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BOSCHFUEL
INJECTIONSYSTEMS
Forbes Aird
HPBooks
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HPBooks
arepublishedbyTheBerkleyPublishingGroup
A divisionofPenguinPutnamInc.375HudsonStreet
NewYork,NewYork10014
Firstedition:July 2001ISBN: 1-55788-365-3@2001ForbesAird10987654321
ThisbookhasbeencataloguedwiththeLibrary ofCongress
BookdesignandproductionbyMichaelLutfyCoverdesignbyBirdStudios
InteriorillustrationscourtesyofBosch,Inc.andtheauthorasnoted
All rightsreserved.No partof thispublicationmaybereproduced,storedinaretrievalsystem,ortransmittedinanyform,byanymeanselectronic,mechanical,photocopying,recordingorotherwise,withoutthepriorwrittenpermissionof thepublisher.
NOTICE: Theinformationinthisbookistrueandcompletetothebestofourknowledge.All recommendationsonpartsandproceduresaremadewithoutanyguaranteesonthepartof theauthororthepublisher.Authorandpublisherdisclaimall liabilityincurredin connectionwiththeuseof thisinformation.Althoughmanyof theillustrationsin thepagesthatfollowweresuppliedbyBoschandusedwiththeirpermission,thispublicationis a whollyindependentpublicationofHPBooks.
I amgratefultoRobertBoschGmbHin thepersonsofGerhardKopany,for permissionto reproducecopyrightphotosandillustrations,andof WolfgangBoerkel,foranswerstosometechnicalquestions.ThanksarealsoduetoWolfgangHustadtof BoschNorthAmericaandtoBillRoth,forfurthertechnicalinformation.
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A;thOUghgasolinefuelinjection(FI) hasbeenaroundjust aboutaslongastheautomobile'tself, it has always been a mysterioustechnology.Until about1970it wasbothrareandexpensive,restrictedtosomeaircraftapplications,andtoa hand-fullof exotic,highperformancecarsandracers.Productioncars- evenhighperformancesportscars-madedowithcarburetors.
Thirty-plus years later, and as a result of the"electronicsrevolution,"thatsituationhasbeenverynearlyturnedon its head.While carsin manyracingclasseswearcarburetors,virtuallyeveryproductioncarintheworldhasFI! Yetitremainsamysterytomost.
Thisbookis anattemptto de-mystifyfuelinjection.Whileit dealsprincipallywiththevariouselectronicfuelinjection systemsproducedby theRobert Boschcompany,muchof whatis saidin thefollowingpagesalsoappliestoothersystems.
No bookof thissize-indeed,likelynobookof anysize-could fully describetheminorvariationsin FIinstallationsbetweenonevehiclemodelandanother.
Still,it ishopedthatsufficientdetailis providedtobeofbenefitto mechanicsbothamateurandprofessional,whilethegeneralprinciplesdescribedwill beusefulforthoseattemptingperformancetuning,andinformativeforreaderswhosimplyseektounderstandthemystery.
CONTENTS
CHAPTER 1FoodForEngines,FoodForThought
CHAPTER 2FuelInjection:ThenandNow
CHAPTER 3BoschIntermittentElectronicFI
CHAPTER 4MotronicEngineManagement
CHAPTER 5TroubleshootingBoschIntermittentElectronicFI
CHAPTER 6BoschContinuousInjection
CHAPTER 7TroubleshootingBoschContinousInjection
CHAPTER 8PerformanceModifications
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123
If acertainfixedquantityofair-or anyothergas- isconfinedinaclosedcon-tainerandthenheated,thepressureinsidethecontainerwill rise.If oneof thewallsof thecontainerismoveable,theinter-nal pressurewill pushthatwall outwardwithacertainamountof force,accordingtohowmuchheatwasputintothetrappedgas.
That,in a nutshell,is theworkingprinci-pleof allinternalcombustionengines:Eachcylinderis aclosedcontainer,andeachpis-tonrepresentsamoveablewallof thatcon-tainer;theheatis suppliedbytheburningofafuel,usuallygasoline,andthetrappedgasis whatevermixtureof gaseouscompoundsleftoveraftertheburning.
Meanwhile,theothermovingpartsof anenginearethereforoneortheotherofjusttwosupportingfunctions.The"bottomend"convertsthemovementof thepistonsintorotarymotionand,byreturningthemtothetopoftheirstrokes,restorestheclosedcon-tainerstotheiroriginalsize;thevalvegearandeverythingelseatthe"topend"aretheresimplyto providefor theemptyingoutofthe spentgassesandtherefillingof thecylinderswitha freshchargeof burnablemixture.
Thismayallseemveryobvioustoanyonewitheventhemostbasicunderstandingofhow engineswork,butlurkingwithinthesimplefactsoutlinedaboveis a wealthofdetail.Considerthefuel,forexample.Somefuels containmorechemicalenergyperpoundthanothers,andsocanproducemoreheatwhenburned.Evenlimitingthediscus-sionto gasoline,thefactis thatordinarypumpgasolineis a mixtureof hundredsofdifferentflammablecompounds,andeachofthosecompoundshasadifferentpotential
abilityto generateheatwhenburned.Theexactnatureof themixtureof thesecom-
poundsvariesfromonepumptoanotherandfromoneseasontothenext,soapoundofgasolinefromonepumpononedaymightreleasesomewhatmoreor lessheatwhen
burnedthanwoulda poundfromanotherpump,or fromthesamepumpon someotherday.
Whileeachis unique,all thehundredsofcompoundsthatmakeupgasolinehaveonethingin common-theyareall hydrocar-bons.Thatis, theyareallmadeofjusttwokindsof atoms,hydrogen(H) andcarbon(C). The differencebetweenoneof thesehydrocarbonsandanotherliesin eitherthenumberofhydrogenandcarbonatoms,orinthewayin whichthesetwocomponentele-mentsarearranged,orboth.
Now,burningisaprocessofoxidation-acombiningwithoxygen(O)-so, reducedtoits basics,whena hydrocarbonfuel likegasolineburns,individualhydrocarbonmol-eculesfromthegasolinecombinewithindi-vidualmoleculesof oxygenfromtheair.Thehydrogen(H) in thehydrocarboncom-bineswithsomeoftheoxygen(0) intheairto producewater(H2O),whilethecarbon(C) in thehydrocarboncombineswiththerestof theoxygento formcarbondioxide(CO2)'In thisprocess,a largeamountofenergygetsreleased,in theformof heat.Thischemicaldanceamountsbasicallytoareversalof theprocessesthatwentintocre-atingthehydrocarbonsinthefirstplace.Seethebox,"SunlightbytheGallon."
Air, too, is a mixtureof substances,althoughallofthemaregassesatroomtem-perature.About78 percentof our atmos-phereis nitrogen(N);onlyabout21percent
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