Diesel engine and fuel system repair fifth edition

Combustion Dynamics, 53Technician Professionalism and Image, 1 Fuel Injection Timing, 56 Career Advancement, 3 Retarded versus Advanced Timing, 58 ASE Diesel Engines Task List, 4 Summary

Diesel Engine and

Fuel System Repair

Upper Saddle River, New JerseyColumbus, Ohio

Library of Congress Cataloging-in-Publication Data

1 Diesel motor-Maintenance and repair 2 Diesel motor-Fuel systems-Maintenance

and repair I Brady, Robert N II Title.

TJ799 033 2001

Editor in Chief: Stephen Helba

Editor: Edward Francis

Production Editor: Christine M Buckendahl

Production Coordinator: Carlisle Publishers Services

Design Coordinator: Robin G Chukes

Cover Designer: Linda Fares

Cover photo: International Stock

Production Manager: Brian Fox

Marketing Manager: Jamie Van Voorhis

This book was set in Palatino by Carlisle Communications, Ltd., and was printed and bound by Courier

Kendallville, Inc The cover was printed by The Lehigh Press, Inc.

Prentice-Hall International (UK) Limited, London

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Editora Prentice-Hall do Brasil, Ltda., Rio de Janeiro

Copyright © 2002, 1998, 1994, 1988, 1982 by Pearson Education, Inc., Upper Saddle River, New Jersey 07458 All rights reserved Printed in the United States of America This publication is protected by Copyright and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or

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10 9 8 7 6 5 4 3 2 1 ISBN 0-13-092981-6

To all of the creative individuals who have allowed

me to gain knowledge and skills from their

benchmark experiences and to the many motivatedstudents, friends, and SAE colleagues within thediesel and automotive industry who have shared theirstandards of excellence This book is a reflection of adiversity of backgrounds of truly remarkable peoplewho provided me with their time and support I trustthat the finished product meets your high standardsand expectations

In the United States, a recently conducted detailed scribe the function, operation, and troubleshooting ofstudy of over a hundred highly skilled professions by these specific systems The various fuel injection shopsthe GAO (General Accounting Office)determined that and technicians who are members of ADS (Association

the needed skill levels of both automotive and diesel of Diesel Specialists), and who are tested and certifiedtechnicians were on a par with X-ray technicians and in this highly specialized area, are the best personnel tocomputer programmers! To be successful, they pro- handle this type of repair

jected that a minimum of a high school diploma with Each chapter was reviewed, updated, and addedemphasis on math, science,physics, English, and com- to where appropriate to reflect the latest technology Aputer literacy accompanied by a preferred one to two wide range of new illustrations and photographs inyears of college training in the,irspecific technical field two-color format was chosen to accentuate the techni-

be viewed as prerequisites." w cal descriptions, and also to improve the visual The technological advancements in internal com- pretation aspects under discussion The new materialbustion engines and equipment, with their high degree added highlights the latest technology currently in use

inter-of electronics controls, demand that tomorrow's tech- by all of the major diesel engine OEMsworldwide, nicians be vigilant to lifelong learning techniques and ticularly the new designs of engine component parts,the continual absorption of new knowledge In this, the electronic fuel injection systems, and electronic gover-

par-fifth edition of Diesel Engine and Fuel System Repair, nor controls Several new chapters dealing with enginePrentice Hall and I have contacted a number of readers run-in and dyno testing, engine diagnosis and trou-and instructors to review the suggested new material bleshooting, and an excellent simplified chapter de-

to solicit their views, thoughts, and ideas of what a re- scription/ coverage of the basic theory, operation, andvised textbook in this subject area should offer It is diagnosis of diesel electronic fuel injection systems willnever an easy task to incorporate all of the required prepare the reader to successfully challenge those spe-preferences that individuals would like to see, due to cificareas of ASE and/ or TQ testing

the size and cost limitations of the finished product To support technician professionalism, ASE-typeThe major key elements and subject matter finally task lists, test specs content areas, and ASE-typereviewchosen were based upon the necessity to offer and com- questions facilitate your study habits, and provide aply with both the ASE(Automotive ServiceExcellence) structured guide for both technician trainees and tech-and TQ (Trade Qualification) test areas As a base, I nical instructors Liberal use of suggested repair or re-have incorporated information that is relevant to ASE's placement flowcharts throughout the book chaptersmedium/heavy truck and diesel engines testing areas will promote decision making as to the most effectiveConsequently, detailed subject material not included in and efficient method to follow when conducting re-ASE testing areas such as mechanical diesel fuel injec- pairs The incorporation of appropriate website ad-tion and governor major overhaul, phasing, and cali- dresses offers a library of additional knowledge quicklybrating was n9t deemed necessary, although we do de- available to the reader and instructor to expand and

support their study habits and to obtain specific repair

instructions and diagnostic/troubleshooting tips and

advice Appropriate sidebars, technical tips, and

diag-nostic examples accompanied by frequently asked

questions support and encourage the readers'

under-standing of the text under discussion

No textbook of this type can truly reflect all of the

wishes and needs of everyone within the diesel

indus-try, but through the support, encouragement, and

as-sistance I received from many of my colleagues, I trust

that the finished product is reflective of their

commit-ment to the highest standards of excellence, and that

you, the reader, are pleased with the approach and

material contained in this new edition I wish you well

in your pursuit of new knowledge, since your study of

this book, coupled with hands-on tasks, will enhance

your ability to understand, service, and diagnose the

latest electronically controlled diesel engines,

equip-ment, and systems These skills will make you a

valu-able employee, and will provide you with a rewarding,

challenging, and fulfilling career for many years to

come Many of you will become tomorrow's

supervi-sors, shop foremen, lead-hands, service managers, fleet

maintenance directors, business owners, OEM field

service representatives, and service engineers Take

ad-vantage of the material contained within this

publica-tion and whet your appetite for new knowledge byaccessing in-house employer training programs, OEMtraining, local community college courses, and infor-mation/ data readily available on the web Exchangeideas and technical knowledge with your colleagues inbroadening your skills library, and treat others withrespect Remember, we were all rookies at one time oranother in our careers The difference between a greattechnician and a good technician is one who is alwaysopen to new ideas and suggestions, and is willing toexchange thoughts, ideas, and tips with colleagues Agreat technician is also hungry for knowledge and re-spects customers and their equipment concerns.Finally, your thoughts, ideas, and constructivecriticism about the material presented in this textbook

is a valuable resource to me and other users We gladlysolicit and listen to your comments in attempting to im-prove the quality of the information and data that wedeliver

You can write to me through the publisher's dress contained at the front of the book

ad-Thank you for your interest!

R N (Bob) Brady

Special Note

No textbook of this kind can be written for potential The information in this textbook is not designedtechnicians without the support and cooperation of to supplant the excellent information in originalmany unique individuals, colleagues, companies, and equipment manufacturer (OEM) service literature orcorporations Constructive criticism,reviews, and feed- service training programs through the local distribu-back from prior users of the first four editions of this tor or factory service training schools To obtain spe-book have been of great assistance I have within the cific details about a certain area, it is always best to re-confines of this book, and where most appropriate to fer to the engine manufacturer's own service manuals,the greatest cross section of users, attempted to include slide training programs, videos, or CD-ROMs.Instruc-the most up-to-date information and as many sugges- tors in the specialty content areas of medium/heavytions as possible in this fifth edition trucks and diesel-powered equipment have access to aSome suggestions for specific overhaul data and diversified selection of software and hardware to as-information related to component rebuild and testing sist them in developing courses and programs that ad-

of mechanical and electronic fuel injection system parts dress the task lists required to challenge ASE or TQare best obtained by contacting the equipment manu- type certification If you download ASE's preparationfacturer This highly technical and specialized area is guides from its website (www.asecert.org), you willbest handled and addressed through a professional as- find no reference or necessity for potential servicesociation such as the Association of Diesel Specialists technicians to prepare to certify in the area of over-(ADS), whose members are employed to specifically haul, testing, or adjustment of mechanical or electronicoverhaul, rebuild, and test fuel injection and other fuel injection pumps, mechanical or electronic unit in-components with the assistance of complex and costly jectors, mechanical or electronic governors, or nozzleequipment If you review the various Automotive Ser- rebuilds They do, however, have to be capable of pop-vice Excellence (ASE) and Trade Qualification (TQ) testing nozzles and unit injectors for correct crackingskills tasks and tests lists for a certified service techni- or popping pressures and correct spray patterns.cian in the medium/heavy truck, commercial trans- When special equipment is available, some techni-port (truck and bus), heavy-duty equipment, marine, cians may be taught to flow-test individual unit injec-industrial, or agricultural specialty areas, it is not a pre- tors for recommended fuel volume, but again it is notrequisite for the technician to have specific skills for an ASE or TQ necessity

each area Typical servi<;etechnicians are expected to Vocational!technical and college students, and have the skills and knowledge to remove and reinstall, piring service technicians who choose to use this text-diagnose, perform minor adjustments to on-engine book, will find appropriate and diversified informa-fuel systems, troubleshoot, analyze failure, maintain, tion related to subjects directly referenced in both theand repair or replace faulty parts and components ASE and TQ testing areas However, no theoreticalwhere needed course of study alone can prepare students to develop

as-application of the diversified content areas in which company owners, and possible future engineers Inthey hope to challenge themselves and gain certifica- essence, they are key to the success of the diversifiedtion The ServiceTechniciansSociety (STS)and ASEof- diesel industry.

fer various publications to help you study for certifica- The many diagrams throughout this book appeartion in the different ASE content areas Learn to access through the kindness and support of various OEMsthe many appropriate websites that offer numerous who are strongly supportive of well-trained and tech-topics to broaden your scope of learning and to inform nologically up-to-date service technicians Withoutyou about new developments Learn to apply and their support, this book could not have been presentedshare knowledge with your fellow service technicians; in its current format Note that courtesy lines accom-study, retain, and apply knowledge and skills learned pany each diagram for the name of the specific com-from experienced service technicians Exchange pany and product features

knowledge by becoming an active member in profes- In addition, thank you to ASE for allowing me tosional organizations such as STS,and set a goal to be- describe the various content areas and skills tasks forcome a certified Blue Seal ASE or a Red Seal Trade the different certification tests that they offer to im-Qualification Interprovincial (TQ-IP) Canada-wide prove the skills of technicians, particularly in the dieselrecognized professional technician Attend local and field Thanks also to SAE's Service TechniciansSocietynational meetings of STSand other appropriate techni- for its role in encouraging the high standards of today'scal societies Dedicate your future career to lifelong and tomorrow's technicians To anyone associatedlearning by availing yourself of the many company with the diesel industry from technicians to salespeo-and OEM training programs and local community col- pIe, your everyday actions contribute to the economiclege courses open to you A highly motivated service development of the industry

technician with first-class technical and human re- Many thanks!

source development skills is the catalyst to fulfilling

the current shortage of qualified personnel Such per- R N.(Bob) Brady

sons are likely to be tomorrow's supervisors, service

About the Author

Robert N (Bob) Brady has been involved in the auto- tions Evaluation and Awards Committee He served asmotive, heavy-duty truck/bus, and equipment field a Regional Coordinator, where he worked with thesince 1959, having served a recognized indentured ap- B.C., Alberta, and Manitoba Sections in Canada, andprentice ship as both an automotive and heavy-duty was an acting RC for the NW /Spokane-Intermountain,truck/bus and equipment technician He is a certified Washington, and Oregon sections He also served as aautomotive, commercial transport, and heavy-duty member of SAE's Total Quality Committee He wasequipment technician A graduate of Stow College of elected to SAE's worldwide International Board of Di-Engineering, where he majored in the Thermodynam- rectors, serving from 1994 through 1996, and was oneics of Heat Engines, he holds a degree in Mechanical of two SAEboard of directors appointed to the Ad HocEngineering Technology He also holds a degree in Committee that in March 1996 initiated the develop-Adult Education ment and organization of the STS (ServiceTechniciansHis experience includes positions as a shop fore- Society), an affiliate of SAE International

man and service manager for a number of major heavy In 1987 he established his own company, HiTechtruck companies and OEMs, as well as a Fleet Mainte- Consulting Ltd., which specializes in technical trainingnance Superintendent with a large North American program design/implementation aimed specifically attruck fleet Other experience includes positions as heavy-duty, on- and off-highway equipment He hasManager of National TechnicalTraining, Canada; Sales delivered specialized training courses for engineers,Application Engineer; Field Service Engineer for De- service technicians, and maintenance personnel at atroit Diesel Corporation; Diesel Engineering and Diesel number of companies and corporations Other func-Mechanic/Technician college instructor; and Depart- tions include fleet maintenance and failure analysisment Head of the program at Vancouver Community programs as well as equipment specing He has ap-College, where he also served a two-year term as Pres- peared as an expert witness in a number of cases in-ident of the Faculty Association volving patent infringement and engine/equipment

He is a full member of SAE International (Society failure

of Automotive Engineers), for which he has served as He is the author of fourteen textbooks for Prenticethe chair of the British Columbia Section Under his Hall dealing with automotive fuel injection and elec-leadership in 1989-90, the section received an SAE tronics/ computers, diesel, and heavy-duty trucks AAward of Merit for outsfanding technical meetings At member of the TWNA (Truck Writers of North Amer-the International level of SAE,he served three years on ica), he writes monthly technical/maintenance articlesthe worldwide Sections Board as Vice-Chair and then for two of Canada's major newspaper/magazines:Chair Other activities in SAE at the Sections-Board Trucknews, Canada's National Trucking Newspaperlevel included chairing the Executive Committee, the and Equipment Buyer's Guide, and Grainews, a na-

Administrative Committee, the Brazil Ad Hoc Com- tional farmer's monthly newspaper distributed in bothmittee, and the International Sections and Affiliates Canada and the United States, where his monthly arti-Committee He has also served as a member of the Sec- cles deal with truck and equipment maintenance

Combustion Dynamics, 53Technician Professionalism and Image, 1 Fuel Injection Timing, 56

Career Advancement, 3 Retarded versus Advanced Timing, 58

ASE Diesel Engines Task List, 4 Summary, 59

Service Technicians Society, 8 Self-Test Questions, 62

2 DIESEL ENGINE OPERATING

CONSIDERATIONS, 63Diesel Engine Classifications, 10

Engine Cleaning Procedures, 75Four-Stroke-Cycle Operation, 10

Two-Stroke-Cycle Operation, 15 Safe Work Habits When Cleaning, 75

Comparison of Two- and Four-Stroke-Cycle Quality Assurance, 77

Engine Firing Orders, 21 Self-Test Questions, 78

Summary, 22

Self-Test Questions, 22

6 THE CYLINDER BLOCK AND LINERS, 79

Understanding Power Terms, 26 Cylinder Block Structure, 82

Heating Value Equiv<:tlents,47 Diesel Engine Cylinder Blocks, 84

Self-Test Questions, 48 Block Flowchart Inspection, 89Systematic Overview of Engine Block Checks, 93

Final Inspection, Testing, Reconditioning,

Cylinder Hones, 105

The Combustion Process, 50 Self-Test Questions, 116

7 CRANKSHAFTS, MAIN BEARINGS, 9 THE CYLINDER HEAD

FLYWHEELS, AND FLYWHEEL

ASE Certification, 196

ASE T2 Test Specifications, 119 Service Recommendations, 201

ASE M2 and M3 Test Specifications, 119 Summary, 227

Crankshaft Structure and Function, 120 Self-Test Questions, 227

Crankshaft Cleaning and Inspection, 123

Repair or Replacement of Crankshaft Main 10 CAMSHAFT, CAM FOLLOWERS,

Main Bearing Defects and Remedies, 126 TIMING GEAR TRAIN, 229

Spun Main Bearings, 134

Main Bearing Specifications and Crankshaft ASE Certification, 230

Main Bearing and Crankshaft Installation, 136 Camshaft Cleaning and Inspection, 237

Crankshaft Seals, 140 Carn Follower Inspection, 240

Purposes of Flywheels, 148 Valve Adjustment, 243

Flywheel Designs and SAE Size, 149 Inspection, Replacement, and Assembly of theFlywheel Timing Marks, 149 Timing Gear Train, 245

Removing and Inspecting the Flywheel, 149 Summary, 249

Ring Gear Replacement, 152 Self-Test Questions, 249

Pilot Bearing Replacement, 154

Flywheel Housing, 156

Self-Test Questions, 158 Lubrication System Function, 250

System Components, 252

8 PISTONS, PISTON RINGS, AND Engine Lube Oil, 258

CONNECTING ROD ASSEMBLY, 161 Waste Oil Disposal, 262Lube Oil Dilution, 262

ASE Diesel Engines Test, 161 Oil Analysis, 263

ASE Engine Machinist Tests, 161 Inspection and Overhaul of Components, 263ASE Assembly Specialist Tests, 162 System Testing, 267

Piston Structure and Function, 162 Testing and Troubleshooting the Lube System, 267Two-Piece Piston Designs, 164 Engine Prelubrication, 268

Piston Crown Shapes, 168 Starter Motor Prelube Systems, 270

Piston Operating Temperatures, 169 Summary, 270

Piston Removal from the Block, 173 Self-Test Questions, 270

Pistons and Piston Rings, 174

Piston Scuffing Identification, 177 12 COOLING SYSTEMS, 272

Piston Rings Inspection.Details, 180

Inspecting the Connecting Rods, 182 ASE Certification, 272

Checking Rod Bore Ovality, 183 Cooling System Function, 273

Piston Pin Inspection, 185 Engine Heat Loads, 274

Final Assembly of Pistons, Piston Rings, Coolant Flow Determination, 277

Thermostats, 283 15 TYPES OF FUEL SYSTEMS, 379Coolant, 287

Cylinder Liner Pitting, 288 ASE or TQ Certification, 379

Fill-For-Life Coolant, 289 Basic Fuel Injection System, 379

Coolant Filters, 292 Delphi Distributor Pumps Overview, 389

Pressure Checking the Cooling System, 295 DPCN, 393

Expansion Tanks and Heat Exchangers, 296 EPIC, 394

Intake and Exhaust System Flow, 306 Governor Function, 400

Air Ducting Inspection, 316 Mechanical Governor Operation, 401

Exhaust Mufflers and Particulate Traps, 334 Zero-Droop Governors, 407

Gear-Driven Blowers, 335 Adjustable-Droop Governors, 408Marine Engine Applications, 338 Electronic Governors, 414

Troubleshooting Using Manometers, 339 Summary, 416

Exhaust Brake Devices, 343 Self-Test Questions, 416

Exhaust Brakes, 344

Williams Exhaust Brake, 344

Engine Compression Brakes, 346 17 INJECTION NOZZLES, 419

Electric Retarder, 358

Use of Starting Fluids, 359 ASE Certification, 419

Nozzle Structure and Function, 423

FUEL/WATER SEPARATORS, 365 Nozzle Components, 425Bosch Nozzles, 426

ASE Certification, 365

Injector Nozzle Sac Volume, 427Diesel Fuel Oil Gra-des, 365

Nozzle Problems, 427Specific Gravity of a Fuel, 366

Nozzle Removal, 427Heat Value of a Fuel, 366

Testing Nozzles for Performance, 429Fuel Filtration, 368

Nozzle Disassembly and Cleaning, 432Fuel Filters, 369

Injection Nozzle Reassembly, 436Fuel Filter /Water Separators, 371

Nozzle Installation, 438Fuel Heaters, 376

Summary, 438Summary, 377

Self-Test Questions, 438Self-Test Questions, 377

18 THEORY OF ELECTRONIC FUEL 20 MACK ELECTRONIC FUEL SYSTEMS, 564

SYSTEMS, 439

VMAC System Troubleshooting, 565

Electronic Fuel System Background, 442 Self-Test Questions, 568

Advantages of Electronic Engines, 443

Fuel System Structure and Function, 444

21 DETROIT DIESEL CORPORATION FUELECM Serial Data/Sensor Communications, 450

SYSTEMS, 569Engine Protection System, 460

Electronic Unit Injectors, 464

ASE Certification, 569Electronic Control Modules, 469

Troubleshooting Options, 474 Engine Labels, 569

Diagnostic Tooling, 478 Basic Fuel System Functions, 570

Minimum Fuel-Line Sizes versus Restriction, 574

19 ROBERT BOSCH CORPORATION FUEL Priming the Fuel System, 575Filter Replacement, 575

Fuel System Troubleshooting, 579Company Background, 489

DOC Two-Stroke-Cycle Engine Tune-Up:

Overview, 490

Non-DDEC Engines, 583Product Overview, 491

Tune-Up Sequence, 583Pump Features, 493

Detroit Diesel Series 50/60 Four-Stroke-CycleInline Pump Fuel System, 497

Engines-Tune-Up, 593Fuel Supply Pump Operation, 498

Model 790 Jake Brakes-Flatbrake, 594Injection Pump Operation, 499

Detroit Diesel Electronic Systems, 596Fuel Metering (Measurement), 499

Diagnostic Tooling, 609Helix Shapes and Delivery Valves, 502

Optimized Idle, 614Inline Pump-to-Engine Timing, 504

Electronic Unit Pump System, 615Overview: Static Spill Timing, 506

Summary, 616Air-in-the-Fuel System, 509

Self-Test Questions, 616Cummins C Model Timing Check, 510

Timing PF Jerk Pumps, 514

22 CUMMINS FUEL SYSTEMS, 620

Automatic Timing Advance Device, 515

Basic Fuel System Troubleshooting, 516

Robert Bosch Governors, 520 ASE Certification, 620

Aneroid/Boost Compensator Control, 529 Company Background, 620

Altitude Pressure Compensator, 530 PT Fuel System, 621

Robert Bosch Electronic Diesel Control, 531 PT Fuel Pumps, 625

Robert Bosch Model VE Injection Pump, 535 Manual Fuel Shutoff, 630

Checking Injection Pump Static Timing, 547 PT Pump Checks and Adjustments, 630

Robert Bosch VE Injection Pump Engine-to-Injector Timing, 631

Troubleshooting, 0548 Step Timing Control System, 637

Electronic Distributor Pump, 550 Cummins Celect System, 643

Testing/Setting Injection Pumps, 552 Diagnostic Fault Codes, 654

Bosch Common-Rail Fuel Systems, 555 ISB Engine Electronic Fuel System, 663

CAPS Fuel System, 669 Troubleshooting Tips, 753

Cummins ISX/Signature Series Engines, 679 Engine Idling, 755

Self-Test Questions, 690 General Procedure for Checking Engine

and Vehicle, 756

23 CATERPILLAR FUEL SYSTEMS, 694

Exhaust Smoke Color, 758Exhaust Smoke Detection, 761

ASE Certification, 694

Checking the Fuel System, 765Primary Engine Checks, 767Company Background, 694 Troubleshooting Charts, 769

System Structure and Function, 694 Summary, 790

New Scroll Fuel System: 3306 and 3406 Self-Test Questions, 790

Engines, 695

Governor, 699

Automatic Timing Advance Unit, 700 AND STARTER MOTORS, 793

Static Engine Timing, 702 Part A: Batteries, 793

Dynamic Engine Timing, 704

Fuel Injection Pump: 3406B Engine, 705 Batteries, 793

Valve Adjustment: 3406 Engine, 706 Self-Test Questions-Batteries, 800

New Adjustment Procedure for Jake Brake Part B: Alternator Charging Systems, 801(Models 340/340A/340B) Slave Piston Alternator Function, 801

Caterpillar Electronic Fuel Systems, 708 Types of Alternators, 802

Caterpillar Electronic Diagnostic Tooling, 717 Heavy-Duty Alternator Test: On Vehicle, 803HEUI Fuel System, 727 On-Vehicle Alternator Output Test, 805

Operation-Engine Start Up, 729 Troubleshooting Leece-Neville Alternators, 806High-Pressure Oil System, 729 Self-Test Questions-Alternator Charging

Self-Test Questions, 735 Part C: Starter Motors, 809Starter Motor Function, 809

Electric Starter System Structure, 809

24 ENGINE RUN-IN AND DYNO 12 and 24 Volt Circuits, 810

Solenoid Switch Components and Operating

General Information, 738 Electric Starter Troubleshooting, 814

Engine Dynamometers, 739 Air Starter System, 822

Chassis Dyno Run-In Procedures, 745 Self-Test Questions-Starter Motors, 823On-Highway Engine Run-In Procedures, 748

Off-Highway Equipment Run-In INDEX, 825

Overview Catalog, International System of Book Numbering (ISBN) The diesel engine industry is highly diversified, exposing 0-13-181470-2, or contact a local bookstore Original the potential service technician to approximately 5000 equipment manufacturers (OEMs) publish outstanding different applications in which the diesel engine is used textbooks dealing specifically with their own equipment.

as the primary power source The different application Use these texts to broaden your knowledge of particular areas are generally categorized as follows: models of machinery"

• Automotive (cars, vans, pickups)

• Medium/heavy-duty truck/tractor/trailer TECHNICIAN PROFESSIONALISM

• Public transit (city and intercity buses) AN 0 IMAG E

• Manne

• Off-highway" " d b ·Id"equipment"If· Id(construction,) logging, Recent and ongomg technological changes m automo- '

A I' I " bve, heavy-duty truck, bus, and eqUipment technology

• gncu tura" have advanced to such a degree that the "new breed"

• Locomotive or self-powered railcars of techn· lC1annee sd t b f0 e ami lar Wi·1' ·tha vane' ty f d0 a

-Within this textbook we offer broad coverage of the vanced technologies to be able to function as a highly

mechanical and electronic details of diesel engine and skilled, trained, and dedicated professional Evolving

fuel systems including their function, operation, repair; technology is responsible for causing changes in the

overhaul, maintenance, diagnosis, and troubleshooting. type of individual who is able to perform automotive

Due to space limitations we cannot include details on the and heavy-duty truck service Many vocational schools

special equipment that is used in each of the above cat- and colleges now offer two-year bachelor programs

egories The key to a successful career in the diesel in- that include management training in addition to the

dustry, however; is to fully comprehend and understand needed technical skills and computer training to enter

the function and operation of the main power plant in and succeed within the industry Instructors at the

var-each of these applications, which restswith the diesel en- ious schools and colleges can provide the needed

cata-gine itself Take time to preview the table of contents for lyst to motivate and encourage students and

techni-this book to find the subjects and topics described cians to reach for that higher standard of excellence

herein.' and to improve the image of service technicians in the

A number of well-written texts on the market deal eyes of the general public

with specific categories of the diesel engine and their Technician certification is a vital part of improving

types of applications If you are interested in medium/ professionalism and image The mechanical and

elec-heavy-duty trucks, power trains, systems, and service, re- tronic advances that now permeate every facet of

fer to Robert N Bradys 950-page textbook of the same heavy-duty trucks, engines, and equipment demand

name, published by Prentice Hall, Inc., Upper Saddle that a new breed of service repair and diagnostic

tech-River; New Jersey 07458 See the Library of Congress nician be created In a fairly recent study by the U.S.

1

General Accounting Office in Washington, D.C., after that CPAsignifies Certified Public Accountant analyzing the collected data of the skills and capabili- ations and professions use certification to recognizeties required to successfully achieve benchmark indus- qualified and competent individuals The certificationtry standards, both heavy-duty truck technicians and process is one of the single most important steps in ca-automotive technicians were adjudged to require skills reer development Here are the top ten reasons an au-equivalent to that for computer programmers and tomotive professional should consider becoming ASE-

Professionalism has three key dimensions: qualifi- 1 Certification grants you professional cations, individual attitude and a philosophy of one's tials Since it recognizes your individual accomplish-own standards, and a perception of industry bench- ments, ASE's certification serves as an impartial, third-mark standards and customer expectations Although party endorsement of your knowledge and experiencecertification is not mandatory at this time in the United on a national, even international basis

creden-States in the areas of automotive and heavy-duty truck 2 Certification demonstrates your commitmentmaintenance, general public and customer demands to the automotive service and repair profession Re-have placed an ever increasing emphasis on quality ceiving ASEcertificationshows your peers, supervisorsand standards from maintenance, repair, and diagnos- and, in turn, the general public, your commitment totic technicians All major OEMs currently spend hun- your chosen career and your ability to perform to setdreds of millions of dollars annually on creating train- standards

ing programs offered at both the factory and local level 3 Certification enhances the profession's

im-to ensure that their distribuim-tor and dealer personnel age ASE's certification program seeks to grow, are continually kept abreast of the latest technological mote and develop certified professionals, who canadvancements in their products stand" out in front" as examples of excellencein the au-

pro-In Canada, provincial certification is required in tomotive service and repair industry

the automotive, heavy-duty equipment, commercial 4 Certification reflects achievement ASE transport, and autobody repair sectors Certification is fication is a reflection of personal achievement becauseobtained through 8000 hours of experience during a the individual has displayed excellence in his or herrecognized and structured apprenticeship, or by being field by meeting standards and requirements estab-able to prove that equivalent experience has been ac- lished by the entire automotive industry

certi-cumulated to allow a challenge of the TQ test Some 5 Certification builds self-esteem ASE provinces have recently enacted legislation to prohibit cation is a step toward defining yourself beyond a jobanyone who is not qualified in a specific area of ex- description or academic degree while gaining a sensepertise from practicing in this area of personal satisfaction

certifi-Technicians must be provided with an opportu- 6 Certification can improve career nity to stay abreast of current technology, which ties and advancement ASE certification can give youchanges faster than most people outside of the indus- the "edge" when being considered for a promotion ortry can imagine In the United States, several avenues other career opportunities ASE certification clearlyare open to automotive and heavy-duty truck mechan- identifies you as an employee who has demonstratedics and technicians to elevate their knowledge and ex- competency in specific technical specialty areas basedpertise The two most recognized organizations now in on accepted industry standards

opportuni-existence that offer technicians an opportunity to vol- 7 Certification may provide for greater untarily improve their professionalism and certifica- ings potential Many automotive professionals whotion are the National Institute for Automotive Service have become ASEcertified experience salary and wageExcellence (NIASE),more commonly known as ASE, increases based on their certification status ASE-certi-and the Service Technicians Society (STS),which was fied professionals are in high demand throughoutcreated in February 1996 as a,naffiliate of the Society North America

eam-of Automotive Engineers (SAE)International ASEhas 8 Certification improves skills and knowledge.offered voluntary testing and certification for 25 years Typically,achieving ASE certification requires training,for both automotive and heavy-duty truck technicians study and "keeping up" with changing technology

in a variety of specialty areas ASE certification showcases your individual

compe-tence by confirming proficiency and knowledge

1a Reasons to Become ASE-Certified 9 Certification prepares you for greater Everybody knows that MD following an individual's job responsibilities Since ASE certification is a clearname means Medical Doctor And most people know indicator of your willingness to invest in your own pro-

on-the-Introduction 3

fessional development Certified professionals are about 65% of the journeyman rate, receiving an aware of the constantly changing technology and envi- crease of about 5% every additional six months At theronment around their profession and possess the de- completion of the apprenticeship in the year2001, ser-sire to anticipate and respond to change vice techs can expect a salary of approximately $28 to

in-10. Certification offers greater recognition $30 (Canadian) per hour

from peers As an ASE-certified professional, you can Working regular hours, a US certified serviceexpect increased recognition from your peers for tak- technician can expect yearly earnings of betweening that extra step in your professional development $35,000 and $40,000. In a busy shop of a major equip-

ment dealer / distributor, overtime can be a normal

between $60,000 and $80,000 (U.s.) per year Such The diesel industry offers both challenging and re- so~el as shop s~pervisors, service managers.for majorwarding opportunities for tomorrow's technician Once e~gme and eqUlpment dea~ers, and fleet mamtenanceyou have attained certification as a service technician dIrectors can expect salanes as hIgh as $85,000 toyou can progress into one of the following careers: $140,000 (U.s.) per year plus benefits

per-• Master mechanic/technician (any equipment cat- ASE CERTIFICATION

egory)

• Lead hand or shop foreman In Canada and in other countries worldwide

manda-• Flee~ supervisor tory trade apprenticeships of between four 'and five

• Serv~ce manager years is common to gain certification as a journeyman

• Serv1Ce/s~les Throughout the training and learning period the

ap-• OEM servIc~ representatIve prentice must attend classes at a vocational/ technical

• Fleet or e~Ulpme~t management school or college where a combination of theory and

• OEM ~ervice e~gm~er hands-on instruction is then tested before the

appren-• T~chnical trammg mstructor (pnvate or commu- tice is certified in each specific trade skills area In the

• Parts sales

• Factory service representative or application • ~eavy-duty ~quipment mechanic/ technician

• Business owner • CommercIal transport mechamc/techniCIan (truck

and bus)

Financial Rewards • Diesel engine specialist

The financial rewards available to you are limited only Generally this technical training is accommodated

by your education, experience, motivation, and com- either through regular day-release classes, or by mitment to excellence Because learning is a lifelong tending instruction modules of between four and sixchallenge, you will more than likely have to supple- weeks or longer throughout each subsequent year ofment your service technician knowledge and education the apprenticeship At the completion of the appren-with a variety of courses in human resource develop- ticeship, candidates must pass a TQ test to receive a De-ment (HRD), which involves sales and management partment of Labor trade certificate

at-training as a means to successful promotion in the fu- In the United States an apprenticeship such as ture Most dynamic companies and corporations today scribed is currently not required to gain certification;offer excellent in-house training for their employees on however, the widely accepted method by industry is to

de-a regulde-ar bde-asis voluntarily become certified through a series of testsTypical financial reyvards for an apprentice or be- administered by the NIASE (ASE) This choice pro-ginner can vary widely between Canadian provinces vides an industry-recognized avenue for automotiveand US states Another factor is the exchange rates be- and medium/heavy truck diesel technicians to chal-tween different currencies The hourly rate for begin- lenge themselves and become certified in one or moreners, however, is approximately $10 (US.), rising to areas of the trade, and thus earn the most valuable cre-about $22 when certified In the United States, certifi- dentials as recognized throughout the United States.cation can be attained in two years by passing the ASE ASE encourages you to take these tests and to join thetest Pay rate will also be affected if a shop is a union fa- proven professionals who wear the ASEblue seal patchcility Currently in Canada, an apprentice will earn of excellence (see Figure1-1).

Diesel Engines-T2 Test Specifications B Hydraulic brakes

diagnosis and repair 18 30%Content Questions Percentage 1 Hydraulic system (8)

area in test of test 2 Mechanical system (6)

3 Power assist units

8%

C En3ine b~ock diagnosis D Wheel bearin}s

cooling systems

13%

diagnosis and repair 9

E Air induction and

Suspension and Steering- T5 Test Specificationsexhaust systems

diagnosis and repair 9 13% and Task List

F Fuel system diagnosis

components (9)

A Steering system

2 Electronic

diagnosis and repair 4 6% 2 Steering units (6)

diagnosis and repair 13 26%Drive Train- T3 Test Specifications and Task List C Wheel alignment

di~osi~, adjustment,

Content Questions Percentage D Wheels and tires

E Frame service and

A Clutch diagnosis and

C Drive shaft and

Electrical/Electronic Systems-T6 Testuniveral joint

diagnosis and repair 11 22% Specifications and Task List

D Drive axle diagnosis

Percentage

Brakes-T4 Test Specifications and Task List A General electrical

Content Questions Percentage B Battery diagnosis andrepair 6 12%area in test of test C Starting system

A Air brakes diagnosis

and repair

1 Air supplt &service

E Lighting systemssystems ( 7)

2 Mechanical!

1 Headlights, p'arking,foundation (11)

clearance, tall, cab,

3 Parking brakes (5)

and dash lights (3)

Introduction 7

signals, hazard light, 5 Lubrication system (2)

2 Charging system (4)Content Questions Percentage 3 Lighting system (2)

A HVAC systems

1 Air brakes (4)

2 Hydraulic brakes (2)di'1nosi~, service,

B A/C system and

service, and repair 16 40% 5 Tires and wheels (3)

temperature control (1) 2 Electrical systems (6)

Total 40 100% 5 Cab / sleeper heating

and air conditioning (4)Preventive Maintenance Inspection (PMI)- 6 Engines (12)

TB Test Specifications and Task List a General! major

components (4)Content Questions Percentage b Fuel system (2)

d Lubrication

Diesel Engine Operating

Fundamentals

In this chapter we discuss the operating fundamentals of what is commonly referred to as the direct-injection

both two- and four-stroke-cycle diesel engines This dis- (01) open-combustion-chamber concept, or

alterna-cussion will provide you with a solid foundation on tively, on the indirect-injection (101)

closed-combus-which to pursue and understand the other technologi- tion-chamber design All heavy-duty high-speed diesel

cal and engineering characteristics relative to the suc- engines now in use operate on the direct-injection

prin-cessful operation of the diesel engine Direct-injection ciple Figure 2-1 briefly illustrates the difference

be-(01) and indirect-injection (101)designs are described as tween 01 and 101 combustion-chamber design;

corn-well as important characteristics of valve timing and rela- bustion chambers are discussed in more detail in

tive piston positions during engine operation We study Chapter 4

the advantages and disadvantages of two-cycle and An understanding of the operation of two- and

four-cycle engines, and the different firing orders com- four-stroke-cycle diesel engines will facilitate your

ef-monly used by engine OEMs. forts when troubleshooting engines and fuel systems

Although there is no specific ASE or TO test area The operating characteristics of each type of design

dealing with the information in this chapter; it is impera- will exhibit problems common only to that style of

en-tive that any aspiring certified service technician be fully gine The majority of high-speed diesel engines

manu-conversant with the operation of both two- and four- factured today are of the four-stroke-cycle design, so

stroke-cycle engines, the different firing orders used, and we begin with a study of its basic operating cycle The

how valve timing affects engine performance In Chap- fundamental operation of both four-stroke-cycle

gaso-ters9 and J0, when you study the cylinder head and line and diesel engines is the same: They require two

valve train, your basic understanding of valve timing ac- complete revolutions of the engine crankshaft, or 7200,

quired within this chapter will help to clarify the impor- to complete the four piston strokes involved in one

tant task of proper camshaft/valve timing and the neces- complete cycle of events

sity for correct valve clearance (lash) adjustment Valve

lash adjustment is described in Chapters 20 through 23 FOUR-STROKE-CYCLE OPERATION

of this book End-of-chapter questions are supplied to

permit you to self-test your newly acquired knowledge. There are two major differences between a gasoline

and a diesel engine:

DIESEL ENGINE CLASSIFICATIONS 1 A diesel engine requires a much higher

com-pression ratio, because with no spark plug to initiateDiesel engines can be classified by two major charac- combustion, the heat generated by compressing the airteristics: their operating cycle design and the type of in the cylinder is what causes the high-pressure in-combustion chamber they employ By this we simply jected diesel fuel to ignite

mean that the engine can operate on either the two- or 2 On the intake stroke of a diesel engine, only airfour-stroke-cycle design In addition, either one of is supplied to the cylinder, whether the engine is natu-

10

Diesel Engine Operating Fundamentals 1 1

Direct injection (a) defines the category where the fuel is

injected directly into the combustion chamber volume

formed between the cylinder head and the top of the piston.

Mixing is achieved by using a multi-hole fuel injection nozzle

and/or causing the intake air to swirl High injection

pres-sures are required (18,000-30,000 psi)

(124110-206850 kPa) for fine atomization which promotes good

con-tact between air and fuel.

Indirect Injection (b) occurs where fuel is injected into a

pre-chamber which communicates with the cylinder through

a narrow passage During the compression stroke, air

enters the pre-chamber, which is usually about one half of

the total compression volume Mixing is achieved by

spraying fuel into the turbulent air in the pre-chamber

(generally with a single-hole pintle nozzle) where ignition

occurs The burning air-fuel mixture then enters the

cylinder where it mixes with the remaining air to complete

the combustion This chamber has a small throat area so

that inflow and exit velocities are high Low injection

pressures (5000-14,000 psi) (34475-96530 kPa) are used

and the chamber is not as sensitive to the degree of fuel

atomization.

FIGURE 2-1 (a) Principle of DI (direct-injection) and (b) principle of IDI (indirect-injection) combustion chamber design.

rally aspirated or turbocharged In a gasoline engine a atmospheric Basically, the intake stroke accounts formixture of air and gasoline is taken into the cylinder on 1800of piston movement, which is one half of a crank-the intake stroke and then compressed A spark plug shaft revolution During this time the piston has com-then initiates combustion of this premixed fuel charge pleted one complete stroke down the length of theThe four piston strokes in a four-stroke-cycle cylinder The weight or percentage of air that is re-diesel engine are commonly known as (1) the intake tained in the cylinder during this time is known as vol-stroke, (2) the compression stroke, (3) the power or ex- umetric efficiency (VE).In most naturally aspirated en-pansion stroke, and (4) the exhaust stroke Figure 2-2 gines that rely only on piston movement to inhale air,illustrates the four piston strokes in schematic form in VE is between 85 and 90% of atmospheric pressure In

a direct-injection engine Next we consider the se- turbocharged or gear-driven blower engines, the VE isquence of events involved in one complete cycle of op- always greater than atmospheric or 100%; therefore,eration of the four-stroke-cycle engine VEvalues between 120and 200%are common on these

I t I St k engines The power output of any engine depends on

n a.<e roo e the cylinder air charge at the end of the intake stroke.Dunng the mtake stroke, the exhaust valves are closed Th nk h ft d fl h 1 h t t d

but the mlet valves are open; therefore, the downward- th h t 1 1800

movmg plston m uces a ow0 alr mto t e cy mer

This air pressure will be less than atmospheric which is Compression Stroke

14.7PSI(101.3kPa)at sea level on a naturally aspirated During the compression stroke, both the intake and engine, whereas on a turbocharged or blower- haust valves are closed as the piston moves up the cylin-equipped engine, this air pressure will be higher than der The upward-moving piston causes the trapped air

ex-to be placed under compression ex-to approximately 450ex-to Power or Expansion Stroke

550 psi (3103to 3792 kPa) and 1000 to 1200°F(538 to The combustion chamber of the cylinder is formed649°C)as a mean average Both pressures and tempera- between the space that exists between the top of thetures vary based on the actual engine design and com- piston (crown) and the cylinder head The pressurepression ratio Cylinder compression pressures and released by the burning fuel in the combustiontemperatures are affected by the ambient air tempera- chamber forces the piston down the cylinder Theture, turbocharger boost pressure, engine compression peak cylinder firing pressures on today's high-speedratio, valve timing, and engine speed and load Conse- heavy-duty truck engines can range between 1800quentIy, some engines may exhibit compression pres- and 2300 psi (12,411 to 15,856 kPa), with tempera-sures into the 600s,with their air temperature being at tures between 3000 and 4000°F (1649 to 2204°C) forthe high end of the previous figures as quoted Just be- very short time periods This motion is transferredfore the piston reaches the top of the cylinder, high- through the piston, the piston pin, and the connect-pressure diesel fuel is injected into this hot air mass and ing rod to the engine crankshaft and flywheel There-fuel is ignited, causing a substantial pressure and tem- fore, the straight-line motion of the piston is con-perature rise within the combustion chamber Fuel is verted to rotary motion at the crankshaft andinjected continually to maintain this high pressure, flywheel from the connecting rod The length of thewith the number of degrees of injectionbeing related to power stroke is controlled by how long the exhaustengine load and speed as well as to the specific model valves remain closed Basically,the piston has movedand type of engine being used Once again the piston down the cylinder from the top to the bottom and inhas completed approximately 180° of crankshaft rota- so doing traveled through approximately 1800.tion Added to the crankshaft rotation from the intake Therefore, added to the already completed intakestroke, the engine crankshaft and the flywheel have and the compression strokes, the crankshaft and fly-now rotated through approximately 360° or one full wheel have rotated through approximately 5400 ofturn of rotation within the cycle of events the cycle of events

DieselEngine Operating Fundamentals 13

The engine camshaft has now opened the cylinder ex- operation for one cylinder of a turbocharged engine ishaust valves; therefore, the exhaust gases, which are at shown in a basic schematic in Figure 2-3.

a higher pressure than atmospheric, will start to flow

out of the open exhaust valves The upward-moving

NOTE The valve timing diagram shown in piston will positively displace these burned gases out

Fig-of the cylinder as it moves from the bottom Fig-of its stroke ure 2-3 represents 720° of crankshaft rotation For

to the top This involves another 180° of crankshaft and simplicity, two complete circles have been flywheel rotation, which will complete the cycle of imposed on one another.

super-events within 720°, or two complete revolutions Four

piston strokes were involved to achieve one power To ensure complete scavenging of all the exhauststroke from this individual cylinder The sequence of gases from the cylinder at the end of the exhaust strokeevents will be repeated once again and prior to the start of the intake stroke, the engine

manufacturer actually has the camshaft open the

in-Valve Timing take valve before the upward-moving piston has

com-During the four-stroke cycle of events just described, pleted its exhaust movement The action of the burnedthe opening and closing of the intake and exhaust gases flowing out of the exhaust valve ports allows avalves are accomplished by the action of the gear- ram-air effect to occur once the intake valve is opened.driven and rotating engine camshaft Each engine This ensures complete removal of the exhaust gases.manufacturer determines during the design phase just When the piston has reached top dead center (TDC) onhow long each valve should remain open to obtain the its exhaust stroke and the piston starts to move downdesired operating characteristics from that specific en- on its intake stroke, the exhaust valves remain open togine model One simplified example of the sequence of ensure complete scavenging of any remaining exhaust

FIGURE 2-3

Typicalfour-stroke-<)de diesel engine polar valve

tim-i1g diagram showing the relative

psron strokes for intake,

compres-5ion. power and exhaust Specific

degrees are also shown for the

du-r.iion of each stroke as well as the

actUal start of fuel injection BTDC

fbefore top dead center) (Courtesy

dCaterpillar,Inc.)

gases caused by the inrushing air through the intake four-stroke-cycle Mack MIOS06.20.30Midliner truckvalve ports The exhaust valves are closed a number of diesel engine Such a diagram is commonly referred todegrees after top dead center (ATOC)by the camshaft as a polar valve timing diagram, since both TOC and BOC

lobe action The fact that the intake valves are opened are always shown The positions of both TOC and BOCbefore the piston reaches TOC on its exhaust stroke and are similar to that of the north and south poles on athe exhaust valves do not close until the piston is mov- globe of the earth, hence the technical term polar valve

ing down on its intake stroke creates a condition timing Keep in mind that the actual number of degrees

known as positive valve overlap, which simply means varies between engine makes and models Typicalthat both the intake and exhaust valves are open at the stroke degrees for a high-speed diesel engine may in-same time for a specified number of crankshaft rotation clude the following four conditions:

degrees For example, if the intake valves open 16°be- 1 I t k t k " I t 16° BTOC d

n a e s ro e va ves open a anfore top dead center (BTOC)and the exhaust valves do 1 t 36° ABOC' t t 1 d t· 232° f

not c ose unh rt ,t e va ve over ap con Ihon IS k h ft t f

The downward-moving piston would reach bot- 2 ~ower stroke Starts at TOC and coontinu~s

un-tom dead center (BOC)and start its upward stroke for hI the.ex~aust :alves open at 60 BBOC,totalthe compression cycle However, note in Figure 2-3 durahon IS120

that the intake valves do not close until a number of de- 3 Compression stroke Occurs when the intake

grees after bottom dead center (ABOC).This ensures valves close at 36°ABOC until TOC; total that a full charge of air will be retained in the cylinder ration is 144°

du-Remember that the greater the air retained at the start 4 Exhaust stroke Valves open at 60° BBOCand

of the compression stroke, the greater the engine's vol- close at 16° ATOC; total duration is 256° ofumetric efficiencyand power output capability Simply crankshaft rotation

put, VE is the difference in the weight of air contained

in the cylinder with the piston at BOC with the engine Piston Positions

stopped versus what it would be with the piston at The sequence of events just described represents theBOCwith the engine running cycle of events in one cylinder of a multicylinder en-The compression stroke begins only when the in- gine In a six-cylinder four-stroke-cycle engine applica-take valves close (exhaust valves are already closed) tion, for example, six cylinders are in various stages ofFuel is injected BTOCby the fuel injector or nozzle, de- events while the engine is running The technicianpending on the type of fuel injection system used must understand what one cylinder is doing in relationAgain, the start of fuel injection is determined by the to another at any given position of the crankshaft, be-engine manufacturer, based on the load and speed re- cause often when timing an injection pump to the en-quirements of the engine Fuel injection will begin ear- gine or when adjusting exhaust valves or timing unitlier (farther away from TOC) with an increase in speed injectors, a specific sequence of adjustment must be fol-and load, whereas it will begin later (closer to TOC)un- lowed Knowing the firing order of the engine andder low speed and load conditions what piston/cylinder is on what stroke can save timeWhen the piston is forced down the cylinder by when performing timing and valve adjustments Wethe pressure of the expanding and burning gases (air mentioned earlier that the sequence of one cycle oc-and fuel), the power stroke will continue until such curs within two complete revolutions of the crank-times as the engine camshaft opens the exhaust valves shaft, or 720° of rotation of the engine Therefore, in a

In the simplified diagrams shown in Figures 2-2 and six-cylinder four-stroke-cycle engine each piston2-3, the exhaust valves open before bottom dead cen- would be 120° apart in the firing stroke Simply put,ter (BBOC)to allow the burned gases to start moving we would have six power strokes occurring withinout and through the exhaust ports, exhaust manifold, two crankshaft revolutions on a six-cylinder engine.exhaust piping, and muffler When the piston turns at To demonstrate such an example, refer to FigureBOC and starts to come 'back up the cylinder, it will 2-4, which simplifies the complete cycle of events andpositively expel all burned exhaust gases from the where each piston would be and on what stroke whencylinder As the piston approaches TOC, the camshaft piston 1 is at TOC starting its power stroke For sim-once again opens the intake valves for the cylinder, and plicity we have shown the 720° of crankshaft rotationthe sequence of events is repeated over again in two individual circles as well as in one sketch thatFigure 2-3 illustrates one example of the duration shows both circles superimposed on top of one an-

of degrees involved in each piston stroke of a typical other, which is the commonly accepted method in the

DieselEngineOperatingFundamentals 15

industry The example shows a firing order of movements, are required to complete the intake, 1-5-3-6-2-4 for an engine that rotates clockwise (CW) pression, power, and exhaust strokes On a two-stroke-when viewed from the front cycle engine, this sequence of events is completed in

com-only one complete turn of the crankshaft, or 3600of

ro-TWO-STROKE-CYCLE OPERATION tation involving only two piston movements This is

accomplished basically by eliminating the separate The largest manufacturer of two-stroke-cycle high- take and exhaust stroke~, which ~re a ne~essary part ofspeed heavy-duty diesel engines in the world is Detroit four-str?ke-cycle operation Dunng the mtake and ex-Diesel, now owned by Daimler-Chrysler Although hau~t pIst~n movements of,the four-stroke ~ycle, t~ethere are two-stroke-cycle engines that do not employ engme bas~cally acts as an air pump by drawmg aIr mvalves but operate on ports only, Detroit Diesel two- and ~umpu:g bu~ed ~~aus.t gases out stroke-cycle engines employ a set of intake ports 10- 0 ~chleve t e ehmmat~on of t~ese two speCIfIccated around the center of the cylinder liner, with con- strokes.m the m.:~-cycl~ engme reqUires the use of aventionally operated pushrod-type exhaust valves at gear-dnven, posItive-dIsplacement blower ~ssembly,the top of each cylinder The operation of the two- com~only kn?wn as a Roots-type blower ~IS blowerstroke-cycle engine is illustrated in Figure 2-5, which supphes the aIrflow necessary for several actions:depicts the layout of a V-configuration engine The • Scavenging of exhaust gases from the cylinder.only difference between the V and inline two-stroke • Cooling of internal engine components, such asDetroit Diesel engines is in the basic cylinder arrange- the cylinder liner, the piston, and exhaust valves

In a four-stroke-cycle engine, 720 crankshaft de- achieved by airflow from the blower and grees or two complete revolutions, plus four piston bocharger

tur-FIGURE 2-5 Two-stroke-cycle

V-configu-ration diesel engine principle of opeV-configu-ration.

(Courtesy of Detroit Diesel Corporation.)

• Combustion purposes mercury (in Hg) or between 20 and 25 psi (140 to 172

• Crankcase ventilation by controlled leakage of air kPa) to the intake ports in the cylinder liners When thepast the oil control rings when the piston is at engine is operating under load, a bypass valve built

the air pressure on both sides of the blower (inlet andMost models of Detroit Diesel two-stroke-cyde engines outlet) to equalize In this way the horsepower re-are equipped with both a gear-driven blower and an quired to drive the blower is reduced, and basically theexhaust-gas-driven turbocharger The blower supplies airflow is being supplied by the exhaust-gas-driven

a positive displacement of air, which is required at idle turbocharger

and light-load operation since the turbocharger does Two-stroke-cyde Detroit Diesel engines arenot receive a high enough exhaust gas pressure / flow equipped with exhaust valves only,with four per cylin-

to cause it to supply sufficient air to the engine The der being used for better scavenging purposes Theblower is capable of producing approximately 4 to 7 psi cylinder liner is arranged so that it has a series of ports(27 to 48 kPa) throughout the engine speed range Un- cast and machined around the liner circumference ap-der heavy loads the turbocharger boost will increase proximately halfway down its length These ports actand supply between approximately 40 and 50 in of basically as intake valves

Diesel Engine Operating Fundamentals 17

The engine block is designed so that all liners are the two-cycle engine, there are twice as many of them

surrounded by an air box that runs the length of the When the piston is at TDC, a regulated amount of airblock The air box is somewhat like a plenum chamber, box pressure is designed to leak past the oil controlwhere the blower air is pumped in to ensure that there ring drain holes of the piston to ensure positive

will always be an adequate volume for the four func- crankcase ventilation

tions listed Any time that a piston in a cylinder has

un-covered the liner ports, the air box pressure is free to Exhaust

flow into and through a cylinder The operational Exhaust occurs when the exhaust valves start to openevents are described next by camshaft and rocker arm action The power stroke,

therefore, effectively ends at this point, as the burnedScavenging gases escape into the exhaust manifold either to driveDuring scavenging the liner ports are uncovered by a turbocharger or to flow freely to a muffler The ex-the piston and the exhaust valves are open The an- hau~t valves have to ~pen bef~re the piston uncoversgled ports in the liner provide a unidirectional flow of the hner ports; otherwIse, the h~gher pres~ure of the.ex-pressurized air into and through the cylinder to scav- haust gases would blow back mto the au box agamstenge the exhaust gases through the open exhaust the much lower blower pressure

valves This action also cools the internal components, Once the piston crown uncovers the liner ports,such as the piston, liner, and valves, with appro xi- usually about 60° BBDC,the air box pressure is highermately 30% of engine cooling provided by this air- than the exhaust pressure and scavenging beginsflow This leaves the cylinder full of clean, cool fresh again This continues until the piston has reached BDCair for combustion purposes when the piston covers and starts back up in the cylinder and ends when thethe liner ports piston has again recovered the liner ports to start the

compression stroke once more

two-Compression begins when the piston moves up from stroke-cycle engme ISbasIcally a compressIOn stroke,BDC and covers the previously open liner intake and every downstroke is a power stroke The intakeports The exhaust valves are timed to close a few de- and exhaust events oc~ur only during the time that thegrees after this occurs, to ensure positive scavenging exhaust valve~ and lmer ports are open Scavengealong with a positive charge of fresh air for combus- blowthrough (lmer ports open) takes place through ap-tion purposes proximately 120°of crankshaft rotation, although keep

in mind that the exhaust valves open at about 90 to 95°

re-The initial start of fuel injectionvaries between series of covered the liner ports as it moves upward The engines and the year of manufacture; however, gener- haust valves are therefore open for approximately 155ally speaking, this is between 12 and 15° BTDC,with to 160°of crankshaft rotation

ex-the engine running at an idle speed between 500 and

600 rpm Advancement of injection occurs automati- Valve Timing

cally through throttle movement via a helical cut injec- The polar valve timing diagram shown in Figure 2-6 tor plunger in non-DDEC-equipped engines, or elec- lustrates one example of the various degrees of porttronically in DDEC (Detroit Diesel Electronic Control) opening, valves opening, and closure for a two-stroke-systems as the engine speed is increased cycle non-DDEC-equipped V92 engine The specificWhen the unit injector sprays fuel into the com- year of manufacture of the engine, the particular en-bustion chamber, there is a small delay before ignition gine series, specific model, and application as well asoccurs; then the intense heat generated by combus- the fuel delivery rate can result in different degrees oftion of the fuel increases both the temperature and valve timing as well as injection duration

il-pressure of the air / fuel charge Injection continues for If you compare this valve timing diagram with

a number of degrees and the resultant force of the that shown in Figure 2-3 for the four-stroke-cycle high-pressure gases drives the piston down the cylin- gine, you will see that there are substantial differencesder on its power stroke The length of the power in the duration of the various strokes and the numberstroke in Detroit Diesel two-stroke-cycle engines will of crankshaft degrees involved A thorough under-vary slightly, but at 90 to 95° ATDC, the exhaust standing of the differences between the two- and four-valves will start to open Compare this with a power stroke operating cycles will serve you well when con-stroke of between 120 and 140°on a four-stroke-cycle sidering their operation and when attempting toengine; but although the power stroke is shorter on troubleshoot the engine in some cases

en-the front and identifies en-the left and right cylinder banksfrom the flywheel end, although it numbers the cylin-ders on each bank from the front of the engine If we as-sume that cylinder 1 on the left bank is at TDC com-pression, the other cylinders would be spaced 26.5°,63.5°,26.5°,and so on, throughout the firing order By re-ferring to Figure 2-6, which illustrates a typical example

of a two-stroke 8V-92TA(turbocharged and aftercooled)engine polar valve timing diagram, you can determineexactly what stroke each piston is on in Figure 2-7

Although the two-stroke-cycle engine has twice asmany power strokes as that of its four-cycle counter-part, it does not produce twice the power output at theengine crankshaft or flywheel This is due, in part, tothe fact that the length of the power stroke is muchshorter in the two-stroke than in the four-stroke engine.Average power stroke length in the two-cycle enginecan be between 90 and 95 crankshaft degrees, while thefour-cycle engine tends to have a power stroke of be-tween 120 and 140°

The two-stroke-cycle engine, however, generally

FIGURE 2 6 E I f ty I tw t k I delivers more power for the same weight and cylinder

diesel engine polar valve timing diagram (Courtesy of Detroit dlsplace~ent, or the sam,e ba~lc horsepower, from a

power differences as follows:

1 In a four-stroke-cycle engine, there is a longer

Piston Positions period available for the scavenging of exhaust gases

In Figure 2 4we considered an example of the relative and the separation of the exhaust and inlet strokes Inpiston positions for a six-cylinder four-stroke-cycle en- addition, with a shorter valve overlap period versusgine This diagram allowed us to visually interpret the port/valve concept in the two-stroke engine, therewhere each piston is in relation to the others as well as tends to be a purer air charge at the start of the com-what stroke each piston is on Now assume that in the pression stroke in a four-cycle engine than in a conven-two-stroke-cycle Detroit Diesel engines we are to con- tional blower-air-supplied two-stroke engine How-sider where each piston is at a given time and what ever, once a turbocharger is added to the two-strokestroke it is on Most of us would simply assume that engine, the airflow delivery rate is increased substan-since the sequence of events occurs in 360crankshaft de- tiallYi therefore, two-stroke-cycle engines such as De-grees, we can divide the degrees by the number of cylin- troit Diesel's 71 and 92 series engines equipped withders and we would know where each piston was If we both a blower and a turbocharger match the character-were to consider an 8V-71 or 92 series model, logic istics of the four-stroke engine

would tell us to divide 360°by 8=45°.This conclusion 2 Both four- and two-stroke-cycle engines havewould be reasonable if the engine were a 900V configu- pumping losses The four-stroke-cycle losses occur dur-

rationi in fact, however, these engines have a 63.5°angle ing the intake and the exhaust strokes, whereas in thebetween the banks Therefore, the firing impulses be- two-stroke-cycle engine the power losses required totween two cylinders must add up to 90° Figure 2-7 il- drive the gear-driven blower reduce the net enginelustrates how Detroit Diesel does this on these series of power output In addition, two-stroke engines require aengines for a right-hand rotation model with a firing or- much larger airflow capacity to operate since the pur-der of 1L-3R-3L 4R 4L-2R-2L-1R.Keep in mind that pose of the airflow is to (a) scavenge the burned exhaustthe manufacturer determines the engine rotation from gases from the cylinder in a short interval (usually be-

Diesel Engine Operating Fundamentals 19

FIGURE 2-7 Example of the firing order and

piston positions in degrees between each

cylin-der for a Detroit Diesel two-stroke-cycle 63.50

designV-type diesel engine with a right-hand fCW

from front) rotation and a firing order of

Il-3R-3L-4R-4L-2R-2L-1 R. Note that the left

bank and right bank are determined from the rear

orflyvvheel end of the engine block Cylinders are

numbered from the front to rear on each bank.

tween 100and 150°);(b)cool the internal engine compo- ever, the four-cycle engines' pumping losses tend to benents, such as the cylinder liner, the piston crown, and about two-thirds that for the two-cycle engine Two-the exhaust valves (approximately 30%of the cooling of cycle engines that employ both a turbocharger and a

a two-stroke-cycleengine is done by airflow);(c)supply bypass blower-such as Detroit Diesel 71, 92, and 149fresh air for combustion purposes; and (d) provide air series engines-have changed this ratio substantially.leakage for positive crankcase ventilation 4 The thermal (heat) loading on the piston,

3 Pumping losses occur in a four-stroke-cycle valves, cylinder head, and cylinder liner tend to beengine during the intake and exhaust strokes Equiva- lower on a four-stroke-cycle engine because thelent losses to drive the gear-driven blower exist in the power stroke occurs only once every two crankshafttwo-stroke engine, plus as much as 40% of the engine revolutions versus once per revolution on a two-friction However, this has been reduced substantially stroke engine

in current Detroit Diesel two-cycle engines by the use 5 It is easier to lubricate the pistons, rings, and

of a bypass blower to reduce pumping losses once the liners in a four-cycleengine, due to the absence of portsturbocharger boost increases to a predetermined level that are required in the two-cycle liner

Generally, on a nonturbocharged two-cycle engine the 6 The two-cycle engine tends to have a slightlyblower power loss is less than the four-cycle pumping higher fuel consumption curve due to its double-losses when the engines are operating at less than 50% power-stroke principle throughout the same 720°for a

of their rated speed From 50%up to rated speed, how- four-cycle engine

7 Generally, the two-stroke-cycle engine can more detail and describe how to determine the BMEPproduce more power per cubic inch (cubic centimeter) of any engine.

of displacement than that for a four-cycle engine when 10 The brake specific fuel consumption (BSFC)high-power applications are required, such as in high- of a two-stroke-cycle engine tends to be higher thanoutput marine and off-highway mining trucks In that for a comparably rated four-cycle engine BSFCisheavy-duty on-highway truck applications, one exam- simply the ratio of fuel burned to the actual horse-pIe is the Detroit Diese18V-92TA-DDECmodel rated at power produced Engine manufacturers always show500bhp (373kW) at 2100rpm from 736in3(12.1L) This their projected BSFC for an engine at different loadssame engine can pump out up to 765 bhp (571 kW) in and speeds in their sales literature Later in this chap-high-output marine applications, which is more than ter we discuss BSFCin more detail; examples of BSFC

1 hp / in3of displacement The Cat 3406Eat 500bhp has for several well-known engine makes and models are

a displacement of 893 in3or 14.6L, while the Cummins illustrated and discussed Electronically controlledN14 at 500 bhp has a displacement of 855 in3 (14 L) heavy-duty diesel engines are capable of returning fuelMack's six-cylinder E7 model at 454bhp (339kW) from economy superior to mechanical models, which con-

728 in3 (12 L), however, is a good example of high firms that these engines have a higher thermal efficiency

power from small displacement in a four-stroke-cycle (heat efficiency) as well as the ability to meet the

Envi-8 The compression ratio (CR) on four-stroke en- ronmental Protection Agency (EPA)

gines tends to be lower than that on an equivalent- We can summarize the two cycles by consideringrated two-cycle engine Consider that the Caterpillar that the piston operation is divided into closed and open3406E engine has a CR of 16.25:1;the Cummins N14 periods The closed period occurs during the power stroke

has a CR of 16.2:1,Detroit Diesel's series 60 12.7-Land and the open period during the time the inlet and exhaust

series 50 each have a CR of 15:1while its two-cycle 92 strokes are occurring Consider the following sequence:has a CR of 17:1 However, Volvo's VE D12 electroni-

cally controlled six-cylinder four-stroke model has a Two-Stroke Cycle

two-cyc e engme onSl er t at a etrOlt lese se- 0 d

ries engine rated at 450 bhp (336 kW) at 2100 would • pen peno

h BMEP f 115 (793 kP ) th t d-e: blowdown or escape of pressunzed exhaust

500 bhp (373 kW) would have a BMEP of 128 pSI (883 g

kP ) C thO 'th th f t k l' e-f scavengmg of e?,haust gases by the blower

a ~mpare IS WI e our-s r? e-cyc e engme and/ or blower-turbocharger combination

models m the same general power ratmg category The

Caterpillar 3406E rated at 475 bhp (354 kW) at 1800 f-g mr supply for the next compressiOn strokerpm would have a BMEP of 234 psi (1613kPa), and at All of the above events occur within 360°, onethe peak torque point of 1200 rpm, its BMEP climbs to complete turn of the engine crankshaft/ flywheel

295 psi (2037kPa) A Cummins N14 at 500 bhp at 2100

rpm would develop a BMEP of 221 psi (1524 kPa) A Four-Stroke Cycle

Detroit Diesel series 60 12.7L rated at 370bhp (276kPa). • Close penod d

at 1800 rpm would develop a BMEP of 210 pSI (1460kP) h . t 470 bh (351kW) ld h a-b compresSiOnof trapped au.'

a BMEP of 229 psi (1579 kPa) Mack's E7-454bhp (339 b-c:.heat cr~ated by the combustIon processkW) model has a BMEP of 274 psi (1890kPa), while its CO-d.expa~sd10n or power stroke

• pen penoE9 V8 rated at 500 bhp (373 kW) develops a BMEP of209 (1440kP ) '7 1 ' 1 . I' d 1, d-e blow down or escape of pressunzed exhaust pSI a vO vo s atest SlX-CYm er e ectrom- gases

cally controlled VE D12 rated at 415 bhp (310 kW) at. e- : ex aus s ro ef h t t k

1900 rpm develops a BMEP of 234 pSI (1612 kPa) As. f·-g: mean1 t dex aus va ve over aph t 1 1

you can see, four-cycle engmes tend to have BMEPs al-. h f h 1· d h g- m uc iOns ro eh·' d t· t k

most tWIce t at or t e two-cyc e engmes rate. at t e h -1: compresSIOn

same horsepower You may have notIced that the

smaller the four-cycle engine displacement, the higher All of these events require 720° of crankshaft/ flywheelthe BMEP value will be In Chapter 3 we discuss in rotation, in contrast to the 360° in the two-cycle engine

Diesel Engine Operating Fundamentals 2 1

ENGINE FIRING ORDERS The actual firing order of an engine, and therefore

the position of the individual cranks on the shaft, canThe number of cylinders and the engine configuration be established today by computerized analysis The(inline versus V) and the directional rotation of the en- following parameters must be considered:

gm.e determine the actual firing order In Chapter 7 we • M· b 1 d h d· t 1· d f·

discuss the Purpose and function of crankshaft

counter-sequenceweights, engine balance shafts, and vibration dampers • E b 1

ngme a ance

in the overall balance of a running engine EveryCylin- • 'r 1 ·b t· f th k h ft

~orslOna VI ra Ions0 e cran s ader in an engine produces what are commonly referred • I 1 th· fl t f

n some speCla cases, e aIr ow In er erence m

toas disturbingforces that act along the axis of each cylin- the intake manifold

der as a result of the acceleration and deceleration of the

rotating connecting rod and piston assembly as the in- Figure 2-8 illustrates typical firing orders used fordividual cranks rotate through 360° various engines with differing numbers of cylinders

for both two- and four-stroke-cycle engines

Two-stroke crankshaft arrangements tend to be more

com-plicated than those in a four-cycle engine, because the

two-stroke engine must fire all cylinders in one

crank-shaft rotation (360°versus 720°).It is common in

four-cycle engines to repeat, or "mirror," the two halves of

the crankshaft to eliminate coupling forces (equal

masses positioned opposite one another) This also

of-ten allows a number of firing orders to be obtained

from a single crankshaft arrangement The discussion

of crankshaft balance and the forces involved is a

spe-cialized area in its own right, so we will not delve into

details here In many current high-speed

V-configura-tion engines the desired firing order is often achieved

by employing offset con-rod (connecting rod) journals

- r d r firin order for FIGURE 2-9 Cylinder and valve locations for a model

The most wIdely used SIXcy m e g 3512 !V) 2) four-stroke-cycle engine (Reprinted courtesy of

a CW-rotation (from the front) two- ~r four-st~oke.cycle Caterpillar, Inc.)

engine is 1-5-3-6-2-4 If the engme rotatIOn IS

re-versed, such as for some twin-engine marine

applica-tions, a typical firing order might be 1-4-2-6-3-5

When V-engine configurations are employed, the firing numbered from the front to rear on each bank, as order is determined based on the engine rotation and trated in Figure 2-10 for a series of V models In addi-whether it is a two- or four-stroke-cycle type Most en- tion, Detroit Diesel engines determine the crankshaftgine OEMs identify cylinder numbering from the front rotation from the front of the engine, not from the fly-

illus-of the engine; however, in some cases the cylinder wheel end Anytime the engine rotation is changednumber is determined from the rear In addition, on V from CW (right hand) to CCW (left hand), the engineengines most manufacturers identify the left and right firing order is always different, as indicated in Figurecylinder banks from the flywheel end 2-10

Standard rotation on many engines is based on the

SAE (Society of Automotive Engineers) technical stan- SUMMARY

dard in which rotation is determined from the flywheel

end N~rmally, this ~s counterc~ock.wise (CC~) which This chapter has provided you with a solid results m a CW r?tatIon :vhen vIe,:mg the engm~ fro~ standing of the concept of operation for both two- andthe front OpposIte rotatIon accordmg to the SAEISs.tIll four-stroke-cycle engines Youhave also been providedviewed from the flywheel end; howe:er, the engme with the concept of operation for both IDI and DI en-crankshaft would rotat~ CCW when ':'Iewed.from ~he gine designs Knowing engine firing orders, relativefront Note that CaterpIllar nun:bers ~ts engme cylm- piston positions, and valve timing information willders ~rom t~e front to t~e rear, wIth cylmder ~ bemg on contribute to your ability to set and adjust both the in-the nght sIde and cylmder 2 on the left sIde when take and exhaust valve clearances and to discuss andvie,:ed from the rear This means that th~ left and right compare the advantages and disadvantages of differ-engme banks on a V model are determmed from the ent types of internal combustion engines

under-flywheel end For example, a four-cycle V12Caterpillar

3512engine model with a standard SAErotation would SE LF- TEST QU ESTI a N S

have a firing order of 1-12-9-4-5-8-11-2-3-10-7-6;

the cylinder numbering system wo~ld app~ar a.sillus- 1 TechnicianA says that the piston strokes in a trated in Figure 2-9 ThIs same engme runnmg m SAE stroke-cyclediesel or gasoline engine involve intake,opposite rotation would have a firing order of compression,power, and exhaust TechnicianB says1-4-9-8-5-2-11-10-3-6-7-12 that the order is compression,intake, power, and ex-

four-A two-stroke-cycle V configuration, such as those haust Whois correct?

manufactured by Detroit Diesel in V6, V8, V12, V16, 2 TechnicianA says that a four-stroke-cycledieselengineand V20 models, determines left and right cylinder requires 720°(two full turns) of crankshaftrotation tobanks from the flywheel end, with the cylinders being produce one power stroke.TechnicianB says that two

Diesel Engine Operating Fundamentals 23

FIGURE 2-10 Engine cylinder designation and firing orders for tvvo-stroke-cycle V6, VB, V12, and VI6 models.

fCourtesy of Detroit Diesel Corporation.)

power strokes are produced within 720°.Which techni- than 100%.Technician B says that no engine can run at dan is correct? VEs in excess of 100%, due to frictional losses Which

3 Technician A says that during the intake stroke on a technician is correct?

gasoline engine, both air and fuel are mixed Technician 9 Technician A says that typical cylinder pressures at the

B says that only air is inhaled into the cylinder Who is end of the compression stroke (prior to injection of fuel) correct? range between 1000and 1200psi (6895to 8274kPa) Tech- 4 Technician A says that on a diesel engine, only air is in- nician Bsays that they would be closer to the range 450 to haled on the intake stroke Technician B says that both 600psi (2758to 4137kPa) Which technician is correct? air and fuel are taken into the cylinder on the intake 10 Technician A says that typical compression tempera- stroke Who is right? tures range between 1000 and 12000p (538 to 6490C).

5 Technician A says that the term volumetric efficiency (VE) Technician B says that they would be closer to 20000P refers to the weight of air retained in the cylinder at the (1093°C).Who is correct?

end of the intake stroke Technician B says that it is the 11 Technician A says that peak cylinder firing pressures in pressure of the air at the end of the compression stroke electronically controlled high-speed heavy-duty diesel Which technician is correct? engines range between 1200 and 1400psi (8274 to 9653

6 Technician A says that in naturally aspirated engines, kPa) Technician B believes that they are closer to 1800 the VE will always be less than 100%.Technician B says and 2300 psi (12,411and 15,856kPa) Who is correct? that the engine would starve for air if this were the case, 12 Technician A says that the intake valves open at BTOC and therefore it must have at least a VE of 100% (atmo- and close at ABOe Technician B says that they open at spheric pressure) TOC and close at BOe Who is correct?

7 Technician A says that atmospheric pressure at sea level 13 TechnicianA says that the term positive valve overlap

indi-is approximately 14.7 psi (101.3kPa) Technician B says cates that both the intake and exhaust valves are open for that it is closer to 16 psi (110.3kPa) Who is correct? a given number of degrees before and after me Techni-

8 Technician A says that the VE in turbocharged engines cian B says that both the intake and exhaust valves are

is always greater than atmospheric pressure, or higher open before and after BOe Which technician is correct?

14 Technician A says that a polar valve timing diagram in- 24 Technician A says that on two-cycle DDC engines, the dicates the duration of all strokes Technician B says that blower supply air pressure is between 20 and 25 psi (138

it only indicates the duration of the power stroke Who to 172 kPa) Technician B says that it ranges between 4

is correct? and 7 psi (28 to 48 kPa) Who is correct?

15 Technician A says that two-stroke-cycle DDC engine 25 Technician A says that average turbocharger boost models employ both intake and exhaust valves Techni- sures on both two- and four-cycle heavy-duty high- cian B says that only exhaust valves are used in these en- speed diesel engines range between 40 and 50 in (102 to gines since the cylinder liners are designed with a row 127cm) of mercury, or approximately 20 to 25 psi (138 to

pres-of intake ports Which technician is correct? 172 kPa) Technician B says that it is closer to 8 to 10 psi

16 Which of the following two strokes are eliminated from (55 to 69 kPa) Who is correct?

a two-stroke-cycle engine? 26 Technician A says that scavenge blowthrough of the

a intake and exhaust cylinder liners in two-stroke-cycle DDC engines occurs

b compression and exhaust when the piston is approximately 40° ABDC Technician

c intake and compression B says that it occurs approximately 60° BBDC until

d compression and power about 60° ABDC, for a duration of 120° Which

techni-17 Technician A says that in a two-stroke-cycle DDC en- cian is correct?

gine, every upstroke of the piston produces compres- 27 Technician A says that two-cycle DDC 71 and 92 series sion, and every downstroke produces power Techni- V-configuration engines are designed with a 63.5° angle cian B says that this is impossible since the engine between the banks Technician B says that they are 90° would not run without both an intake and an exhaust Vs Who is correct?

stroke Which technician is correct? 28 Technician A says that the average duration of a

two-18 Technician A says that a two-stroke engine has a longer stroke-cycle engine power stroke is about 90 to 95° power stroke in crankshaft degrees than that of a four- Technician B says that they are closer to between 120 cycle engine model Technician B says that the four- and 140°.Who is correct?

strok~-~ycl~ engine ;'as a longer power stroke Which 29 Technician A says that pumping losses occur in all technIcIan IScorrect stroke-cycle engines during the intake and exhaust

two-19 A typical firing order for a six-cylinder four-stroke-cycle strokes These losses occur in a four-stroke-cycle engine engine would be according to technician B Who is correct?

~ 1-5-2-4-6-3 30 Technician A says that the compression ratio tends to be

· 1~-3-6-2-4 higher on four-cycle engines than on two-cycle models.

c 1 -2-6-3-5 Not so, says technician B; it is the other way around.

20 Technician A says that in a two-stroke-cycle DDC en- Who is correct?

gine, the gear-driven blower is used to supply the air re- 31 'T' hn·· A th t th BMEP' I tw I

qUlred for both the scavengmg and mtake strokes Tech- th f I d I 'T' hn·· B

mClan B says that the blower ISused to supercharge the th t ·t· th t ·t t t hn·· A' t t t Who h hn'" ? a 1 IS e exac OppOSle 0 ec 1C1an s sa emen engme 1C tec 1ClanIScorrect Who is correct?

21 Technician A says that a supercharged engine is any en- 32 'T' hn·· A th t th BSFC t d t b h· h f

gme that has pressurIzed aIr added to It or any engme tw I N t t hn·· B th f

o-cyc e engme 0 so, says ec 1Clan ; e that uses a turbocharger or blower Techmc1an B d1S- I· f Ith th tw t k

our- cyc e engme uses more ue an e o-s ro e engme agrees and says that to supercharge an engme, you must Wh t?

close the valves early enough to trap the hIgh-pressure

turbo or blower air in the cylinder; therefore, a super- 33 True or F.alse: Standard e~gme r~tahon accordmg ~o charged engine is any engine that takes air into the SAE (SoClety o.f Automohve Engmeers) standards IS cylinder at higher than atlnospheric pressure and then counter-clockwIse from the flywheel end.

compresses it Which technician is correct? 34 Technician A says that the cylinder number for most

en-22 Technician A says that all DDC two-cycle engines must gines is determined from the front end of the engine.

be supercharged since they employ a gear-driven Technician B says that cylinder numbers are always blower Technician B disagrees and says that the blower termined from the flywheel end Which technician is air is simply used to scavenge exhaust gases and supply correct?

de-fresh air for combustion purposes Which technician is 35 Technician A says that most OEMs determine the left correct? and right banks on a V-configuration engine from the

23 Technician A says that approximately 30% of the engine flywheel end Technician B says that they are cooling in a two-stroke-cycle DDC engine is achieved by mined from the front Who is correct?

deter-blower airflow Technician B believes that possibly 10% 36 True or False: The duration of the power stroke in cooling might be achieved by blower airflow Which shaft degrees is longer on a two-cycle diesel engine than technician is correct? it is on a four-cycle engine.

crank-Diesel Engine Operating Fundamentals 25

._ Draw a circle and sketch in the duration of each indi- 40 Repeat the process that was described in Question 39 for 1ridualstroke for a four-stroke-cyclediesel engine Show a two-stroke-cycle engine.

the start and end of injection at an idle speed as well as 41 List the advantages and disadvantages of a the positive valve overlap condition that exists cycle engine in comparison to an equivalent four-cycle

two-stroke-_ Repeat the process described in Question 37 for a two- model.

slmke-cycle diesel engine 42 Technician A says that current heavy-duty high-speed

311 Sketch and show the relative piston firing positions for DI diesel engines employ single-hole pintle-type

injec-a six-cylinder CW-rotinjec-ation four-stroke-cycle engine tion nozzles Technician B says that they employ with a firing order of 1-5-3-6-2-4 using the degrees hole nozzles/injectors for better fuel distribution and

multi-aeared in Question 37, and describe where each piston penetration Who is correct?

is and what stroke it is on.

FIGURE 3-1 (al The

horse is applying force

against a large rock, but

the rock is not moving

Therefore, no work is

be-ing done (b) Injected fuel

creates high pressure on

the piston crown to rotate

the crankshaft (Courtesy

of the American Association

for Vocational Instructional

Work

Work is done when a force travels through a distance(Figure 3-2) If force is exerted and no movement oc-curs, no work is being done Work is also done in

"braking" or slowing down a vehicle such as a tractor

or truck

Force and distance can easily be measured in most

cases, so the amount of work can be calculated by ing the following formulas:

(1 N =4448 pounds-force)

330 ft-lb X 4.448=1468 N

work =1468 newtons X 30.5 meters

=44,774 joules (J)or newton-meters(N·m)

Work, along with energy and force, is the

begin-ning of determibegin-ning power Since the only kind of

work we have discussed so far has been accomplished

by pulling or pushing, we need to look at another

kind of work, that which is developed by rotating

mo-tion such as an engine crankshaft. The amount of

work done is still determined by multiplying the force

in pounds times the distance the weight is moved in

feet

Power

Theterm power is used to describe how much work has

been done in a given period of time The rate at which

work can be done is measured in terms of power, or

how many units of work (ft-Ib) have been done in a

unit of time We can show this simply as

Normally, power is expressed as how many

foot-pounds of work is done per minute If enough work is

performed in a given period of time, we can start to

compare it with the word horsepower, which is used to

describe the power output of all internal combustion

engines (see Figure 3-lB) A detailed description of

horsepower follows

Horsepower

What is horsepower? The term is peculiar to the U.s

customary system In the SI system, watt is the term

used for power

1 horsepower =746 watts

The term horsepower was introduced by James

Watt when he observed how much power one horse

could develop He found that a medium-size draft

horse could pull 330 pounds a distance of 100 feet in 1

minute This became a standard unit of measure, one

that he used to rate his steam engine By multiplying

330 lb times 100 ft, he set 33,000 ft-Ib/min as defining 1

horsepower The formula for horsepower thus is

Thus, 1 horsepower is the ability to do 33,000 ft-Ib

of work in 1 minute, or 550 ft-Ib of work in 1 second

(33,000 divided by 60 seconds equals 550)

Note that in Figure 3-2 the horse is lifting a 330-lb

weight to a height of 100 ft in 1 minute Using the

for-Understanding Horsepower and Related Terms 29

mula, the number of horsepower represented is mined as follows:

deter-In Figure 3-3a the horse is dragging at the rate 100ft/min a weight that requires 330 lb of pull to move it

In this example it is not necessary to know the value ofthe weight The pulling force is determined by how dif-ficult the weight is to pull You apply the horsepowerformula as follows:

This is typical of how you determine the drawbar

horse-power of a tractor.

In Figure 3-3b, force by pulling is replaced by ashaft turning (rotating force) This is the way power ismeasured at the engine flywheel and at the power take-off (PTO) shaft of tractors If we assume that it takes 1minute to lift the 330-lb weight to a height of 100 ft, youcan determine horsepower as follows:

Let us consider the work that is produced by ing a weight of 100 lb (45.36 kg) through a distance of

mov-10 ft (3 m) in a time of 4 seconds (sec or s) The powerexpended would be

How much horsepower have we expended in doingthis work? One horsepower is considered as being 550ft-lb/sec,33,OOO ft-Ib/min, or 1,980,000 ft-Ib/hr There-fore, we can compute horsepower as follows:

ment is an American equivalent; in the metric system 1

hp is considered as being 735.5W, or 75 kg m/ s TheGerman abbreviation for this unit of measurement is

PS (Pferdestiirke), where 1 PS (European horsepower) =

0.986 hp The French equivalent is CV (cheval vapeur),

where 1 ch= 1 PS= 0.07355kW This means that ric horsepower is approximately 1.5% less than theAmerican unit of measurement! Other measures thatyou will encounter have been established by the Inter-You can see that if work is performed at a slower national Standardization Organization (ISO),Deutschesrate, less horsepower is produced; therefore, we can Institut fur Normung-German Institute for Standard-

met-safely say that the word horsepower is an expression of ization (DIN), and Society of Automotive Engineershow fast work can be done.Inan internal combustion (SAE), headquartered in Warrendale (Pittsburgh),engine this work is produced within the cylinder due Pennsylvania

to the expanding gases The faster the engine speed, the

quicker the work is produced Horsepower Formulas

Metric Horsepower Work is done when a force is exerted over a distance

In the metric system, power is expressed by the word This can be defined mathematically as work equals

dis-kilowatt (kW), used initially to express the power of tance (0) multiplied by a force (F) As horsepower is a

electrical machinery, where 1 hp is considered equal to measure of the rate (speed) at which the work is done,

746 watts (W) in the English equivalent (A watt is an we can show this mathematically as

ampere X a volt; an ampere is a measure of

volume/ quantity and a volt is a measure of electrical

pressure.) Since 1 kW equals 1000 W, we can show 1

Understanding Horsepower and Related Terms 3 J

2 Indicated horsepower (ihp) This is the power

de-veloped within a cylinder based on the amount of heatreleased but does not take into account any frictionallosses The cylinder's mean indicated pressure can bemonitored by installing a special test gauge to recordthe maximum firing pressure If a maximum pressureindicator gauge is available and the cylinder pressure

is known, you can factor out indicated horsepower ing a formula

us-Horsepower Performance Curves

One easy way to show engine performance curves is toview an OEM sales specification sheet These sheets in-clude graphs indicating the horsepower, torque, andfuel performance curves for various engine models.Figure 3-4 shows several engine ratings for DetroitDiesel's four-stroke-cycle, 12.7 L series 60, electroni-cally controlled heavy-duty truck engine By picking

an engine rpm along the horizontal line of each graph,

we can draw a vertical line upwards until it bisects thehorsepower curve and the torque curve, where we can

Brake HorsepowerThe formula for brake horsepower can be stated as

read the respective values desired Note the ratings as the BSFCline in Figures 3-5 and 3-6 Most heavy-dutyshown They are achieved through electronic program- electronically controlled diesel engine-mounted ECMsming of the engine electronic control module (ECM) are programmed to provide this type of operational re-

On the 430/470 and 430/500 bhp (321/373 kW) mod- sponse The fuel consumption and torque curves areels, the engine can be programmed to provide a lower discussed later in the chapter.

power setting at rated speed, climbing to the higher The performance curves of brake horsepower wepower setting from 1500 rpm This feature allows the have been discussing are typical of most of the neweroperator to run the vehicle in a cruise mode at a lower electronically controlled unit injector heavy-duty truckengine speed, which also provides a lower brake spe- engines manufactured by Caterpillar, Cummins, De-cific fuel consumption, but with a higher horsepower troit Diesel, Mack, Isuzu, and Volvo On mechanically

at this lower speed Both engine models also offer a governed and injected engines, however, the constant horsepower setting from 2100 rpm down to power generally tends to decrease with a reduction in

horse-1800 rpm, while the vehicle operates in the cruise con- engine speed (rpm) from the full-load-rated setting astrol mode Programming electronic engines to produce the engine rpm is reduced due to an increasing load,their best power at a lower speed results in a gear-fast- since the rate/speed of doing the work is slower Elec-run-slow concept (lower numerical axle ratio) This, tronic controls provide tremendous flexibility for tai-coupled with higher power and torque curves, pro- loring engine performance that is not possible withvides better vehicle performance overall Some of the mechanical controls Proper selection of turbochargingperformance graphs in Figure 3-4 illustrate a fairly flat and air-to-air-charge cooling, high top piston rings,power line, commonly known as a constant horse- piston bowl geometry, and the use of low-sulfur dieselpower curve, since there is no loss of power with a re- fuel all help to provide this improvement in engineduction in engine speed for several hundred rpm performance and reduce the exhaust emissions so that

they can comply with the EPA-mandated limits

NOTE Horsepower is related to BMEP but is Regardless of the type of horsepower calculated,

most diesel technicians in the field choose to use thealso influenced by both the speed of the engine

following simplified formula to determine and the cylinder/engine displacement Horse-

horse-power, particularly when the engine torque and speedpower cannot be multiplied

are known:

Figure 3-5 illustrates the performance curve and

relative information for the Caterpillar 3406E

electroni-cally controlled unit injector truck engine Figure 3-6

il-lustrates an engine performance curve for a Cummins

N14-460E electronically controlled heavy-duty truck

engine Note in this example and others that the engine

brake horsepower performance curve is tailored so that

the maximum power and best fuel economy are

achieved at a speed within the operating range where

most driving is done on a heavy-duty truck application

Cummins refers to the point on the engine performance

curve where this occurs as the "command point." In

Figure 3-7 note how the engine horsepower begins to

drop as the operator revs the engine beyond 1700 rpm

Also note in Figure 3-6 that the engine torque starts to

decrease fairly quickly beyond 1500 rpm and the fuel

consumption starts to increase This design feature

"forces" the truck driver to use a progressive shift pattern,

which means that the engine is accelerated only high

enough to get the vehicle rolling; then a shift is made to

the next higher gear By using this shifting technique,

not only does the higher engine torque move the vehicle

gradually up to road speed, but it also keeps the engine

within the most fuel-efficient curve, as you can see from