Gasoline Engine Management

Konrad Reif Ed.

Systems and Components

Bosch Professional Automotive Information

Bosch Professional Automotive Information

Bosch Professional Automotive Information is a definitive reference for automotive engineers. The series is compiled by one of the world´s largest automotive equipment suppliers. All topics are covered in a concise but descriptive way backed up by diagrams, graphs, photographs and tables enabling the reader to better comprehend the subject. There is now greater detail on electronics and their application in the motor vehicle, including electrical energy management (EEM) and discusses the topic of intersystem networking within vehicle. The series will benefit automotive engineers and design engineers, automotive technicians in training and mechanics and technicians in garages.

Konrad ReifEditor

Systems and Components

Gasoline Engine Management

Editor

Prof. Dr.-Ing. Konrad Reif Duale Hochschule Baden-Württemberg Friedrichshafen, Germany reif@dhbw-ravensburg.de

ISBN 978-3-658-03963-9 ISBN 978-3-658-0396 -6 (eBook)DOI 10.1007/978-3-658- -6

Springer Vieweg

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VForeword

The call for environmentally compatible and economical vehicles necessitates im-

mense efforts to develop innovative engine concepts. Technical concepts such as gas-

oline direct injection helped to save fuel up to 20 % and reduce CO2-emissions.

Descriptions of the cylinder-charge control, fuel injection, ignition and catalytic

emission-control systems provides comprehensive overview of today´s gasoline en-

gines. This book also describes emission-control systems and explains the diagnostic

systems. The publication provides information on engine-management-systems and

emission-control regulations.

Complex technology of modern motor vehicles and increasing functions need a relia-

ble source of information to understand the components or systems. The rapid and

secure access to these informations in the field of Automotive Electrics and Electron-

ics provides the book in the series “Bosch Professional Automotive Information”

which contains necessary fundamentals, data and explanations clearly, systemati-

cally, currently and application-oriented. The series is intended for automotive pro-

fessionals in practice and study which need to understand issues in their area of work.

It provides simultaneously the theoretical tools for understanding as well as the

applications.

▶ Foreword

VI Contents

2 History of the automobile

2 Development history

4 Pioneers of automotive technology

6 Robert Bosch’s life’s work (1861–1942)

8 Basics of the gasoline (SI) engine

8 Method of operation

12 Cylinder charge

16 Torque and power

18 Engine efficiency

20 Specific fuel consumption

22 Combustion knock

24 Fuels

24 Fuels for spark-ignition engines (gasolines)

29 Alternative fuels

32 Cylinder-charge control systems

32 Electronic throttle control (ETC)

36 Variable valve timing

39 Dynamic supercharging

42 Mechanical supercharging

44 Exhaust-gas turbocharging

47 Intercooling

48 Controlled charge flow

49 Exhaust-gas recirculation (EGR)

50 Gasoline injection systems over the years

50 Overview

52 Beginnings of mixture formation

60 Evolution of gasoline injection systems

76 Fuel supply

76 Fuel delivery with manifold injection

78 Fuel delivery with gasoline direct injection

79 Evaporative-emissions control system

80 Electric fuel pump

83 Gasoline filter

85 High-pressure pumps for gasoline

direct injection

92 Fuel rail

93 Pressure-control valve

94 Fuel-pressure regulator

95 Fuel-pressure damper

96 Manifold injection

96 Overview

97 Method of operation

100 Instants of injection

101 Mixture formation

105 Ignition of homogeneous air/fuel mixtures

106 Electromagnetic fuel injectors

110 Gasoline direct injection

110 Overview

110 Method of operation

111 Combustion process

114 Operating modes

117 Mixture formation

119 Ignition

120 High-pressure injector

122 Operation of gasoline engines on

natural gas

122 Overview

124 Design and method of operation

125 Mixture formation

127 Natural-gas injector NGI2

130 Natural-gas rail

130 Combined natural-gas pressure and

temperature sensor

131 DS-HD-KV4 high-pressure sensor

132 TV-NG1 tank shutoff valve

133 PR-NG1 pressure-regulator module

136 Ignition systems over the years

136 Overview

138 Early ignition evolution

146 Battery ignition systems over the years

152 Inductive ignition system

152 Design

153 Function and method of operation

155 Ignition parameters

159 Voltage distribution

160 Ignition driver stage

161 Connecting devices and interference

suppressors

162 Ignition coils

162 Function

163 Requirements

164 Design and method of operation

170 Types

174 Ignition-coil electronics

175 Electrical parameters

177 Simulation-based development of

ignition coils

▶ Contents

VIIContents VII

178 Spark plugs

178 Function

179 Usage

180 Requirements

181 Design

184 Electrode materials

185 Spark-plug concepts

186 Electrode gap

187 Spark position

188 Spark-plug heat range

190 Adaptation of spark plugs

194 Spark-plug performance

196 Types

203 Spark-plug type designations

204 Manufacture of spark plugs

206 Simulation-based spark-plug development

207 Handling spark plugs

212 Electronic Control

212 Open- and closed-loop electronic control

218 Motronic versions

224 System structure

226 Subsystems and main functions

234 Sensors

234 Automotive applications

235 Temperature sensors

236 Engine-speed sensors

238 Hall-effect phase sensors

240 Hot-film air-mass meter

243 Piezoelectric knock sensors

244 Micromechanical pressure sensors

246 High-pressure sensors

248 Two-step lambda oxygen sensors

252 LSU4 planar broad-band lambda

oxygen sensor

254 Electronic control unit (ECU)

254 Operating conditions

254 Design

254 Data processing

260 Exhaust emissions

260 Combustion of the air/fuel mixture

261 Main constituents of exhaust gas

262 Pollutants

264 Factors affecting untreated emissions

268 Catalytic emission control

268 Overview

269 Three-way catalytic converter

272 NOX accumulator-type catalytic converter

274 Catalytic-converter configurations

276 Catalytic-converter heating

280 Lambda control loop

284 Emission-control legislation

284 Overview

286 CARB legislation (passenger cars/LDTs)

289 EPA legislation (passenger cars/LDTs)

291 EU legislation (passenger cars/LDTs)

294 Japanese legislation (passenger cars/LDTs)

294 US test cycles for passenger cars

and LDTs

296 European test cycle for passenger cars and

LDTs

297 Japanese test cycle for passenger cars and

LDTs

298 Exhaust-gas measuring techniques

298 Exhaust-gas test for type approval

300 Exhaust-gas analyzers

303 Evaporative-emissions test

304 Diagnosis

304 Monitoring during vehicle operation

(on-board diagnosis)

307 On-board-diagnosis system for passenger

cars and light-duty trucks

324 Diagnosis in the workshop

326 ECU development

326 Hardware development

330 Function development

332 Software development

336 Application-related adaptation

343 Quality management

VIII Authors

History of the automobile

Dipl.-Ing. Karl-Heinz Dietsche,

Dietrich Kuhlgatz.

Basics of the gasoline (SI) engine

Dr. rer. nat. Dirk Hofmann,

Dipl.-Ing. Bernhard Mencher,

Dipl.-Ing. Werner Häming,

Dipl.-Ing. Werner Hess.

Fuels

Dr. rer. nat. Jörg Ullmann,

Dipl.-Ing. (FH) Thorsten Allgeier.

Cylinder-charge control systems

Dr. rer. nat. Heinz Fuchs,

Dipl.-Ing. (FH) Bernhard Bauer,

Dipl.-Phys. Torsten Schulz,

Dipl.-Ing. Michael Bäuerle,

Dipl.-Ing. Kristina Milos.

Gasoline injection systems over the years

Dipl.-Ing. Karl-Heinz Dietsche.

Fuel supply

Dipl.-Ing. Jens Wolber,

Ing. grad. Peter Schelhas,

Dipl.-Ing. Uwe Müller,

Dipl.-Ing. (FH) Andreas Baumann,

Dipl.-Betriebsw. Meike Keller.

Manifold injection

Dipl.-Ing. Anja Melsheimer,

Dipl.-Ing. Rainer Ecker,

Dipl.-Ing. Ferdinand Reiter,

Dipl.-Ing. Markus Gesk.

Gasoline direct injection

Dipl.-Ing. Andreas Binder,

Dipl.-Ing. Rainer Ecker,

Dipl.-Ing. Andreas Glaser,

Dr.-Ing. Klaus Müller.

Operation of gasoline engines on natural gas

Dipl.-Ing. (FH) Thorsten Allgeier,

Dipl.-Ing. (FH) Martin Haug,

Dipl.-Ing. Roger Frehoff,

Dipl.-Ing. Michael Weikert,

Dipl.-Ing. (FH) Kai Kröger,

Dr. rer. nat. Winfried Langer,

Dr.-Ing. habil. Jürgen Förster,

Dr.-Ing. Jens Thurso,

Jürgen Wörsinger.

Ignition systems over the years

Dipl.-Ing. Karl-Heinz Dietsche.

Inductive ignition system

Dipl.-Ing. Walter Gollin.

Ignition coils

Dipl.-Ing. (FH) Klaus Lerchenmüller,

Dipl.-Ing. (FH) Markus Weimert,

Dipl.-Ing. Tim Skowronek.

Spark plugs

Dipl.-Ing. Erich Breuser.

Electronic Control

Dipl.-Ing. Bernhard Mencher,

Dipl.-Ing. (FH) Thorsten Allgeier,

Dipl.-Ing. (FH) Klaus Joos,

Dipl.-Ing. (BA) Andreas Blumenstock,

Dipl.-Red. Ulrich Michelt.

Sensors

Dr.-Ing. Wolfgang-Michael Müller,

Dr.-Ing. Uwe Konzelmann,

Dipl.-Ing. Roger Frehoff,

Dipl.-Ing. Martin Mast,

Dr.-Ing. Johann Riegel.

Electronic control unit (ECU)

Dipl.-Ing. Martin Kaiser.

Exhaust emissions

Dipl.-Ing. Christian Köhler,

Dipl.-Ing. (FH) Thorsten Allgeier.

Catalytic emission control

Dr.-Ing. Jörg Frauhammer,

Dr. rer. nat. Alexander Schenck zu Schweinsberg,

Dipl.-Ing. Klaus Winkler.

Emission-control legislation

Dipl.-Ing. Bernd Kesch,

Dipl.-Ing Ramon Amirpour,

Dr. Michael Eggers.

▶ Authors

IXAuthors

Exhaust-gas measuring techniques

Dipl.-Phys. Martin-Andreas Drühe.

Diagnosis

Dr.-Ing. Matthias Knirsch,

Dipl.-Ing. Bernd Kesch,

Dr.-Ing. Matthias Tappe,

Dr.-Ing. Günter Driedger,

Dr. rer. nat. Walter Lehle.

ECU development

Dipl.-Ing. Martin Kaiser,

Dipl.-Phys. Lutz Reuschenbach,

Dipl.-Ing. (FH) Bert Scheible,

Dipl.-Ing. Eberhard Frech.

and the editorial team in cooperation with the

responsible in-house specialist departments.

Mobility has always played a crucial role inthe course of human development. In al-most every era, man has attempted to findthe means to allow him to transport peopleover long distances at the highest possiblespeed. It took the development of reliableinternal-combustion engines that were op-erated on liquid fuels to turn the vision of a self-propelling “automobile” into reality(combination of Greek: autos = self andLatin: mobilis = mobile).

Development history

It would be hard to imagine life in our mod-ern day without the motor car. Its emergencerequired the existence of many conditionswithout which an undertaking of this kindwould not have been possible. At this point,some development landmarks may be worthyof note. They represent an essential contribu-tion to the development of the automobile:� About 3500 B.C.

The development of the wheel is attri -buted to the Sumerians

� About 1300Further refinement of the carriage withelements such as steering, wheel suspen-sion and carriage springs

� 1770Steam buggy by Joseph Cugnot

� 1801Étienne Lenoir develops the gas engine

� 1870Nikolaus Otto builds the first four-strokeinternal-combustion engine

In 1885 CarlBenz enters theannals of his-tory as the in-ventor of thefirst automo-bile. His patentmarks the be-ginning of therapid develop-ment of the automobile

powered by the internal-combustion engine.Public opinion remained divided, however.While the proponents of the new age laudedthe automobile as the epitome of progress,the majority of the population protestedagainst the increasing annoyances of dust,noise, accident hazard, and inconsideratemotorists. Despite all of this, the progress of the automobile proved unstoppable.

In the begin-ning, the acqui-sition of an au-tomobile repre-sented a seriouschallenge. A road network

was virtually nonexistent; repair shops wereunknown, fuel was purchased at the drugstore,and spare parts were produced on demand bythe local blacksmith. The prevailing circum-stances made the first long-distance journey byBertha Benz in 1888 an even more astonishingaccomplishment. She is thought to have beenthe first woman behind the wheel of a motor-ized vehicle. She also demonstrated the relia-bility of the automobile by journeying the thenenormous distance of more than 100 kilome-ters (about 60 miles) between Mannheim andPforzheim in south-western Germany.

In the early days, however, few entrepreneurs– with the exception of Benz – consideredthe significance of the engine-powered vehi-cle on a worldwide scale. It was the Frenchwho were to help the automobile to great-ness. Panhard & Levassor used licenses forDaimler engines to build their own automo-biles. Panhard pioneered construction fea-tures such as the steering wheel, inclinedsteering column, clutch pedal, pneumatictires, and tube-type radiator.

In the years that followed, the industrymushroomed with the arrival of companiessuch as Peugeot, Citroën, Renault, Fiat, Ford,Rolls-Royce, Austin, and others. The influ-ence of Gottlieb Daimler, who was sellinghis engines almost all over the world, addedsignificant impetus to these developments.

2 History of the automobile Development history

History of the automobile

Daimler Motorized Carriage, 1894(Source: DaimlerChrysler Classic,Corporate Archives)

The first journey with anengine-powered vehicleis attributed to JosephCugnot (in 1770). His lumbering, steam-powered, wooden three-wheeled vehiclewas able to travel for all of 12 minutes on a single tankful of water.

The patent issued to Benzon January 29, 1886 wasnot based on a convertedcarriage. Instead, it was atotally new, independentconstruction(Source: DaimlerChrysler Classic,Corporate Archives)

K. Reif (Ed.), Gasoline Engine Management, Bosch Professional Automotive Information, DOI 10.1007/978-3-658-03964-6_1, © Springer Fachmedien Wiesbaden 2015

Taking their original design from coachbuild-ing, the motor cars of the time would soonevolve into the automobiles as we know themtoday. However, it should be noted that eachautomobile was an individual product ofpurely manual labor. A fundamental changecame with the introduction of the assemblyline by Henry Ford in 1913. With the Model T,he revolutionized the automobile industry inthe United States. It was exactly at this junc-ture that the automobile ceased to be an arti-cle of luxury. By producing large numbers of automobiles, the price of an automobiledropped to such a level that it became accessi-ble to the general public for the first time. Although Citroën and Opel were among the

first to bringthe assemblyline to Europe,it would gainacceptance onlyin the mid-1920s.

Automobile manufacturers were quick to real-ize that, in order to be successful in the market -place, they had to accommodate the wishes oftheir customers. Automobile racing victorieswere exploited for commercial advertising.With ever-advancing speed records, profes-sional race drivers left indelible impressions ofthemselves and the brand names of their auto-mobiles in the minds of spectators. In addition,efforts were made to broaden the product line.As a result, the following decades produced avariety of automobile designs based on the pre-vailing zeitgeist, as well as the economic andpolitical influences of the day. E.g., streamlinedvehicles were unable to gain acceptance prior toWWII due to the demand for large and repre-sentative automobiles. Manufacturers of thetime designed and built the most exclusive au-

tomobiles, suchas the Merce -des-Benz 500 K,Rolls-RoycePhantom III,Horch 855, orBugatti Royale.

WWII had a sig-nificant influenceon the develop-ment of smallercars. The Volks -wagen modelthat came to beknown as the“Beetle” was designed by Ferdinand Porscheand was manufactured in Wolfsburg. At theend of the war, the demand for cars that weresmall and affordable was prevalent. Respond-ing to this demand, manufacturers producedautomobiles such as the Goliath GP 700,Lloyd 300, Citroën 2CV, Trabant, Isetta, andthe Fiat 500 C (Italian name: Topolino = littlemouse). The manufacture of automobiles be-gan to evolve new standards; there was greateremphasis on technology and integrated acces-sories, with a reasonable price/performanceratio as a major consideration.

Today, the em-phasis is on ahigh level ofoccupantsafety; the ever-rising trafficvolumes andsignificantlyhigher speeds compared with yesteryear aremaking the airbag, ABS, TCS, ESP, and intel-ligent sensors virtually indispensable. Theongoing development of the automobile hasbeen powered by innovative engineering onthe part of the auto industry and by the con-stant rise in market demands. However, there are fields of endeavor that continue to present a challenge well into the future.One example is the further reduction of environmental burdens through the use ofalternative energy sources (e.g., fuel cells).

One thing, however, is not expected tochange in the near future – it is the one con-cept that has been associated with the auto-mobile for more than a century, and whichhad inspired its original creators – it is theenduring ideal of individual mobility.

History of the Automobile Development history 3

More than 15 millionunits were produced ofthe Model T, affection-ately called “Tin Lizzie”.This record would betopped only by the Volkswagen Beetle in the 1970s

(Photos: Ford, Volkswagen AG)

Contemporary studiesindicate what auto -mobiles of tomorrowmight look like (Photo: Peugeot)

In 1899 the BelgianCamille Jenatzy was thefirst human to break the100km/h barrier. Today,the speed record standsat 1227.9km/h.

Mercedes-Benz 500 KConvertible C, 1934(Source: DaimlerChrysler Classic,Corporate Archives)

Pioneers of automotive technology

Nikolaus AugustOtto (1832–1891),born in Holzhausen(Germany), devel-oped an interest intechnical matters atan early age. Besidehis employment as a traveling salesmanfor food wholesalers,

he was preoccupied with the functioning ofgas-powered engines.

From 1862 onward he dedicated himselftotally to engine construction. He managedto make improvements to the gas engine invented by the French engineer, ÉtienneLenoir. For this work, Otto was awarded thegold medal at the 1867 Paris World Fair. Together with Daimler and Maybach, he developed an internal-combustion enginebased on the four-stroke principle he hadformulated in 1861. The resulting engine isknown as the “Otto engine” to this day. In1884 Otto invented magneto ignition, whichallowed engines to be powered by gasoline.This innovation would form the basis forthe main part of Robert Bosch’s life’s work.

Otto’s singular contribution was his abilityto be the first to build the four-stroke inter-nal-combustion engine and demonstrate itssuperiority over all its predecessors.

Gottlieb Daimler(1834–1900) hailedfrom Schorndorf(Germany). He studied mechanicalengineering at thePolytechnikum engi-neering college inStuttgart. In 1865 he met the highly

talented engineer Wilhelm Maybach. Fromthat moment on, the two men would bejoined in a lasting relationship of mutual

cooperation. Besides inventing the first mo-torcycle, Daimler mainly worked on develop-ing a gasoline engine suitable for use in roadvehicles. In 1889 Daimler and Maybach in-troduced the first “steel-wheeled vehicle” in Paris featuring a two-cylinder V-engine.Scarcely one year later, Daimler was market-ing his fast-running Daimler engine on aninternational scale. In 1891, for example, Armand Peugeot successfully entered a vehi-cle he had engineered himself in the Paris-Brest-Paris long-distance trial. It proved boththe worth of his design and the dependabilityof the Daimler engine he was using.

Daimler’s merits lie in the systematic devel-opment of the gasoline engine and in the international distribution of his engines.

Wilhelm Maybach(1846–1929), a na-tive of Heilbronn(Germany), com-pleted his appren-ticeship as a techni-cal draftsman. Soonafter, he worked as a design engineer.Among his employ-

ers was the firm of Gasmotoren Deutz AG(founded by Otto). He already earned thenickname of “king of engineers” during hisown lifetime.

Maybach revised the gasoline engine andbrought it to production. He also developedwater cooling, the carburetor, and the dual-ignition system. In 1900 Maybach built arevolutionary, alloy-based racing car. Thisvehicle was developed in response to a sug-gestion by an Austrian businessman namedJellinek. His order for 36 of these cars wasgiven on condition that the model was to benamed after his daughter Mercedes.

Maybach’s virtuosity as a design engineerpointed the way to the future of the contem-porary automobile industry. His death sig-naled the end of the grand age of the auto-motive pioneers.

4 History of the Automobile Pioneers of automotive technology

Owing to the large number of people whocontributed to the devel-opment of the automo-bile, this list makes noclaim to completeness

1866: Nikolaus AugustOtto (Photo: Deutz AG)acquires the patent forthe atmospheric gas machine

Wilhelm Maybach(Photo: MTUFriedrichshafen GmbH)

Gottlieb Daimler(Photo: DaimlerChrysler Classic,Corporate Archives)

Carl Friedrich Benz(1844–1929), bornin Karlsruhe (Ger-many), studied me-chanical engineeringat the Polytech-nikum engineeringcollege in his home-town. In 1871 hefounded his first

company, a factory for iron-foundry products and industrial components inMannheim.

Independently of Daimler and Maybach,he also pursued the means of fitting an en-gine in a vehicle. When the essential claimsstemming from Otto’s four-stroke enginepatent had been declared null and void,Benz also developed a surface carburetor,electrical ignition, the clutch, water cooling,and a gearshift system, besides his own four-stroke engine. In 1886 he applied for hispatent and presented his motor carriage tothe public. In the period until the year 1900,Benz was able to offer more than 600 modelsfor sale. In the period between 1894 and1901 the factory of Benz & Co. produced the“Velo”, which, with a total output of about1200 units, may be called the first mass-pro-duced automobile. In 1926 Benz mergedwith Daimler to form “Daimler-Benz AG”.

Carl Benz introduced the first automobileand established the preconditions for the in-dustrial manufacture of production vehicles.

Henry Ford(1863–1947) hailedfrom Dearborn,Michigan (USA). Although Ford hadfound secure em-ployment as an engineer with theEdison IlluminatingCompany in 1891,

his personal interests were dedicated to theadvancement of the gasoline engine.

In 1893 the Duryea Brothers built the firstAmerican automobile. Ford managed to eventhe score in 1896 by introducing his own car,the “Quadricycle Runabout”, which was toserve as the basis for numerous additional de-signs. In 1908 Ford introduced the legendary“Model T”, which was mass-produced on as-sembly lines from 1913 onward. Beginning in1921, with a 55-percent share in the country’sindustrial production, Ford dominated thedomestic automobile market in the USA.

The name Henry Ford is synonymous withthe motorization of the United States. It washis ideas that made the automobile accessi-ble to a broad segment of the population.

Rudolf ChristianKarl Diesel(1858–1913), bornin Paris (France),decided to becomean engineer at theage of 14. He gradu-ated from the Poly-technikum engi-neering college in

Munich with the best marks the institutionhad given in its entire existence.

In 1892 Diesel was issued the patent for the “Diesel engine” that was later to bear hisname. The engine was quickly adopted as astationary power plant and marine engine. In 1908 the first commercial truck was pow-ered by a diesel engine. However, its entranceinto the world of passenger cars would takeseveral decades. The diesel engine became thepower plant for the serial-produced Mercedes260 D as late as 1936. Today’s diesel enginehas reached a level of development such thatit is now as common as the gasoline engine.

With his invention, Diesel has made a majorcontribution to a more economical utiliza-tion of the internal-combustion engine. Al-though Diesel became active internationallyby granting production licenses, he failed toearn due recognition for his achievementsduring his lifetime.

History of the Automobile Pioneers of automotive technology 5

1886: As inventor of thefirst automobile fitted withan internal-combustionengine, Benz enters theannals of world history(Photo: DaimlerChrysler Classic,Corporate Archives)

Rudolf C. K. Diesel(Photo: HistoricalArchives of MAN AG)

Henry Ford(Photo: Ford)

Robert Bosch’s life’s work(1861–1942)

Robert Bosch, born on September 23, 1861 inAlbeck near Ulm (Germany), was the scion ofa wealthy farmer’s family. After completing hisapprenticeship as a precision fitter, he workedtemporarily for a number of enterprises, wherehe continued to hone his technical skills andexpand his merchandising abilities and experi-ence. After six months as an auditor studyingelectrical engineering at Stuttgart technicaluniversity, he traveled to the United States towork for “Edison Illuminating”. He was lateremployed by “Siemens Brothers” in England.

In 1886 he decided to open a “Workshop for Precision Mechanics and Electrical Engineering” in the back of a dwelling inStuttgart’s west end. He employed anothermechanic and an apprentice. At the begin-ning, his field of work lay in installing andrepairing telephones, telegraphs, lightning

conductors, and other light-engineeringjobs. His dedication in finding rapid solu-tions to new problems also helped him gaina competitive lead in his later activities.

To the automobile industry, the low-voltagemagneto ignition developed by Bosch in 1897represented – much unlike its unreliable pre-decessors – a true breakthrough. This productwas the launching board for the rapid expan-sion of Robert Bosch’s business. He alwaysmanaged to bring the purposefulness of theworld of technology and economics into har-mony with the needs of humanity. Bosch wasa trailblazer in many aspects of social care.

Robert Bosch performed technological pio-neering work in developing and bringing thefollowing products to maturity: � Low-voltage magneto ignition� High-voltage magneto ignition for higher

engine speeds (engineered by his colleagueGottlob Honold)

� Spark plug� Ignition distributor� Battery (passenger vehicles and motor cycles)� Electrical starter� Generator (alternator)� Lighting system with first electric headlamp� Diesel injection pumps� Car radio (manufactured by “Ideal-Werke”,

renamed “Blaupunkt” in 1938)� First lighting system for bicycles� Bosch horn� Battery ignition� Bosch semaphore turn signal (initially

ridiculed as being typical of German senseof organization – now the indispensabledirection indicator)

At this point, many other achievements, also in the area of social engagement, wouldbe worthy of note. They are clear indicatorsthat Bosch was truly ahead of his time. Hisforward-thinking mind has given great im-petus to advances in automobile develop-ment. The rising number of self-driving mo-torists fostered a corresponding increase inthe need for repair facilities. In the 1920sRobert Bosch launched a campaign aimed

6 History of the Automobile Robert Bosch’s life’s work

“It has always been anunbearable thought tome that someone couldinspect one of my pro -ducts and find it inferiorin any way. For that rea-son, I have constantlyendeavored to makeproducts that withstandthe closest scrutiny –products that provethemselves superior in every respect.”

Robert Bosch

(Photos: Bosch Archives)

First ad in the Stuttgartdaily “Der Beobachter”(The Observer), 1887

at creating a comprehensive service organi-zation. In 1926, within Germany, these ser-vice repair centers were uniformly named“Bosch-Dienst” (Bosch Service) and thename was registered as a trademark.

Bosch had similarly high ambitions with regard to the implementation of social-careobjectives. Having introduced the 8-hour dayin 1906, he compensated his workers withample wages. In 1910 he donated one millionreichsmarks to support technical education.Bosch took the production of the 500,000thmagneto as an occasion to introduce thework-free Saturday afternoon. Among otherBosch-induced improvements were old-agepensions, workplaces for the severely handi-capped, and the vacation scheme. In 1913 theBosch credo, “Occupation and the practice ofapprenticeship are more knowledgeable edu-cators than mere theory” resulted in the in-auguration of an apprentice workshop thatprovided ample space for 104 apprentices.

In mid-1914 the name of Bosch was alreadyrepresented around the world. But the era of great expansion between 1908 and 1940would also bring the strictures of two worldwars. Prior to 1914, 88% of the productsmade in Stuttgart were slated for export.Bosch was able to continue expansion withthe aid of large contingents destined for themilitary. However, in light of the atrocities ofthe war years, he disapproved of the resultingprofits. As a result, he donated 13 millionreichs marks for social-care purposes.

After the end of WWI it was difficult to regaina foothold in foreign markets. In the UnitedStates, for example, Bosch factories, sales of-fices, and the corporate logo and symbol hadbeen confiscated and sold to an Americancompany. One of the consequences was thatproducts appeared under the “Bosch” brandname that were not truly Bosch-made. Itwould take until the end of the 1920s beforeBosch had reclaimed all of his former rightsand was able to reestablish himself in theUnited States. The Founder’s unyielding de-

termination to overcome any and all obstaclesreturned the company to the markets of theworld and, at the same time, imbued theminds of Bosch employees with the interna-tional significance of Bosch as an enterprise.

A closer look at two specific events may serve to underscore the social engagement of Robert Bosch. In 1936 he donated funds to construct a hospital that was officiallyopened in 1940. In his inaugural speech,Robert Bosch emphasized his personal dedi-cation in terms of social engagement: “Everyjob is important, even the lowliest. Let noman delude himself that his work is moreimportant than that of a colleague.”

With the passing of Robert Bosch in 1942,the world mourned an entrepreneur whowas a pioneer not only in the arena of tech-nology and electrical engineering, but alsoin the realm of social engagement. Until thisday, Robert Bosch stands as an example ofprogressive zeitgeist, of untiring diligence, of social improvements, of entrepreneurialspirit, and as a dedicated champion of edu-cation. His vision of progress culminated inthe words, “Knowledge, ability, and will areimportant, but success only comes fromtheir harmonious interaction.”

In 1964 the Robert Bosch Foundation was inaugurated. Its activities include the pro-motion and support of health care, welfare,education, as well as sponsoring the arts andculture, humanities and social sciences. The Foundation continues to nurture thefounder’s ideals to this day.

History of the Automobile Robert Bosch’s life’s work 7

First offices in London’sStore Street (Photo:Bosch Archives)

“To each his own automobile”Such was the Boschclaim in a 1931 issue ofthe Bosch employeemagazine “Bosch- Zünder” (Bosch Ignitor).

The gasoline or spark-ignition (SI) internal-combustion engine uses the Otto cycle 1)and externally supplied ignition. It burns anair/fuel mixture and in the process convertsthe chemical energy in the fuel into kineticenergy.

For many years, the carburetor was respon-sible for providing an air/fuel mixture in theintake manifold which was then drawn intothe cylinder by the downgoing piston.

The breakthrough of gasoline fuel injec-tion, which permits extremely precise meter-ing of the fuel, was the result of the legisla-tion governing exhaust-gas emission limits.Similar to the carburetor process, with man-ifold fuel injection the air/fuel mixture isformed in the intake manifold.

Even more advantages resulted from the development of gasoline direct injection, inparticular with regard to fuel economy andincreases in power output. Direct injectioninjects the fuel directly into the engine cylin-der at exactly the right instant in time.

Method of operation

The combustion of the air/fuel mixturecauses the piston (Fig. 1, Pos. 8) to performa reciprocating movement in the cylinder (9).The name reciprocating-piston engine, orbetter still reciprocating engine, stems fromthis principle of functioning.

The conrod (10) converts the piston’s re ciprocating movement into a crankshaft(11) rotational movement which is main-tained by a flywheel at the end of the crank-shaft. Crankshaft speed is also referred to asengine speed or engine rpm.

Four-stroke principleToday, the majority of the internal-combus-tion engines used as vehicle power plants areof the four-stroke type. The four-stroke prin-ciple employs gas-exchange valves (5 and 6)to control the exhaust-and-refill cycle. Thesevalves open and close the cylinder’s intakeand exhaust passages, and in the process con-trol the supply of fresh air/fuel mixture andthe forcing out of the burnt exhaust gases.

8 Basics of the gasoline (SI) engine Method of operation

Basics of the gasoline (SI) engine

Fig. 1a Induction strokeb Compression strokec Power (combustion)

stroked Exhaust stroke

1 Exhaust camshaft2 Spark plug3 Intake camshaft4 Injector5 Intake valve6 Exhaust valve7 Combustion

chamber8 Piston9 Cylinder

10 Conrod11 Crankshaft

M Torque α Crankshaft angles Piston strokeVh Piston displacementVc Compression

volume

1) Named after Nikolaus Otto (1832–1891) who presentedthe first gas engine with compression using the 4-strokeprinciple at the Paris World Fair in 1878.

α

M

sVh

Vc

BDC

a1

b c d

TDC

23

4

5

7

8

1011

9

6

Complete working cycle of the 4-stroke spark-ignition (SI) gasoline engine (example shows a manifold-injection engine with separate intake and exhaust camshafts)

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1st stroke: InductionReferred to Top Dead Center (TDC), the pis-ton is moving downwards and increases thevolume of the combustion chamber (7) sothat fresh air (gasoline direct injection) orfresh air/fuel mixture (manifold injection) is drawn into the combustion chamber pastthe opened intake valve (5).

The combustion chamber reaches maxi-mum volume (Vh+Vc) at Bottom Dead Center (BDC).

2nd stroke: CompressionThe gas-exchange valves are closed, and thepiston is moving upwards in the cylinder. Indoing so it reduces the combustion-chambervolume and compresses the air/fuel mixture.On manifold-injection engines the air/fuelmixture has already entered the combustionchamber at the end of the induction stroke.With a direct-injection engine on the otherhand, depending upon the operating mode,the fuel is first injected towards the end of thecompression stroke.

At Top Dead Center (TDC) the combus-tion-chamber volume is at minimum (compression volume Vc).

3rd stroke: Power (or combustion)Before the piston reaches Top Dead Center(TDC), the spark plug (2) initiates the com-bustion of the air/fuel mixture at a given ig nition point (ignition angle). This form of ignition is known as externally supplied ignition. The piston has already passed itsTDC point before the mixture has combustedcompletely.

The gas-exchange valves remain closed andthe combustion heat increases the pressure inthe cylinder to such an extent that the pistonis forced downward.

4th stroke: ExhaustThe exhaust valve (6) opens shortly beforeBottom Dead Center (BDC). The hot (ex-haust) gases are under high pressure andleave the cylinder through the exhaust valve.The remaining exhaust gas is forced out bythe upwards-moving piston.

A new operating cycle starts again with theinduction stroke after every two revolutionsof the crankshaft.

Valve timingThe gas-exchange valves are opened andclosed by the cams on the intake and exhaustcam shafts (3 and 1 respectively). On engines with only 1 camshaft, a levermechanism transfers the cam lift to the gas-exchange valves.

The valve timing defines the opening andclosing times of the gas-exchange valves. Sinceit is referred to the crankshaft pos ition, timingis given in “degrees crankshaft”. Gas flow andgas-column vibration effects are applied to im-prove the filling of the combustion chamberwith air/fuel mixture and to remove the ex-haust gases. This is the reason for the valveopening and closing times overlapping in agiven crankshaft angular-position range.

The camshaft is driven from the crankshaftthrough a toothed belt (or a chain or gear pair).On 4-stroke engines, a complete working cycletakes two rotations of the crankshaft. In otherwords, the camshaft only turns at half crank-shaft speed, so that the step-down ratio be-tween crankshaft and camshaft is 2:1.

Basics of the gasoline (SI) engine Method of operation 9

Fig. 2I Intake valveIO Intake valve

opensIC Intake valve

closesE Exhaust valveEO Exhaust valve

opensEC Exhaust valve

closesTDC Top Dead CenterTDCO Overlap at TDCITDC Ignition at TDCBDC Bottom Dead

CenterIT Ignition point

ITIO

IC

EO

BDC

EI

EC

TDCO

ITDC

com

pres

sion

exhaust

combustion

intak

e

40…60° 45…60°

10…15°0…40° 5…20°

Valve timing diagram for a four-stroke gasoline-engine

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CompressionThe difference between the maximum pistondisplacement Vh and the compression volumeVc is the compression ratio

ε = (Vh + Vc)/Vc.

The engine’s compression ratio is a vital factor in determining � Torque generation� Power generation� Fuel economy and� Emissions of harmful pollutants

The gasoline-engine’s compression ratio εvaries according to design configuration andthe selected form of fuel injection (manifoldor direct injection ε = 7...13). Extreme com-pression ratios of the kind employed in dieselpowerplants (ε = 14...24) are not suitable foruse in gasoline engines. Because the knock re-sistance of the fuel is limited, the extremecompression pressures and the high combus-tion-chamber temperatures resulting fromsuch compression ratios must be avoided inorder to prevent spontaneous and uncon-trolled detonation of the air/fuel mixture. Theresulting knock can damage the engine.

Air/fuel ratioComplete combustion of the air/fuel mixturerelies on a stoichiometric mixture ratio. A

stoichiometric ratio is defined as 14.7 kg ofair for 1 kg of fuel, that is, a 14.7 to 1 mixtureratio.

The air/fuel ratio λ (lambda) indicates theextent to which the instantaneous monitoredair/fuel ratio deviates from the theoreticalideal:

induction air massλ =

theoretical air requirement

The lambda factor for a stoichiometric ratiois λ 1.0. λ is also referred to as the excess-airfactor.

Richer fuel mixtures result in λ figures ofless than 1. Leaning out the fuel producesmixtures with excess air: λ then exceeds 1. Be-yond a certain point the mixture encountersthe lean-burn limit, beyond which ignition isno longer possible. The excess-air factor has adecisive effect on the specific fuel consump-tion (Fig. 3) and untreated pollutant emis-sions (Fig. 4).

Induction-mixture distribution in thecombustion chamber Homogeneous distributionThe induction systems on engines with mani -fold injection distribute a homogeneousair/fuel mixture throughout the combustionchamber. The entire induction charge has asingle excess-air factor λ (Fig. 5a). Lean-burnengines, which operate on excess air under

10 Basics of the gasoline (SI) engine Method of operation

Fig. 3a Rich air/fuel mixture

(air deficiency)b Lean air/fuel mixture

(excess air)

0.8 1.0 1.2

a b

P

be

Pow

er P

,sp

ecifi

c fu

el c

onsu

mpt

ion

be

Excess-air factor λ

Influence of the excess-air factor λ on the power Pand on the specific fuel consumption be under con-ditions of homogeneous air/fuel-mixture distribution

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0.6 1.0 1.4

Rel

ativ

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antit

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of

CO

; H

C;

NO

X

Excess-air factor λ0.8 1.2

COHC NOX

Effect of the excess-air factor λ on the pollutant composition of untreated exhaust gas under condi-tions of homogeneous air/fuel-mixture distribution

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specific operating conditions, also rely on ho-mogeneous mixture distribution.

Stratified-charge conceptA combustible mixture cloud with λ ≈ 1 sur-rounds the tip of the spark plug at the instantignition is triggered. At this point the remain-der of the combustion chamber contains either non-combustible gas with no fuel, or an extremely lean air/fuel charge. The cor-responding strategy, in which the ignitablemixture cloud is present only in one portion ofthe combustion chamber, is the stratified-charge concept (Fig. 5b). With this concept,the overall mixture – meaning the averagemixture ratio within the entire combustionchamber – is extremely lean (up to λ ≈ 10). Thistype of lean operation fosters extremely highlevels of fuel economy.

Efficient implementation of the stratified-charge concept is impossible without directfuel injection, as the entire induction strategydepends on the ability to inject fuel directlyinto the combustion chamber just before ig-nition.

Ignition and flame propagationThe spark plug ignites the air/fuel mixture bydischarging a spark across a gap. The extentto which ignition will result in reliable flamepropagation and secure combustion dependsin large part on the air/fuel mixture λ, whichshould be in a range extending from λ =0.75...1.3. Suitable flow patterns in the areaimmediately adjacent to the spark-plug elec-trodes can be employed to ignite mixtures aslean as λ ≤ 1.7.

The initial ignition event is followed by for-mation of a flame-front. The flame front’spropagation rate rises as a function of com-bustion pressure before dropping off againtoward the end of the combustion process.The mean flame front propagation rate is on the order of 15...25 m/s.

The flame front’s propagation rate is thecombination of mixture transport and com-bustion rates, and one of its defining factors isthe air/fuel ratio λ. The combustion rate peaksat slightly rich mixtures on the order of λ = 0.8...0.9. In this range it is possible to ap-proach the conditions coinciding with an idealconstant-volume combustion process (refer tosection on “Engine efficiency”). Rapid com-bustion rates provide highly satisfactory full-throttle, full-load performance at high enginespeeds.

Good thermodynamic efficiency is produced by the high combustion tempera-tures achieved with air/fuel mixtures of λ = 1.05...1.1. However, high combustiontemperatures and lean mixtures also promotegeneration of nitrous oxides (NOX), whichare subject to strict limitations under officialemissions standards.

Basics of the gasoline (SI) engine Method of operation 11

Fig. 5a Homogeneous

mixture distributionb Stratified charge

a

b

Induction-mixture distribution in the combustionchamber

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Cylinder chargeAn air/fuel mixture is required for the com-bustion process in the cylinder. The enginedraws in air through the intake manifolds(Fig. 1, Pos. 14), the throttle valve (13) ensur-ing that the air quantity is metered. The fuelis metered through fuel injectors. Further-more, usually part of the burnt mixture (exhaust gas) from the last combustion is retained as residual gas (9) in the cylinder orexhaust gas is returned specifically to increasethe residual-gas content in the cylinder (4).

Components of the cylinder chargeThe gas mixture trapped in the combustionchamber when the intake valve closes is re-ferred to as the cylinder charge. This is com-prised of the fresh gas and the residual gas.

The term “relative air charge rac” has beenintroduced in order to have a quantitywhich is independent of the engine’s dis-placement. It describes the air content in the cylinder and is defined as the ratio of the current air quantity in the cylinder tothe air quantity that would be contained inthe engine displacement under standardconditions (p0 = 1013 hPa, T0 =273 K). Ac-cordingly, there is a relative fuel quantity rfq;this is defined in such a way that identicalvalues for rac and rfq result in λ = 1, i.e., λ = rac/rfq, or with specified λ : rfq = rac/λ.

Fresh gasThe freshly introduced gas mixture in thecylinder is comprised of the fresh air drawnin and the fuel entrained with it. In a mani-fold-injection engine, all the fuel has alreadybeen mixed with the fresh air upstream ofthe intake valve. On direct-injection systems,on the other hand, the fuel is injected di-rectly into the combustion chamber.

The majority of the fresh air enters thecylinder with the air-mass flow (Fig. 1, Pos. 6, 7) via the throttle valve (13). Addi-tional fresh gas, comprising fresh air andfuel vapor, is directed to the cylinder via theevaporative-emissions control system (3, 2).

For homogeneous operation at λ � 1, theair in the cylinder directed via the throttlevalve after the intake valve (11) has closed is the decisive quantity for the work at thepiston during the combustion stroke andtherefore for the engine’s output torque. Inthis case, the air charge corresponds to thetorque and the engine load. Here, changingthe throttle-valve angle only indirectly leadsto a change in the air charge. First of all, thepressure in the intake manifold must rise sothat a greater air mass flows into the cylindervia the intake valves. Fuel can, on the otherhand, be injected more contemporaneouslywith the combustion process and meteredprecisely to the individual cylinder. There-fore the injected fuel quantity is dependenton the current air quantity, and the gasolineengine is an air-directed system in “conven-tional” homogeneous mode at λ � 1.

During lean-burn operation (stratifiedcharge), however, the torque (engine load) –on account of the excess air – is a directproduct of the injected fuel mass. The airmass can thus differ for the same torque.The gasoline engine is therefore fuel-di-rected during lean-burn operation.

12 Basics of the gasoline (SI) engine Cylinder charge

Fig. 11 Air and fuel vapor

(from evaporative-emissions controlsystem)

2 Canister-purge valve with variablevalve-opening cross-section

3 Connection to evap-orative-emissionscontrol system

4 Returned exhaustgas

5 Exhaust-Gas Recirculation valve (EGR valve)with variable valve- opening cross-section

6 Air-mass flow (ambient pressure pa)

7 Air-mass flow (manifold pressure pm)

8 Fresh-gas charge(combustion- chamber pressure pc)

9 Residual-gas charge(combustion- chamber pressure pc)

10 Exhaust gas (exhaust-gas back pressure pe)

11 Intake valve12 Exhaust valve13 Throttle valve14 Intake manifold

α Throttle-valve angle

1

6 713

14

108

3

4

11 12

9

5

2

α

Cylinder charge in a gasoline engine1

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Almost always, measures aimed at increasingthe engine’s maximum torque and maxi-mum output power necessitate an increasein the maximum possible fresh-gas charge.This can be achieved by increasing the en-gine displacement but also by supercharging(see section entitled “Supercharging”).

Residual gasThe residual-gas share of the cylinder chargecomprises that portion of the cylinder chargewhich has already taken part in the combus-tion process. In principle, one differentiatesbetween internal and external residual gas.Internal residual gas is the exhaust gas whichremains in the upper clearance volume of thecylinder after combustion or which, whilethe intake and exhaust valves are simultane-ously open (valve overlap, see section entitled“Gas exchange”), is drawn from the exhaustport back into the intake manifold (internalexhaust-gas recirculation).

External residual gas is exhaust gas whichis introduced via an exhaust-gas recircula-tion valve (Fig. 1, Pos. 4, 5) into the intakemanifold (external exhaust-gas recircula-tion).

The residual gas is made up of inert gas 1)and – in the event of excess air, i.e., duringlean-burn operation – of unburnt air. Theamount of inert gas in the residual gas isparticularly important. This no longer con-tains any oxygen and therefore does not par-ticipate in combustion during the followingpower cycle. However, it does delay ignitionand slows down the course of combustion,which results in slightly lower efficiency butalso in lower peak pressures and tempera-tures. In this way, a specifically used amountof residual gas can reduce the emission ofnitrogen oxides (NOX). This then is the benefit of inert gas in lean-burn operationin that the three-way catalytic converter isunable to reduce the nitrogen oxides in theevent of excess air.

In homogeneous engine mode, the fresh-gascharge displaced by the residual gas (consist-ing in this case of inert gas only) is compen-sated by means of a greater opening of thethrottle valve. With a constant fresh-gascharge, this increases the intake-manifoldpressure, therefore reduces the throttlinglosses (see section entitled “Gas exchange”),and in all results in reduced fuel consump-tion.

Gas exchangeThe process of replacing the consumedcylinder charge (exhaust gas, also referred toin the above as residual gas) with fresh gas isknown as gas exchange or the charge cycle. It is controlled by the opening and closing ofthe intake and exhaust valves in combina-tion with the piston stroke. The shape andposition of the camshaft cams determine theprogression of the valve lift and thereby in-fluence the cylinder charge.

The opening and closing times of thevalves are called valve timing and the maxi-mum distance a valve is lifted from its seat isknown as the valve lift or valve stroke. Thecharacteristic variables are Exhaust Opens(EO), Exhaust Closes (EC), Intake Opens(IO), Intake Closes (IC) and the valve lift.There are engines with fixed and others withvariable timing and valve lifts (see chapterentitled “Cylinder-charge control systems”).

The amount of residual gas for the followingpower cycle can be significantly influencedby a valve overlap. During the valve overlap,intake and exhaust valves are simultaneouslyopen for a certain amount of time, i.e., theintake valve opens before the exhaust valvecloses. If in the overlap phase the pressure in the intake manifold is lower than that in the exhaust train, the residual gas flowsback into the intake manifold; because theresidual gas drawn back in this way is drawnin again after Exhaust Closes, this results inan increase in the residual-gas content.

Basics of the gasoline (SI) engine Cylinder charge 13

1) Components in the combustion chamber which behaveinertly, that is, do not participate in the combustion process.

In the case of supercharging, the pressure be-fore the intake valve can also be higher duringthe overlap phase; in this event, the residualgas flows in the direction of the exhaust trainsuch that it is properly cleared away (“scav-enging”) and it is also possible for the air toflow through into the exhaust train.

When the residual gas is successfully scav-enged, its volume is then available for an in-creased fresh-gas charge. The scavenging effectis therefore used to increase torque in thelower speed range (up to approx. 2000rpm),either in combination with dynamic super-charging in naturally aspirated engines orwith turbocharging.

Volumetric efficiency and air consumptionThe success of the gas-exchange process ismeasured in the variables volumetric effi-ciency, air consumption and retention rate.The volumetric efficiency is the ratio of thefresh-gas charge actually remaining in thecylinder to the theoretically maximum possi-ble charge. It differs from the relative aircharge in that the volumetric efficiency is referred to the external conditions at the timeof measurement and not to standard condi-tions.

The air consumption describes the totalair-mass throughput during the gas-exchangeprocess, likewise referred to the theoreticallymaximum possible charge. The air consump-tion can also include the air mass which istransferred directly into the exhaust trainduring the valve overlap. The retention rate,the ratio of volumetric efficiency to air con-sumption, specifies the proportion of the air-mass throughput which remains in the cylin-der at the end of the gas-exchange process.

The maximum volumetric efficiency fornaturally aspirated engines is 0.6...0.9. It de-pends on the combustion-chamber shape, theopened cross-sections of the gas-exchangevalves, and the valve timing.

Pumping lossesWork is expended in the form of pumpinglosses or gas-exchange losses in order to re-place the exhaust gas with fresh gas in thegas-exchange process. These losses use uppart of the mechanical work generated andtherefore reduce the effective efficiency of theengine. In the intake phase, i.e., during thedownward stroke of the piston, the intake-manifold pressure in throttled mode is less than the ambient pressure and in particular the pressure in the piston returnchamber. The piston must work against thispressure differential (throttling losses).

A dynamic pressure occurs in the combus-tion chamber during the upward stroke of the piston when the burnt gas is emitted, particularly at high engine speeds and loads;the piston must expend energy in order toovercome this pressure (push-out losses).

If with gasoline direct injection stratified-charge operation is used with the throttlevalve fully opened or high exhaust-gas recir-culation is used in homogeneous operation(λ � 1), this increases the intake-manifoldpressure and reduces the pressure differentialabove the piston. In this way, the engine’sthrottling losses can be reduced, which inturn improves the effective efficiency.

SuperchargingThe torque which can be achieved during homogenous operation at λ � 1 is propor-tional to the fresh-gas charge. This means thatmaximum torque can be increased by com-pressing the air before it enters the cylinder(supercharging). This leads to an increase involumetric efficiency to values above 1.

Dynamic superchargingSupercharging can be achieved simply by taking advantage of the dynamic effects insidethe intake manifold. The supercharging leveldepends on the intake manifold’s design andon its operating point (for the most part, onengine speed, but also on cylinder charge).The possibility of changing the intake-mani-fold geometry while the engine is running(variable intake-manifold geometry) means

14 Basics of the gasoline (SI) engine Cylinder charge

that dynamic supercharging can be appliedacross a wide operating range to increase themaximum cylinder charge.

Mechanical superchargingThe intake-air density can be further in-creased by compressors which are drivenmechanically from the engine’s crankshaft.The compressed air is forced through the intake manifold and into the engine’s cylinders.

Exhaust-gas turbochargingIn contrast mechanical supercharging, thecompressor of the exhaust-gas turbochargeris driven by an exhaust-gas turbine locatedin the exhaust-gas flow, and not by the en-gine’s crankshaft. This enables recovery ofsome of the energy in the exhaust gas.

Charge recordingIn a gasoline engine with homogeneous λ = 1 operation, the injected fuel quantity is dependent on the air quantity. This is nec-essary because after a change to the throttle-valve angle the air charge changes only grad-ually while the fuel quantity can be variedfrom injection to injection.

For this reason, the current available aircharge must be determined for each com-bustion in the engine-management system(charge recording). There are essentiallythree systems which can be used to recordthe charge:� A hot-film air-mass meter (HFM) mea-

sures the air-mass flow into the intakemanifold.

� A model is used to calculate the air-massflow from the temperature before thethrottle valve, the pressure before and after the throttle valve, and the throttle-valve angle (throttle-valve model, α/n system 1)).

� A model is used to calculate the chargedrawn in by the cylinder from the enginespeed (n), the pressure (p) in the intakemanifold (i.e., before the intake valve), the temperature in the intake passage andfurther additional information (e.g., cam -shaft/valve-lift adjustment, intake-mani-fold changeover, position of the swirl con-trol valve) (p/n system). Sophisticatedmodels may be necessary, depending onthe complexity of the engine, particularlywith regard to the variabilities of the valvegear.

Because only the mass flow passing into theintake manifold can be determined with ahot-film air-mass meter or a throttle-valvemodel, both these systems only provide acylinder-charge value during stationary en-gine operation. Stationary means at constantintake-manifold pressure; because then themass flows flowing into the intake manifoldand off into the engine are identical.

In the event of a sudden load change(change in the throttle-valve angle), the in-flowing mass flow changes spontaneously,while the off-flowing mass flow and with it the cylinder charge only change if the intake-manifold pressure has increased or reduced. The accumulator behavior of the intake manifold must therefore also be imitated (intake-manifold model).

Basics of the gasoline (SI) engine Cylinder charge 15

1) The designation α/n system is historically conditionedsince originally the pressure after the throttle valve wasnot taken into account and the mass flow was stored in a program map covering throttle-valve angle and enginespeed. This simplified approach is sometimes still used today.

Torque and powerTorques at the drivetrainThe power P delivered by a gasoline engineis defined by the available clutch torque Mand the engine speed n. The clutch torque is the torque developed by the combustionprocess less friction torque (friction losses inthe engine), pumping losses, and the torqueneeded to drive the auxiliary equipment(Fig. 1). The drive torque is derived from the clutch torque plus the losses arising atthe clutch and transmission.

The combustion torque is generated inthe power cycle and is determined in en-gines with manifold injection by the follow-ing variables:� The air mass which is available for com-

bustion when the intake valves close� The fuel mass which is available at the

same moment, and� The moment in time when the ignition

spark initiates the combustion of theair/fuel mixture

Direct-injection gasoline engines function at certain operating points with excess air(lean-burn operation). The cylinder thuscontains air, which has no effect on the gen-erated torque. Here, it is the fuel mass whichhas the most effect.

Generation of torque The physical quantity torque M is the pro -duct of force F times lever arm s :

M = F · s

The connecting rod utilizes the throw of the crankshaft to convert the piston’s lineartravel into rotary motion. The force withwhich the expanding air/fuel mixture drivesthe piston down the cylinder is convertedinto torque by the lever arm generated bythe throw.

The lever arm l which is effective for thetorque is the lever component vertical to theforce (Fig. 2). The force and the leverage an-gle are parallel at Top Dead Center (TDC).

16 Basics of the gasoline (SI) engine Torque and power

Fig. 11 Auxiliary equipment

(A/C compressor,alternator, etc.)

2 Engine3 Clutch4 Transmission

Air mass(fresh-gas charge)

Fuel mass

Ignition angle(ignition point)

Gas exchange and friction

Auxiliary equipment

Clutch losses

Transmission losses and ratio

Combustiontorque

Enginetorque

Clutchtorque

Drivetorque

– –– –

Clutch Trans-mission

1 1 2 3 4

Engine

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This results in an effective lever arm of zero.The ignition angle must be selected in such away as to trigger mixture ignition while thecrankshaft is rotating through a phase of in-creasing lever arm (0...90 °crankshaft). Thisenables the engine to generate the maximumpossible torque. The engine’s design (for in-stance, piston displacement, combustion-chamber geometry, volumetric efficiency,charge) determines the maximum possibletorque M that it can generate.

Essentially, the torque is adapted to the requirements of actual driving by adjustingthe quality and quantity of the air/fuel mix-ture and the ignition angle. Fig. 3 shows thetypical torque and power curves, plottedagainst engine speed, for a manifold-injec-tion gasoline engine. As engine speed in-creases, full-load torque initially increases toits maximum Mmax. At higher engine speeds,torque falls off again as the shorter openingtimes of the intake valves limits the cylindercharge.

Engine designers focus on attempting to obtain maximum torque at low enginespeeds of around 2000 rpm. This rpm rangecoincides with optimal fuel economy. Engines with exhaust-gas turbochargers are able to meet these requirements.

Relationship between torque and powerThe engine’s power output P climbs alongwith increasing torque M and enginespeed n. The following applies:

P = 2 · π · M · n

Engine power increases until it reaches itspeak value at rated speed nrat with ratedpower Prat. Owing to the substantial decreasein torque, power generation drops again atextremely high engine speeds.

A transmission to vary conversion ratiosis needed to adapt the gasoline engine’storque and power curves to meet the requirements of vehicle operation.

Basics of the gasoline (SI) engine Torque and power 17

Fig. 2Changing the effectivelever arm during thepower cyclea Increasing lever

arm l1b Decreasing lever

arm l2

Fig. 3Typical curves for a manifold-injection gasoline engine

α

M

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l1l1 l2l2

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Engine speed n nrat

P

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Mmax

Prat

M

Torque and power curves3

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Engine efficiencyThermal efficiencyThe internal-combustion engine does not con-vert all the energy which is chemically availablein the fuel into mechanical work, and some ofthe added energy is lost. This means that an en-gine’s efficiency is less than 100% (Fig. 1).Thermal efficiency is one of the important linksin the engine’s efficiency chain.

Pressure-volume diagram (p-V diagram)The p-V diagram is used to display the pressure and volume conditions during a complete working cycle of the 4-strokeIC engine.

The ideal cycleFigure 2 (curve A) shows the compressionand power strokes of an ideal process as defined by the laws of Boyle/Mariotte andGay- Lussac. The piston travels from BDC to TDC (point 1 to point 2), and the air/fuelmixture is compressed without the additionof heat (Boyle/Mariotte). Subsequently, the mixture burns accompanied by a pressurerise (point 2 to point 3) while volume re-mains constant (Gay-Lussac).

From TDC (point 3), the piston travels to-wards BDC (point 4), and the combustion-chamber volume increases. The pressure ofthe burnt gases drops whereby no heat is released (Boyle/Mariotte). Finally, the burntmixture cools off again with the volume remaining constant (Gay-Lussac) until theinitial status (point 1) is reached again.

The area inside the points 1 – 2 – 3 – 4 showsthe work gained during a complete workingcycle. The exhaust valve opens at point 4 andthe gas, which is still under pressure, escapesfrom the cylinder. If it were possible for thegas to expand completely by the time point 5is reached, the area described by 1 – 4 – 5would represent usable energy. On an ex-haust-gas-turbocharged engine, the partabove the atmospheric line (1 bar) canto some extent be utilized (1 – 4 – 5�).

Real p-V diagramSince it is impossible during normal engineoperation to maintain the basic conditionsfor the ideal cycle, the actual p-V diagram(Fig. 2, curve B) differs from the ideal p-V diagram.

Measures for increasing thermal efficiencyThe thermal efficiency rises along with increasing air/fuel-mixture compression. The higher the compression, the higher thepressure in the cylinder at the end of thecompression phase, and the larger is the en-closed area in the p-V diagram. This area is an indication of the energy generated duringthe combustion process. When selecting the compression ratio, the fuel’s antiknock qualities must be taken into account.

Manifold-injection engines inject the fuelinto the intake manifold onto the closed in-take valve, where it is stored until drawn into the cylinder. During the formation of the air/fuel mixture, the fine fuel droplets vaporize. The energy needed for this process is in the form of heat and is taken from theair and the intake-manifold walls. On direct-injection engines the fuel is injected into the combustion chamber, and the energyneeded for fuel-droplet vaporization is takenfrom the air trapped in the cylinder whichcools off as a result. This means that the compressed air/fuel mixture is at a lower tem-perature than is the case with a manifold-in-jection engine, so that a higher compressionratio can be chosen.

Thermal lossesThe heat generated during combustion heatsup the cylinder walls. Part of this thermal energy is radiated and lost. In the case ofgasoline direct injection, the stratified-chargeair/fuel mixture cloud is surrounded by ajacket of gases which do not participate in thecombustion process. This gas jacket hindersthe transfer of heat to the cylinder walls andtherefore reduces the thermal losses.

18 Basics of the gasoline (SI) engine Engine efficiency

Further losses stem from the incompletecombustion of the fuel which has condensedonto the cylinder walls. Thanks to the insulating effects of the gas jacket, these lossesare reduced in stratified-charge operation.Further thermal losses result from the resid-ual heat of the exhaust gases.

Losses at λ = 1The efficiency of the constant-volume cycleclimbs along with increasing excess-air factor(λ). Due to the reduced flame-propagationvelocity common to lean air/fuel mixtures, atλ > 1.1 combustion is increasingly sluggish, afact which has a negative effect upon the SIengine’s efficiency curve. In the final analysis,efficiency is the highest in the range λ =1.1...1.3. Efficiency is therefore less for a ho-mogeneous air/fuel-mixture formation with λ= 1 than it is for an air/fuel mixture featuringexcess air. When a 3-way catalytic converter isused for emissions control, an air/fuel mix-ture with λ = 1 is ab -solutely imperative for efficient operation.

Pumping lossesDuring the exhaust and refill cycle, the enginedraws in fresh gas during the 1st (induction)stroke. The desired quantity of gas is con-trolled by the throttle-valve opening. A vacuum is generated in the intake manifoldwhich opposes engine operation (throttling losses). Since with a gasoline direct-injection engine the throttle valve iswide open at idle and part load, and thetorque is determined by the injected fuelmass, the pumping losses (throttling losses)are lower.

In the 4th stroke, work is also involved inforcing the remaining exhaust gases out ofthe cylinder.

Frictional lossesThe frictional losses are the total of all thefriction between moving parts in the engineitself and in its auxiliary equipment. For in-stance, due to the piston-ring friction at thecylinder walls, the bearing friction, and thefriction of the alternator drive.

Basics of the gasoline (SI) engine Engine efficiency 19

Fig. 2A Ideal constant-

volume cycleB Real p-V diagram

a Inductionb Compressionc Work (combustion)d Exhaust

IT Ignition pointEO Exhaust valve opens

Cyl

inde

r pr

essu

re p

Volume V

Vc Vh

A

2

3

4

15

B

b

c

EOd 5

a1 bar

IT

Sequence of the motive working process in the p-V diagram

2

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Useful work, drive

Frictional losses, auxiliary equipment

Pumping losses

Losses due to λ =1

Thermal losses in the cylinder, inefficient combustion, and exhaust-gas heat

Thermodynamic losses during the ideal process (thermal efficiency)

13%10%

10%7%

15%

45%

Efficiency chain of an SI engine at λ = 11

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Specific fuel consumptionSpecific fuel consumption be is defined as themass of the fuel (in grams) that the internal-combustion engine requires to perform aspecified amount of work (kW · h, kilowatthours). This parameter thus provides a moreaccurate measure of the energy extractedfrom each unit of fuel than the terms litersper hour, litres per 100 kilo meters or milesper gallon.

Effects of excess-air factorHomogeneous mixture distributionWhen engines operate on homogeneous in-duction mixtures, specific fuel consumptioninitially responds to increases in excess-airfactor λ by falling (Fig. 1). The progressive reductions in the range extending to λ = 1.0 are explained by the incomplete combustion that results when a rich air/fuel mixture burns with inadequate air.

The throttle plate must be opened to widerapertures to obtain a given torque during op-eration in the lean range (λ > 1). The resultingreduction in throttling losses combines with enhanced thermodynamic efficiency to furnish lower rates of specific fuel con-sumption.

As the excess-air factor is increased, the flamefront’s propagation rate falls in the resulting,progressively leaner mixtures. The ignition timing must be further ad-vanced to compensate for the resulting lag in ignition of the combustion mixture.

As the excess-air factor continues to rise,the engine approaches the lean-burn limit,where incomplete combustion takes place(combustion miss). This results in a radicalincrease in fuel consumption. The excess-airfactor that coincides with the lean-burn limitvaries according to engine design.

Stratified-charge conceptEngines featuring direct gasoline injectioncan operate with high excess-air factors intheir stratified-charge mode. The only fuel in the combustion chamber is found in thestratification layer immediately adjacent tothe tip of the spark plug. The excess-air factor within this layer is approximately λ = 1.

The remainder of the combustion chamberis filled with air and inert gases (exhaust-gas recirculation). The large throttle-plateapertures available in this mode lead to a reduction in pumping losses. This combineswith the thermodynamic benefits to provide a substantial reduction in specific fuel con-sumption.

Effects of ignition timingHomogeneous mixture distributionEach point in the cycle corresponds to an optimal phase in the combustion processwith its own defined ignition timing (Fig. 1).Any deviation from this ignition timing will have negative effects on specific fuel consumption.

Stratified-charge conceptThe range of possibilities for varying the igni-tion angle is limited on direct-injection gaso-line engines operating in the stratified-chargemode. Because the ignition spark must be triggered as soon as the mixture cloud reachesthe spark plug, the ideal ignition point is largelydetermined by injection timing.

20 Basics of the gasoline (SI) engine Specific fuel consumption

gkW h

580

500

420

340

Spe

cific

fuel

con

sum

ptio

n αz

20°

30°

40°

50°

0.8 1.0 1.2 1.4

Excess-air factor λ

Effects of excess-air factor λ and ignition timing αzon fuel consumption during operation with homo -geneous mixture distribution

1

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Achieving ideal fuel consumptionDuring operation on homogeneous induc-tion mixtures, gasoline engines must operateon a stoichiometric air/fuel ratio of λ = 1 tocreate an optimal operating environment forthe 3-way catalytic converter. Under theseconditions using the excess-air factor to ma-nipulate specific fuel consumption is not anoption. Instead, the only available recourse is to vary the ignition timing. Defining igni-tion timing always equates with finding thebest compromise between maximum fueleconomy and minimal levels of raw exhaustemissions. Because the catalytic converter’streatment of toxic emissions is very effectiveonce it is hot, the aspects related to fueleconomy are the primary considerationsonce the engine has warmed to normal operating temperature.

Fuel-consumption mapTesting on an engine dynamometer can beused to determine specific fuel consumptionin its relation to brake mean effective pres-sure and to engine speed. The monitoreddata are then entered in the fuel consump-tion map (Fig. 2). The points representinglevels of specific fuel consumption are

joined to form curves. Because the resultinggraphic portrayal resembles a sea shell, thelines are also known as shell or conchoidcurves.

As the diagram indicates, the point ofminimum specific fuel consumption co -incides with a high level of brake mean effective pressure pme at an engine speed of roughly 2600 rpm.

Because the brake mean effective pressurealso serves as an index of torque generationM, curves representing power output P canalso be entered in the chart. Each curve as-sumes the form of a hyperbola. Althoughthe chart indicates identical power at differ-ent engine speeds and torques (operatingpoints A and B), the specific fuel consump-tion rates at these operating points are notthe same. At Point B the engine speed islower and the torque is higher than at Point A. Engine operation can be shifted toward Point A by using the transmission to select a gear with a higher conversion ratio.

Basics of the gasoline (SI) engine Specific fuel consumption 21

Fig. 2Engine data:

4-cylinder gasoline engine

Displacement: VH = 2.3 litres

Power: P = 110kW at 5400rpm

Torque peak: M = 220N · m at 3700...4500rpm

Brake mean effectivepressure:

pme = 12bar (100%)

Calculating torque Mand power P with nu meri cal value equations:

M = VH · pme /0.12566P = M · n / 9549

M in N · mVH in dm3

pme in barn in rpmP in kW

00

20%

40%

60%

80%

100%

500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 rpm

Bra

ke m

ean

effe

ctiv

e pr

essu

re p

me

16%

E

cono

my

adva

ntag

e

Engine speed n

Constant power curve: P=30 kW

105%102%

B

A

100% (best fuel economy)

110%

115%

125%

175%( 1- 1.

05 )

1.25

Fuel-consumption map for gasoline engine with homogeneous induction mixture2

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