Electronically Controlled Gasoline Fuel-Injection System ...

~ BOSCH

Electronically Controlled Gasoline Fuel-Injection System with

Lambda Closed-Loop Control

KE-Jetronic

The things an automobile has to go through ...

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KE-Jetronic

A gasoline injection system must inject precisely the correct amount of fuel for the various operating condi tions. Whereas the increase in engine power was the main object at the start of development work on gasoline injection, today we are spurred on by the necessity to improve the fuel-consumption figures and to reduce the toxic emissions in the exhaust gas to as Iowa level as possible. The purely mechanical systems are not able to fulfi ll these stringent requi rements. For this reason, the well-proven K-Jetro nic was retained as the basic injection system but was uprated to a more intelligent and more efficient system by the addition of electronic ci rcui try. This synthesis, comprising the mechanical basic functions coupled wi th electronic adap­tation and opti mization funct ions, is the

KE-Jetronic.

The spark'lgnltion engine , The 4'$troke principle FueL management Fuel' management syetems

The KE·Jetronic fuel'injection , system System overview. advantages of the j(E·Jel ron ic

B;>sic fun<;:tlons , Fuel supply Fuct rnl)tering

Mixture adaptation " Basic mi , ture adaptation EIec1rOmC control un it (EeU) Electro -hydraulic pressure actuator Cold'start, warm·up. acceleration. fu ll·load. id le

SuppLementary functions " Overrun fuel cut·off Engine·speed l imiting Mi , ture adaptation at high alt itudes

Clean emissions " Cata lytic altert",atment Lambda closed·loop C<lntrol

Electrical circu itry " The front cover shows t~ mi,ture-control un it together ... ,th the air·ll".. sensor. inleg,al fuel distributor. cleclro'hydraulic pressure actualor. and alec\tonic conlrol unit (EeU).

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The Spark-Ignition Engine

The spark-ignition engine, also known as the Otto­cycle engine"), is an engine with externally supplied ignition that converts the energy contained in the fuel into work. In the spark·ignition engine. a fuel·indue­lion system OIJtsidelhe combustion cham­ber forms an ai,·fuel mi,'ure. This mi.ture, drawn in bythepiston'sdownward (intake) stroke. Hows into the combustion cham­ber. During the upward (compression) stroke 01 the piston this mi>1ure is com­pressed. and timed e"mnat ignition froma spark plug initiales i l8 combu8lion. The heal energy released by this combustion increases the com pressed gu's pres­sure, and it is this combustion pressure which delivers the mechanica l work through the piston and the crankshalt when the piston islorced downward again during its combustion (pow",) stroke. AUer each combustion (power) stroke, the piston again reverseS itsdirectionand dur' ing its upward (exhaust) sHoke lorces oot the burr>ed gase •. The 4'5troke cycle has nOw been compteted, and begins again when the piston draws a Iresh charge 01 air·luel mi.ture into the combustion cham· ber during its ne. t downward (intake) stroke. In motor vehicles, the gas cycle takes place predominantly using the 4· stroke cycle described above: one cycle taking place every two reVOlutions 01 the crankshaft.

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The 4-stroke cycle in detail

1 at st roke: intake 2nd Slroke: compression 3rd stroke: combustion (power) 4th st.ch: exhaust Control 01 the gas cyde in a 4'S!foke spark·ignition engine is by means 01 valves whiCh open the intake and exhaust passages in aCCOfdance with the cam­shafl positiot'l.

Intake stroke Intah val ve: open Erhaust valve: closed Piston movement: downward Combustion: none As it moves downwa.d. the piSlon enlarges the cylinder volume and draws in Iresh air·fuel milrture through the open intake valve.

Piston movement upwa.d Combustion: init ial phase (igni1l0n) As it moveS upward. the piston reduces the cylinder volume and comp.esses the ai.·luel mi.ture, The compression 'atio is in the o.der of belween 8:1 and 12: 1 depending upon engine design. The high· er the compression. the htgher the engi. ne's thermal ellic iency and the bette. Ihe fuel is ut ilized. The compression ratio is limited by Iheengir.e·soctane requirement (knocking l imit). Knocking is the irregular, uncont rolled combustion of the ignited mi.w.eaccompanied by a la.ge p.essure increase. Knock leads to engine damage. By means of unifo.m air-fuel mi.tu.e distri ­bution in the cylinder. and utilization of the How effects in the intake passage. as well ss appropriale combusl ion-chamber

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design. the knocking limitcan be shiltedto permit higher ma. imum compression .alios. Just be/ore the piston .eaches TOC. the spark plug igniles the compressed ai.· fuel mixtu.e and initiates Ihe combustion.

Combustlon(powerl stroke Intake ~alve: closed E>haust valve: closed Piston motion: downward Combustion: burn·through phase Aller the spark plug has ignited the com· pressed ai, -fuel mi.ture. the temperature and Ihe p.essure increase rapidly. The pressu.e drives the piston downwa.d. and delivers wo.k to the crankshalt by way 01 the connecting rod. Thiswork is available as angiM power output. Power inc.eases along with increasing engine speed, and for this ruson it is necessary 10 usea gea.· box 10 efficiently malch the engine speed to Ihe vehicle speed,

Exhaust s troke Intake ~alye: closed E>haust valve: open Piston motion: upward Combustion: none Moving upward. Ihe piston forces out the burned (exhaust) gaseslhrough the open ",,!\aust valve . After Ih is fourth stroke, the cycle starts again. In practice, the valves' opening times overlap somewhat in order 10 utilize gas flow and hydrodynamic pul· salionslor bettf)fcharging and purging of the cylinde.,

' ) Named afte. Nikolaus Augusl Otto, t 832·1891. Otto showed the lirst gas engine with compression operating according 10 the 4 ·stroke princip1e at the 1878 Paris World's Fair_

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Fuel management

Air·fu e l mixture I.hL-§Rid'Jg!.!ilil!!l.....ngine requires s JPocific air·luel ratio for its olleration. The tbeorelical air·luel ratio;, 14 7·t Co",!.,. lion of Ihe aiduef ratio is required for lhe ~R!!Ul!!!g cpnd·tions.

The specific fuel consumption 01 a spark· ignition engine IS dependent princIpally u~n theair·fuel ratio. Theoretically. fortull combustion and Iberefore mInimum fuel consumption. Ihe greatesl poss,ble amounl of e.cns air would be desirable: but fo, ,easons 01 liammabihly and Ihe limite<:! lime available for combustion. this is not possible. Fo,contem~raryengines, ma. imum luel economy occurs al an air· fuel .atioolapp,o.imately 15 ... 18 kgairto 1 kg luel. In other words, some 10,000 lit .. ,s of air are neces8arylo. Ihecombus' lion 01 1 lite, of fuel. The chemical mini· mum for complete combustion is I"rmoo Ihe Slo,ch,omelric rati", and '5 14.7:1. Because ""hicle engines are ope.aled mOSI of the lime at pan load. tbey are designed 10. maximum fuel economy in Ibis range. For Iheother operating condi· lions. such as idle and full load, mi.lu.es are called lor Ihat a,e ,icher in luel. The !uel·managemenl sySlem must be able 10 meet Ihese varying requirements.

Air ratio To ind icate how la, the aClual air·luel raho deviates from Ihe theo,elica l (14.7:1). Ihe ai, ralio, denoted by the Greek lener ), (lambda) has been chosen:

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theoret'cal a" requ"ement

).K 1 Theaclual inducled aor quanlity equals Ihe theoretical air l'<K1ui.emenl.

;'<1 Shortage 01 aor, or mixture 100 riCh. inc'casoo power at ~ . 0.85 ... 0 .95.

,,, Excess air, a. lean minure at I. .. 1 .05 ... 1.3. reduced fuel consumption and ,e<:!uced powe,.

~> 1.3 The mixtu.e will r>O longe. ignite, the mis· I"e limit has been e.eceded.

I. " 0.95 ... 0.65 Spark·ignitionengines develop the" rna';' mum power al 5 ... 15% ai, shortage.

), .. 1.1. .. 1.2 Ma.imum luel eCOr>Omy ocCurS at about 20% e.cess air.

A appro •. 1.0 Perleel ,die ope<ation at sioichiometric ratio.

i. " 0 .85 ... 0.75 Good Iransilionsal15 ... 25%airshorlage. 'Transition" is defined as Ihe change I,om agi.en load range 108nothe,. For instance, from idle to part a. !ullioad. Good t,an , i· lion is usually synonymous with good acceleration. The illustral>ons show the dependenceo! power. specific !uel consumption. and pol. lutants emission on the air ,alio. As can be seen. the.e is no single optimum air 'alioa! which all factors are ideal .

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Fuel-Management Systems

~g~.iW!li.whethgrolthe Cilrburetor or lueHn~~~ tu!Lo!..~g..J.!lt..Mlt:possibl o ai .. lue! mi.lure lor the panjcular o~g cond'liRIIs of th!tengiM.

ThecBrburetorottha luel·injectionsystem prepareS the air-fuel mi. ture lor t~e spark· ign ition engine. During Ihe lasl lew years, Ihe Irend has become st[('"gar towards manifold lue(.injection. T~,s !tend '5 sup­ported by the advantages oHerod by l uel injection in connection witll the demands lor economy. efliciency, excelfent drive' abil ity. and low-pollution ,.~aust gas. ThereaSons lorthesaadvantages fiein the fact thai manifold injection p<l'tmits exlre· mely precise metering ol the fuet as a fac· tor ol the operating and loading condit ions of the engine. white at the same time tak· ing environmental condid .. fations into account. In the process, Ille composition of the mixture is contrclle<! so precisely Ihat the pollulant level in the "haust gas remainSlaw.Fu rlhermore. theallocation 01 an injectian va lve la each cylinder results rn rmprave<! d,stribution al the mi.ture. Since the carburetor can be dispense<! with. this means that the induction paths Can be designe<! to achieve the best·pos· sible charging 01 the cylinder with air-IYel mixture. This leads toa higher torque.

Mechanlcalluel-lnjecllon system s The K-Jetronic is today the most wide· s!,read mechanical fuel-injection system. It requires 0(1 drive, sod injects the l uel continuously. The K·Jetfonic .yslem is described in delail in Ihe hooklel "K-Jelronic" in the BoSch Technical Instruction ser ies.

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Combi ned mechanlcal ·e lectron lc lueHnjectio n system The basic mechanical system from Ihe K-Jetronic serves as tho basis lOt Iha KE· Jelronic. Due 10 the "'tended process­ing of operational daiS, electronically controHed au.il iary functions w<)re inoo.· porated 10 adapt Ihe injected luel quantity ta Iha various eng ine opera~ng condi· tions.

Electronic luel·ln jectlo n systems The L· Jetronic aod ilS variants are electro· nically controlled fuel ·injection systems Solenoid'operSle<! inject ian val vas meter the luel intermittently to the intake ports. The system is described in t~ booklet "L'Jetronic' in Iha Bosch Technical InstruClion series.

Combined Ign it ion system and luel ­Injection system " Molfo nlc" Gaspjir;e injection systems can only pro· vide the answers to someoithe prob lems. In o.der to improve Ihe O."all combustion process. Ihe ignition point must also be adapted to the engine aperating condi· tions. The Motfaniccamb ines the ignition system and the luef.injection system. bOlh 01 whicharecontrol le<! bya si"glecomput­er in accordance with common optimi~a' tion cri teria. For mOre details. refer to the booklet "Motronic' in Ihe Bosch Technical Instruction series.

Advant ages o l luel lnjeclion • Increase<!luel economy Wit~ a carburetor. or carburetors. Ihe ai .­luel mi>ture5 arriving at the individual cyfinders are dillerent due to the air-fuel separation which OCCurS in the re.pective intake passages. By forming a mixture lhat provides even the most unfavorably local­ed cylinder wit~ sufficient fuel. the typical carburetor meters too much fuel overall. Aparl from this, during tead changes a film olluel is deposited on the intake-passage walls which is subsequent ly vaporiled again. This leads 10 furl her unwanted

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variations in lhe mi.ture. arriv,ng al t~e cylinders. and I~ resull ,s e.cessive fuel consumpt,on aod uneven cyfinder load· ing. On the other hand. both the K- and L·Jetron'c systems allocate an individual injection valve to each cylinder. These valves are cenlrally cont.olled. and this enSures that all cyhnde.s are provided wilh the same. precisely Controfle<! lue! quantity at all times and under all condi· tions. Nomoresnd no less than is absolu· tely necessary.

• Highe, power autpul Jetronic fue!·injectionsystems permitoplo' mum ,ntake'passage design, and by virtue 01 the improved cylinde, fi lling this p.o· vides higher lorque. Theoverall resu ltnre hig~er specilic power output and a torque curve which betler satisfies practical driv· ing r~u""ments.

• Immediate throWe response Jatronic syslems respond 10 chang ing load cond,Ioons virtually without any lag at all. because the injection va l.es inject the fuel directly at Iha engine's intat<e valves.

• Improved cold slat! and warm·up Due to Ihe prec ise melering of the luel in accordance with the engine temperalure and tha crankir>g speed. starling times arc short and the run-up to idle speed presents no problems. Du~ng warm·up. the precise adaptat ionol the injecte<!luef quantity re.ulls in smoolh running and imme<!iate throllla response along with minimum fuel consumption .

• Low e.haust emissions The poflutant concenlrations in Ihe exhaust gas are directly relaled to the air­luel .aloO. II one wants 10 operate the et1gine at tha minimum emissions point. the luel-managemenl systom muSI be cap· able of "aclly mainlaining the co"o, sponding air·luel ,oti(l. The K· sod I.·Jetronic systems are SO accurate that they provide the predsion of mi!1ur" con· trol whiCh is necessary ta comply with the particular emission regulations.

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The KE-Jetronic gasoline injection system

System overview

A mechanical I>ydfauhc '''teehon s,stem p.ew,d.,.,II<! ba", lot the KE·JetronH; the same as 11 dOGe lor I"e K·Jetron,c (see Ihe publication "K·Jetton,c· ftom the Bosch Technical In.lfuCloon ... ,ies). The Siream of ." df. wn ; n by t he eng. ne de/lee!o a """. so. plate, which ,n lu,n controls Ihe luel­meu"'''11 plung .... DependIng upon ns POSitIon. Ih,. plur.g8f open. Or closes Ihe ,,,e1-me, .. ,"9 IIIIL The ba"e function 01 the KE"-Jelronoc ,'10 rnelG'tlhe fuel 10 Ihe ""!I,ne dependent upon thequanh'y oIai, d.awn in by lhe eng,ne!th" ma,n acluar'ng vanable). aul in COflI.Ulto tho K-Jet • ., .. "c. the KE·jet'oroc 11110 uke$ • number of add,tlONI .no"" """"'''ng data intO account by mN'" 01 "nSOts. TI\e OUlpyt .. 9""'1 from the, .. .ensor. are proceSleod by an elOCiron,,; con1tol uM (ECU) which eo<>I,oI1 an ellICtr<>hyd.auhc p'elIsure acluato. whICh adapts th. ,nj<!(:led luel quantity to the .arious operating condit"'ns. tn ... "" of matiunction. Ihe KE·Jm,onic OIler.tM solely w,th lhe buic function. and Ihe d ..... Ihen has a system al ru. d"llOsal wh,ch pro.,des good limp·home ... pab,h" .. wh .. n the ongine i. warm.

Advantages of the KE-Jetro nic l owor luef..::onlumpUon With convont,OtIIIlluer'malll!}etnenl sys, lem'. the dill'rencel ,n the lengths 01 th. ,ntate. pori. rllult ,n d,lI .. enl air·I"e! m,,' IU<1l' II the ind,.id"al cylioderS. With the KE·JO I,on,e. each eyhoder ,s allocaled itt own I ueH nlo<:lIon valve wh,eh ,njects con· t,nuilly onla the intake .al.o. The in!"Cted fuel •• pari.e. Ind mi". inlensively wilh the.or drawn in by the P'SIOn. Ttr;s mean. tllal inadditionta the p,ec,aemelering. the l"eI 'I ,.onlyd,,,,,b .. ,ed belween Ille ,od,· vldu.1 eng,ne c)'hnd ..... Be'ng as Ihe .nlak, man, fold. anly "",ve 10 ca,f}' the ,ntaMl .. r 10 Ihe c yhnd .. , .. the condensa' toon of the luel on the ma n, fold walls. a ph,· ..-.enon ,n eClr'-'1oona1 systems whrch ",c.o._ the fuel cont"mpllOn. is pn .. :t'· ... It)' ruled CIUI. The KE·Jetronrc systom ent""a thalcon"derablyless lueI" uled fNirtrcularty du,,"11 the w .. m·up phase. du,,"11 ..,cel .... I'on enrrchment. at lull' load. and dunng Overrun wilen ,I swilcheS

Rapi d a d . pt. llo n to o p e ra Unli co ndi lions The fuel reC!urrement dilfcrlgreally from Ihe normal t.gu"tI during lhe poststan per,od. dunng warm·up. and during acce. le,at,Oll and lull·load. By means 01 com· mand. recer~ from ,ta EeU.lhe KE·Jelrc­nie into,ven" in Ihe proparalion oltho air· f"el m .. t"re and increases or decreas" th .. in)GCted IU'GI quant,ty aru;ordingly. The KE·Jelronoc: syslem incorpooates addil>Or'lal ""nlOfl for the 'eg,strat,on of the ""g''''' tempet'''"re. the throWe· ... I.e posrtron (load IIgMI). and tM sensor·plale dellec· t,on (QO".,.ponds .ppro~tely 10 the cha""e ,n eng,ne poweo- 0'ttI, t,mel. Wilh tho ard 01 theM .. _ .. II>e ECU com· mand. the hydrl"hc pressur .. actuator 10 eo I her "lean'OW the mi"ure or "richen' i In approprial ... The KE·Jetronic re&ponds rap,dly 10 I'" ".""'0'" ,n eng"'o ope,at· ing cond lt'o .... and ,mp'o.es lhe torq"e che,aCler,IIic •• 1 well as Iho ong,ne lie .. · b,lrty, Th,. r'Su lll in d,'hnC I advantages whan d" v, ngalene 'IIY ·al I,c,ont lowengi na speeds snd in II high. gear as pOssible. aod al.., in an improvement 01 driv...,bihty. Rehablo atlning i. l nother 01 Ihe out· ltaod,,,,, festu," 01 the KE·Jetronic . The overrun lue! cUI'01l respOnds to eng,ne Sf!"fId and tempet'ature and cull off I'" supply ol luel du"ng decelerahOt\. Ther. ere 1'10 unpleasent Jflfk. when lhe luellJUpp!ycull back inagain. TIII.system resulta ,n I redUCt'on 01 the luel consump' tion and. ber"" ,. combu,!ion cea .... dun"" IU'GI cUI'OlI. there 's no em,saron OilOlrc , . ha,," ga. ..... Cle'ner • • h.u.' illS .. The pre, 'C!u i.n .. lor m' n,m um pOllutants ,n the Glhault g .. i, the prael,eally complele combustion 01 tho luel. The KE')etfonic ,upplios o.ch c yli nder with precisely th~1 amounl of luel wh,ch ,s appropriate lot the particul.r onq'no ope,a""" cond,l,on and lot chlnges ,n Ioad'ng. For ,nstance, the 'eqUl(ed a,,·luel m"lure is pre<:!sely main· t.Ilned II the l""eI nGCfIs"f)' lot m,n,mum IOI 'C em, .. rona by reduQng the post·start ennd'lment a. lOon .. possible. or by the flpid r"pon" 01 the accelorltion en· "ehment. Further ,mpr-o..eme<>ls ,n the exhauSl g •• can I)., ..,1rieYed by employ,,,,, the Lambda clo .... Hoop conlrol together wilh o. hautl?, .llertrealmenl "si"" • catalytrc convert ....

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Hig her pO we r o ulp ul pe, Uter The elhc_tlr dearllned ,,,,ntako Irslem 01 the KE·Jlltro..,c permits an ,ncreas. in power due 10 improved cyhndor chargo. The fuel·,nJecHon palhs .. e shofler, wilh the ' •• ulllh.1 thero Ire no Ital spot. when acceleration il needed. Simila, to allt h. Olher Jetron,e . ytlom •. Iho KE'JOlron,c Ich,e.o. I p,onounced oncreasod ,n eng,n, pO_r lor tho sam .. piSlon displa· cement. but noIlt the COlrt 01 ,ncrea.ed lue! con,umpt'on. It allows economical eng,rreslObedel'gned whichlesl"r, hogh pow"''OUlpUI per lot ..... whole al the sama hme d,.pl,Y''''' 900d 1I000ibility c:oupled wuh e l ettllent dri....triluy.

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Basic functions

Fuel supply

~yslem conl!istsol an elocl'~ fuel Rump, luel accumulator. luel f,l te,. and p..d: .!!!.W'~~1!!!!2! The KE·Jetfonic fuel system dillers only sllghlly from that 0/ the lammar K·Jelronic. An ele<;tricrolle,·C(!1I pump feeds fuel from the lank to the pressure accumulator at a p,essu,e of 5.4 ba" and from Ihere through Ihe fuel filler lothefuel disuibulO' (in &Ome cases. Ihe pressu,e is e.en high· er, e.g. 5.5 ... 6.5 bar~. The primary'pres'

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Sure regulalo, mainta ins the supply pres· :::;:;;.:=.::=.::;;; ; ;;::=.:===:::; SLlre in Ihe system conslant. Md returns Ihe surplus luel to the lan"- Due to the I rl O~er. ri"" "'TOIre,~.rI,,~mp conslant flow of fuel through the fuel· I S""r"'" ,.<Ie. 2 Raror pJ. , • . 3 R<>il. ,. supply system, cool fuel is always avail· ' Raile< ,. cop/.ro,s PI ... u,. , .<Ie. able. This pre.ents the formation of vapor bubb les and enSures good hol'slarling properties.

Electric fuel pump The eleel ris: fuel RlI!!!P dr a we I be lu@l!Wtof the tank and deliyers il to Ihe II!!!I dr . uibu·

"" TIliI fuel pump ilself is an electrrcally driv' en roll.,r,<;ell pump. It is self-priming. and is filled inacommon housing logetherwith the permanent·magnet eleclric molor (Fig. 101. The malar is cooled by the luel which permanenlly suft""nds it and the pump. The luel pump always delivers more luel Ihan Ihe engone needs. so 1P'>a1 Ihere is always sufficienl pressure in Ihe fuel sys­lem under all conditions. The roller'cell pump itself consisls 01 a hollow cylindrical chamber in which the

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eccentric rOlor plate rolale .. The rollers , ____________ '--_--.J ride in grooves localed ar""nd Ihe rotor's perip~ry. and the cenlrrlugallorce resull­ir;g from rotation lorces Ihem outwards so Iha! Ihey lunction as seal$. The pumping action lakes place whan Ihe rollers. afte, having closed the inlel bore. force Ihe Irapped fuel around in Irani of Ihem unlil it canescapelrom thepumpthrOlJghlheout· lei bore(Fig. II). A non·relurn .alve inlhe pump{Fig. 10) pre.ents luef from flowing back to the tank. as wefl as deoouphng Ihe ILlef system I,pm the tank.

Fuel iIi ! ,

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The filler is installed in tha luef line downstream of the luel aecumula!", (Fig. 9). When the fi lter IS changed, it is ;mp.erati.e Ihal the throughllow dire<;tion as indicated by thit arrow on the housing is complied with.

Fuel accumul,tor The luel accumulalor maintains the p.rH; au" in !he fuel syslem lor a cerlain lime aile! the en{liM bas bAAn I wilchedoff Aher switch-(lff, the luel accumulator maintains the P'O$sure in the I"el system in order to lacolaale reSlarttng. particularly when Iha engine is hal. The design of the accumulator housing i. such thaI il dead· enS Ihe sound 01 the fuel pump when the engrne is runn'ng. The inlerior 01 the fuel accumuialor ,8 d ivided inlO two chambers by means 01 a diaphragm. One chamber Serves as Ihe accumulator for the luel. while the olher represenlS the compensa· tion volume and is connected 10 thealmos· phere. by meanS 01 a vent litting. eilher direclly Or th rough IhefueHank vent,lation sySlem. Du,ingoperatron.lhe accumulalor chamber is filled wilh fuel and the dia­ph'sgm iscaused tobend back againSllhe lorce 01 the .pring unlil il is hailed by Ihe SlopS in the spring Chamber. The dra· phragm remains ,n this pos,tion. which corresponds to the ma.imum accumulator volume. as long as Ihe engine is running. The fuel pump starts 10 pump as soon a$ the rgnllion/start swilCh iSlurned. and con · I,"ues 10 run when the e"gine starts. A

'J) F"el occu",u'. '", a: empty, b: ,,,~ I Spl,n9 ohamber. 2 S"""9. 3 SI"" • D"'phf09 .... 5 AccumU'OKl' """me, 6 F"~ ,.,.' OT ". " ... 7 Conn""" .. " '" , ... ,,,,,,.,,t>e,,,,

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salely circua prevents pumping when the Ignrtron is on and Ihe engine stalionary.fo, e.ample alter an accident. The pump is mounled in the immediale vicinily 01 Ihe fuel lank and is maintenance·lree.

P / imarY'pressure . eg ulato. IhU!ti!!!a.ry,~gulat(}( mainlains .!!1i..ll!PIU1-I>rQssyrt CQnstant. In contrasl to Ihe K·Jelronic. in which a warm·up regu lalor regulales the conlrol pressure, Ihe hydraul ic counle,pressure actrng upon Iha conlrol plunger in theKE· J"'ronic (see Page 11). is identical to the primary pressu,e. The control pressure mUll be held conSlant. even when fuel delivery hom Ihe 5upply pump. and injecl· ed fuel quantily, varyconsiderabl~. Thi, is due 10 the laCllhat any varial'on of the con­Irol pressure has a direct eflecl upon the arr·fuel ratio. Fig. 14 shows a sectionlhroughlhlt p,es · sure regulator. The fuel enlers on lhe left. and on Ihe right is the relurn fuel connec· lion from the luel diSlribulor. The return line to the tank is connected at Ihe lOp. Wh en the fuel pump slarls. il generates p,essure and Ihis lorees Ihe control dia· phragm 01 t~ pressure accumulalor

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F"" 01 011. '" ".. .. "'" dtopo 1_ ,10._ """'''1)''''''''''' /0 ""Ioe .""'"9 ",",,",, •• 1M ".. .... ,' '-11«10 ",I (2). /( ,,,.,. d" .. '" '5"'''' du, '" rho _ , <IIlho /utl """"_ . ' 01, Ie ,. • • " .. ( ! / wh",h .. I/;n _ ". ,,,., '"10<"0"-" '" _"'9 pr."ufe (4 / .

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-dowt'lward. T~ prusure ot lhe coun· 'G.sp"ng IOreet Ih, oal., body to follow Ihe dIaphragm unlil. after a very sho.' dis­tance. il comes up .gains! ~ alop and I~ pressure-controllunction s lat's. Theluef relurn,"V from ,he fuel distribulor. com­priling IIIe luel llow'''II1h'OUllh the pru­a .. ro a<;luato, pi ... Ihe contrOl-plunger leakage , ell .. now flow back through lhe open v.1~(I teat 10 the u.nk togelhe< ..,th the e.ceu fuel. When lhe engine •• SWItChed ott, ' .... lueI pump .Iso.'ops and the S).' &m prell .... dropa.Asaresul\.lhe ... 1 .... pill' __ back up agaIn and .ub-8equenlly pushes the .al .... body upward &gaon" Ill. lore. oftl\e c;ounlerspring unl,1 the teal clo ... the ,,,'urn to the tan k. The p.enuflln the .y.tem then .inh rapidly to betow the injectiOl1'vat"" opening pres· su.e WIth the ... ult thet the valves then clo..,. The , ystem pressu.a then in· C •• II .. 1IIIIn to Ihe value dete.mined by the luel accumu laIO'.

'li $pr., p.".mo II'om • /(['JO'"","" f1J.r-ln;'.,im ...... wi'h '/"'M>u6i~, (Ia_J . r06 wi'hOlt' (.bo..,). 7110 IN, h ..... or,...,..M .~, oM ",omit .. Ih. ' • • 1 ..... b.,,,, (la_I.

The inJeCtIOn ",I""s 'flJeCt ,he 1 ... 1 allocat· ed by the Iutl d,.t.ibutor into the intake portt di_'~ in l'OI1t of the cylinder intaka vI I""s. The InjeCtIon valves are secu.ed In a .pee"'l holder In order to insulate them f.om the engIne he.t. This insulatIon p.e· venlf vapor bubbl .. lo,mlng in the lue!· injectIon lines whIch would lead to poor 51arlinll behaviour when the engine i. hoI. The iniectlon valv .. have nO melering function. They open 01 the" own ac<:o<d when the opening pressu.e of. 10' in· stance, :l.!S beri.exceeded. Thayare li tted wIth • • , 've t>eedle whIch vib.ates ("chat· t ... s") audIbly" hillh Irequency when fuel " be,,,,, InjeCted. Th" results In e<cellen\ It>eI atomIzation. oven WIth the 5II1allest of ,nj4ICl&!! quantltl'" When the engIne Ie

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Iw,tched on. Ihe injection valves ciou IIghlly as loon .. the fuel'sys tem pres su,. drOPI below thell opening pressu.a. Tlti, moans thaI no more luel CIIn enter Ihe Inlake PO'" once the engiflil has boon SWItched ofl.

Air-sh ro uded luel·lnjectlon valves ",,·sh.ouded injection valves imp.O"ffl the ml .. tu,. pt~,.tiOl1 panlCUl.,~ at idle (Fig. 16). The ai,·,IIfoudlng p.inciple,. baud upon tlte lact thaI a pon"", ol lhe ai. d,awn in by the engIne enters tllfough the I ..... ·injection val_ (Fog. 18) WIth tlte 'Hull that the lue! II HPe¢I,111 well atom· ized It the POInt of e.'1. Ai, sh.ouding il pan,eul.,ly ,nee!Iv, when combined with the thin. contInuously """rali "9 K· Jel.onic val""" and ,ea~II' in .. ,educ lion ollue! consumptIon and .. lowe. leval of to.ic emiSSIon , .

Fuel metering

8 .. ic11l1, luel metering ta~" pllce through the air-flow sen_ and the fuel distributor, In a number 01 operating model how_, the amount 01 luel .equi.ed d\IYiates g, .. tly from lhe "st.n· dlld" qUllltity. and it become, .....ellary 10 ,nl_ne in the fuel·management 'y" tem. Such """nu ..... a.e deah WIth .n the ChlrptC1 on ""'i<lu.e ad,pl.at.on".

, air quafllity _. II the ..... in Klua"ng Ylriable for deletmining lhe ba· tic i"fICtion q......,tity. " ., \he ,pp<opnate phyaical qUlntity 10/ deriving the luel requ. remenl, Ind ctranget in lhe i ndur;tion chlr.acto.iltic, 01 the engi ... h •• e no effect upon Ihe formation of the . i.·fuel mixture, Since the air drawn in by the eng in. m uti pass Ih'''''g h the ai.·flow 8en· _ befo'l il reaches Ihe engine, th •• ...... n. th.ll il h.I, been measured and the conl.oI,.gl\lll generaled before il aClual.,. lmar.lhe engine cylinder • . The ~Iull i. 1h.l1 .n tddition to othC1 meUures <ie,' c .ibed below, the correcl ".;.1"'1 adapl.a· I.on take, pl_ at all limn. The ai.·flow . enso. i. ioealed upstream of lhe Ih.ottle .llve lO Ihal it measurn all the air which ente •• Iheengine cytinder • . II comprises an Ii. funnel in which Ihe len'or flap (. uspended body) i8 free to pivot. Tho .ir flowing through the funnel deflects lhe . en..,.. plale by a given amount oul of .IS .. ro poaitron. and this mo.emenl II tranl' milled by. 1\lYe< s)'$lem 10 a conltol plun· gC1 which det .... mine. lhe ba.i<: injactlOf\ quanlil)' .equired fOllhe basic func:t.on .. Cotr, iderable "",S8u~ ,hocks can OCCUr in the .ntake 1)<Slem if backlirrng takes place in the intake manifOld. For this

reason, Ihe air-flow len_ i, so designed that the senlO' pl.tecan awing back in the opposite direct.on in caS(! of misfire, and pa st its ••• o pos; tion to open a relief c.oss· section in Ih, funnel. In tho case ollhe down-Orslt .;.·flow senso •• an e<lension spring compenNtel 1001he _ight of the IIInIOr 1'111. and lhe lever mechanism. An adjusUlble INf Ipri~ i, filled 10 a"", .. the correct .ero position in the switched' off phase.

Fuel dl'lrlbutot

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close, the slits 10 a gruler or lesse. d&g'H, The fuel Itows through the open section of th""e slill to Ihe diffe.ential· p.ellu,e valves snd Ihen 10 tho fuel·injec· t.on valves. If lensor'pl"tetravel •• only very ,m.II, lhe cont.oI plunger is only lilted . ,ightly and. "' result. only a alflllil .a<:tion of the ,lit, i, opened fOlthe porssag.e of ,,,,,I. On the other h1rn.d, with. 1"{Ie< plunge' I •• vel, t"­plunger opens a larget sect ..... of the Ilill .nd mote 1",,1 can flow. The .. il' linear "llIionlhip between sen_·plate t,.vel Ind lhe llit laction in tIM barrel which is oponod for fuel flow. A hyd,aulio fo.ce is applied 10 thl cont.ol plunger, Illd acts in opposition 10 lhe movement ... sulting Irom tl're sen"""plate deflection. A constant lir·fuel preuu.e drop at the sensor pille il tl're r •• utl, ,nd th.. SRiurel lhat tho control plunger alwaya followa the movement of the sen· _·pI.te I ....... In some version ... a pree' lur •• pring is used to ."ill this hyd.,utic

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force (F'g. 21 ).U prevents Ihecontrol plun· ger Irom beIng drawn up due to vacuum elfecls when the sySlem cools down. I I IS imperative Ih al Ihe primary pressure , 8 accurately controlled. otherwise varia· lions would have a direct effect upon the air·fuel ratio (i.·value). A damping thronle (Fig. 21) serves to dampen ","cillations that could be caused by sensor·plate forces. When Ihe MgiM is switched ofl. the control plunger sinks until it comes to resl againsl an axial seal ring (Fig. 24). This ,s secured by an adju8tabl,ucrew and ClIn be set to the COllect helght to enSure that the metering slils are closed correctly by the plunger when it is in its zero poSilion. Whereas with theK·Jellonic.lhezero posi. tionol Iheplunger i8 determined byitabut· ti ng agai nSI t he sensor· plale lever. with Ihe KE·Jetronic the plunger rests upon Ihe .... ial seal ring due 10 Ihe force applied to il by Ihe residual primary pressure. This measure serves 10 prevent pressure loss due 10 leakage past the control plunger.

~') F •• I d;$lri&""" w;rh "m',.Au.,· p~ ... re •• ,.. ... , F.eI''''eI (p,,,,,,,,, P"''''''.). 2 Uppo' c.ombo' 0' d.lI.ron".,·p""." •• "'0. 3 L.n. '0' •• Ioel·'"i«' "'" ' ."" • • C."'roi ",."geT. S COni"" edg. ond '''''''''"9 .M. 6 V .. ,... 'P''"9. 1 v. ".. tJ;~ .. g"'. 11 Low., c"""'~' • 1 ""_"".p, ... "," •• ". •. 9 A ... ,_

""9. '0 ""' .. ute "".09. " F""II",,,, , ... oI«lro·hyd' ."'''' "", .. "~ oo'u.'.,. ,2 ThroW'"9 "'''''0''''''. 13 Re'"," ,;"..

u) P"<>CIpie Df ,h • • it·R_ ,CA."'. o. S",. II .""",", 01 ." dr."", In, .,n"" pl. 'e """.,.~od '~9"'r. I>: Lo' ge ''''''''0' 0/." d, . .. " ,no M"_ p"',e,. /JrerJ con.Id".0I1 I",,~,.

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and thus prevenlS the fuel accumu lator from emptying through the conllol· plunger gap. The luel accumulator must remain full. because it has the job of ma,nta,ning the primary pressure above that fuel·vapor pressure which is appli· cable lor Ihe panicu l.r fuel temperature preva,ling when theengineis switched off.

22) D;ffo,. Ali.,· p~ ... ~ • • m . 0; 0pt0"M9 po ...

."" ... , •• m"" '"1*""'" Q"anlllr &: 0""..,,"11 poor'ion .-;,/0

'"'ge '"I""'''''' quon"'r·

upper and lower chambers constant. ,nde· pend""t of fuel Ihroughflow. The differ· ence ,A pressureis u$uallyO.2 bar,and th,s ensureS 8 h'gh degree of metering accu · racy. The differential·pressure .alve. are of the lIat·seat type. and a,e located in the fuel dist"butor. The upper and lower chambers are separ.ted by meanS of a diaphragm (F'g. 21). The fowerchambers of all the .alves arB provided with a helical spring and a,e connected to one anothe, by means 0 1 a ling main. as well as 10 the electro·hydraulic pressute aCluator. The valve seat is located in the upper chamber. and each uppe' chamber is connected toa metering slit and its cOffesponding fuel· injection line. The upper chambers are complelely sealed ofl from each (llher. The pressured itlerenti al al t he meter; ng slits i s determ,ned by the force of Ihe helical spring in Ihe lowerct>amber. togelherwilh Ihe effect,.e diaphragm diameter and the eleclro·hydraulic pressure actualor. II a large basic injeCI,on quanmy flows ir.to Ihe upper chamber. thed,aphragm bends downwa,ds and opens the outlet croSS· section of the val.euntil thesel diffetenlial p,essure i8 , .. ached again. If the through· flow quantity drops. the valve cross· section is reduced due to Ihe equilibrium 01 fotces at the diaphragm until a ptessure dilfl!fcntial 01 0.2 bar prevails agai~ . This means that an equilibrium of forces e,ist. at the diaphragm wh,ch ClIO be maintsined fo, e.ery b .. ic Injection quanl'ty by controll ,ng the valve Ctoss· section. An additional line liller with a separator for feffomagnetic contamina· tion is litted in Ihe luoll ine to the electro· hydraulic pressure aClualor.

24) S..,.I with m ... rlng .un .M <"",toI plun"". . , Z.", (;"_~ted po.,'.on). b: p." Iood. c: lull 1<>.0". I F",,' inl. '. 2 Con'roJ pI"n~o'. 3 M.'.""9 01";" r ... N ,re/. 4 COII'roI edg •. 5 s,,,,e/. /; Ax,., _ 7 r~",m,"g ... ,''''''''".

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Mixture adaptation

Basic mixture adaptation

For ea~h oporM,ng mode IllS necessary to carry 001 milt",. adaptation in o,der 10 provide the '''iI,n, Wllh Ihe opti mat ai t· j uel "".<lUI'. In p!'aclice, thi. muna that. ,,,,he. m .. I\". " '~UI'ed .1 'die and lull· load, and .Ioa ...... "". !Ure lor the ~-Ioad range ........ ,ed abo-te. the basic adap ... · lIon II by 'pp!'opnalfl all_pong 011'" .i., lul'ltMtl. For in'lanc:e, ilthe funnel ,. flatter (Fog. 26c) I"'n the basic form (which was lpec:,li&d 01'11' nally tor • 1I' .... n mi. lure, e. g. at,, · 1 ),lhen them,,'ur.islear'le<. lf,on the olher hand, 1he funnel walls are Sleepet (Fig. lib, b) lhan in \he ba~"c form.lhe mi. -1ur,,' ,;che, beea" Ie the sen"" , plale de" lectsfu, th,. 10' the .. me .ir throughflOw and the con I rot pi ungm mol .. ", more luel.1 t I. p .... 'ble 10 ,h.pe Ihe ai. funnel so Ihat an .,,·1"0' mi.luro cOflesponding 10 the "n"'f-pl.t, po"lion (klle, pan load, and luliload) can be me1eroo 10 lhe engil\8, In '''''CIHOI IheKE"Je1ronic. I"".rt lunnel i. prelerably 1IO.nape<! lhal an air.fuel mi ," IUle w,lh 1. .. 1 <Quit, actoas the whole operallng ran"e.

I

1t! I~JluItllC. 01 __ ~ """" ......... __ ,.. ... IhIlKNott "" 01'-.., "'_,/op"L a: r". b, .. ", 1Io~"" 0li<l,. ...... 11. '" ., ...... 'b", b: s .. ~ 110""., ... """ _ '" __ ..... "flll . "h' /0, "'""''''~ .;, ,h""'ph"..,. c: Fl."", /u"".,.,,- ",un, ;" ted.c'" de"K'_ 'h'/o, id.",,,,~ • ., 'hrnughpu" CI A""",,, .... __ by'''' 'en""

pia .. (ode",<c~ ,n •••• "b",.1td "C"J.

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A(J.p,.~"" o' th. '''"'.nh.' 0lI.,.. , FtN .. ,,,"'"'" _.1 FtN,.,,_. !F",_

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Electronic control unit

Senso" lor Ihe re"tst ral lo n 01 opelaltn" dltl Add,' ional O/ite" ... boYe a nd beyond t lMo <IItorMal1On como"" I.om lhe intake ai. quantity. a'l teq ";,ed in orclet to ""t .... m' ne lhe oplim-, 1..eI q..- nlity require<l by the """il\8. TII_ mull be "'9;S'ete<l by ""'" _I and rlported 10lhe ECU" TlMo sensorl a •• dll$Cl'becj wolh .eI ... ence to lhe cot ... spondn,,, adaptatoon iuncloon.

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0" '11" end lunellon Dependinv upoII lhe ' unctlOnal scope. \he electronIC eorcu,lry u'" e;ther analog technique. or mlted .nalogldigif.allechni· c,ues. St.rt'"\1 wIth the "Europe" unil. lhe module. lor ,dl,-m ... "., conlrol and lOt lambda cloled·loc.p control ca n be add · ed. EeU', wilh. mOre ' .Ienaiye rang e of I .. nclio"s .r. desig ned uSing digital tec h­niquel . The ellICtronic components are installed on. PC·board and include IC', (e.g. op6fltion.1 .mplifi~ •• compa,alOrs, and voI\.lge . 1.bOlizer.), l.ans;ll0' •. diodel. ,eli"orl. and .... pacilors. The pc. oo..dl .t, ,nserted in .he Ee U housing ... hie" can be eqlOlpped with. p'esstIf~ equal,nllion ... ment. The ECU Isconne<:l­ed to Ih, ban.".. !Ollie Ie ........ and \0 the actu.olor by. 2~·poI. pI...g. The EeU processes the incoming signals from lhe d, tt,'ane ..... IJOt •• and from 'hem ulcul"e1lhe COIII.ol c .. " .... l loI the e lee­'ro-hydraulic prell"" IClu,'OI.

VO'Utg e . , . bUlntlon The eeu muSI be powered byaslable . oll· age. which rem.ins conslanl indepen' dent of the vo ll .ge of the • • hicl. eleetrielll sySlem. The CurrO", applied to the pres· IWre actualOr. which depends upon lhe incoming sensor "g","ls elI.rying lhe dala on the engine ope<"ing conditions. i. g.nOt.ted ' rOtl'l thi. stabilized voltag •• the alabili" lion of whic:h tak .. place in a spe­co.IIC.

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Input flll .. s TIIHe filt", OUI...,. interference which m.y be pr ..... 1 in the .ncom.ng signals frOtl'l lhe ""sora.

Add . r Her •. the e.slu8tOO se nSOr s;gnal s are combine-d. Th, .Iect.icalty processed COr' recti.e .ign.II" •• dded in an operat ional ciroui l and Ih.n trans mined to the current ragul"C>r.

Oulpulsllg. The out""t st~ g.neral .. the conlrol signal lor the pressu" aCluatC>r. whereby il i. possibl. 10 in""t opposing currenlS into lhe prellu" aclualOr in order to .tICI .... C>r d_eue the pressure drop. The magnilud. 01 the current in the pres" IUr, Ktu.tC>r elIn be .djusled al win in the pos.t"" d" e<:t.on by me .... 01 • perma" nenlly triggert'd IranaistC>r. The current i. reverH<l during 'OYer",n' (oyerrun lue! cut-oU) .• nd influeflCes the differe ntial pre"",, al the d iff.rential·pren ur, .al"el so that lhe flow of luelto the ;njec­tion ",t".1 i. in lerrupted.

Addltl o nll output s tlges II nec .... ry •• ddit",",,1 output s lages elIn be incorpe>rlted. Tile .. elIn se",e to trig· II"r lhe •• 1 .... lor EGR. and to control the bypass coos.-Mellon .round the throttl. nl ... " .~uited lor idla·m .. ture control. 10 name but two .ppfiClltlont..

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ttl _.,...,_ 011"" /IE·h_lieu. ...... ...., t«JWouo .. 1"" _""f "'til ..... _ ""'_'" 010<:1:1.,. __ ... ~ _ ... ge. r,..,. .,. ,,,.,, •• ~ .. ''''' ... "", • ... go -.'u.".i'~ ro ,lie _uo-hydtoulr<; ~_,. ""uO .... ~ FuY'_ ""'_''''. SAS ", .. ,.n/.", 0.,-01/ ~ A«otor .. ", • .,."ohnro"

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Electro-hydraulic pressure actuator

Design The eleclro-hydraulic pressure aclualO< (Fig. 30) ism ou nted on I he fuel d I Slribu lor. rhe acluator i s a din erentil l-pr ,,5sure con· Iroller which tun(:lions according 10 the nOZ2lelbaffl" plate principle. and ,t. pros­sure d rop i s controlled by Ihe cu r renl 'nput Irom t he feU. In a housing of nonmag ne1 ic male rial. an a r mature is suspended on I ric­lionless taul-band suspension elements. be1ween IWO double magnetic poles. The armature is in Ihe form of a diaphragm plale made Irom rnilient malerial.

Fun(tlon The mag",,' ic III" of a permanMI magnel (broken lines Fig. 30). and lhal of an elec­troma~nel (unbroken lines Fij' 30). are superimposed upon each 01 Or in Ihe magnelic poles and their air gaps. The per· manenl magnel is actuslly lurned through goo referred 10 the focal plane. The palhs la ken by Ihe magnelic flu.es through Ihe lwo pair. 0 1 poles are symme­t rical a nd 01 eq uall engl h. a nd II ow from Ihe poles. across Ihe air gaps 10 Ihe armature, and then through Ihe armalur •. In the Iwo diagonally opposed air gaps (Fig. 30, L2.L3). the permanenl-magnet 1Iu.. and the electro·magneillu. resufling Irom Ihe incomin~ EeU control signal. are added. whereas <n Ihe olher two air gaps (Fig. 30. L I.L4) the lIu,es are subtracted Irom each other. This means thai in each air gap the armalur.e. which moves too b-ame plale, is subJecled to a lorce of atlraction proportional 10 Ihe squareof the magne1ic flu •. Being as the permanent-magnet flu. remaons constan!. and is proporlional to the con I rol current 1 rOm I he feU flowing i n Ihe electromagnet coil. the resu lting t",-

j ue is proponionalto this control currenl. he basic moment 01 lorce applied to the

armalure has been selected so lhal when no currenl is applied from Ihe EeU. there results a basic differential pressure which corresponds prelerablytoA - I. Thisalso means that in case 01 control current fai· lure, limp-home Jacililies are available wilhout any further correction measures bein~ necessary. '"'lei of fuel which enters through the non e altempts 10 bend Ihe baffle plale away against Ihe prevatlinij mechanical and magnetic l",ce8. Taking a luel throughflow which is delermined by a Ii, ed restriction located in series with the pressure actuator. the diffe'ence in pres­sure between Ihe i nlel a nd ouHe1 (Fig. 2 8, 3 & 5) is proportional 10 the control currenl applied from Ihe EeU. This means thai the va,i able pressure drop all he nozzle i s also proportional to Ihis EeU conlrol currenl. and resuUs in a variable lower-chamber

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prnsure. At the .ame time. the pressure;n the upper chambers changes by Ihe same arooun!. Th,s in lurn resulls in a change 'n lhe difference at lhe melering slits be· Iween the upper-chamber preasure and Ihe primary pressure. and Ihis is appl ied as a means for varying Ihe fuel quanlity delivered to the injection valves . As a result 01 the small electromag""'ic lime conSIMts. and Ihc small maSSeS which must be moved. the pressure aclua· tor r eacls e., re mel y qu ic kl Y 10 v ariali ons in Ihe control curre nl lrom Ihe EeU. If the direction of Ihe control current is reversed. the armatur., pulls Ihe baIlie plate away from the n02zle and a p,essure drop of only a few hundredlhs of • bar OCCurS at the pressuro aCluator. This can be used for au, iliary lunctions such as oWlrrun luel cut -off an d engi no 'speed I i mi­t.alion. The laller function t.akes place I)y inlerr upti ng I he flow of I uel to Ihe ,n jecli on valves (see Page 21 ).

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Full-lo ad e nrichment b~ means ol lhe pressu.e aelualo. I ~ oo ~trast to part load_ where the cali bra­.ion is for minimum luel consump"on and I OW e missions, a I I uilioad it i s neees sary to enrich Ihe air-Iuel mi. lu.e. Thi. enrich­me nt is programmed to be engine ­spe<Kl dependenL I. provides ma. imum possi ble .o.que over Ihe e ntire e ngine ­s peed range_ and Ihis enSureS oplimum luel-economyf igures in thefull-Ioad mode_ Ai fuilioild_ e_g_ in Ih .. .. ngine s pe<Kl rang .. s be twee n 1500 and 3000 min- ' , and above 4000 min- '_ the KE-JeI.onic enriches Ihe a ir-Iu&1 millu.e_ The lull-load s ignal is deli ­vered by. full-load s wilCh on Ih& throttle valve_ or by a microswilch on Ihe accelera­lOr-pedal linklg e. Th e informalio~ on engin& spe<!d is .aken Irom the ignilion. Fro m this data. the ECU calcula.es the addi liona l luel quanti.y ne<Kled. and Ihis is put in.o e ffec. by the pressure aeluator.

The throttl e-val ve switch (Fig . 36) is mounled on the throltl e body and aclualed by 'ha throUI&'valve s haft A Separale con­tact is closed ler each 01 the Ihroll le·va lV<! end positions. i.e . • , id le and 1.1 lull load.

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Controlling the Idle speed by meanS ollhe auxiliary illr device The higher Irictional resistances in the cold engine must be OVe.come by increas­ing Ih& air-Iue l mixlu,e input. In o,der 10 achie ve Smoolhe, , unning al idle. the idle­speed conlrol increases Ihe idle speed. This also leads to a mo,e 'epid wa,m,.,p of Ille eng ine. Oepending upon engine tem ­perature. an electrically heated au.ilia'y­ai, de.ice in Ihe lorm of a bypass a rour\CI I he I h,o\1le plale a llows Ihe engine 10 d ,aw in more ai,. This auxiliary air is also mea­sured by Ihe air-flow sensor. and leads.o Iha KE')et,onic providing .he engine wilh mOre fu .. 1. P,ecise adaptation is by means ollheelectrical healinglacili.y. The engine lempe,ature Ihen del&rmines how much

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I

auxiliary air is led in initially I",eugh Ihe bypass. and lhe e lecl rical heal in 9 i s mainly responsible fo' subsequenll y reducing th& auxil isry air as a funclion of lime. The au. il iaty-ai r device i nCOlporalesa per­fOlalOO plale (Fig8. 38. 39, 42) which is actuated by the bi metallic 8trip and which conlrol8 Ihe cr08S seclion of Ihe bypass passage. Initially, the bypass CrOSS sec· tion opened by the perforated plate is dete,minOO by the engine 'emperatu ,e, $0

lhat d~ring a c~d Sl8l1 the bypass open­ing is adequato 10' the auxiliary a i' required . The opening closes Sl&adily sloog wilh incr .... sing e ngine tempe,atu,e unlil finally il i9 closed completel y. The bimetal si rip iseleclrically healed and this limits Ihe opening time, starling lrom the initial setting which is dependenl upon engine .emperatu'e. The auxilia,y ... ;r de.ice is fit led in the best possibte posi _ lion on the engine fer it 10 assume eng ine temperatu r ... It does "<ll function when Ihe eogine is wa,m.

3~J tlKtriul/r' h ... red eQ. illo"..;. <1<>-';'; • • , f lee";';.1 e<>n_'io~. 2 EIee'''''' ' Mo'i"9. 3 e;lmtlOl ."ip. 4 PeIlrNOIed pI~' • .

•

If

Idle 5feed 5 t IlP///Z e l' by means 01 the

ExcessIve idle speed ,nCreases the fuel consumphon at idle and. as a result. Iha vehicle's overall fuel consumption. Thi, problem is addressed by the idle·mixture conirol, which always provides e,actly Ihe rig hi am Gunl 01 m, .tu '" in o.d 8f 10 main lain I~ ,die speed, no mallerwhallhe engine load (e .g. cold engine with increne<! frie­lional resistance). Furthermore, Ihe emis· sion ligures ,emain COllstant in Ih" long term without having 1(1 adjust the idle speed. To a certain e,tent. Ihe idle-mi.ture control also compensates lor changes in lheeogine which ar" attribulablelosgeing. 11 also slabili~es the idle speed through­out the entire service life of tile engine, Depending upon Ihe signal applied to il. the rotary idle actuator opens Or closu I he

4()) Role'Y jd/e ..:Ioel'" I';~!I/e-wj"dm~ tar.". eOl"el",). r Ele<:w".1 CO"_" .... 2 H"" •• ",. S Rewm 'p"",. ~ W;~·",. 5 Ror".ng_,,,,,,Me. I; ,l.j, p .... g •• , blfn ... "",od ", • • hfOII/e pl • ••• 1 MI.".blo ,tw>. a Ro •• r."f) ,ltd • .

bypass passage around Ihe lhrOll1e val'e. Oue to Ihelacl Ihal Ihe KE-Jelnmic regis· lers tl>\l resulting enr. a;r w,th its sensor plale. tl>\l injecled luel quaMily changes accordingly. In conlrast 10 other idle· speed conlroi S on Ihe market, I his idle' mi. · lure device controls Ihe idle sp""d effi· ciently due to i tactually carrying oul a com· parison between desired and aclual values and. in caseol dIWialion. correcting accordingly.

The rotary idle actualor 01 Ihe KE· Jetronic (Figs. 40. 41) r~ives ilS conlrol signal from I he E CU. This conlrol s ignal depends upon engine spOOd and tomperature, and ca uses the rotating plato in tho idlo aclua· tor 10 Change Ihe bypass opening. The rotary idle acluator is powered by a rotary·magnet drive comprisir>g a wind,ng and a magnetic circui!' lIS rolalional rang e is limiled to 60°. The ,olallng shdo is anached 10 Ihe a,malure shah and opens Ihe bypass pusage lar enough 10' the

4 I) RotlHy I~/e .01 •• 10< (o;"s!e-wlodm9 tOl.'Y ..:IU",OI).

specified idle speed 10 be mainlained independenl 01 engine loadir>g. The clos· ed·loop conlrol circuil in Ihe ECU, which i~ provided by the engine'8peOO sensor wilh Ihe n~ssary inlo,mal ion concern' ing engine speed, compares this with Ihe programmed specified idle speed and adjusts tl>\l ai, Ih,oug hllow by meanS of Ihe idle acluBtOl until the actual idle speed coincides wilh the set idle speed. Wilh the eng,ne warm and unloaded, Ihe bypass opening is very nea, to ils lower limit. Further inpulS lrom the ECU, such as tern· perature and throttle.yalV<l poSilion. ensu,e Ihat errOrS do not <xcur at low lem· pe,atu,es or due \0 accelerator·pedal movements. The ECU transforms the en· gine'8pood signal into 8 voltage signal which it compares with a voltage corre· sponding to these!valua. The ECU gene' ,ales a control ~,gna! lrom the diffe,ence voltage, and inputs this to Ihe rotary idle actuator. A pulsaling OC is applied to Ihe w,nding ol lhe co, l and causes a torqu e at the rOlaling arma!u", which aclS against the ,alurn spring. The resulting bypass open,ng depends on tl>\l Strenglh 01 the curren!. In the abseMe of current (vehicle mallunclion). 11>\1 ,alum spring forces Ihe rotating slide against an adjuslable stop and p,ovides an emergency opening. At 11>\1 ma.imum on/off ,alio 01 the applied pu lsalir>g OC, the bypass is lully opened.

42) Auxl~"I .. jr . e/vlr (lop) !HId I.",,,.r.'. __ Un_ /or k!!e'S/Jud ."",taI.

If

Supplementary functions

Overrun (deceleration)

C~l1jng olf lhe fuel during decele ralion ,educes luel consumption no! merely on long downhill run. and during braking, but also in lown Ira/fie. Be<;ause no fuel ;$ burned. the,e are no emissions. When 1 he driver ta~es h is fOOl off the a<:<:e­leralor pedal while driving. the Ih,otHe valv" relurns 10 Ihe 2ero position. The throttle-valve switch ,eports Ihe "th roWo· va lve closed" corldition 10 Ihe EeU, which all he same time receives I rom t he j gn ilion Ihe dala concerning the engine speed. II the aclual engine speed is within the ope­rating range 01 the overrun cul 'Of! (Iha! i., above idle), Ihe feU reve rSeS Ihe curren l in the e lectro-hydraulic pre,.u." actuator. The pressure d rop 81 the actuator is Ihen practically zero. This means Ihal in Iha lu," diSlribUlor. the d ifferential'pressure .. alves are closed by Iha springs in Ihair lower chambers (Fig_ 44) and interrupllhe flow 01 fuel 10 Ihe injection .. alves. Being as Ihe injeclion .. alves inject conlin' uously. Ihe overrun fuel cut·oU opera les perfectly smoothly. liS response is also dependenl upon Ihe coolant temperatura (Fig. 46). and in order 10 avoid con tinuous switching in and oul al a given engina speed. adiUerent swi tching poinl is speci· fied depending upon whether Ihe engine speed is decreasing or increasing. The switch ing thresholds are chosen to be as low as possible fOf the wa rm engine in order lhal ma.imum fuel savings are achieved. On Ihe Olher hand. wilh a cold engine Ihe th resl>olds are somew"'l high· er $0 Ihat the engine does nol stop when Ihe clutch pedal is suddenty pressed.

r .. , ,. i'ia. ~J) Wl>en ,~. do ... , ,.ke. /". /001 011 'N IO«.to,oro< "....,. 1M, .,.,,,," /uti C~I-oIt , •• ponM oltd SI.P> Ih. /Iowot/uo! to Iho ;ni«r;"" ,owe ..

rut I. Fig. 44) Futl cu,-oII.IIe,;,;.e durinll ove>"",n, Who" ,,.. cu,,,,.' .. """"_ ,h""'lIh 111<1 wiltd'"11 (! I) ," ,,,. .o--"u", .<tu''''''. ,h. I>ollto pi". (!~) i. pullo<! . woy ,"'"' ,11<1 •• ,,," (IO). TI>I. Uu,,, III<IIow.,."h.",oer ,DIe"u'" to riM 0"""" "" ,"" """01 tho {""'"'' P, ••• u,. •• 1td ,"" 'PrI"g' in 'M, """otd._IS closo ,,.. infers (S "nd 5) "" ,"" "'joerlOll ,01> •• wo,h ,,.. diopirr"J'" (8/. IF",,' disrriburo<. ~ Fuel into, • • "" I~e <oId·,,"~ ,aWe. 6 '0 ,11<1 pri~rrP"'''u''' "'go/ar",. 1 U~, .h __ r. ~ L-., ch.mber. If

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.6) rho 10""" ~"g;n. 'p""d lot' ,h. Q'.""" fuel <"'.oW fllCdily depond. "pM! cool8M '.mp.,~'u",.

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'='~"i;~..,~~;;~~ 211-10010 30 r.o 70 !IO \\ooc eooa-_"., .....

.7} U",;/inIJ ,ho m.,imum "nllin" 'Peed ... 01 >loppinll 'he ".W of f" . 1 ,. 'he ;"ieer"", •• 11' ••• -' ..... ",00_ " ,w"'<ho<Ioft

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Engi ne-speed limiting

'!'iM"_"-P~i!!.u;I1ee<l is r .... ched. Ill. ECU suppresses Ih. iuel·inj!l£!iru!

""'" ConV<!nt lonal mechanical eng,no'speed limIters haveadiSlribulor '0101 arranged to shon·c;reuil the ignition when the maxi· mum permissible eng,ne speed is reaclled. Today. for ,eaSonS 01 ... hausl­gas emISSIons and fuel e<Xlnomy. Ihls method is no longer entirely salisfaclory. An ob .. ous m<lthod i510 apply electronics to engine-speed limi,ing by switching off the luel injeeri"n. When Ihe current through Ihe eleclro-hydrauhc aCluator is reversed. Ihe bame plale is pulled away from lhe nozzle (Fig. 44). Ihe pressur" d rop approaches zerO and lhe dia' phragms inlhedifferenlialpressu re valves SlOP Ihe flow 01 luel 10 lhe injeClion valves. The same process lakes place as wilh Ihe overrun luel cul-aU faCIlity {rel" r 10 Page:20). In the ECU. the aClual engine speed is compared wllh the programmed ma .. mum speed II •. If Ihe maximum speed is exceed­ed. the ECU suppresses Ihe inje<:lion pulses. This lunClion operates within a bandwidth of 80 min~' above afld below tho permissible ma ximum speed {FIg. 4 7). This e locl,onic er>gine·speed limiting facility prevents the engine Irom -Overr<)V­"';ng-. bUI without Ihe adverse eUects inherent in the mechanical sySlem men­tioned above,

Adaptation of the air-fu el mixture at high altitudes

AI high ali'ludes. due 10 the lower air den · sily. Ihe volumetric flow measured by Ihe air·llow sensor corresponds toa 10we<!l1r: ~. Depending upon Ihe I3cil:ties inco'p",ated in Ihe particular KE·Jetronic. this error Can be compensated for by cor­reeling the inject'on time. Ovcr-enrich­ment is aV(>1ded and. therefo,e, exces­s ive luel consumption at hIgh aliiludes. The alt'lude compensation is prOVIded by a~ wh,Ch meaSureS theair PreSSure. In accordance with the prevaIling ." pres­sure. the senSor ,npulS a signal to Ihe ECU which changes the press"re-actunior Cjt!; rent accOfdongly. (hIS allcrs Ihe lower­Chamber pressure. and therelo,ethepfes· sure d i!ferance at 1he metMing SlilS. and Ihis ,,!'Sulls in a change In the inj(lCted fu&l quanuly. It is also possible 10 incorpora le continuo ous adaptation oflhe injected ruel quanlity according to the char>ging.If prIl'SSu,e,

T~., toFjg. 4S At c<,,,,.~,aOl. n..gh .. 4_ ..... 1 • ..-1. ,h.,. '. • .igm~.'" dilf.",,,,,. boI_ ,h. "",a,u"'" ." "".n"'1 ~nd ,,. ",'u-' 1M ... n", IS duo , •• " Mn" 'r d"",. ... nu _, ~'f1/> -,,,,ude •. A""",· me'"" _'",rxI • ..,n,,,, ,"0"=' rho." p,. .. = .nd ropon, ,h,. ro ' .. £CV wh-ch .dJ""~ 'ho mJflO"'" fue' Q""""'1 KCOIdinll'r by """n' 0' 'ho oI<re,,,,h y<J, .,,"" jUo".'" """,,01.

Clean emissions

Fuel combustion in the engine working cylindo< is more Or leSS incomplete, The less complete Ihecombustion, the higher is Ihe emission ollo.ic substances in the exhaust gas. Perfect Of 101al, combustion of the fuel is impossible even when Sur· plus air is avai lable in plenty. In order to ,educe Ihe load on the environm""t. it is imperative thai engine ... "'-uSI·gas emis­sions ar" reduced drastically. All measure" taken to reduce the to.ic emiss ions in compliance with a variety "I legal requirements, aim at achievir>g as clean an .. ,lIauslgas as possible, while al Ihe same lime featunng optimum fuel·eco­nomy figures. ".cel len! driveabilily. high mileage ligures, and low inSlal lation COS1S. In addition 10 a large p",centageol harm· less substan~s. tf>e e.haus t gas 01 a spark·ignilion engine conlains cotn~· nenlS which are harmlul to tf>e environ· ment when they QCcur in high concanlra· lions. About! ,"of thee.haustguis harm· lui. and ""nsistsol carbon mono. id .. (COJ. o.ides ot nitrogsn (NO.). and hydrocar· bons (He). The major problem in this respect is the lact that although these th ree to.ie substances arB dependent upon the air·luel ,al,O. when Iheconcentra· lion 01 eo and He inc'eases the concen' t,ation 01 NO. dec reases, atld yice "ersa.

Cata lytic aftertreatment

The e.haust·gas emiss ion level 01 an engine can be inHuenced at th,oodiHe,ent points . Thel,rst possib<lity 01 influencing Ihe omiasions is du,inglr.e mi.ture·lorma· lion Slag .. before th .. engin ... Tho second possibil ily is the use ot spedal design measu,es on the eng ine itsell (tor in· atar.ce, optimind combuSlion·chamber shape). The lhird possibility is alterlreat· ment ollhe e.haust gases on the e.haust side of the engine. whereby the task is to complete the combustion 01 the luei. This is carried OUI by means 01 a calalytic conve"e, (Fig. 48) which has two notable chafacleristics, • The catalytic converter promotes tho afterbu,ning 01 eo and He to harmless ca,bon dio.ide (CO,) and water (H,O). . Atthe same time, thecatalyticconye'ter reduces the nilrogen 01 o.ide (NOJ to nit,ogen (N) , l! ia Ihe'elo'e perteclly clear that the cata· lytic allertreatment of the e.haust gas is considerably mOre eltective than lor in· stance the purely the, mal aftcrburning 01 the e .hauat gases in a thermal reactor.

[email protected]<;atalyliccon"er1er m01elhan90% gltbe lo. ic substa!!Ces can b@cQ"Y@rlid \0 ha'mless substances.

The thr~.way catalyt ic converter has come into widespread use. Theconvetle, shell contains a ceramic 'honeycomb" which is coated with a noble melal, pre' ferably platinum. When lhe exhaust gas ffows th,ough thi s honeycomb. the plati· num acceleratea the cf>emical conversion of Ihe toxic substa r.ces. Only lead·I,ee gasolir>e may be used with such COnver· ters because the lead othe,wise destroys the catalytic property cl the noble-metal calalyst. At p,esent. lead·I,~ gasoline is only available in Japan and in the USA. and loa limited e. tent in the Federal Republic 01 Germany. For this reason. catalylic COn' ve,te" can only be used in these coun· Iries. The prerequisitelorcatalyticconversion i. that the engine burns an optimum ,i,·luel mi.ture. This optimum. or s toichiometric. mi.lure (s~ Page4) isa[(iyed alwhen pre· cisely thalamount of fuel i. injecled 100the inducted air quantity in order 10 enSure that. theo,etically. perfect combushon can lake place. Such an air·fuel mi. tu'e ia charact",i.ed by lhe e.cess·air factor ;. '"' 1.00. Wilh Ihis e.cess·ai. lac tor. the cata lytic converter operates with high e Ui· cier.cy. This means therelore.thattheactual dilli· culty encountered when using 'catatytic aflertreatment' hes in maintaining A at precisely 1 .00 10' all operating modes. because even a deviation 01 only 1')ji has consideflble adverse ellects on the afte,· treatment. 8utt he best.Q~~ is ir.capable 01 holding the air·luel mi.lure within such close tolerances. and the onty solulion is 10 apply an extremely accurate ~~totheair·lualmi.lure· managemenl syslem. The reason ,s that althwgh an open.loop miJlure conlrol cal· culltes and mele.s the required fuel quan· tily, it does not monito, the results, One speaks 01 an S!pen co!!lro! loop, Tf>e £l2: ~~ol themi.tur .. ontheother hand measures the composition 01 the e.haust gas and uses theresults tOCOfrect Ihe calculated fuel quantity. This is referred to as a (;(osed eon1rgJ (oop. The Lambda oxygen sensor lacil ity inco<po,al' ed in Ihe KE·Jelronic syslemcoMerts whal would otherwise be an open· loop control into a closed·loop cont.ol , This lorm of conlrol is particularfy effective on luel· injection engines because lhey do nol have the additional delay limes caused by the long intake paths found on carbu,etor engines.

2

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f8) c.'MrIk; <Oq,"'.,. WIt •• •• ho~ .. g. •• • lIow ,h"'ugh 'h" <''''pi<; "" .... ".' •• Ito pl.oMam ..:oele, .. , • • rlto ch.",;co' <10<"",1'00'."" <>I ,Ito 10"< ,ul>$'ooe .. , r COlO"'" m.'c'~ c",,'od ""'h <lI'.'p",,,,,, 00 ••• mo,.,,;a, (pIa".um). 2 S,HI _Io, 'rx:."~g pu'PO"''' 3 Co"M'" .h-".

49) ~Ifce'in .... <>I,he colo!ytk; do"""," "",.1 of , .. ".",1 g .. ".j.~ III" Umbd. r;lo •• d./oOp _''''', Ro.g. 10, .po",amo,,.,,,.1 ",;,tu,.: I. • 0.99 _ 1.00. To.",c""',,,"" o -lIt!.l!!s!tao 1r. ", .. ,· "",n( b - !!:!!l! airOtf",. """n( He hfdto<o_ CO 00'_ """,",-d •• NO. ",.d .. 0' ",,"'ge • . Tho Ifi.g,.m below d • ...,."' ... . lito co.,;· doIob! • • " • • , 10 ,,/loch .,h' ''''·g'' om,., ,ion, co. bo -'aceO I>y , • • opplic""," 01 C''''y'''' . 1",,,,,,arm.,,, and by lito .,,·/Uol m .. ,,,, •• Th •• _a'. -= ..... y 10,. h;9" d<:g ... 01 co.,'''' OCC"'"CY " •• ""'. by ,h. _anced ;nc ..... in <0,1>0. mO/""id. (CO)/usP boIo ... ,h.;' . I,OOpoin, ... well • • by II,. ,add •• iump i. 'ho "",1 .. , 01 Mtogen (NOJ con"'n' / ""' . 1>0 ... 'ho ;' _ 1.00 por.'. SQ," CO ond NO.~~"" .nc ..

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Lambda closed-loop control

, " range 01 the

Operation The sensor protrudes into the exhaust-gas stream and is designed so that the outer electrode is surrounded by e.haust gas. and the inner elecl rod e i s connected to t he atmospheric air.

.en ..... r--::::::--,-----, -"

·~.,.-.,.,.-"l,;='luF=c,c. .• ,',~.

5!) PuiliOlfinll ollho t..m~d • • en .... in 0 duo. exhou .. • "lem.

52.1 Funclion oIlhe Lombdo '.n''''. , S •• ,,,, c.,omoe. :1 Ehtctrode .. 3 Con,"e". 4 EI.-;,,;"ol conIKr'"g ro ,he • .,."mll. 5 E,buor p'<>O. 6 P",'e<I". c&T'''''c roye' r_.1

Basically. tile sensor is constructed hom an element of special ceramic. the surisee 01 which is cooted with micropo'ous platinum electrodes. The operalion of the SSnSor is based upon tha lactthat ceramic male"at is porous and permits d iffusion 01 Ihe o.ygen p'esent in the air {solid electrolyte). At higher temperatures. it becomes conductive. and il too o'1gen concentration on one sideol the etectrode is dillerem to that on the other. then a vohage is generated belween the e lec· trodes. In the area of stoiChiometric air· luel mixtu ,e p . .. 1.00). a jump takes place in the senSOr voitago output curve. This voltage represents the measured signal {Fig. 50).

Const,uctlon Th e ceramic S<)nsor body is held in a threaded mounting and provided with a protecli.e tube and electflcal connec' tions. The su rtace 01 the S<)nSOr ceramic bod y has a microporOlJs platinum layer which on the one side decisively in· tluences the se n$Or chalacteristic while on the other serving as an electrical conlact. A highly adhesive and highly porOlJsceramiccoating has beenapplie-d over the platinum layer at the end 01 the ceramic body that i~ exposed 10 Ihe exllaustgas. This protective layarprevents Ihe solid particles in the e.haust gas Irom eroding the platinum layer. A protective metal aleoW! is filled over the senSOr on Ihe electrical conneclion end and crimped to the s,,"$Or housing. This sloe.e is provided wilh a bore to enSure pressule compensation in the sen$O' in· terior. and a lso serves as the support lor the disc spring. The connection lead is c.imped tothecontact e lement and is led thlough an insulaling sleeve to the outside 01 the SenSOr. In order to . eep combustion deposits in the e. haust gas away from Ihe c<lfamic body. the end 01 the exhaust sen· sO< which protrudes into the e,haust'gao flow is p'olected bya special tube having

$3) t.mbdo •• nsor_

slots so designed thai the exhausl gas and lhe solid particles entraIned in it do not come into direct contact with Ihe ceramic body.

Using the close<I-loop cont,oI circuit lormed wilh the aid 01 the Lambda senso'. deviations Irom a speci fied ai,·fuel ratio can be detected and corrected. This con· Irol principle is based upon the measure' menl 01 100 e.haust·gas oxygen by the Lambda senSOr. The e.haust·gas oxygen is a measure for lhe compos ition of theair· luel mi.ture supplie<l to the engine. The Lambda sensor acts as a probe in the e.hausl pipe and delivers the inlormation as 10 wh ethel I he mi xtu' e is ric hel '" lea nar than ~. 1.00. In case 01 a deviation 110m this ~ .. 1.00 ligure. the voltageolthe sensoroutpul s ig· nal changes ab.uplly. This pronounced change is evalualed by the EeU which is provided with aclosad -loopconlrol circuit for this purpose. This inlluellCes Ihe co<· rection 01 the injecled'luel quantity which has been worked oul electronically by tile KE·Jel'onic. Using this concept. it is pos ­si blo to control the fuel metering sO accu· rately thatthoair·luel lalio is optimum in a ll operating ranges independent olload and errgine speed. Tolerances and the effects 01 engine ageing are of no importance. II. tor instance. ~ • 1.03 (slighlly lean mi.· tureJ.lhe Lambda conlrol circuil compen' sates 10' this excess air by inc reasing the amount olluel injecled. The plOCesS is reversed it the mi.lure is slightly rich (e.g. i. - 0.(7). Thiscontinuing adjustment of the mi. ture to the). • t.OO figure is the prerequisite for ensuring thai the upst ream catalytic converter can carry out Ihe aftertleatment 01 the e.haust gas with ma. imum el/ICiMCy.

I C""t""t elom.nt. , PIO,..,t; .. co"""" eI .... nl. 3 SC"OO< C,,,,,'''. 4 P",'IX'''''' rub< ( • • ~.u", oitIo.I. 5 E/t:el""ol COIf"eel_. G Qt." .,,'.09. 7 PtD'""',,,. ._. (.,""'.""..,..: sxI.). 6 H(><I.mg (-). 9 Ele<rtodo r-i. '" ['''''Irod. (+)

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Electrical circuitry

by the ""'0< sutile •• tor Ih" relay 10 II<! 'wo'ched on. E"9,ne .tart IS $>g~led by lh, pul," from Terminal 1 of t he igMlon COIl whIch ... .. aluated by tile electroniC

ed (lOt ,nal.nee due to .n accIdent) the control .et.y sWItches 011 .boot 1 second Ifte, the I .. t ""lie " ,ecelved. ThOs .. Iely C"';Ult thus prevents the fuel pump lrom continuing to dellve. ruel when the eng"'e " "",ona'} ond the ig,,;tion is switched 0 •.

Du"ng c"nkong. the '11"",on and Slar,ing Cltcu.' f)' In the eoolrol relay. Upon receipt sw"ell appl,,,s .ollage 10 the control ,elay ollhe Ii,., pul,,,, the! canlfol relayswilches (Fig. !S5) wh'ch sWllches on as soon as the on and appl ies ' Gllage 10 Ihe electric fuel &fIg'ne tum • . Here, Ih" englne speed pump and Ihe au"liary-.i, device. If the reached by lhe engine when it 1$ cranked pulSe! from the ignition 0";1 a,,, inlerfljpt-

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