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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.
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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.
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CONTENTS
CHAPTER 1FoodForEngines,FoodForThought
CHAPTER 2FuelInjection:ThenandNow
CHAPTER 3BoschIntermittentElectronicFI
CHAPTER 4MotronicEngineManagement
CHAPTER 5TroubleshootingBoschIntermittentElectronicFI
CHAPTER 6BoschContinuousInjection
CHAPTER 7TroubleshootingBoschContinousInjection
CHAPTER 8PerformanceModifications
1
19
37
59
75
85
109
123
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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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