Page 1 of 55
`
`FORD 1406
`
`

`
`Ronald K. Jurgen Editor in Chief
`
`McGraw-Hill, Inc.
`New York San Francisco Washington, D.C. Auckland Bogota
`Caracas Lisbon London Madrid Mexico City Milan
`Montreal New Delhi San Juan Singapore
`Sydney Tokyo Toronto
`
`Page 2 of 55
`
`FORD 1406
`
`

`
`Library of Congress Cataloging-in-Publication Data
`
`Automotive electronics handbook I Ronald Jurgen, editor in chief.
`p.
`em.
`Includes index.
`ISBN 0-07-033189-8
`1. Automobiles-Electronic equipment.
`TL272.5.A982
`1994
`629.25'49-dc
`
`I. Jurgen, Ronald K.
`
`94-39724
`CIP
`
`Copyright© 1995 by McGraw-Hill, Inc. All rights reserved. Printed in the
`United States of America. Except as permitted under the United States
`Copyright Act of 1976, no part of this publication may be reproduced or dis(cid:173)
`tributed in any form or by any means, or stored in a data base or retrieval
`system, without the prior written permission of the publisher.
`
`1 2 3 4 5 6 7 8 9 0 AGM/AGM 9 0 9 8 7 6 5 4
`
`ISBN 0-07-033189-8
`
`The sponsoring editor for this book was StephenS. Chapman, the editing
`supervisor was Virginia Carroll, and the production supervisor was
`Suzanne W B. Rapcavage. It was set in Times Roman by North Market
`Street Graphics.
`
`Printed and bound by Arcata Graphics/Martinsburg.
`
`McGraw-Hill books are available at special quantity discounts to use as pre(cid:173)
`miums and sales promotions, or for use in corporate training programs. For
`more information, please write to the Director of Special Sales, McGraw(cid:173)
`Hill, Inc., 11 West 19th Street, New York, NY 10011. Or contact your local
`bookstore.
`
`Information contained in this work has been obtained by McGraw(cid:173)
`Hill, Inc. from sources believed to be reliable. However, neither
`McGraw-Hill nor its authors guarantee the accuracy or complete(cid:173)
`ness of any information published herein, and. neither McGraw(cid:173)
`Hill nor its authors shall be responsible for any errors, omissions,
`or damages arising out of use of this information. This work is
`published with the understanding that McGraw-Hill and its authors
`are supplying information, but are not attempting to render engi(cid:173)
`neering or other professional services. If such services are
`required, the assistance of an appropriate professional should be
`sought.
`
`This book is printed on acid-free paper.
`
`Page 3 of 55
`
`FORD 1406
`
`

`
`c
`
`TS
`
`Contributors
`Preface
`xvii
`
`xv
`
`Part 1
`
`Introduction
`
`Chapter 1. Introduction Ronald K. Jurgen
`
`1.1 The Dawn of a New Era I 1.3
`1.2 The Microcomputer Takes Center Stage I 1.4
`1.3 Looking to the Future I 1.5
`References I 1.6
`
`Part 2 Sensors and Actuators
`
`Chapter 2. Pressure Sensors Randy Frank
`
`2.1 Automotive Pressure Measurements I 2.3
`2.2 Automotive Applications for Pressure Sensors
`2.3 Technologies for Sensing Pressure I 2.15
`2.4 Future Pressure-Sensing Developments I 2.23
`Glossary I 2.24
`Bibliography I 2.24
`
`2.5
`
`Chapter 3. linear and Angle Position Sensors Paul Nickson
`
`3.1 Introduction I 3.1
`3.2 Classification of Sensors I 3.1
`3.3 Position Sensor Technologies I 3.2
`3.4 Interfacing Sensors to Control Systems I 3.16
`Glossary I 3.17
`References I 3.17
`
`Chapter 4. Flow Sensors Robert E. Bicking
`
`4.1 Introduction I 4.1
`4.2 Automotive Applications of Flow Sensors I 4.1
`4.3 Basic Classification of Flow Sensors I 4.3
`4.4 Applicable Flow Measurement Technologies I 4.4
`Glossary I 4.8
`Bibliography I 4.9
`
`1.3
`
`2.3
`
`3.1
`
`4.1
`
`vii
`
`Page 4 of 55
`
`FORD 1406
`
`

`
`viii
`
`. CONTENTS
`
`Chapter 5. Temperature, Heat, and Humidity Sensors Randy Frank
`
`5.1
`
`5.1 Temperature, Heat, and Humidity I 5.1
`5.2 Automotive Temperature Measurements I 5.5
`5.3 Humidity Sensing and Vehicle Performance I 5.12
`5.4 Sensors for Temperature I 5.14
`5.5 Humidity Sensors I 5.21
`5.6 Conclusions I 5.22
`Glossary I 5.23
`Bibliography I 5.23
`
`Chapter 6. Exhaust Gas Sensors Hans-Martin Wiedenmann,
`Gerhard Hotze/, Harald Neumann, Johann Riegel, and Helmut Wey/
`
`6.1
`
`6.1 Basic Concepts I 6.1
`6.2 Principles of Exhaust Gas Sensors for Lambda Control I 6.5
`6.3 Technology of Ceramic Exhaust Gas Sensors I 6.11
`6.4 Factors Affecting the Control Characteristics of Lambda= 1 Sensors I 6.14
`6.5 Applications I 6.18
`6.6 Sensor Principles for Other Exhaust Gas Components I 6.20
`Bibliography I 6.22
`
`Chapter 7. Speed and Acceleration Sensors William C. Dunn
`
`7.1
`
`7.1 Introduction I 7.1
`7.2 Speed-Sensing Devices I 7.2
`7.3 Automotive Applications for Speed Sensing I 7.6
`7.4 Acceleration Sensing Devices I 7.8
`7.5 Automotive Applications for Accelerometers I 7.18
`7.6 New Sensing Devices I 7.22
`7.7 FutureApplications I 7.24
`7.8 Summary I 7.26
`Glossary I 7.27
`References I 7.28
`
`Chapter 8. Engine Knock Sensors William G. Wolber
`
`8.1 Introduction I 8.1
`8.2 The Knock Phenomenon I 8.2
`8.3 Technologies for Sensing Knock I 8.4
`8.4 Summary I 8.9
`Glossary I 8.9
`References I 8.9
`
`Chapter 9. Engine Torque Sensors William G. Wolber
`
`9.1 Introduction I 9.1
`9.2 Automotive Applications of Torque Measurement I 9.3
`9.3 Direct Torque Sensors I 9.6
`9.4 Inferred Torque Measurement I 9.8
`9.5 Summary I 9.13
`Glossary I 9.13
`References I 9.14
`
`8.1
`
`9.1
`
`Page 5 of 55
`
`FORD 1406
`
`

`
`CONTENTS
`
`ix
`
`10.1
`
`Chapter 10. Actuators Klaus Muller
`
`10.1 Preface I IO.I
`10.2 Types of Electromechanical Actuators I I 0.2
`10.3 Automotive Actuators I I O.I9
`10.4 Technology for Future Application I I 0.27
`Acknowledgments I I 0.30
`Glossary I I 0.30
`Bibliography I I 0.3I
`
`Part 3 Control Systems
`
`Chapter 11. Automotive Microcontrollers DavidS. Boehmer
`
`11.3
`
`11.1 Microcontroller Architecture and Performance Characteristics I 11.3
`11.2 Memory I 11.24
`11.3 Low-Speed Input/Output Ports I 11.3I
`11.4 High-Speed I/0 Ports I 11.36
`11.5 Serial Communications I 11.4I
`11.6 Analog-to-Digital Converter I 11.45
`11.7 Failsafe Methodologies I 11.49
`11.8 Future Trends I 11.5I
`Glossary I 11.54
`Bibliography I 11.55
`
`Chapter 12. Engine Control Gary C. Hirsch/ieb, Gottfried Scftiller,
`and Shari Stottler
`
`12.1 Oqjectives of Electronic Engine Control Systems I I2.I
`12.2 Spark Ignition Engines I 12.5
`12.3 Compression Ignition Engines I I2.32
`
`Chapter 13. Transmission Control Kurt Neuffer, Wolfgang Bullmer,
`and Werner Brehm
`
`13.1 Introduction I 13.I
`13.2 System Components I 13.2
`13.3 System Functions I 13.7
`13.4 Communications with Other Electronic Control Units I 13.17
`13.5 Optimization of the Drivetrain I 13.I8
`13.6 Future Developments I 13.I9
`Glossary I 13.20
`References I 13.20
`
`Chapter 14. · Cruise Control Richard Valentine
`
`14.1 Cruise Control System I I4.I
`14.2 Microcontroller Requirements for Cruise Control I 14.3
`14.3 Cruise Control Software I 14.4
`14.4 Cruise Control Design I 14.6
`14.5 Future Cruise Concepts I 14.7
`Glossary I I4.8
`Bibliography I I4.8
`
`12.1
`
`13.1
`
`14.1
`
`Page 6 of 55
`
`FORD 1406
`
`

`
`X
`
`CONTENTS
`
`Chapter 15. Braking Control Jerry L. Cage
`
`15.1 Introduction I 15.1
`15.2 Vehicle Braking Fundamentals I 15.1
`15.3 Antilock Systems I 15.8
`15.4 Future Vehicle Braking Systems I 15.14
`Glossary I 15.15
`References I 15.16
`
`Chapter 16. Traction Control Armin Czinczel
`
`16.1 Introduction I 16.1
`16.2 Forces Affecting Wheel Traction: Fundamental Concepts I 16.3
`16.3 Controlled Variables I 16.5
`16.4 Control Modes I 16.6
`16.5 Traction Control Components I 16.11
`16.6 Applications on Heavy Commercial Vehicles I 16.13
`16.7 Future Trends I 16.14
`Glossary I 16.14
`Bibliography I 16.15
`
`15.1
`
`16.1
`
`Chapter 17. Suspension Control Akatsu Yohsuke
`
`17.1
`
`17.1 Shock Absorber Control System I 17.1
`17.2 Hydropneumatic Suspension Control System I 17.4
`17.3 Electronic Leveling Control System I 17.5
`17.4 Active Suspension I 17.8
`17.5 Conclusion I 17.17
`Glossary I 17.18
`Nomenclature I 17.18
`Bibliography I 17.18
`
`Chapter 18. Steering Control. Makoto Sato
`
`18.1 Variable-Assist Steering I 18.1
`18.2 Four-Wheel Steering Systems (4WS) I 18.15
`Glossary I 18.33
`References I 18.33
`
`Chapter 19. Lighting, Wipers, Air Conditioning/Heating
`Richard Valentine
`
`19.1 Lighting Controls I 19.1
`19.2 Windshield Wiper Control I 19.9
`19.3 Air Conditioner/Heater Control I 19.15
`19.4 Miscellaneous Load Control Reference I 19.20
`19.5 Future Load Control Concepts I 19.25
`Glossary I 19.26
`Bibliography I 19.27
`
`18.1
`
`19.1
`
`Page 7 of 55
`
`FORD 1406
`
`

`
`Part 4 Displays and Information Systems
`
`Chapter 20. Instrument Panel Displays Ronald K. Jurgen
`
`20.3
`
`CONTENTS
`
`xi
`
`20.1 The Evolution to Electronic Displays I 20.3
`20.2 Vacuum Fluorescent Displays I 20.3
`20.3 Liquid Crystal Displays I 20.4
`20.4 Cathode-Ray Tube Displays I 20.6
`20.5 Head-up Displays I 20.6
`20.6 Electronic Analog Displays I 20.8
`20.7 Reconfigurable Displays I 20.9
`References I 20.9
`
`Chapter 21. Trip Computers Ronald K. Jurgen
`
`21.1 Trip Computer Basics I 21.1
`21.2 Specific Trip Computer Designs I 21.2
`21.3 Conclusion I 21.4
`References I 21.6
`
`Chapter 22. On- and Off-Board Diagnostics Wolfgang Bremer,
`Frieder Heintz, and Robert Hugel
`
`22.1 Why Diagnostics? I 22.1
`22.2 On-Board Diagnostics I 22.6
`22.3 Off-Board Diagnostics I 22.7
`22.4 Legislation and Standardization I 22.8
`22.5 Future Diagnostic Concepts I 22.15
`Glossary I 22.18
`References I 22.19
`
`21.1
`
`22.1
`
`Part 5 Safety, Convenience, Entertainment,
`and Other Systems
`
`Chapter 23. Passenger Safety and Convenience Bernhard K. Mattes
`
`23.3
`
`23.1 Passenger Safety Systems I 23.3
`23.2 Passenger Convenience Systems I 23.11
`Glossary I 23.13
`Bibliography I 23.13
`
`Chapter 24. Antitheft Systems Shinichi Kato
`
`24.1
`
`24.1 Vehicle Theft Circumstances I 24.1
`24.2 Overview of Antitheft Regulations I 24.2
`24.3 A Basic Antitheft System I 24.3
`
`Page 8 of 55
`
`FORD 1406
`
`

`
`11
`i
`
`xii
`
`CONTENTS
`
`Chapter 25. Entertainment Products Tom Chrapkiewicz
`
`25.1
`
`25.1 Fundamentals of Audio Systems I 25.1
`25.2 A Brief History of Automotive Entertainment I 25.4
`25.3 Contemporary Audio Systems I 25.5
`25.4 Future Trends I 25.12
`Glossary I 25.17
`References I 25.18
`
`Chapter 26. Multiplex Wiring Systems Fred Miesterfe/d
`
`26.1
`
`26.1 Vehicle Multiplexing I 26.1
`26.2 Encoding Techniques I 26.9
`26.3 Protocols I 26.23
`26.4 Summary and Conclusions I 26.53
`Glossary I 26.56
`References I 26.64
`
`Part 6 Electromagnetic Interference and Compatibility
`
`Chapter 27. Electromagnetic Standards and Interference
`James P. Muccio/i
`
`27.3
`
`27.1 SAE Automotive EMC Standards I 27.3
`27.2 IEEE Standards Related to EMC I 27.11
`27.3 The Electromagnetic Environment of an Automobile Electronic System I 27.13
`Bibliography I 27.18
`
`Chapter 28. Electromagnetic Compatibility James P. Muccioli
`
`28.1
`
`28.1 Noise Propagation Modes I 28.1
`28.2 Cabling I 28.2
`28.3 Components I 28.4
`28.4 Printed Circuit Board EMC Checklist I 28.9
`28.5 Integrated Circuit Decoupling-A Key Automotive EMI Concern I 28.10
`28.6 IC Process Size Affects EMC I 28.14
`Bibliography I 28.19
`
`Part 7 Emerging Technologies
`
`Chapter 29. Navigation Aids and Intelligent Vehicle-Highway Systems Robert L.
`French
`29.3
`
`29.1 Background I 29.3
`29.2 Automobile Navigation Technologies I 29.4
`29.3 Examples of Navigation Systems I 29.10
`29.4 Other IVHS Systems and Services I 29.15
`References I 29.18
`
`Page 9 of 55
`
`FORD 1406
`
`

`
`Chapter 30. Electric and Hybrid Vehicles George G. Karady, Tracy Blake,
`Raymond S. Hobbs, and Donald B. Karner
`
`30.1
`
`CONTENTS
`
`xiii
`
`30.1 Introduction I 30.1
`30.2 System Description I 30.5
`30.3 Charger and Protection System I 30.6
`30.4 Motor Drive System I 30.8
`30.5 Battery I 30.17
`30.6 Vehicle Control and Auxiliary Systems I 30.19
`30.7 Infrastructure I 30.21
`30.8 Hybrid Vehicles I 30.23
`Glossary I 30.24
`References I 30.25
`
`Chapter 31. Noise Cancellation Systems Jeffrey N. Denenberg
`
`31.1
`
`31.1 Noise Sources I 31.1
`31.2 Applications I 31.5
`Glossary I 31.10
`Bibliography I 31.10
`
`Chapter 32. Future Vehicle Electronics Randy Frank and Salim Momin
`
`32.1
`
`32.1 Retrospective I 32.1
`32.2 IC Technology I 32.1
`32.3 Other Semiconductor Technologies I 32.5
`32.4 Enabling the Future I 32.11
`32.5 Impact on Future Automotive Electronics
`32.6 Conclusions I 32.20
`Glossary I 32.21
`Bibliography I 32.23
`
`32.15
`
`Index I 1.1
`
`Page 10 of 55
`
`FORD 1406
`
`

`
`L
`
`Gary C. Hirschlieb, Gottfried Schiller, and Shari Stottler
`Robert Bosch GmbH
`
`12. 1 OBJECTIVES OF ELECTRONIC ENGINE CONTROL SYSTEMS
`
`The electronic engine control system consists of sensing devices which continuously measure
`the operating conditions of the engine, an electronic control unit (ECU) which evaluates the
`sensor inputs using data tables and calculations and determines the output to the actuating
`devices, and actuating devices which are commanded by the ECU to perform an action in
`response to the sensor inputs.
`The motive for using an electronic engine control system is t0 provide the needed accuracy
`and adaptability in order to minimize exhaust emissions and fuel consumption, provide opti(cid:173)
`mal driveability for all operating conditions, minimize evaporative emissions, and provide sys(cid:173)
`tem diagnosis when malfunctions occur.
`In order for the control system to meet these objectives, considerable development time is
`required for each engine and vehicle application. A substantial amount of development must
`occur with an engine installed on an engine dynamometer under controlled conditions. Infor(cid:173)
`mation gathered is used to develop the ECU data tables. A considerable amount of develop(cid:173)
`ment effort is also required with the engine installed in the vehicle. Final determination of the
`data tables occurs during vehicle testing.
`
`12.1.1 Exhaust Emissions
`
`Exhaust Components. The engine exhaust consists of products from the combustion of the
`air and fuel mixture. Fuel is a mixture of chemical compounds, termed hydrocarbons (HC).
`The various fuel compounds are a combination of hydrogen and carbon. Under perfect com(cid:173)
`bustion conditions, the hydrocarbons would combine in a thermal reaction with the oxygen in
`the air to form carbon dioxide (C02) and water (H20). Unfortunately, perfect combustion
`does not occur and in addition to C02 and H 20, carbon monoxide (CO), oxides of nitrogen
`(NOx), and hydrocarbons (HC) occur in the exhaust as a result of the combustion reaction.
`Additives and impurities in the fuel also contribute minute quantities of pollutants such as
`lead oxides, lead halogenides, and sulfur oxides. In compression ignition (diesel) engines,
`there is also an appreciable amount of soot (particulates) created. Federal statues regulate the
`allowable amount of HC, NOx, and CO emitted in a vehicle's exhaust. On diesel engines, the
`amount of particulates emitted is also regulated.
`
`12.1
`
`Page 11 of 55
`
`FORD 1406
`
`

`
`12.2
`
`CONTROL SYSTEMS
`
`Spark Ignition Engines
`Air/fuel Ratio. The greatest effect on the combustion process, and therefore on the
`exhaust emissions, is the mass ratio of air to fuel. The air/fuel mixture ratio must lie within a
`certain range for optimal ignition and combustion. For a spark ignition engine, the mass ratio
`for complete fuel combustiop. is 14.7:1; i.e., 14.7 kg of air to 1 kg of fuel. This ratio is known as
`the stoichiometric ratio. In terms of volume, approximately 10,000 liters of air would be
`required for 1liter of fuel. The air/fuel ratio is often described in terms of the excess-air fac(cid:173)
`tor known as lambda (A). Lambda indicates the deviation of the actual air/fuel ratio from the
`theoretically required ratio:
`
`A=
`
`quantity of air supplied
`theoretical requirement (14.7 for gasoline)
`
`At stoichiometry: A= 1
`For a mixture with excess air (lean): A> 1
`For a mixture with deficient air (rich): A< 1
`
`Effect of Air/Fuel Ratio on Emissions
`In the rich operating range (A< 1), CO emissions increase almost linearly
`CO emissions.
`with an increasing amount of fuel. In the lean range (A> 1), CO emissions are at their low(cid:173)
`est. With an engine operating at (A= 1), the CO emissions can be influenced by the cylin(cid:173)
`der distribution. If some cylinders are operating rich and others lean with the summation
`acr..ieving A= 1, the average CO emissions will be higher than if all cylinders were operat-
`ing at A= 1.
`.
`HC emissions. As with CO emissions, HC emissions increase with an increasing amount
`of fuel. The minimum HC emissions occur at A= 1.1 ... 1.2.At,very lean air/fuel ratios, the
`HC emissions again increase due to less than optimal combustion conditions resulting in
`unburned fuel.
`NOx emissions. The effect of the air/fuel ratio on NOx emissions is the opposite of HC
`and CO on the rich side of stoichiometry. As the air content increases, the oxygen content
`increases and the result is more NOx. On the lean side of stoichiometry, NOx emissions
`decrease with increasing air because the decreasing density lowers the combustion cham(cid:173)
`ber temperature. The maximum NOx emissions occur at A= 1.05 ... 1.1.
`
`Catalytic Converters. To reduce the exhaust gas emission concentration, a catalytic con(cid:173)
`verter is installed in the exhaust system. Chemical reactions occur in the converter that trans(cid:173)
`form the exhaust emissions to less harmful chemical compounds. The most commonly used
`converter for a spark ignition engine is the three-way converter (TWC). As the name implies,
`it simultaneously reduces the concentration of all three regulated exhaust gases: HC, CO, and
`NOx. The catalyst promotes reactions that oxidize HC and CO, converting them into C02 and
`H 20, while reducing NOx emissions into N2. The actual chemical reactions that occur are:
`2CO + 0 2 ~ 2COz
`
`2CzH6 + 70z ~ 4COz + 6Hz0
`2NO + 2CO ~ N2 + 2COz
`
`In order for the catalytic converter to operate at the highest efficiency for conversion for
`all three gases (HC, CO, NOx), the average air/fuel ratio must be maintained within less than
`1 percent of stoichiometry. This small operating :range is known as the lambda window or cat(cid:173)
`alytic converter window. Figure 12.1 is a graph of lambda (A) versus the exhaust emissions
`both before and after the catalytic converter. Up to 90 percent of the exhaust gases are con(cid:173)
`verted to less harmful compounds by tlJ_e c;:ttalytic converter.
`
`Page 12 of 55
`
`FORD 1406
`
`

`
`ENGINE CONT~ 12.3
`
`iP
`f£t ·w.----- A.-Control Range
`(Catalytic Converter Window)
`________ N 0 x
`
`(/) c
`.Q
`(/)
`-~
`E w
`
`1,05
`1,0
`0,9 0,95
`Lambda A,
`
`1,1
`
`FIGURE U.l Lambda effect on exhaust emissions prior to
`and after catalyst treatment.
`
`To remain within the catalytic converter window, the air/fuel ratio is controlled by the
`lambda closed-loop fuel control system, which is part of the electronic engine control system.
`The key component in this system is the lambda sensor. This sensor is installed in the exhaust
`system upstream of the catalytic converter and responds to the oxygen content in the exhaust
`gas. The oxygen content is a measure of the excess air (or deficiency of air) in the exhaust gases.
`A detailed discussion of the lambda closed-loop control system occurs in Sec. 12.2.1.
`Ignition Timing. The ignition timing is defined as the crankshaft angle before top dead
`center (TDC) at which the ignition spark occurs. The ignition timing of the air/fuel mixture
`has a decisive influence on the exhaust emissions.
`Effect of ignition timing on exhaust emissions.
`• CO emissions are almost completely independent of the ignition timing and are primarily a
`function of the air/fuel ratio.
`• In general, the more the ignition is advanced, the higher the emissions of HCs. Reactions
`initiated in the combustion chamber continue to occur after the exhaust valve opens, which
`depletes the remaining HCs. With advanced timing due to lower exhaust temperatures,
`these postreactions do not readily occur.
`• With increased timing advance, the combustion chamber temperatures increase. The tem(cid:173)
`perature increase causes an increase in NOx emissions regardless of air/fuel ratio.
`
`To provide the optimal ignition timing for exhaust emissions, precise control of the ignition
`timing is required. It is imperative that the ignition timing be coordinated with the air/fuel
`ratio since they have a combined effect on exhaust emissions as well as fuel consumption and
`driveability. Ignition timing is generally controlled by the ECU. Ignition timing control is dis(cid:173)
`cussed in detail in Sec.l2.2.1.
`Exhaust Gas Recirculation (EGR). Exhaust gas recirculation (EGR) is a method of reduc(cid:173)
`ing emissions of oxides of nitrogen. A portion of the exhaust gas is recirculated back to the com(cid:173)
`bustion chamber. Exhaust gas is an inert gas and, in the combustion chamber, it lowers the peak
`combustion temperature. Depending on the amount of EGR, NOx emissions can be reduced by
`up to 60 percent, although an increase in HC emissions would occur at such high levels ofEGR.
`Some internal EGR occurs due to the overlap of the exhaust and intake valves. Additional
`quantities are supplied by a separate system linking the exhaust manifold to the intake mani-
`
`Page 13 of 55
`
`FORD 1406
`
`

`
`12.4
`
`CONTROLSYSTEMS
`
`fold. The quantity of EGR flow to the intake system is metered by a pneumatic or electronic
`valve. The EGR valve is controlled by the ECU. The maximum flow of EGR is limited by an
`increase in HC emissions, fuel consumption, and engine roughness. EGR contrt:>l is discussed
`in detail in Sec. 12.2.1.
`
`Compression Ignition (Diesel) Engines. There are some key distinctions between an SI
`engine and a CI engine. The CI engine uses high pressure and temperature instead of a spark
`to ignite the combustible air/fuel mixture. To achieve this, the CI engine compression ratio is
`in the range of 21:1, as opposed to roughly 10:1 for an SI engine. In a CI engine, the fuel is
`injected directly into the cylinder near the top of the compression stroke. Mixing of the fuel
`and air, therefore, occurs directly in the cylinder.
`Air/fuel ratio. Diesel engines always operate with excess air (A.> 1). Where:
`
`A= quantity of air supplied
`theoretical requirement
`
`The excess air (A.= 1.1 ... 1.2) reduces the amount of soot (particulates), HC, and CO emissions.
`Catalytic Converters. An oxidizing catalyst is used that converts CO and HC to C02 and
`H 20. The NOx reduction that occurs for anSI engine three-way catalyst (TWC) is not possi(cid:173)
`ble with a diesel because the diesel operates with excess air. The optimal conversion of NOx
`requires a stoichiometric ratio (A.= 1) or a deficiency of air (A.< 1).
`In a compression ignition engine, the start of combustion is determined
`Injection Timing.
`by the start of fuel injection. In general, retarding the injection timing decreases NOx emis(cid:173)
`sions, while overretarding results in an increase in HC emissions. A 1 o (crankshaft angle) de vi(cid:173)
`ation in injection timing can increase NOx emissions by 5 percent and HC emissions by as
`much as 15 percent. Precise control of injection timing is critical. Injection timing on some sys(cid:173)
`tems is controlled by the ECU. Feedback on injection timing can be provided by a sensor
`installed on the injector nozzle. Further discussion on injection timing occurs in Sec.12.3.1.
`Exhaust Gas Recirculation (EGR). As with anSI engine, exhaust gas can be recirculated
`to the combustion chamber to significantly reduce NOx emissions. The quantity of EGR
`allowed to enter the intake is metered by the EGR valve. If the quantity is too high, HC emis(cid:173)
`sions, CO emissions, and soot (particulates) increase as a result of an insufficient quantity of
`air. The EGR valve is controlled by the ECU, which determines how much EGR is tolerable
`under the current engine operating conditions.
`
`12.1.2 Fuel Consumption
`
`Federal statutes are currently in effect that require each automobile manufacturer to achieve
`a certain average fuel economy for all their models produced in one model year. The require(cid:173)
`ment is known as corporate average fuel economy or CAFE. The fuel economy for each vehi(cid:173)
`cle type is determined during the federal test procedure, the same as for exhaust emissions
`determination, conducted on a chassis dynamometer. Because of the CAFE requirement, it is
`critical that fuel consumption be minimized for every vehicle type produced.
`The electronic engine control system provides the fuel metering and ignition timing preci(cid:173)
`sion required to minimize fuel consumption. Optimum fuel economy occurs near 'A= 1.1.
`However, as discussed previously, lean engine operation affects exhaust emissions and NOx is
`at its maximum at A,= 1.1.
`During coasting and braking, fuel consumption can be further reduced by shutting off the fuel
`until the engine speed decreases to slightly higher than the set idle speed. The ECU determines
`when fuel shutoff can occur by evaluating the throttle position, engine RPM, and vehicle speed.
`The influence of ignition timing on fuel consumption is the opposite of its influence on
`exhaust emissions. As the air/fuel mixture becomes leaner, the ignition timing must be
`advanced to compensate for a slower combustion speed. However, as discussed previously,
`
`Page 14 of 55
`
`FORD 1406
`
`

`
`advancing the ignition timing increases the emissions of HC and NOx. A sophisticated ignition
`control strategy permitting optimization of the ignition at each operating point is necessary to
`reach the compromise between fuel consumption and exhaust emissions. The electronic
`engine control system can provide this sophisticated strategy.
`·
`
`ENGINE CONTROL
`
`12.5
`
`12.1.3 Driveability
`
`Another requirement of the electronic engine control system is to provide acceptable drive(cid:173)
`ability under all operating conditions. No stalls, hesitations, or other objectionable roughness
`should occur during vehicle operation. Driveability is influenced by almost every operation of
`the engine control system and, unlike exhaust emissions or fuel economy, is not easily mea(cid:173)
`sured. A significant contribution to driveability is determined by the fuel metering and igni(cid:173)
`tion timing. When determining the best fuel and ignition compromises for fuel consumption
`and exhaust emissions, it is important to evaluate the driveability. Other factors that influence
`driveability are the idle speed control, EGR control, and evaporative emissions control.
`
`12.1.4 Evaporative Emissions
`
`Hydrocarbon (HC) emissions in the form of fuel vapors escaping from the vehicle are closely
`regulated by federal statutes. The prime source of these emissions is the fuel tank. Due to
`ambient heating of the fuel and the return of unused hot fuel from the engine, fuel vapor is
`generated in the tank. The evaporative emissions control system (EECS) is used to control
`the evaporative HC emissions. The fuel vapors are routed to the intake manifold via the
`EECS and they are burned in the combustion process. The quantity of fuel vapors delivered
`to the intake manifold must be metered such that exhaust emissions and driveability are not
`adversely affected. The metering is provided by a purge controtvalve whose function is con(cid:173)
`trolled by the ECU. Further discussion on the operation {)f the evaporative emissions control
`system occurs in Sec.12.2.1.
`
`12.1.5 System Diagnostics
`
`The purpose of system diagnostics is to provide a warning to the driver when the control sys(cid:173)
`tem determines a malfunction of a component or system and to assist the service technician
`in identifying and correcting the failure (see Chap. 22). To the driver, the engine may appear
`to be operating correctly, but excessive amounts of pollutants may be emitted. The ECU
`determines a malfunction has occurred when a sensor signal received during normal engine
`operation or during a system test indicates there is a problem. For critical operations such as
`fuel metering and ignition control, if a required sensor input is faulty, a substitute value may
`be used by the ECU so that the engine will continue to operate.
`When a failure occurs, the malfunction indicator light (MIL), visible to the driver, is illu(cid:173)
`minated. Information on the failure is stored in the ECU. A service technician can retrieve the
`information on the failure from the ECU and correct the problem. Detailed examples of sys(cid:173)
`tem diagnostics are discussed in Sec. 12.2.3.
`
`12.2 SPARK IGNITION ENGINES
`
`12.2.1 Engine Control Functions
`
`Fuel Control. For the purpose of discussing fuel control strategies, a multipoint pulsed fuel
`injection system is assumed. Additional discussions of fuel control for different types of fuel
`
`Page 15 of 55
`
`FORD 1406
`
`

`
`12.6
`
`CONTROL SYSTEMS
`
`systems such as carbureters, single-point injection, and multipoint continuous injection
`appear in Sec.l2.2.4 (Fuel Delivery Systems).
`In order for the fuel metering system to provide the appropriate amount of fuel for the
`engine operating conditions, the mass flow rate of incoming air, known as the air charge, must
`be determined.
`
`F ==
`m
`
`Am
`requested air-fuel ratio
`
`where Fm ==fuel mass flow rate
`Am== air mass flow rate
`
`The air mass flow rate can be calculated from:
`
`where Av ==volume flow rate of intake air
`Ad == air density
`
`There are three methods commonly used for determining the air charge: speed density, air
`flow measurement, and air mass measurement. In the speed density method, the air charge is
`calculated by the engine electronic control unit based on the measurement of air inlet tem(cid:173)
`perature, intake manifold pressure, and engine RPM. The temperature and pressure are used
`to determine the air density and the RPM is used to determine the volume flow rate. The
`engine acts as an air pump during the intake stroke. The calculated volume flow rate can be
`determined as follows:
`
`RPM D
`ARPM== ~ x 2 xVE
`
`where RPM== engine speed
`D == engine displacement
`VE ==volumetric efficiency
`
`In an engine using exhaust gas recirculation (EGR), the volume flow rate of EGR must be
`subtracted from the calculated volume flow rate.
`
`The volume flow rate of EGR can be determined empirically based on the EGR valve flow
`rate and the EGR control strategy being used.
`In the air flow measurement method, the air flow is measured using a vane type meter and
`air density changes are compensated for by an air inlet temperature sensor, The vane meter
`uses the force of the incoming air to move a flap through a defined angle. This angular move(cid:173)
`ment is converted by a potentiometer to a voltage ratio. Because only the fresh air charge is
`measured, no compensation is required for EGR.
`In the air mass measurement method, the air charge is measured directly using a hot-wire
`or hot-film air mass flow sensor. The inlet air passes a heated element, either wire or film. The
`element is part of a bridge circuit that keeps the element at a constant temperature above the
`inlet air temperature. By measuring the heating current required by the bridge circuit and
`converting this to a voltage via a resistor, the air mass flow passing the element can be deter(cid:173)
`mined. Again, because only the fresh air charge is measured, no compensation for EGR is
`required. However, sensing errors may occur due to strong intake manifold reversion pulses,
`which occur under certain operating conditions. In such cases, a correction factor must be
`determined and applied.
`
`Page 16 of 55
`
`FORD 1406
`
`

`
`ENGINE CON'l'.!WL
`
`12.7
`
`Calculation of Injector Pulse Width. The base pulse width is determined from the re(cid:173)
`quired fuel mass flow rate (Fm) and an empirical injector constant. The injector constant is
`determined by the design of the injector and is a function of the energized time versus the
`flow volume. This constant is normally determined with a constant differential pressure across
`the injector (from fuel rail to intake manifold). When the pressure across the injector does not
`remain constant (i.e., there is no pressure regulator intake manifold vacuum reference), an
`entire map of injector constants for different manifold pressures may be required.
`The effective injector pulse width is a modification of the base pulse width. The base pulse
`width is adjusted by a number of correction factors depending on operating conditions. For
`example, a battery voltage correction is required to compensate for the electromechanical
`characteristics of the fuel injectors. Injector opening and closing rates differ depending on the
`voltage applied to the injector, which affects the amount of fuel injected for a given pulse
`width. Other common correction factors may include hot restart, cold operation, and transient
`operation corrections. Figure 12.2 is a flowchart of a typical in