.T. and W.C. Harris. The Effect of
Gasoline Hydrocarbon Composition on Auto-
motive Exhaust Emissions. Proc. Amer. Petrol.
Inst. Ref. 45:612-642, May 1968.
16. Gagliardi, J.C. and F.E. Ghannam. Effects of
Tetraethyl Lead Concentration on Exhaust Emis-
sions in Customer Type Vehicle Operation (SAE
Paper No. 690015). Ford Motor Co. Presented at
Automotive Engineering Congress and Exposi-
tion, 1969 Annual Meeting. Detroit. January
13-17, 1969.
17. Jackson, M.W., W.M. Wiese, and J.T. Wentworth.
The Influence of Air-Fuel Ratio, Spark Timing,
and Combustion Chamber Deposits on Exhaust
Hydrocarbon Emissions (SAE Paper No. 486A).
In: Vehicle Emissions, Vol. 6. New York, Society
of Automotive Engineers, Inc., 1964. p. 175-191.
18. Pahnke, A.J. and J.F Conte. Effect of Com-
bustion Chamber Deposits and Driving Condi-
tions on Vehicle Exhaust Emissions (SAE Paper
No. 690017). E.I. Du Pont de Nemours and Co.
Presented at Automotivie Engineering Congress
and Exposition, 1969 Annual Meeting. Detroit.
January 13-17, 1969. 24 p.
19. De Palma, T.V. Applications of Converters to the
Problem of Automotive Exhaust Emissions.
Presented at the Second Annual Air Pollution
Conference. University of Missouri, Columbia.
November 18, 1969.
6-8
20. U.S. Motor Gasoline Economics: Vol. I. Man-
ufacture of Unleaded Gasoline. Bonner and
Moore Associates, Inc. American Petroleum
Institute. New York. June 1967. 245 p.
21. Golothan, D.W. Diesel Engine Exhaust Smoke:
The Influence of Fuel Properties and the Effects
of Using Barium-Containing Fuel Additive (SAE
Paper No. 670092). S.A.E. Transactions.
75:616-640, 1968.
22. McConnell, G. and H.E. Howells. Diesel Fuel
Properties and Exhaust Gas Distant Relations
(SAE Paper No. 670091). S.A.E. Transactions.
76:598-615, 1968.
23. Hum, R.W. The Diesel Fuel Involvement in Air
Pollution. U.S. Dept. of Interior, Bureau of
Mines. Presented at National Fuels and
Lubricants Meeting, National Petroleum Refiners
Association. New York. September 17-18, 1969.
24. Spindt, R.S., C.L. Wolfe, and D.R. Stevens.
Nitrogen Oxides, Combustion, and Engine
Deposits. (SAE Paper No. 638). S.A.E. Transac-
tions. 64:797-807, 1956.
25. Nicholls, J.E., LA. El-Messiri, and H.K. Newhall.
Inlet Manifold Water Injection for Control of
Nitrogen Oxides - Theory and Experiment (SAE
Paper No. 690018). Wisconsin University.
Presented at Automotive Engineering Congress
and Exposition, 1969 Annual Meeting. Detroit.
January 13-17, 1969. 10 p.
26. Lang, H.W., A.J. Sippel, III, and R.W. Freedman.
Effect of Cetane Improvers in the Fuel on Ni-
trogen Oxides Concentration in Diesel Exhaust
Gas. U.S. Dept. of Interior, Bureau of Mines,
Washington, D.C. Report of Investigations
Number RI-7310. October 1969. 5 p.
27. Jackson, M.W. Exhaust Hydrocarbon and
Nitrogen Oxide Concentrations with an Ethyl
Alcohol-Gasoline Fuel (SAE Special Publication
SP-254). General Motors Corp. June 1964, p.
41-49.
28. Kroch, E. Ammonia A Fuel for Motor Buses. J.
Inst. Petrol. London, England. 31(259):2l3-223,
July 1945.
29. Starkman, E.S. et al. Ammonia as a Spark Igni-
tion Engine Fuel: Theory and Application (SAE
Paper No. 660155). S.A.E. Transactions.
75:765-784, 1967.
30. Gray, J.T. et al. Ammonia Fuel Engine
Compatibility and Combustion (SAE Paper No.
660156). S.A.E. Transactions. 75:785-807,
1967.
31. Baxter, M.C. LP-Gas - A Superior Motor Fuel.
(SAE Paper No. 670054). S.A.E. Transactions.
76:466-477, 1968.
32. Baxter, M.C. et al. Total Emissions Control Pos-
sible with LP-Gas Vehicle (SAE Paper No.
680529). Cities Service Oil Co. Cranbury, N.J.
1968.
-------
33. Petsinger, R.E. Innovations in LNG Application. 35. Fact Sheet on F-310 Gasoline, Chevron Research
Cryogenic Eng. News. 3:26-32, March 1968. Company. Standard Oil Company of California.
34. Air Pollution Abatement Qualities of Natural Gas December 1969.
as a Fuel for Internal Combustion Engines. Cali-
fornia Air Resources Board. 1969.
6-9
-------
7. POSSIBLE SUBSTITUTES FOR CURRENTLY USED MOTOR
VEHICLE ENGINES
States may wish to encourage the use of
specific mobile power sources known for their
low emissions. Research and development are
under way toward improvement of historical-
ly proved engine concepts and applications of
subsequent and developing technologies to
concepts new to vehicle application.
1.000
Vehicle speed and range between stops to
refuel or recharge are two very important con-
siderations in the selection of a vehicle power
source. Speed and range characteristics of
several power sources are shown graphically in
Figure 7-1. An engine or other power source
has high specific power if it is lightweight, and
±1. 100
o
S
Q?
UJ
»
O
a.
y
LL
U
UJ
Q_
INTERNAL
COMBUSTION
ENGINE
SODIUM-
SULFUR
NICKEL-
CADMIUM
EXTERNAL
COMBUSTION
ENGINE
LITHIUM-
CHLORINE
lies
NICKEL-
ZINC
ORGANIC
ELECTROLYTE
0.01
JO
O.
or
UJ
S
O
Q.
u
u
0.
to
10 100
SPECIFIC ENERGY, watt-hrs/lb
Note: Assumes 2,000 Ib. vehicle, 500 Ib. motive power source and steady driving.
Power and energy taken at output of conversion device.
Figure 7-1. Vehicle requirements and motive power source requirements.1
7-1
-------
large amounts of energy can be delivered to
the drive wheels in a short period of time so
that the vehicle can travel at high speeds.
Also, an engine or other power source has
high specific energy if it is lightweight, and
large amounts of energy can be stored for
later delivery, regardless of the rate at which
it can deliver this energy. If a vehicle travels at
high speeds, and thus requires high power,
more energy per mile is used and the vehicle's
range is reduced. An automotive power source
should have both high specific power and high
specific energy. The gas turbine and the in-
ternal combustion engine, as presently devel-
oped, have high capabilities in both speed
(specific power) and range (specific energy).
Some of the concepts being advanced as
possible substitute power sources for those
currently in use are treated briefly herein. To
the extent possible, features such as principles
of operation, historical background, emissions
characteristics, practical advantages, and costs
are discussed.
7.1 AUTOMOTIVE GAS TURBINE
7.1.1 Principles
The gas turbine is a member of the internal
combustion family of heat engines, operates
on a modification of the Bray ton cycle, and is
the most promising substitute for currently
used engines. In its simplest form, it consists
of a compressor, combustion chamber
(combustor), and a turbine, as indicated
schematically in Figure 7-2. Inducted ambient
FUEL IN
AIR
INTAKE
EXHAUST
COMBUSTOR
OUTPUT
SHAFT
COMPRESSOR
TURBINE
Figure 7-2. Schematic diagram of simple
gas-turbine engine.1
air is compressed and delivered under pressure
to the combustor, where energy is added by
direct combustion of fuel sprayed into the
chamber. Combustion occurs at essentially
constant pressure. The high-temperature, high-
pressure gas expands through the turbine and
then exhausts to the atmosphere. Part of the
shaft work developed by the turbine is used
to drive the compressor, the remainder being
the useful output work.2
Some of its operating characteristics re-
quire departure from these basic essentials for
application of the turbine to a mobile vehicle.
Compressor and turbine speeds are very high
in load ranges and at idle. Exhaust tempera-
tures are high, and air requirements are 5 to
10 or more times those of conventional gas-
oline engines for the same power level. Vehi-
cle application requires a high degree of
precision in manufacture, assembly, and rotor
balancing to minimize vibration and possibil-
ities of structural failure at the high rotational
speeds. An adequate turbine housing is neces-
sary to insure against exterior damage in the
event of rotor or blade failure, and speed
reduction is necessary between the turbine
and the vehicle transmission. Regenerators or
recuperators are employed to minimize ex-
haust heat loss, improve thermal efficiency,
and relax requirements for exhaust ducting.
Considerably more extensive air filtering and
silencing is required than is necessary for a
conventional gasoline automotive engine. In
addition, the split shaft or free turbine con-
figuration, indicated in Figure 7-3, is em-
ployed to improve operational flexibility.
7.1.2 Historical
Around the end of World War II, Chrysler
in the United States and Rover in Great
Britain began developing an automotive gas
turbine. General Motors began around 1948;
the first Rover turbine-powered automobile
ran in 1949; and Ford began work in 1950.
Principal early automotive turbine develop-
ment problems were noise, poor fuel econ-
omy, lack of durability, and acceleration lag;
Early turbine engines required approximately
7-2
-------
EXHAUST
AIR INTAKE 1
I-AAA/-' COMBUSTOR
n/vV ffTT-i
REGENERATOR)
H
\
w
OUTPUT SHAFT
COMPRESSOR
COMPRESSOR
TURBINE POWER
TURBINE
GAS-GENERATOR SECTION
Figure 7-3. Schematic diagram of regenerative free-turbine engine.1
5 seconds from idle to full power, unaccepta-
ble in throttle response for passenger car use.
In 1963, Chrysler undertook a 2-year con-
sumer evaluation program in which 50
turbine-powered cars were lent for 3-month
periods each to randomly selected families
throughout the United States. According to
press conferences, drivers considered the car
"completely usable," although acceleration
lag still was considered by some to be a
problem. Gas turbines for truck application
have been under development by Ford and
General Motors since the early 1960's. Ford
has reportedly been using turbine-powered
super-transports in heavy-duty interplant
transport. Turbine engines may be used in
some 1970 model trucks, and Detroit Diesel
division of General Motors3 has announced
availability of a heavy-duty turbine for truck
application in mid-1971. It appears that
heavy-duty trucks and buses may be the logi-
cal media for introducing the automotive gas
turbine into the public market. In this appli-
cation, the turbine represents a smaller per-
centage of total vehicle cost than in a passen-
ger car. Its size permits an increase in payload;
styling is less a factor in intake and exhaust
considerations, and fleets usually have well-
organized maintenance facilities and pro-
cedures.
7.1.3 Emissions
Emission data for gas turbines are ex-
tremely sparse by comparison with those for
gasoline-powered motor vehicles. Of all the
fuel-burning engines, however, gas trubine en-
gines are considered to be among those that
have the lowest emissions.4 On a concentra-
tion basis, available information indicates
emissions are extremely low. These figures
cannot be compared directly with existing
gasoline engine standards, however, because
the total mass of gas turbine exhaust is many
times greater than that for the gasoline engine
of equivalent power. It appears, nevertheless,
that gas turbine exhaust can be substantially
cleaner than exhaust from present emission-
controlled engines in regard to HC and CO mass
emissions. Data for levels of NOX emissions
are less conclusive.
The General Motors GT-309 is a
280-horsepower, regenerative turbine devel-
oped in 1964. Emission data for it, converted
to mass basis, indicate HC emissions to be
about 16 percent and CO emissions to be
about 12 percent of those of a 1968 vehicle
equipped with a gasoline engine and exhaust
emission control system. Emissions of NOX,
however, are approximately 1.75 times higher
for the GT-309. A study of the Chrysler
7-3
-------
turbine car5 indicates very low comparative
emissions. Table 7-1 is based on this study.
7.1.4 Advantages and Disadvantages
In addition to its low emission
characteristics, the gas turbine operates satis-
factorily, but not interchangeably, on a
variety of light hydrocarbon fuels, such as un-
leaded gasoline, diesel fuel, or kerosene. Other
characteristics often attributed to it are light
weight, greater simplicity, and reduced main-
tenance and service.1
The simple gas turbine can be a lightweight
engine in terms of pounds of engine weight
per horsepower delivered, but it also has high
fuel consumption in urban operation and at
idle. A gas turbine designed for variable speed
and load is neither a simple nor a lightweight
unit. The Chrysler gas turbine of 130 horse-
power filled the available underhood space
and weighed 410 pounds.1 It is frequently as-
sumed that a minimal transmission would be
required for a multi-spool gas turbine because
of its speed-torque characteristics. Thorough
studies have always shown this assumption to
be incorrect. Real progress with gas turbine
power trains can be expected only when
suitable transmissions are properly integrated
with the gas turbine to capitalize on its advan-
tages and overcome its disadvantages.1
The volume of air required by the gas
turbine engine to hold turbine inlet tempera-
ture to a value that will not damage the
turbine requires larger components through-
out the air handling system than would other-
wise be necessary. Air filters and silencers are
large. Power output is affected significantly
by inlet air pressure drop, which calls for a
large filter-medium area. Dust passing the
filters and blown through the turbine tends to
erode components subject to the impact of
dust particles. Operation under many condi-
tions would require high-efficiency filtration.
Exhaust ducting must be large to handle the
volume of exhaust from the turbine with a
small pressure drop.
Diagnosis of engine problems, maintenance,
and service would undoubtedly require special
training, equipment, and reorientation of
service facilities. Maintenance and assembly at
the present average-skill-level of automobile
mechanics would be out of the question. Air-
lines have developed years of experience with
aircraft maintenance programs, and aircraft
turbines have shown time increments between
major overhauls never attained by reciproca-
ting engines. Aircraft engines do not operate
in the stop-and-go-type service, nor in some of
the adverse environments experienced by the
Table 7-1. EMISSION DATA FOR CHRYSLER TURBINE CAR -
COLD-START, COMPOSITE-CYCLE, DYNAMOMETER TESTS5
Pounds per mile (NDIRa)
Pounds per mile (HC by FIDa)
Grams per mile gas turbine
Grams per mile gasoline engine equipped
with 1968 exhaust emission control sys-
tem (NDIR)
Exhaust emissions
HC
0.0020b
0.0036b
0.91
3.43
CO
0.0155
7.03
35.10C
NOX
0.0041
1.86
6.76C
Abbreviations indicating type of sampling equipment: NDIR non-disper-
sive infrared analyzer, FID flame ionization detector.
^Hydrocarbon emissions measured by FID and converted to NDIR using
factor of 1.80.
cSource - NAPCA - see Table 3-3.
7-4
-------
motor vehicle. It is reasonable to assume,
though, that gas turbines in road vehicles
might show comparable development, pro-
vided that necessary service and maintenance
facilities are reoriented.1
7.1.5 Costs
Estimated costs for a gas turbine in produc-
tion vary widely. Unfortunately, there is no
way of relying on gas turbine use in
other fields of application to estimate its prob-
able cost, because gas turbines are not in mass
production. Small gas turbines for aircraft
propulsion in the 500- to 800-horsepower
class are produced in quantities of about 500
per month and are reported to sell for about
$25 per horsepower.1 At the other end of the
scale are estimates of $2 to $4 per horse-
power.2-6 For a 250-horsepower gas turbine
on these bases, the corresponding price range
is $500 to $6,250. An auto manufacturer's
estimate of approximately three times the
cost of a conventional reciprocating engine
represents a price increase of approximately
$1,000 to $1,500 for the average family auto-
mobile.
7.2 ROTARY COMBUSTION CHAMBER
ENGINE
7.2.1 Principles
The Wankel is the most prominent example
of the rotary combustion chamber engine,
having received more attention and develop-
ment effort than any other. It employs a
three-lobed member rotating within the
confines of an epitrochoidal surface, the
spaces between the two constituting a series
of rotating combustion chambers. It uses gas-
oline fuel on a four-sequence cycle: intake,
compression, power (expansion), and exhaust,
as shown in Figure 7-4. Valving of the air-fuel
charge and exhaust gases is accomplished
through ports uncovered in sequence by the
rotor. Power is taken from the rotor shaft. It
can be built in multiple power increments by
stacking individual power elements on a single
shaft.
7.2.2 Historical
Concepts for rotary combustion chamber
engines are numerous,7'8 and many config-
urations are possible. Dr. Wankel reviewed
and analyzed a great many.9 It is interesting
to note that his is the only one which has had
any degree of commercial success. It has
achieved limited acceptance in Europe and
Japan in small cars, and has been promoted in
the United States by the licensee for small
utility tools, stationary power plants, aircraft,
and marine applications.
7.2.3 Emissions
Emission characteristics are not generally
available, especially for any operating cycle
corresponding to the Federal seven-mode
cycle. Theoretically, HC emission concentra-
tions for an uncontrolled version would be
higher than those of the conventional gasoline
engine, because of the high quench character-
istics of the long combustion chamber with its
high ratio of surface area to volume.10 The
close proximity of the combustion chamber
walls removes heat from the flame front as
combustion propagates down the length of
the chamber, slowing the rate of flame prop-
agation and lengthening the required total
time for combustion. At the same time, the
high exhaust temperatures may indicate some
afterburning effect. Another factor tending to
increase emissions is the flow of blowby di-
rectly to the exhaust instead of to a crank-
case. Two foreign manufacturers, however,
have built versions with controls that have ful-
filled Federal certification requirements.
7.2.4 Advantages and Disadvantages
By avoiding use of reciprocating members
such as pistons and connecting rods, the
rotary combustion chamber engine operates
smoothly and is easily balanced. As a result, it
can operate at high speed with minimum vi-
bration. Power-to-weight and power-
to-volume ratios are comparatively high,
yielding a relatively high-power engine in a
small package. Rotor sealing, seal life, and
spark plug life have been problems with some
engines. Manufacturing and servicing present
7-5
-------
INTAKE
COMPRESSION
IGNITION
EXPANSION
EXHAUST
Figure 7-4. Sequence of Wankel rotary engine cycle events.
problems not encountered with the con-
ventional gasoline engine. The epitrochoidal
combustion and rubbing surface of the outer
member is not a simple figure of revolution
and requires special tooling for manufacturing
and for rebuilding in service.
7.2.5 Costs
One source includes a questionable estimated
of $4 per horsepower for the rotary comb-
ustion chamber engine,1 which is at the high
end of the ranges of costs estimated for the
conventional gasoline engine. Assuming a cost
of approximately 30 percent over the current
gasoline engine, the additional cost to the
consumer for the rotary combustion chamber
engine might be estimated at $600 to $900.
7.3 STEAM ENGINE
7.3.1 Principles
The automotive steam engine (Rankine
cycle) is an external combustion engine in
7-6
which high-pressure steam or some alternative
working fluid vapor is expanded in either a
turbine or a positive displacement (i.e.,
piston-type) expander to produce work.1' -12
Figure 7-5 is a schematic of a typical Rankine
cycle engine. Liquid moves at low pressure
from the reservoir through the high-pressure
liquid pump, then at high pressure through a
heater, where it picks up heat from the ex-
pander exhaust. The liquid then moves at high
pressure through the vapor generator, where
fuel combustion converts it to superheated
vapor. Metered into the expander, the super-
heated vapor expands to low pressure and
temperature and does work by giving up
energy in the expander. It then moves
through the liquid heater where it gives up
more energy, is converted to liquid in a
condenser (typically air-cooled) and returns
to the reservoir through a condensate pump.
This is a closed system in which the working
fluid is not allowed to escape, but is contin-
uously reused.2
-------
OUTPUT
SHAFT
VAPOR-FLOW
CONTROL VALVE
EXPANDER
FAN
VAPOR
GENERATOR
CONDENSER
LIQUID
CONDENSATE
PUMP
LIQUID-RESERVOIR
OR STORAGE TANK
HIGH-PRESSURE
LIQUID PUMP
Figure 7-5. Schematic of typical Rankine cycle steam engine components.2
The majority of recent automotive vapor
engines have piston-type expanders and use
water as the working fluid, although some ex-
perimental work has been done with Freon
and specially compounded fluids. Boilers are
"once through" types, which give good
throttle response and rapid warmup from a
cold start. Conventional hydrocarbon lubri-
cants are used, requiring separation from the
working fluid to avoid boiler fouling. The pos-
sibility of freezing in cold weather is still a
problem.
7.3.2 Historical
Use of Rankine cycle engines dates from
1827 or earlier, when primitive steam engines
powered coaches. Stanley Steamer, Loco-
mobile, White, and Doble cars were sold in
the late 1800's and early 1900's. The Stanley
Steamer was the most popular of 126 dif-
ferent makes produced during the period. It
was in production from 1899 through 1925,
reaching a production peak of 2,500 vehicles
in 1910. Most of the early steam cars used a
large boiler and a noncondensing system.
Large quantities of water necessitated by this
system required as much as a half-hour heat-
ing from a cold start to become operable.
Stanley introduced a condenser in 1915.
Perhaps the most advanced steam car was
the Doble, the last of which was build in
1930. It used a four-cylinder engine rated at
150 horsepower in a condensing system sup-
plied by an electronically controlled,
monotube boiler which could come up to
pressure within 30 seconds.2 ' 3
The only automotive steam power plant
that has been offered for general sale in recent
years is the Williams model. One experimen-
tal, 130-horsepower recent installation by
General Motors is shown in Figure 7-6. Table
7-2 contains data for several automotive
steam engines built or studied since 1950.
7.3.3 Emissions
Table 7-3 is a compilation of emission data
for various external combustion engines, in-
cluding three steam engines. The basis (driving
cycle) under which these data were obtained
is not known. Concentrations are obviously
quite low, however.
7.3.4 Advantages and Disadvantages
Aside from its low emissions characteris-
tics, the steam engine has good low speed
torque, which would not necessarily eliminate
the need for a transmission, but might
simplify it. Its multifuel capabilities are also
an advantage, which as yet have probably not
been explored to full potential. The engine is
quiet and apparently durable. A Doble car
reportedly has run 800,000 miles.6 The steam
engine system, at low production, has been
expensive to manufacture and, historically,
has suffered from lack of service and repair
facilities by comparison with the gasoline-
powered car. The complete system is bulky,
complicated by need for an auxiliary power
7-7
-------
STEAM GENERATOR
oo
AUXILIARY STARTER
TORIC TRANSMISSION
RIGHT-HAND BURNER
FEEDWATER PUMP
COMBUSTION
AIR BLOWER
TEMPERATURE
SENSOR
STEAM
CONDENSER
CONDENSER
FANS
AIR CONDITIONING
COMPRESSOR
STEAM CYLINDER
LUBRICATOR
AIR CONDITIONING
CONDENSER AND FAN
Figure 7-6. Steam engine installation.3
-------
Table 7-2. DATA ON SEVERAL AUTOMOTIVE STEAM ENGINES EITHER BUILT OR STUDIED SINCE 19502
Developer or researcher
Williams Engine Co.
McCulloch Corp.
Gibbs Hosick Trust
Richard J. Smith
USAMERDC
Thermo Electron Engineering
Corporation
Microtech Research Co.
General Dyanamics/Convair
S. W. Gouse, Jr.
Battelle/Northwest
Engine
reference
49
50
51
52
d
53e
54e
55e
25,56e
57e
Rating,
hp
at rpm
150
at 2400
120
at 1200
60
at 2500
250
at 6000
3
at 3600
100
at 1680
175
500
50
Rated
pressure, psia
Temperature, F
1000
1000
2000
900
2000
850
1000
700
700
850
1200
1250
1500
1100
1200
1000
2500
670
Specific
weight,
lb/hp(s)
5.4
8.0
20.0
5.0
17.2
5-10
Specific
volume
ft3hp(s)
0.14
0.67
0.16
Maximum
efficiency,
%
23
28
19
28
16
22
25-30
24
Startup
time3
sec
P0<30
FPCK30
FPO-14
PO-120
FPO-500
FPO<10
Torque
ratiob
3.4
2.3
1.8
1.1
Power-
surge
ratioc
1.67
1.25
1.5-
2.0
Specific
cost,
$/hp(s)
44
3(?)
a PO = time to power output; FPO = time to full power output.
bTorque ratio = the ratio of stall torque to rated torque.
0 Power-surge ratio = the ratio of short-term, "burst," power to continuous rated power.
dEstimated parameters for steam engine currently under test by United States Army Mobility Equipment Research and Development Center.
This engine is not for vehicular application, but is included to illustrate state-of-the-art for small steam engines.
e Paper studies only.
-------
Table 7-3. EMISSION DATA3 FOR EXTERNAL COMBUSTORS
ASSOCIATED WITH STIRLING ENGINES AND STEAM ENGINES2
Fuel
No. 2 diesel
Kerosene
JP-4
Diesel fuel
Type of equipment
GM Stirling engine - 1 0 hpb with
combustion air preheater
Williams steam engine
Thermo-Electron steam engine
Steam engine; developer's name
withheld by request
Philips Stirling engine - 80 hpd with
exhaust-gas recirculation
Reference
3
c
c
c
c
CO,
%
0.008
0.05
0.001
0.3
0.017
HC,
ppm
1
2
20
30-40
__
NOX,
PPm
500
70
110
25-35
38
aWhen comparing the data in this table with those for gasoline engines on a relative mass-emis-
sion-rate basis, the data in this table should be roughly doubled to account for the higher air/fuel
ratio generally used with external combustors.
bOperated at 25:1 air/fuel ratio.
cData supplied by organization developing engine.
Operated with 50 percent of combustion air from recirculated exhaust gases.
system to drive accessory equipment when
the engine is not turning. Possible freezing, or
lack of a suitable substitute for water to
operate at efficient temperature and pressure
ranges, is still a problem, and separation of
the lubricant from the working fluid is dif-
ficult. The possibility of an explosion or
serious vapor leak may be a safety hazard to
be considered carefully. Since it is costly to
provide a condenser capable of condensing all
the working fluid at full load, makeup work-
ing fluid must be added to most engines peri-
odically.
7.3.5 Costs
At the present state of development, costs
are impossible to fix accurately. One refer-
ence sets the cost of an automotive steam en-
gine system at $4 to $6 per horsepower.2 A
recent developer reported a cost of $1,200 for
the stainless steel tubing alone for his flash-
type boiler, which is more than the total cost
of a current conventional V-8 engine.14 These
figures illustrate the inexactness associated
with establishing a production price for an un-
developed item. The Williams Engine
7-10
Company of Ambler, Pennsylvania, was
taking orders in 1967 for a complete power
plant at $6,450 or a Chevelle automobile with
steam system installed for $10,250. These
prices were for lots of ten engines.2
7.4 ELECTRIC DRIVES
7.4.1 Principles
An electric drive system consists essentially
of an electric power source, a drive motor,
and means of controlling energy flow from
the power source to the motor in response to
requirements of vehicle operating modes. All
three components must be considered in
evaluating the electric vehicle, but the electric
power source seems to be the most critical
with respect to development of a practical
electric vehicle.
Three types of electric power systems are
being explored: (1) battery, (2) fuel cell, and
(3) hybrid.15 Hybrid concepts include en-
gine/battery combinations in which an engine
continuously recharges a battery, fuel
cell/battery combinations in which the fuel
cell continuously recharges a battery, and a
battery/battery combination in which a
-------
primary, or nonrechargeable battery, contin-
uously recharges a secondary, or rechargeable
battery. The fuel cell and hybrid systems
(battery/battery to only a limited extent), at
least theoretically, are capable of extended
operation, depending upon fuel replenish-
ment. The battery system must be recharged
periodically.
The electrochemistry of the battery and
fuel cell is similar. Figure 7-7 illustrates the
common lead-acid battery, and Figure 7-8, a
simple hydrogen-oxygen fuel cell.16'17 As
illustrated in Figure 7-7, an electrical load ap-
plied across the anode and cathode results in a
flow of electrons through the load, and within
the battery from the lead peroxide cathode
to the lead anode. Reaction with sulfuric acid
results in formation of lead sulfate on both
and, eventually, battery exhaustion. Reac-
tions are reversed and the lead is regenerated
at the anode, and the lead peroxide at the
cathode, when the battery is recharged. In the
fuel cell in Figure 7-8, anode and cathode
material (hydrogen and oxygen) is supplied
continuously, avoiding the necessity for re-
charging.
One engine/battery hybrid power system,
which to date is only a mockup, is illustrated
in Figure 7-9. The system includes six 12-volt
batteries, a 35-cubic inch displacement, two-
cylinder engine, a flywheel alternator for re-
charging the batteries, a series-wound direct-
current motor, an electronic control system,
and an onboard charger that can be connected
to an external 115-volt alternating-current
power source. Design objectives are
2,100-pound weight, 60-mph maximum
speed, and acceleration from 0 to 40 mph in
12 seconds and 0 to 60 mph in 28 seconds.
The vehicle can operate in either all-electric or
hybrid mode.
7.4.2 Historical
Electric vehicles are not new. The first ex-
perimental versions were built in the 19th
century.1 8 -1 9 Rapid improvement of internal
combustion engines soon made most electric
cars obsolete.18'20 The present state-of-
the-art battery electric vehicles for practical
-AM/WW
Figure 7-7. Illustration of lead-acid storage battery.
7-11
-------
H2
\
\
POROUS HYDROGEN .
ELECTRODE (ANODE)
~!SL
02+H20
I/.
WATER
HYDROGEN
POROUS OXYGEN
ELECTRODE
(CATHODE)
OXYGEN
/ ELECTRICAL
H2+H20 INSULATION 02
Figure 7-8. Illustration of a simple hydrogen-oxygen fuel cell."1
domestic use are chiefly low-performance and
short-range vehicles that utilize lead-acid bat-
teries or hybrid systems.1 6,20,23-30 Most. are
experimental.
Use of electric vehicles in the United
Kingdom has been commonplace throughout
this century, and has increased rapidly since
World War II.31 Powered by lead-acid bat-
teries, the vehicles are used primarily for mul-
tistop delivery service, although attention is
now being given to development of a short-
range passenger car.
7.4.3 Emissions
Battery-powered vehicles are generally re-
garded as being free of contaminating emis-
sions. Lead-acid batteries emit hydrogen and
oxygen, and an accumulation of these might
result in a fire or explosive hazard. Emissions
from other types would depend on the
materials used.
Fuel-cell energy sources would reduce emis-
sions of CO, NOX, and hydrocarbons,
although some would probably be emitted,
7-12
depending upon the materials used. Hybrid
systems using Stirling cycle or internal com-
bustion engines would emit some CO, NOX,
and HC, although at a lower level, because the
engines could be designed to operate at condi-
tions least conducive to emission formation.
7.4.4 Advantages and Disadvantages
Freedom from emissions appears to be a
major advantage of the electric vehicle,
although users in the United Kingdom claim
greater reliability and durability, and lower
cost as compared to gasoline-fueled delivery
vehicles. Quietness and smoothness of opera-
tion are additional advantages.
Some apparent disadvantages are short
operating range, inconvenience imposed by
necessity to recharge batteries, relatively
heavy propulsion system, poor high-speed per-
formance, and higher initial cost. Vehicle
safety is possibly impaired. It is a certainty
that vehicles are involved in collisions; hazards
from spilled electrolyte and electrical fires are
a possibility when a collision occurs.
-------
ELECTRONIC CONTROLLER
GASOLINE
ENGINE
GEAR REDUCTION
AND DIFFERENTIAL
ELECTRIC MOTOR
BATTERIES
Figure 7-9. Phantom view of General Motors XP-883 experimental hybrid car.3
-------
No present, fully-developed, secondary bat-
tery system is capable of powering a full-sized
family automobile with performance, range,
and cost to match its internal-combustion en-
gine counterpart.1 s The objective of future
development is a secondary battery with an
energy density of at least 100 to 120 watt-
hours per pound and 100 watts per pound
power density.15'20-30 This is in sharp
contrast to the lead-acid storage battery,
which has an average energy density of 8 to
13 watt-hours per pound and a maximum
power density of 32 watts per pound.
7.4.5 Costs
Operating costs of battery-powered vehicles
will depend upon the local utility rates. One
reference estimates that a small electric car
might consume 5,270 Btu of energy per
mile.3! The most favorable electrical rates for
battery recharging would result in an electri-
cal cost range of 0.5 to 1.5 cents per mile.
Replacement cost for batteries is expected to
add 2 to 4 cents per mile. By comparison, a
similar sized gasoline-powered vehicle was
estimated to cost 1.24 cents per mile for fuel,
including taxes.
Testimony at hearings before Congress
regarding electric vehicles revealed that in
England over 48,000 lead-acid battery-
powered vehicles were in use in 1966, primari-
ly for multistop delivery service.29 It was
stated that the primary reason for the use of
electric vehicles is the economic advantage
that they offer over gasoline-fueled vehicles.
High petroleum costs and a tax advantage
contributed to the economic advantage of
electrics.
At the present state of development, costs
of fuel cells are very high and prohibitive for
use in automobiles at this time.15
7.5 FREE-PISTON ENGINES
7.5.1 Principles
Basically, the free-piston engine is a two-
stroke, uniflow-scavenged, opposed-piston
diesel engine that is supercharged by directly
connected reciprocating compressor pistons
(Figure 7-10). All of the work produced in
the diesel (or power) cylinder is absorbed by
the compressor pistons and mechanical
friction. The compressor pistons store up
energy in "bounce chambers" to stop piston
BOUNCE
CYLINDER"
AIR
|| INLET
, CHAMBER
-U \
«
r "^^
^
COMPRESSOR
/-^
\
c=>
R
Y
INLET
jl
INJEC"
A
Vr-
s
C3
V S
h*
roR U
n-^T
r
^
/
COMPRESSOR
H
\
X
COMPRESSOR
INLET
VALVE
> BOUNCE
S CYLINDER
CYLINDER-'
POWER^^'^"
CYLINDER
OUTPUT
SHAFT
POWER
TURBINE
EXHAUST
Figure 7-10. Schematic of free-piston engine serving as a gasifier to drive a power turbine.
7-14
-------
motion at the end of the outward piston
stroke and to return the pistons to a center
Position during the inward compression
stroke.
For a vehicle engine, the free-piston engine
would be essentially a gasifier to provide hot
high-pressure gas as a working medium to a
power turbine. As such, it would correspond
in function to the compressor and com-
bustion sections of a gas turbine engine.
7.5.2 Historical
Free-piston engines have been used in
limited numbers in Europe as compressors for
many years. In the last 2 decades, efforts have
been directed toward their development as a
gasifier combined with a power turbine to
furnish power for ships, locomotives, pumps,
electrical power generators, and vehi-
cles.31-33 They have not had significant ac-
ceptance in any vehicle in the United States.
7.5.3 Emissions
It is doubtful that there are any data
regarding emissions characteristics for the
free-piston engine as a motor vehicle power
plant in any driving mode. The combustion
process, pressures, temperatures, etc., are
similar to those of a highly turbocharged
diesel engine, and emission characteristics
should be similar.
7.5.4 Advantages and Disadvantages
As a part of a vehicle power package, the
free-piston engine is comparatively bulky and
heavy, although a wide range of fuels can be
used. Starting requires an auxiliary air source
since there is no mechanical way to drive the
pistons. Maintenance is, reportedly, higher
than for a diesel engine. The added com-
plications of a free-piston engine are difficult
to justify technically or economically by com-
parison with a highly turbocharged diesel
engine.
7.5.5 Costs
Production costs are not available for a
free-piston engine; it is expected, however,
that if a free-piston engine were developed for
vehicular propulsion, costs would exceed that
of a present diesel engine.
7.6 STIRLING ENGINE
7.6.1 Principles
The ideal thermodynamic cycle cor-
responding to the Stirling engine theoretically
produces the highest thermal efficiency that
can be obtained for given temperatures of the
heat source and sink. How closely an actual
Stirling engine approaches this idealized cycle
depends on (among other things) how ef-
ficient (and therefore how heavy, bulky, and
expensive) the regenerator is. Moreover, the
required addition and rejection of heat at
constant volume and isothermal compression
and expansion can only be approximated in
an actual engine.
The Stirling engine is an external com-
bustion "air" engine in which energy is added
to or removed from the closed-cycle working
fluid through heat exchangers. The concept
basically employs two pistons operating in
either the same or separate cylinders. One
piston does not change the volume of active
working fluid in the system, but serves merely
to move the working fluid in and out of heat
exchangers where energy is either added or
removed. The other piston allows the working
fluid to expand and produce work and also
compresses the working fluid prior to the ad-
dition of energy.34 >3 s
7.6.2 Historical
The principles of the Stirling engine have
been known for more than a century. Robert
Stirling first patented an engine in 1816. In
more recent years, development of the engine
has been pursued by Philips Research Lab-
oratories of Eindhoven, Netherlands. In 1958,
Philips and General Motors entered into a co-
operative program to develop the engine for
commercial and military applications.3 5
7.6.3 Emissions
The low exhaust emission level from the
external combustor of the Stirling engine is
one of its most attractive features. Both CO
and HC are at very low levels. Table 7-3 shows
7-15
-------
measured emission levels for the General
Motors and the Philips Stirling engines.
7.6.4 Advantages and Disadvantages
Several advantages are credited to the
Stirling engine. Exhaust emissions are low,
and engine thermal efficiency is higher than
spark-ignited engines and comparable to the
diesel engine. The noise level of a Stirling en-
gine is low since there is no appreciable com-
bustion noise, as in the case of an internal
combustion engine, and the movement of the
mechanical components could be relatively
quiet. A wide range of fuels can be used.
The Stirling engine is a contender for use in
hybrid engine designs where it could be used
to drive a generator to supply electrical power
to storage batteries, which in turn would
propel the vehicle by electric motors. The two
power sources could be coupled together to
provide power for peak demands.
A Stirling engine installed in a passenger car
would be heavier, bulkier, more expensive,
and less flexible than a conventional re-
ciprocating engine. It has a relatively more
complex drive mechanism that must be em-
ployed to move the pistons and extract
power. Ideally, each piston must stop while
the other piston moves its full travel in one
direction or the other. This cannot be easily
achieved in practice; and a compromise
motion is attained with, for example, the
rhombic drive in the General Motors Stirling
engine concept, illustrated in Figure 7-11. The
heat exchangers required for an efficient
Stirling engine are bulky, heavy, and ex-
pensive. For instance, the cooling radiator sur-
face in one concept would be 2.5 times that
required for a comparable internal com-
bustion engine. The heater of this same
concept is composed of small stainless steel
tubes, which must be carefully welded to
form gas-tight joints under high-temperature
operating conditions. Further, a blower may
be required to furnish air to the combustor.
7.6.5 Costs
No production costs of the Stirling engine
are available; it is estimated to be significantly
7-16
more expensive to produce than present auto-
motive engines, however.
7.7 STRATIFIED-CHARGE ENGINE
7.7.1 Principles
The stratified-charge engine is an un-
throttled, spark-ignition engine using fuel
injection in such a manner as to achieve
selective stratification of the air-fuel ratio in
the combustion chamber. The air-fuel ratio
must be in the ignitable range only at the
spark plug, becoming fuel-lean away from it.
The engine takes a full charge of air into the
cylinders on each intake stroke, completely
independent of power output. Power is con-
trolled by increasing or decreasing the amount
of fuel introduced into the cylinder to match
the power demand on the engine. At low out-
puts, surplus air is not mixed with fuel, yet an
ignitable mixture is obtained at the spark plug
and combustion is initiated in normal fashion.
Combustion progresses to the limits of the
combustible mixture, where it is terminated.
7.7.2 Historical
Of the several stratification systems
advanced, the Ford, Texaco, and Witsky have
shown the greatest promise in the United
States. Stratified-charge engines have operated
in road vehicles experimentally.
7.7.3 Emissions
Normally, the stratified-charge engine does
not exhibit less unburned hydrocarbons than
a conventional gasoline engine. At part power,
this is due to the fact that, although com-
bustion is excellent in the stratified fuel cloud
zone, some fuel diffuses into the surplus air
zone prior to combustion. This mixture is too
lean to burn and tends to raise the total level
of exhaust hydrocarbons. CO levels are
reportedly low and NOX, high. Emissions data
for any of the stratified-charge engines under
active development are not considered con-
sistent.
7.7.4 Advantages and Disadvantages
A principal objective in developmental ef-
forts of stratified-charge engines has been
improved fuel economy, especially at idle and
-------
FUEL NOZZLE
COOLED EXHAUST
OUTLET
PREHEATER SPIRAL
PASSAGES
PREHEATER
ASSEMBLY
HOT EXHAUST
HOT SPACE
REGENERATOR
CYLINDER
COOLER TUBES
COLD SPACE
POWER PISTON
RHOMBIC DRIVE
POWER PISTON
CONNECTING
ROD
TIMING GEARS
COMBUSTION CHAMBER
HEATER TUBES
HOT COMBUSTION
AIR
DISPLACER PISTON
COMBUSTION AIR
INLET
COOLING WATER
CONNECTIONS
SEAL
BUFFER SPACE
SEAL ASSEMBLY
DISPLACER
PISTON ROD
POWER PISTON
ROD
POWER PISTON
YOKE
POWER PISTON
YOKE PIN
DISPLACER PISTON
CONNECTING ROD
DISPLACER PISTON
YOKE
Figure 7-11. Schematic drawing of Stirling thermal engine.3^ (Courtesy of SAE Transactions)
part load. This objective apparently is being
achieved. Even though such engines have high
compression ratios, they can operate on low
octane, unleaded fuel, and yet provide ex-
cellent acceleration without overenrichment
of the air-fuel mixture. Mixture distribution
from cylinder to cylinder is good, and no air-
fuel ratio mixture control is necessary to ac-
commodate special power conditions. Ignition
problems were encountered in earlier develop-
mental stages, and apparently still exist,
especially with respect to spark plug life. Fuel
7-17
-------
coking seems to contribute to this and to
injector fouling.
7.7.5 Costs
Production costs are not available for the
stratified-charge engine; it is estimated to be
more expensive to produce than current auto-
mobile engines, however. Costs may be
comparable to those of current engines
equipped with fuel injection systems.
7.8 REFERENCES FOR SECTION 7
1. The Automobile and Air Pollution: A Program
for Progress, Part II. Subpanel Reports to the
Panel on Electrically Powered Vehicles. U.S.
Dept. of Commerce. Washington, D.C. U.S.
Government Printing Office. December 1967.
160 p.
2. Study of Unconventional Thermal, Mechanical,
and Nuclear Low-Pollution Potential Power
Sources for Urban Vehicles. Battelle Memorial
Institute. Columbus, Ohio. March 15, 1968.
3. Progress for Power ShowSteam, Electric
Powered Cars Unveiled at General Motors
Technical Center (XP-883). General Motors
Corp. Detroit News. May 7, 1969, p. 1A, 14A.
4. Jensen, D. A. The Impact of Emission Control on
the Automobile Industry. Ford Motor Co.,
Dearborn, Mich.
5. Korth, M. W. and A.H. Rose, Jr. Emissions From
a Gas Turbine Automobile (SAE Paper No.
680402). U.S. Public Health Service. Presented at
Mid-Year Meeting. Detroit. May 20-24, 1968. 11
P-
6. U.S. Congress. Senate. Committee on Commerce
and Public Works. Automobile Steam Engine and
Other External Combustion Engines. Joint
Hearings Before the Committee on Commerce
and the Sub-committee on Air and Water Pol-
lution of the Committee on Public Works, 90th
Congress, 2nd Session, May 27-28, 1968.
Washington, D.C., U.S. Government Printing
Office, 1968, 272 p.
7. Jones, C. New Rotating Combustion Power Plant
Development (SAE Paper No. 650723). S.A.E.
Transactions. 74: 425-445, 1966.
8. Bentele, M. Further Developments on Rotating
Combustion Engines it Curtiss-Wright (SAE
Paper S 348). Presented at Twin City Section
Meeting. March 21, 1962. 4 p.
9. Wankel, F. Classification of Rotary Re-
ciprocating Engines; Rotary Reciprocating En-
gines with Parallel Axes and Cylinder Walls of
Rigid Material [Einteilung der Rotations
K o 1 benmaschinen; Rotations-Kolbenmaschinen
7-18
mit parallelen Drehachsen und Arbeitsraumum-
wandungen aus starrem Werkstoff ]. Stuttgart,
Deutsche Verlags-Anstalt, 1963. 59 p.
10. Sisto, F. Comparison of Some Rotary Piston En-
gines (SAE Paper No. 770B). Presented at
Combined Power Plant and Transportation
Meetings. Chicago. October 14-17, 1963. 4 p.
11. Kitrilakis, S.S. and E. Doyle. The Development
of Portable Reciprocating Engine, Rankine Cycle
Generating Sets (SAE Paper No. 690046).
Thermo Electron. Presented at Automotive En-
gineering Congress and Exposition, 1969 Annual
Meeting. Detroit. January 13-17, 1969. 9 p.
12. Fraas, A.P. Application of Modern Heat Transfer
and Fluid Flow Experience to the Design of
Boilers for Automotive Steam Power Plants (SAE
Paper No. 690047). Oak Ridge National Lab-
oratory. Presented at Automotive Engineering
Congress and Exposition, 1969 Annual Meeting.
Detroit. January 13-17, 1969. 12p.
13. Borgeson, G. Doble: The First Modern Steam
Cars. Car and Driver. 7(11): 38-43, May 1962.
14. Callahan, J. M. Lear Describes Steam-Engine
Snags. Automotive News. July 7, 1969. p. 1, 34.
15. Ayres, R.U. Alternative Nonpolluting Power
Sources (SAE Paper No. 684613). S.A.E.
Journal. 76: 40-80, December 1968.
16. Austin, L.G. Fuel Cells, A Review of Govern-
ment-Sponsored Research, 1950-1964. National
Aeronautics and Space Administration. Washing-
ton, D.C. NASA SP-120. 1967. p. 31.
17. 'Schlatter, M.J. An Evaluation of Fuel Cell Sys-
tems for Vehicle Propulsion (SAE Paper No.
670453). S.A.E. Transactions. 76:1576-1592,
1968.
18. Martland, L., A.E. Lynes, and L.R. Foote. The
Ford Comuta-An Electric Car for Use in City and
Suburb (SAE Paper No. 680428). Ford Motor
Co. Presented at Mid-Year Meeting. Detroit. May
20-24, 1968. 13 p.
19. Reid, W. T. Types of Power Sources. In: Power
Systems for Electric Vehicles. National Center
for Air Pollution Control. Cincinnati, Ohio. PHS
Publication Number 999-AP-37. 1967. p. 25-26.
20. Swinkels, D.A.J. Electrochemical Vehicle Power
Plants. (SAE Paper No. 680452). Presented at
Mid-Year Meeting. Detroit. May 20-24, 1968. 8
P-
21. Laumeister, B.R. The GE Electric Vehicle (SAE
Paper No. 680430). General Electric Corp.
Presented at Mid-Year Meeting. Detroit. May
20-24, 1968. 8 p.
22. Aronson, R.R. The Mars II Electric Car (SAE
Paper No. 680429). 1968.
23. Ferrell, D.T., Jr. and A.J. Salkind. Battery-
Powered Electric Vehicles. In: Power Systems
for Electric Vehicles. National Center for Air
-------
24.
25
26.
27
28,
29.
Pollution Control. Cincinnati, Ohio. PHS Publi-
cation Number 999-AP-37. 1967. p. 61-69.
Barak, M. European Developments of Power
Sources for Electric Vehicles. In: Power Systems
for Electric Vehicles. National Center for Air Pol-
lution Control. Cincinnati, Ohio. PHS Publica-
tion Number 999-AP-37. 1967. p. 105-109.
Douglas, D.L. Lead-Acid Batteries and Electric
Vehicles. In: Power Systems for Electric Vehi-
cles. National Center for Air Pollution Control.
Cincinnati, Ohio. PHS Publication Number
999-AP-37. 1967. p. 201-208.
Rishavy, E.A., W.D. Bond, and T.A. Zechin.
Electrovair A Battery Electric Car (SAE Paper
No. 670175). S.A.E. Transactions. 76: 981-991,
1968.
Marks, C., E.A. Rishavy, and F.A. Wyczalek.
Electrovan A Fuel Cell Powered Vehicle (SAE
Paper No. 670176). S.A.E. Transactions. 76:
992-1002, 1968.
O'Donnell, L.G. GM Claims It Can Solve the
Problems of Car Quality, Safety and Pollution.
Wall Street Journal. 173(9\):9, May 8, 1969.
U.S. Congress. Senate. Committees on Commerce
and Public Works. Statement of Horace Heyman,
Overseas Services, Ltd., Wickham, Newcastle-
Upon-Tyne, England. In: Electric Vehicles and
Other Alternatives to the Internal Combustion
Engine. Joint Hearings Before the Committee
on Commerce and the Subcommittee on Air and
Water Pollution of the Committee on Public
Works, 90th Congress, 1st Session on S.451 and
S.453. Washington, D.C., U.S. Government Print-
ing Office, 1967. p. 164-174.
30. Friedman, D. Engineering Requirements of Elec-
tric Vehicle Power Trains. In: Advances in
Energy Conversion Engineering. New York,
American Association of Mechanical Engineers,
1967. p. 887-895.
31. Free Piston Engines. Lubrication. 44: 113-132,
September 1958.
32. Specht, D.H. Evaluation of Free Piston-Gas
Turbine Marine Propulsion Machinery in GTS
William Patterson (SAE Paper No. 604A).
Presented at Combined National Fuels and
Lubricants, Power Plant and Transportation
Meetings. Philadelphia. October 29-November 2,
1962. 29 p.
33. Wallace, F.J., E.J. Wright, and J.S. Campbell.
Future Development of Free Piston Gasifier
Turbine Combination for Vehicle Traction (SAE
Paper No. 660132). Presented at Automotive En-
gineering Congress and Exposition, 1966 Annual
Meeting. Detroit. January 10-14, 1966. 12 p.
34. Flynn, G., Jr., W.H. Percival, and F.E. Heffner.
GMR Stirling Thermal Engine, Part of the Stir-
ling Engine Story 1960 Chapter (SAE Paper
118A). S.A.E. Transactions. 68: 665-684, 1960.
35. Kirkley, D.W. A Thermodynamic Analysis of the
Stirling Cycle and a Comparison with Ex-
periment (SAE Paper No. 650078). S.A.E.
Transactions. 74: 363-373, 1966.
7-19
-------
8. REGIONAL EMISSION ESTIMATES AND EMISSION FACTORS
FOR MOBILE SOURCES
8.1 ESTIMATING REGIONAL VEHICU-
LAR EMISSIONS
Average emission factors and the vehicle
miles of travel can be utilized to estimate
motor vehicle emissions within a particular
region.1 The total emissions from all gaso-
line-powered motor vehicles in a region are a
function of the emission factors, the vehicle
miles of travel in the region, and the percent
of travel that is urban. Assuming that the
gasoline-powered vehicle makeup in the re-
gion is the same as the average national make-
up (i.e., with respect to average vehicle age,
make, engine displacement, etc.), and that the
relative travel of gasoline-powered light- and
heavy-duty vehicles is the same as the national
average, the average national emission factors
will apply equally well on the regional basis.
Therefore, in order to estimate regional emis-
sions, all that is needed are the vehicle miles
of travel and the percent of travel that is
urban.
The following equations can be applied to
obtain regional emission estimates:
(1)TE =
(2) UE = (UF) (VMT) (a) (k)
(3) RE = (RF) (VMT) (1 - a) (k)
where:
TE
UE
RE
UF
= Total emissions, tons/year
= Urban emissions, tons/year
= Rural emissions, tons/year
= Urban emission factor, grams/
mile
=. Rural emission factor, grams/
mile
VMT = Vehicle miles of travel, miles/
year
a = Fraction of travel that is urban
k =1.1023 x 10"6 ton/g (a conver-
sion factor).
Table 8-1 presents the emission factors neces-
sary in equations (2) and (3) for calculating
total emissions. Use of this method for pre-
dicting regional emissions presumes the fol-
lowing:
1. All distributions by population, age,
and travel applicable nationally are
applicable in the region.
2. The road route and average route
speeds used in calculating national
emissions are representative of the
regional travel.
3. National average emission levels per
vehicle apply in the region.
As an example, consider the hypothetical
case of a region in which the number of ve-
hicle miles of travel is estimated to be 10.2
billion miles in 1985, and the estimated frac-
tion of urban travel is 0.80. To estimate the
total CO emissions from gasoline-powered
motor vehicles, all the presently established
controls should be considered. Table 8-1 indi-
cates that the urban vehicle emission factor
(UF) for CO in 1985 is 25.7 g/mile and the
rural vehicle emission factor (RF) for CO in
1985 is 10.7 g/mile. Substituting these values
into the equations yields:
UE = (25.7 g/mile) 910.2 x 109
mile/year (0.80) (1.1023 x
10'6 ton/g)
UE =2.31 x 105 ton/year
RE = (10.7 g/mile) (10.2 x 109
mile/year) (0.20) (1.1023 x
10'6 ton/g)
RE = 0.24 x 105 ton/year
8-1
-------
Table 8-1. AVERAGE ON-THE-ROAD EMISSION RATES FOR GASOLINE-
POWERED MOTOR VEHICLES3 (grams/vehicle-mi)
Year
1960
1965
1968
1970
1975
1980
1985
1990
Hydrocarbon
Urban
21.8
20.4
17.9
14.6
7.39
4.20
3.71
3.69
Rural
14.6
13.2
11.4
9.49
4.78
2.65
2.18
2.18
CO
Urban
87.1
87.6
80.9
67.9
40.9
27.6
25.7
25.6
Rural
34.9
35.6
33.0
28.1
17.5
11.9
10.7
10.8
NOY
A
Urban
5.72
5.76
5.92
6.27
6.84
7.08
7.08
7.06
Rural
6.39
6.53
6.70
7.10
7.81
8.18
8.27
8.31
alncludes cars and trucks, and applicable control systems in use as of 1971.
TE
TE
- UE + RE = 2.31 x 105 ton/
year + 0.24 x 105 ton/year
= 2.55 x 105 ton/year
Hence, the estimate of total CO emissions in
1985 for the conditions stated is 2.55 x 105
ton/year.
Vehicle miles of travel for most cities are
available as a result of the Federal Aid High-
way Act of 1962,2 which required cities of
over 50,000 population to initiate a transpor-
tation study in order to qualify for Federal
aid for road construction. Most of these
studies give vehicle travel in some base year
and project travel into future years. Also,
many of these are on-going studies capable of
supplying up-to-date information.
If vehicle miles of travel projections are not
available for a region, a projection can be
made by using the vehicle miles of travel for
any of the base years 1960, 1965, and 1968,
and by assuming that the regional vehicle
travel growth, rate is the same as the expected
average national growth rate. To do this, take
the factor from Table 8-2 under the "base
year" for the year of interest and multiply the
miles of travel in the base year by this factor.
This gives an estimate of vehicle miles of
travel in the year of interest. This method is
not as accurate as using actual projections of
travel for a region, but does serve to give a
rough estimate of future travel.
8-2
Table 8-2. FACTORS FOR ESTIMATING
VEHICLE MILES OF TRAVEL3
Year of
interest
1960
1965
1968
1970
1975
1980
1985
1990
Base year
1960
1.00
1.23
1.34
1.43
1.69
2.00
2.37
2.82
1965
0.82
1.00
1.10
1.17
1.38
1.63
1.93
2.30
1968
0.75
0.91
1.00
1.06
1.26
1.49
1.77
2.11
If neither future travel estimates nor base-
year travel figures are available for emission
estimates, base-year vehicle miles can be
approximated by taking the total number of
vehicle registrations and multiplying by the
factor 9,400 (miles per year per vehicle regis-
tration).
These base-year travel estimates, when used
with Table 8-2 and equations (1), (2), and
(3), allow regional emission estimates to be
made from vehicle registration data. This
method is less accurate than either of the two
vehicle travel methods, but it does provide
rough estimates when travel information is
not available.
No rule of thumb is available for determin-
ing what fraction of regional miles of travel is
urban. One should try to distribute the travel
-------
into a bi-modal distribution, that is, urban
travel at a 25-mph-average route speed and
rural travel at a 45-mph-average route speed.
The local transportation planning staff or the
local traffic engineer may have valuable input
for determining the best urban-rural distribu-
tion. It should be emphasized that this is a
8.2 EMISSION FACTORS
Tables 8-3 and 8-4 present emission factors
for aircraft and diesel engine emissions.
8.3 REFERENCES FOR SECTION 8
1. National Air Pollution Control Administration.
Determination of Air Pollutant Emissions from
Table 8-3. EMISSION FACTORS FOR AIRCRAFT BELOW 3,500 FEET4
(lb/flight)a
Type of emission
Carbon monoxide
Hydrocarbons (as C)
Oxides of nitrogen (as NO2)
Jet aircraft,
four engine^.0
Conventional
35
10
23
Fan-jet
20.6
29.0
9.2
Turboprop
aircraft
Two
engine
2.0
0.3
1.1
Four
engine
9.0
1.2
5.0
Piston-engine
aircraft
Two
engine
268.0
50.0
12.6
Four
engine
652.0
120.0
30.8
aA flight is defined as a combination of a takeoff and a landing.
"No water injection on takeoff.
cFor three-engine aircraft, multiply these data by 0.75; and for two-engine aircraft, multiply these data by
0.5.
Table 8-4. EMISSION FACTORS FOR DIESEL
ENGINES4
(lb/1,000 gal diesel fuel)
Type of emission
Carbon monoxide
Hydrocarbons (as C)
Oxides of nitrogen (as NO2)
Emission factor
60
136
222
critical step in estimating regional emissions
because of the significant differences in the
urban and rural emission factors.
Gasoline-Powered Motor Vehicles. U.S. DHEW,
PHS, EHS. Durham, North Carolina. (Scheduled
for publication in 1970.)
2. Federal-Aid Highway Act of 1962, Public Law
87-866, 87th Congress, 2nd Session, October 23,
1962. In: U.S. Statutes at Large. 76: 1145-1149,
1963.
3. Landsberg, H.H. et al. Resources in America's
Future. Resources for the Future, Inc. The Johns
Hopkins Press. Baltimore. 1963.
4. Duprey, R.L. Compilation of Air Pollutant Emis-
sion Factors. U.S. DHEW, PHS, EHS, NAPCA.
Raleigh, North Carolina. PHS Publication No.
999-AP-42. 1968.
8-3
-------
9- VEHICLE EMISSIONS RESEARCH AND DEVELOPMENT
9.1 GOVERNMENTAL
Under the Clean Air Act, as amended, the
Secretary of Health, Education, and Welfare
was assigned the responsibility for special
emphasis on research and development into
new and improved methods having industry-
wide application for the prevention and con-
trol of air pollution resulting from the com-
bustion of fuels. In accordance with that
assignment, research has been undertaken
under the direction of the National Air Pollu-
tion Control Administration (NAPCA) to
develop solutions to problems of air contami-
nation from mobile sources. Areas of research
include low-emission power plants, improved-
emission control methods for current types of
engines, fuel modification, and indirect
approaches such as mass transportation. Fed-
eral organizations active in relevant programs1
are indicated in Appendix A. Additional pro-
grams sponsored by the National Air Pollu-
tion Control Administration1 are listed in
Appendix B.
As the pioneering organization in the con-
trol of vehicular emissions (as the former
CMVPCB), the California Air Resources
Board is continuing in research efforts to this
end.
9.2 INDUSTRIAL
United States industrial companies and in-
dustrial associations, such as the American
Petroleum Institute (API) and the Auto-
mobile Manufacturer's Association (AMA),
are doing research and development work to
alleviate the vehicle emissions problem indi-
vidually and jointly as members of cooper-
ating groups.2'3 Among the latter are the
Coordinating Research Council and the Inter-
Industry Emission Control Program.
The Coordinating Research Council was
established to coordinate research within the
automotive and petroleum industries, which
includes vehicle emissions research under the
guidance of the Air Pollution Research Ad-
visory Committee (APRAC). Council mem-
bership includes representation from the Fed-
eral Government and the automotive and
petroleum industries. Appendix C of this doc-
ument lists some projects sponsored by
APRAC to reduce emissions from mobile
sources.1
Qualified research organizations conduct
designated projects under contract with the
Council, which assigns project monitors from
among its membership. Several projects under
way, especially significant to this document,
embrace the subjects of surveillance, inspec-
tion, and maintenance procedures for mini-
mizing automotive emissions. Information
from them will not be available until 1971 or
1972, however. Identified according to the
specified objective,4 they are:
CAPE*-14 Develop a short-duration
emissions inspection and maintenance pro-
cedure for state-owned and franchised in-
spection facilities.
CAPE-15, Task I Develop a short-dura-
tion (approximately 3 min.) and a com-
prehensive (approximately 30 min.) en-
gine/device parameter inspection and
maintenance procedure.
CAPE-15, Task II and CAPE-16 - Execute
a fleet testing program to evaluate emission
and engine/device inspection and corre-
sponding maintenance procedures.
CAPE-17 - Develop a short-duration emis-
sion inspection procedure to be used for
surveillance purposes and plan an optimum
surveillance program.
*CAPE - Cooperative Air Pollution Engineering.
9-1
-------
CAPE-18 - Prepare an economic effective-
ness model and use it in the selection of
inspection, maintenance, and surveillance
procedures as well as to plan an "opti-
mum" surveillance program.
Another teaming of industrial efforts is the
Inter-Industry Emission Control program,
conceived and established by the Ford Motor
Company and Mobil Oil Corporation. This
team, composed of U.S. and foreign auto
manufacturers and U.S. oil companies, is now
conducting a number of extensive programs
to develop more effective methods of control-
ling automobile emissions. The program goal
is to find a way to achieve even lower levels of
automobile exhaust emissions than those
called for by the 1970 standards. Fifteen pro-
jects toward this end are scheduled for com-
pletion by the spring of 1970. Chrysler and
Esso Corporations are also cooperating in
research to reduce vehicular emissions.
Most research and development relating to
vehicle emissions is being conducted by pri-
vate industry. Because of the proprietary
nature of this research, however, no data are
available on specific research funds or plans.
Furthermore, the nature of the research itself
is often kept secret until there are results to
be announced. Some of the specific types of
programs believed to be under way are dis-
cussed, however.1
9.2.1 Automobiles and Other Four-Stroke-
Cycle, Spark-Ignited Engines
In anticipation of future regulations, the
automobile, petroleum, and related industries
are conducting considerable research both
collectively and individually on the following
control devices:
1. Afterburners, both catalytic and ther-
mal.
2. Manifold reactors.
3. Exhaust recirculation.
4. Engine modification.
5. Fuel modification.
6. Evaporative control devices.
7. Filling and spillage control devices.
These areas probably make up the greatest
part of all nongovernmental research aimed at
reducing vehicle emissions.
9-2
9.2.2 Motorcycles and Other Two-
Stroke-Cycle, Spark-Ignited Engines
Manufacturers of two-stroke-cycle engines
are considering redesign of the engine to
reduce emissions, or the use of an alternative
engine, such as the Wankel engine. Very little
research has been done to date, however.
9.2.3 Diesel Engines
Diesel manufacturers have been engaged in
research on the reduction of nitrogen oxides,
hydrocarbons, odor, and smoke through en-
gine modifications and fuel additives.
9.2.4 Aircraft
Turbine engine manufacturers have con-
ducted research into reducing visible smoke in
the next generation of jet and turboprop
engines. Little or no work has been done on
piston engines.
9.2.5 Heat Engines
Automotive experience with Rankine cycle
(steam) engines of recent design is very
limited. Although the automobile manufac-
turers have not shown much interest, several
industrial firms are pursuing Rankine research
as a result of recent Congressional interest.
The Brayton cycle, or turbine engine, seems
to be the unconventional engine of greatest
interest to automobile manufacturers. It is
considered the most desirable both for emis-
sion control and engineering feasibility. Manu-
facturers are conducting considerable research
on this engine. One manufacturer has been
testing several generations of prototype
turbine automobiles for years. Other manu-
facturers, both in the United States and
abroad, are directing their developments
toward large commercial vehicle applications.
One Detroit manufacturer has invested a
considerable amount of resources in develop-
ing Stirling cycle engines.
9.2.6 Electric Power Systems
Lithium-chlorine and sodium-sulfur battery
systems are being developed by two automo-
bile manufacturers. A petroleum manufac-
turer is far along in developing a capacitive
high-temperature battery.
-------
One of the most prominent programs on
zinc-air batteries is being conducted by a
consortium of British and American industrial
firms. Various other industrial and chemical
firms are developing zinc-air, sodium-air, and
lithium-air batteries.
9.2.7 Hybrid Systems
Two joint ventures by an automobile
manufacturer and a battery manufacturer are
under way to produce a fuel cell-battery
hybrid in one case, and a battery-battery
hybrid in another. The latter approach is also
being taken by an electric equipment manu-
facturer.
9.2.8 Photochemical and Atmospheric
Research
Organic solvent manufacturers as well as
the automobile and petroleum industries are
sponsoring research concerning atmospheric
photochemical reactions.
9.3 REFERENCES FOR SECTION 9
1. National Air Pollution Control Administration.
Federal Research and Development Plan for
Mobile Sources Pollution Control Fiscal Years
1970-1975. U.S. DREW, PHS, EHS. Arlington,
Virginia. (Scheduled for publication in 1970.)
2. Callahan, J.M. GM Details 19 Power Plants.
Automotive News. May 26, 1969. p. 20-21.
3. Progress for Power Show-Steam, Electric
Powered Cars Unveiled at General Motors. Tech-
nical Center (XP-883). General Motors Corp.
Detroit News. May 7, 1969. p. 1A, 14A.
4. APRAC Status Report. Air Pollution Research
Advisory Committee of the Coordinating Re-
search Council, Inc. 30 Rockefeller Plaza, New
York. April 1969. p. 25-29.
9-3
-------
APPENDIX A
Federal Agencies Involved in Programs to Reduce Emissions
from Mobile Sources
Agency
National Air Pollution Control Administration
Atomic Energy Commission
Department of Defense
Department of the Interior
Program Area and Dates
Controlling agency for all air pollution pro-
grams funded by U.S. Department of
Health, Education, and Welfare (See
Appendix B)
Organic Rankine-Cycle Technology Investiga-
tion (1969-72)
Status of High Energy Battery Developments
(1969-70)
Bimetallic Systems Program (electric power)
(1969-75)
Stratified Charge Engine (1969-70)
Smoke Reduction in Turbine Aircraft Engines
(1969-70)
Industrial Gas Turbine Family (1969-75)
AGT-1, 500 Gas Turbine Development (1969)
Electrochemical Energy Storage for Vehicle
Propulsion (1969-73)
Exploratory Fuel Control Research (1969)
Basic Combustion Research on Internal Com-
bustion (1969-75)
Interactions Between Fuel Composition and
Engine Factors Influencing Exhaust Emis-
sions (1969-75)
Products of Combustion of Distillate Fuels
Used in Mobile Systems (1969-75)
Evaluation of Fuel Composition Effects on
Continuous Flow Combustion Propulsion
Systems (1969-75)
Characteristics of Photochemical Reactivity
of Vehicle Emissions (1969-75)
A-l
-------
Department of Transportation
General Services Administration
National Aeronautics and Space Administration
Post Office Department
Measurement of Smoke from Gas Turbine
Engines (1969)
Computer Programs to Define the Influence
of Combustion Parameters in Turbine
Engines (1970)
Study of Visible Exhaust Smoke from Air-
craft Jet Engines (1969)
Rankine-Cycle
(1969-70)
Rankine-Cycle
(1969-70)
Freon-Engine Bus System
Steam-Engine Bus System
Stirling-Cycle Bus Systems (1970-71)
Hybrid/Electric Bus System (1970-71)
Providing Fleets of Vehicles for Use in Dem-
onstration and Mileage Accumulation Tests.
Fleet Test of Natural-Gas-Powered Vehicles
(1970)
Development of Thermal Reactors for Vehicle
Pollution Control (1969-71)
Studies on Boilers, Pumps, Radiators, and
Condensers (1969-72)
Metal-Air Batteries (1971-75)
Interagency Advanced Power Group (1969,
1971) (Includes AEC, DOD, HEW, and
NASA)
Fleet Test of Natural-Gas-Powered Vehicles
(1970)
A-2
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APPENDIX B
Programs Sponsored by NAPCA To Reduce Emissions from Mobile Sources
High Efficiency Induction Systems Evaluation (1969-71)
Carburetors, Reduction of Engine Exhaust Emissions (1969-70)
Influence of Fuel Atomization, Vaporization, and Mixing on Exhaust Emissions (1969-70)
Kinetics of Nitric Oxide at High Temperatures (1969-70)
Alternate Low Emission Fuels for Motor Vehicle Propulsion (1969-70)
Effects of Gasoline Additives on Carburetor and PCV System Performance as They Relate to
Exhaust Emissions (APRAC - CAPE-2) (1969-70)
Emission Control Technique Evaluation (1969-70)
Evaluation of Exhaust Gas Recirculation for NOX Control (1969-71)
Demonstrate Feasibility of Control of NOX Emissions (1969)
Control of Nitrogen Oxides Emissions from Mobile Sources (1969-70)
Control of Particulate Emissions from Mobile Sources (1969-70)
Evaluation of Effects of Fuel Composition and Fuel Additives on Particulates in Exhaust
Emissions (1969-70)
Fuel Volatility Effects on Driveability and Emissions (APRAC - CAPE-4) (1969-70)
Automotive Fueling Emissions (APRAC - CAPE-9) (1969-70)
Study of Two-Stroke-Cycle Spark-Ignition Engine Emissions (1969-70)
Development of Emission Factors for Off-Highway Internal Combustion Engine (1970)
Control of Emissions from Diesel-Powered Mobile Sources (1970)
Control of Particulate Emissions from Mobile Sources (diesel) (1970)
Fuel Injection System Analysis: Diesel Smoke Reduction (1969-70)
Investigation of Diesel-Powered Vehicle Odor and Smoke (1969-70)
B-l
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Diesel Fuel Combustion Chemistry as Related to Odor (1969)
Control of Emissions from Aircraft (1969-70)
Rankine-Cycle Propulsion Systems for Vehicles (1969-70)
Low Emission Continuous Flow Combustors for Vehicle Propulsion Systems (1969-70)
Rankine-Cycle Bus Emission Evaluation (1970)
Gas Turbine Exhaust Emission Analysis (1969-70)
Irradiation Chamber Studies (1969-70)
Photochemistry and Kinetic Investigations (1969-70)
Elementary Reactions in Photochemical Smog (1969-70)
Field Studies of Photochemical Air Pollution (1969-70)
Atmospheric Reaction Studies in Los Angeles Atmosphere (APRAC - CAPE-7) (1969-70)
New Techniques for Exhaust Emissions (sampling) (1969-70)
Analytical Methods for Aromatics and Particulates in Auto Exhaust (APRAC - CAPE-12) (1970)
Improved Instrumentation for Determination of Exhaust Gases for NOX and Oxygenate Content
(APRAC - CAPE-11) (1969-70)
Chamber Reactivity Studies (APRAC - CAPA-1) (1970)
Response of Urban Population Groups to Diesel Exhaust Odors (1970)
Diesel Exhaust Odor Characterization (APRAC - CAPE-7) (1969-70)
Sampling System Evaluation (1969-70)
CO Profile Study (1970)
Diffusion Model of Urban Atmosphere (APRAC - CAPA-3) (1969-70)
Study of Air Pollution Aspects of Various Urban Forms (1970)
Development of Initial Guideline Document (1970)
Air Pollution Aspects of Various Roadway Configurations (Lower Manhattan Expressway)
(1969-70)
Development of a Long-Range Program Plan for the Air Pollution Aspects of Environmental
Planning (1969-70)
B-2
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Engine Emission Reduction by Combustion Control (1969)
Kinetics of Nitrogen Oxides Automotive Pollution (1969-70)
UCB-ENG-2045 -Combustion Gas Composition (1969-70)
Kinetics of Oxidation and Quenching of Combustibles in Exhaust Systems of Gasoline Engines
(APRAC - CAPE-8) (1969-70)
Relation of Fuel Composition to Gaseous Exhaust Emissions from Automotive Vehicles
(1969-70)
UCV-ENG-2365-Aromatic By-Products of Combustion (1969-70)
Liquid Fuel Ignition and Combustion (1969-70)
Gasoline Composition and Vehicle Exhaust Polynuclear Aromatic Content (APRAC - CAPE-6)
(1969-70)
Combustion Process Analysis (1969)
Oxygenates in Automotive Emissions (1969-70)
Use of Electric Fields in Combustion (1969-70)
Long-Range R/D Program Plan for the Development of Motor Vehicle Control Technology
(1969)
Long-Range Program Plan for Combustion Research (1969)
Long-Range R/D Program Plan for Air Pollution Instrumentation (1969)
Cost Effectiveness of Hydrocarbon Control (1969)
Technical Seminars, Advisory Committees, Etc. (1969)
B-3
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APPENDIX C
APRAC Sponsored Projects Related to Emissions from Mobile Sources
ENGINEERING PROJECTS Effects of Gasoline Additives on Carburetor and PCV System
Performance As They Relate to Exhaust Emissions
Fuel Effects on Combustion Chamber Deposits and Emissions
Fuel System Time-Temperature Histories of Driver Habits
Fuel Volatility Effects on Driveability and Emissions
Gasoline Composition and Vehicle Exhaust Polynuclear
Aromatic Content
Diesel Exhaust Odor Characterization
Kinetics of Oxidation and Quenching of Combustibles in
Exhaust Systems of Gasoline Engines
Automotive Fueling Emissions
Improved Instrumentation for Determination of Exhaust Gas
NO2 and Oxygenate Content
Analytical Methods for Aromatics and Particulates in Auto
Exhaust
ATMOSPHERIC PROJECTS Irradiation Chamber Studies
Dispersion of Pollutants in an Urban Area
C-l
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SUBJECT INDEX
Adsorption regeneration systems, 5-9-5-11
Aircraft, 5-20-5-22, 9-2
Aircraft gas-turbine engines,
2-5-2-7,2-10-2-11,5-21-5-22
Air-fuel ratio engines, 2-9
Air injection systems, 5-7-5-8
Atmospheric research, 9-3
Automobiles and other four-stroke-cycle,
spark-ignited engines, 5-11-5-15, 9-2 [See
also: Emission control systems]
Automotive gas-turbine engines, 7-2-7-5
B
Batteries, 7-10-7-11
[See also: Substitutes for currently used
motor vehicles - electric drive]
Blowby gases 6-1
Bus systems, 4-13
Carbon monoxide and hydrocarbons,
2-12-2-13
Carbon monoxide and nitrogen oxides emis-
sions effects of fuel modification on, 6-6
Catalytic converters, 5-18, 5-20
Catalytic oxidation, 5-13
Catalytic reduction, 5-14
Cetane improvers, 6-6
Clean Air Act of 1963, 3-1
Compliance, 3-63-10
Compressed natural gas (CNG), 6-6-6-7
Compression-ignition engines, 6-6
Control of older vehicles, 4-13-4-14
Control system inspection oxides of nitro-
gen, 4-12
Control systems - costs, 5-22
Control systems - current, 5-15-8
Crankcase emission control device inspection,
4-11-4-12
Crankcase ventilation systems, 5-1
D
Definitions, 2-1-2-3
Diesel engines, 2-4, 2-9-2-10, 5-18-5-19, 6-6,
9-2
Diesel fuel modification, 6-56-6
Distributor shafts, 2-9
Driver training, 4-15
Electric-drive engines, 7-107-14
Electric power systems, 9-29-3
Electrochemistry, 7-11
[See also: Substitutes for currently used
motor vehicles - electric drive]
Emission control device inspection crank-
case, 4-11-4-12
Emission control programs, 3-13-13
Emission control systems, 5-15-22
Emission factors 8-3
Emission standards, 3-43-6
Emissions
control device inspection, 4-114-12
control systems, 5-15-22
control systems inspection, 4-114-12
effects of emission reductions, 3-103-12
effects of maladjustment on CO and HC,
4-2
estimates and factors for moving sources,
8-1-8-3
exhaust measurement, 4-6-4-11
factors, 8-3
Federal control program, 3-1-3-13
nationwide levels, 2-152-16
1-1
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nature and formation, 2-112-12
nitrogen oxides, 2-132-15
quantities, 2-52-16
reactivity, 2-15
standards, 3-43-6
state control options, 4-14-16
vehicular estimations (regional), 8-18-3
Engine air-fuel ratio factors 5-14
Engine design - advanced, 5-18
Engine redesign, 5-18
Engine factors, 5-12
Engine modification systems, 5-25-7
Engine refinements, 5-19
Engines
aircraft gas turbine, 2-5-2-7, 2-10-2-11,
5-21-5-22
aircraft piston, 5-205-21
automotive gas turbine, 7-2-7-5
diesel (compression-ignition), 2-4,
2-9-2-10,5-18-5-19,6-6,9-2
electric drive, 7-10-7-14
electric power systems, 9-29-3
free pistio, 7-14-7-15
heat, 9-2
hybrid systems, 7-10-7-11, 9-3
internal combustion, four-stroke-cycle,
spark-ignited, 2-5-2-7, 2-9-2-10
internal combustion, four- and two-stroke-
cycle, compression-ignited, 2-52-7,
2-9-2-10
motorcycles and other two-stroke-cycle,
spark-ignited, 5-15, 9-2
rotary combustion chamber, 7-57-6
spark-ignited piston, 2-72-9, 6-6
steam, 7-6-7-10
Stirling, 7-15-7-16
stratified-charge, 7-16-7-18
Wankel engines, 5-18
Evaporative controls, 4-12, 5-85-9
Exhaust control systems, 5-15-2
Exhaust gas recirculation, 5-135-14
Exhaust measurements, 4-6-4-11
Exhaust reactor with secondary air supply,
5-18
Exhaust systems, 2-9
Federal emission control programs, 3-13-13
Fuel additives, 5-20
1-2
Fuel cells, 7-11
[See substitutes for currently used motor
vehicles - electric drive]
Fuel modification and substitution, 5-15,
6-1-6-9
Fuel studies, 5-18-5-19
Gasoline volatility reduction, 6-16-3
H
Heat engines, 9-2
Hybrid systems, 7-10-7-11, 9-3
Hydrocarbon and carbon monoxide control in
vehicle exhaust, 5-115-13
Ignition and fuel control, 5-13
Inspection and/or maintenance procedures,
4-6-4-12
Internal combustion engines - four-stroke-
cycle, 2-5-2-7, 2-9-2-10
Lead - effects on emissions, 6-5
Legislation
Federal emission control programs,
3-1-3-4
Schenck Act, 3-1, 3-2
state emission control options, 4-44-6
Liquefied natural gas (LNG), 6-66-7
Liquefied petroleum gas (LPG), 6-66-7
Long-range plans, 4-144-15
M
Maintenance personnel certification, 4-15
Methane, 6-7
Motorcycles and other two-stroke-cycle,
spark-ignited engines, 5-15, 9-2
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N
Nitrogen oxides control in vehicle exhaust,
5-13-5-15
Nitrogen oxides formation equilibrium con-
siderations, 2-13-2-14
NOX concentrations - engine variables,
2-13-2-15
NOX control system inspection, 4-12
O
Olefin removal
effects on emissions, 6-3-6-5
costs, 6-5
Road design and traffic control, 4-13
Rotary combustion chamber engine, 7-5-7-6
Schenck Act, 3-1, 3-2
State emission control options, 4-14-16
State programs, 4-2-4-4
California, 4-3
New Jersey, 4-34-4
[See also: State emission control options]
Steam engines, 7-67-10
Stirling engine, 7-15-7-16
Stratified-charge engine. 7-167-18
Substitutes for currently used motor vehicle
engines, 7-1-7-19
Peak combustion temperature
5-20
Photochemical research, 9-3
Piston engines
aircraft, 5-21-5-22
free piston engines, 7-147-15
spark-ignited, 2-7-2-9, 6-6
Power plants, 2-5-2-7
Public transportation
bus systems, 4-13
rail systems, 4-13
reduction,
Quenching, 2-13
R
Rail systems, 4-13
Regional emission estimates and emission
factors, 8-1-8-3
Regulations, 3-4-3-10
Tune-ups, 4-7-4-9
Turbine engines aircraft, 2-52-7,
2-10-2-11,5-21-5-22
Turboprop engines, 2-10
Vapor-recovery systems, 5-9
Vehicle emissions research and development,
9-1-9-3
Vehicle propulsion systems, 4-15
Visual inspections, 4-6
Volatility reduction
effects on performance, 6-2
effects on emissions, 6-26-3
costs, 6-3
W
Wankel engines, 5-18
1-3
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