Gasoline Fuel-Injection System K-Jetronic Fuel-Injection System K-Jetronic Gasoline-engine management Technical Instruction

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Gasoline Fuel-InjectionSystem K-JetronicGasoline-engine management Technical InstructionPublished by: Robert Bosch GmbH, 2000Postfach 3002 20,D-70442 Stuttgart.Automotive Equipment Business Sector,Department for Automotive Services,Technical Publications (KH/PDI2).Editor-in-Chief:Dipl.-Ing. (FH) Horst Bauer.Editorial staff:Dipl.-Ing. Karl-Heinz Dietsche,Dipl.-Ing. (BA) Jrgen Crepin.Presentation:Dipl.-Ing. (FH) Ulrich Adler,Joachim Kaiser,Berthold Gauder, Leinfelden-Echterdingen.Translation:Peter Girling.Technical graphics:Bauer & Partner, Stuttgart.Unless otherwise stated, the above are allemployees of Robert Bosch GmbH, Stuttgart.Reproduction, copying, or translation of thispublication, including excerpts therefrom, is only toensue with our previous written consent and withsource credit.Illustrations, descriptions, schematic diagrams, and other data only serve for explanatory purposesand for presentation of the text. They cannot beused as the basis for design, installation, or scopeof delivery. We assume no liability for conformity ofthe contents with national or local legal regulations.We are exempt from liability. We reserve the right to make changes at any time.Printed in Germany.Imprim en Allemagne.4th Edition, February 2000.English translation of the German edition dated: September 1998.Combustion in the gasoline engineThe spark-ignition or Otto-cycle engine 2Gasoline-engine managementTechnical requirements 4Cylinder charge 5Mixture formation 7Gasoline-injection systemsOverview 10K-JetronicSystem overview 13Fuel supply 14Fuel metering 18 Adapting to operating conditions 24Supplementary functions 30Exhaust-gas treatment 32Electrical circuitry 36Workshop testing techniques 38K-JetronicSince its introduction, the K-Jetronicgasoline-injection system has pro-ved itself in millions of vehicles.This development was a direct resultof the advantages which are inherentin the injection of gasoline with regard to demands for economy ofoperation, high output power, andlast but not least improvements tothe quality of the exhaust gasesemitted by the vehicle. Whereas thecall for higher engine output was theforemost consideration at the start ofthe development work on gasolineinjection, today the target is toachieve higher fuel economy andlower toxic emissions. Between the years 1973 and 1995,the highly reliable, mechanical multi-point injection system K-Jetronicwas installed as Original Equipmentin series-production vehicles. Today,it has been superseded by gasolineinjection systems which thanks to electronics have been vastly im-proved and expanded in their func-tions. Since this point, the K-Jetronichas now become particularly impor-tant with regard to maintenance andrepair. This manual will describe the K-Jetronics function and its particu-lar features.The spark-ignition or Otto-cycle engineOperating conceptThe spark-ignition or Otto-cycle1)powerplant is an internal-combustion (IC)engine that relies on an externally-generated ignition spark to transform thechemical energy contained in fuel intokinetic energy. Todays standard spark-ignition enginesemploy manifold injection for mixtureformation outside the combustionchamber. The mixture formation systemproduces an air/fuel mixture (based ongasoline or a gaseous fuel), which is then drawn into the engine by the suctiongenerated as the pistons descend. Thefuture will see increasing application ofsystems that inject the fuel directly into thecombustion chamber as an alternateconcept. As the piston rises, it compressesthe mixture in preparation for the timedignition process, in which externally-generated energy initiates combustion viathe spark plug. The heat released in thecombustion process pressurizes thecylinder, propelling the piston back down,exerting force against the crankshaft andperforming work. After each combustionstroke the spent gases are expelled fromthe cylinder in preparation for ingestion ofa fresh charge of air/fuel mixture. Theprimary design concept used to governthis gas transfer in powerplants forautomotive applications is the four-strokeprinciple, with two crankshaft revolutionsbeing required for each complete cycle.The four-stroke principleThe four-stroke engine employs flow-control valves to govern gas transfer(charge control). These valves open andclose the intake and exhaust tractsleading to and from the cylinder:1st stroke: Induction,2nd stroke: Compression and ignition,3rd stroke: Combustion and work,4th stroke: Exhaust.Induction strokeIntake valve: open,Exhaust valve: closed,Piston travel: downward,Combustion: none.The pistons downward motion increasesthe cylinders effective volume to drawfresh air/fuel mixture through the passageexposed by the open intake valve.Compression strokeIntake valve: closed,Exhaust valve: closed,Piston travel: upward,Combustion: initial ignition phase.Combustion in the gasolineengine2Combustion in the gasoline engineReciprocating piston-engine design conceptOT = TDC (Top Dead Center); UT = BDC (BottomDead Center), Vh Swept volume, VC Compressedvolume, s Piston stroke.Fig. 1UMM0001EOTUTOTUTVhsVC1) After Nikolaus August Otto (18321891), whounveiled the first four-stroke gas-compression engineat the Paris World Exhibition in 1876.As the piston travels upward it reducesthe cylinders effective volume tocompress the air/fuel mixture. Just beforethe piston reaches top dead center (TDC)the spark plug ignites the concentratedair/fuel mixture to initiate combustion.Stroke volume Vhand compression volume VCprovide the basis for calculating thecompression ratio = (Vh+VC)/VC.Compression ratios range from 7...13,depending upon specific engine design.Raising an IC engines compression ratioincreases its thermal efficiency, allowingmore efficient use of the fuel. As anexample, increasing the compression ratiofrom 6:1 to 8:1 enhances thermalefficiency by a factor of 12%. The latitudefor increasing compression ratio isrestricted by knock. This term refers touncontrolled mixture inflammation charac-terized by radical pressure peaks.Combustion knock leads to enginedamage. Suitable fuels and favorablecombustion-chamber configurations canbe applied to shift the knock threshold intohigher compression ranges.Power strokeIntake valve: closed,Exhaust valve: closed,Piston travel: upward,Combustion: combustion/post-combus-tion phase.The ignition spark at the spark plugignites the compressed air/fuel mixture,thus initiating combustion and theattendant temperature rise.This raises pressure levels within thecylinder to propel the piston downward.The piston, in turn, exerts force againstthe crankshaft to perform work; thisprocess is the source of the enginespower.Power rises as a function of engine speedand torque (P = M).A transmission incorporating variousconversion ratios is required to adapt thecombustion engines power and torquecurves to the demands of automotiveoperation under real-world conditions.Exhaust strokeIntake valve: closed,Exhaust valve: open,Piston travel: upward,Combustion: none.As the piston travels upward it forces thespent gases (exhaust) out through thepassage exposed by the open exhaustvalve. The entire cycle then recommenceswith a new intake stroke. The intake andexhaust valves are open simultaneouslyduring part of the cycle. This overlapexploits gas-flow and resonance patternsto promote cylinder charging andscavenging.Otto cycle3Operating cycle of the 4-stroke spark-ignition engineFig. 2UMM0011EStroke 1: Induction Stroke 2: Compression Stroke 3: Combustion Stroke 4: ExhaustTechnical requirementsSpark-ignition (SI)engine torqueThe power P furnished by the spark-ignition engine is determined by theavailable net flywheel torque and theengine speed.The net flywheel torque consists of theforce generated in the combustionprocess minus frictional losses (internalfriction within the engine), the gas-exchange losses and the torque requiredto drive the engine ancillaries (Figure 1). The combustion force is generatedduring the power stroke and is defined bythe following factors: The mass of the air available forcombustion once the intake valveshave closed, The mass of the simultaneouslyavailable fuel, and The point at which the ignition sparkinitiates combustion of the air/fuelmixture.Primary engine-management functionsThe engine-management systems firstand foremost task is to regulate theengines torque generation by controllingall of those functions and factors in thevarious engine-management subsystemsthat determine how much torque isgenerated.Cylinder-charge controlIn Bosch engine-management systemsfeaturing electronic throttle control (ETC),the cylinder-charge control subsystemdetermines the required induction-airmass and adjusts the throttle-valveopening accordingly. The driver exercisesdirect control over throttle-valve openingon conventional injection systems via thephysical link with the accelerator pedal.Mixture formationThe mixture formation subsystem cal-culates the instantaneous mass fuelrequirement as the basis for determiningthe correct injection duration and optimalinjection timing.Gasoline-engine management 4Gasoline-engine management Driveline torque factors1 Ancillary equipment(alternator,a/c compressor, etc.),2 Engine,3 Clutch,4 Transmission.UMM0545-1EFig. 1Air mass (fresh induction charge)Fuel massIgnition angle (firing point)EngineGas-transfer and frictionAncillariesClutch/converter losses and conversion ratiosTransmission losses and conversion ratiosCombustion output torqueEngineoutput torqueFlywheel torqueDrive force ClutchTrans-mission1 1 2 3 4Cylindercharge5IgnitionFinally, the ignition subsystem de-termines the crankshaft angle thatcorresponds to precisely the ideal instantfor the spark to ignite the mixture.The purpose of this closed-loop controlsystem is to provide the torquedemanded by the driver while at thesame time satisfying strict criteria in theareas of Exhaust emissions, Fuel consumption, Power, Comfort and convenience, and Safety.Cylinder chargeElementsThe gas mixture found in the cylinderonce the intake valve closes is referred toas the cylinder charge, and consists ofthe inducted fresh air-fuel mixture alongwith residual gases.Fresh gasThe fresh mixture drawn into the cylinderis a combination of fresh air and the fuelentrained with it. While most of the freshair enters through the throttle valve,supplementary fresh gas can also bedrawn in through the evaporative-emissions control system (Figure 2). Theair entering through the throttle-valve andremaining in the cylinder after intake-valve closure is the decisive factordefining the amount of work transferredthrough the piston during combustion,and thus the prime determinant for theamount of torque generated by theengine. In consequence, modifications toenhance maximum engine power andtorque almost always entail increasingthe maximum possible cylinder charge.The theoretical maximum charge isdefined by the volumetric capacity.Residual gasesThe portion of the charge consisting ofresidual gases is composed of The exhaust-gas mass that is notdischarged while the exhaust valve isopen and thus remains in the cylinder,and The mass of recirculated exhaust gas(on systems with exhaust-gas recircu-lation, Figure 2).The proportion of residual gas is de-termined by the gas-exchange process.Although the residual gas does notparticipate directly in combustion, it doesinfluence ignition patterns and the actualcombustion sequence. The effects of thisresidual-gas component may be thoroughlydesirable under part-throttle operation.Larger throttle-valve openings to com-pensate for reductions in fresh-gas fillingCylinder charge in the spark-ignition engine1 Air and fuel vapor,2 Purge valve with variable aperture,3 Link to evaporative-emissions control system,4 Exhaust gas,5 EGR valve with variable aperture,6 Mass airflow (barometric pressure pU),7 Mass airflow (intake-manifold pressure ps),8 Fresh air charge (combustion-chamber pressure pB),9 Residual gas charge (combustion-chamber pressure pB),10 Exhaust gas (back-pressure pA),11 Intake valve,12 Exhaust valve, Throttle-valve angle.UMM0544-1YFig. 216 7 1082 35411 129are needed to meet higher torquedemand. These higher angles reduce theengines pumping losses, leading tolower fuel consumption. Precisely reg-ulated injection of residual gases canalso modify the combustion process toreduce emissions of nitrous oxides (NOx)and unburned hydrocarbons (HC).Control elementsThrottle valveThe power produced by the spark-ignition engine is directly proportional tothe mass airflow entering it. Control ofengine output and the correspondingtorque at each engine speed is regulatedby governing the amount of air beinginducted via the throttle valve. Leavingthe throttle valve partially closed restrictsthe amount of air being drawn into theengine and reduces torque generation.The extent of this throttling effectdepends on the throttle valves positionand the size of the resulting aperture.The engine produces maximum powerwhen the throttle valve is fully open(WOT, or wide open throttle).Figure 3 illustrates the conceptualcorrelation between fresh-air chargedensity and engine speed as a functionof throttle-valve aperture.Gas exchangeThe intake and exhaust valves open andclose at specific points to control thetransfer of fresh and residual gases. Theramps on the camshaft lobes determineboth the points and the rates at which thevalves open and close (valve timing) todefine the gas-exchange process, andwith it the amount of fresh gas availablefor combustion.Valve overlap defines the phase in whichthe intake and exhaust valves are opensimultaneously, and is the prime factor indetermining the amount of residual gasremaining in the cylinder. This process isknown as "internal" exhaust-gasrecirculation. The mass of residual gascan also be increased using "external"exhaust-gas recirculation, which relieson a supplementary EGR valve linkingthe intake and exhaust manifolds. Theengine ingests a mixture of fresh air andexhaust gas when this valve is open.Pressure chargingBecause maximum possible torque isproportional to fresh-air charge density, itis possible to raise power output bycompressing the air before it enters thecylinder.Dynamic pressure chargingA supercharging (or boost) effect can beobtained by exploiting dynamics withinthe intake manifold. The actual degree ofboost will depend upon the manifoldsconfiguration as well as the enginesinstantaneous operating point(essentially a function of the enginesspeed, but also affected by load factor).The option of varying intake-manifoldgeometry while the vehicle is actuallybeing driven, makes it possible to employdynamic precharging to increase themaximum available charge mass througha wide operational range.Mechanical superchargingFurther increases in air mass areavailable through the agency ofGasoline-engine management 6Throttle-valve map for spark-ignition engineThrottle valve at intermediate apertureUMM0543-1EFig. 3Fresh gas chargeRPMmin. max.Throttle valve completely openThrottle valve completely closedIdleMixtureformation7mechanically driven compressors pow-ered by the engines crankshaft, with thetwo elements usually rotating at an in-variable relative ratio. Clutches are oftenused to control compressor activation.Exhaust-gas turbochargersHere the energy employed to power thecompressor is extracted from the exhaustgas. This process uses the energy thatnaturally-aspirated engines cannotexploit directly owing to the inherentrestrictions imposed by the gas ex-pansion characteristics resulting from thecrankshaft concept. One disadvantage isthe higher back-pressure in the exhaustgas exiting the engine. This back-pressure stems from the force needed tomaintain compressor output.The exhaust turbine converts theexhaust-gas energy into mechanicalenergy, making it possible to employ animpeller to precompress the incomingfresh air. The turbocharger is thus acombination of the turbine in the exhaust-fas flow and the impeller that compressesthe intake air. Figure 4 illustrates the differences in thetorque curves of a naturally-aspiratedengine and a turbocharged engine.Mixture formationParametersAir-fuel mixtureOperation of the spark-ignition engine iscontingent upon availability of a mixturewith a specific air/fuel (A/F) ratio. Thetheoretical ideal for complete combustionis a mass ratio of 14.7:1, referred to asthe stoichiometric ratio. In concrete termsthis translates into a mass relationship of14.7 kg of air to burn 1 kg of fuel, whilethe corresponding volumetric ratio isroughly 9,500 litres of air for completecombustion of 1 litre of fuel.The air-fuel mixture is a major factor indetermining the spark-ignition enginesrate of specific fuel consumption.Genuine complete combustion andabsolutely minimal fuel consumptionwould be possible only with excess air,but here limits are imposed by suchconsiderations as mixture flammabilityand the time available for combustion.The air-fuel mixture is also vital indetermining the efficiency of exhaust-gastreatment system. The current state-of-the-art features a 3-way catalyticconverter, a device which relies on astoichiometric A/F ratio to operate atmaximum efficiency and reduce un-desirable exhaust-gas components bymore than 98 %.Current engines therefore operate with astoichiometric A/F ratio as soon as theengines operating status permitsCertain engine operating conditionsmake mixture adjustments to non-stoichiometric ratios essential. With acold engine for instance, where specificadjustments to the A/F ratio are required.As this implies, the mixture-formationsystem must be capable of responding toa range of variable requirements.Torque curves for turbocharged and atmospheric-induction engines with equal power outputs1 Engine with turbocharger,2 Atmospheric-induction engine.UMM0459-1EFig. 41214123411Engine torque MdEngine rpm nnExcess-air factorThe designation l (lambda) has beenselected to identify the excess-air factor(or air ratio) used to quantify the spreadbetween the actual current mass A/F ratioand the theoretical optimum (14.7:1): = Ratio of induction air mass to airrequirement for stoichiometric com-bustion. = 1: The inducted air mass correspondsto the theoretical requirement. < 1: Indicates an air deficiency,producing a corresponding rich mixture.Maximum power is derived from =0.85...0.95. > 1: This range is characterized byexcess air and lean mixture, leading tolower fuel consumption and reducedpower. The potential maximum value for called the lean-burn limit (LML) isessentially defined by the design of theengine and of its mixture for-mation/induction system. Beyond thelean-burn limit the mixture ceases to beignitable and combustion miss sets in,accompanied by substantial degener-ation of operating smoothness.In engines featuring systems to inject fueldirectly into the chamber, these operatewith substantially higher excess-airfactors (extending to = 4) since com-bustion proceeds according to differentlaws.Spark-ignition engines with manifoldinjection produce maximum power at airdeficiencies of 5...15% ( = 0.95...0.85),but maximum fuel economy comes in at10...20% excess air ( = 1.1...1.2).Figures 1 and 2 illustrate the effect of theexcess-air factor on power, specific fuelconsumption and generation of toxicemissions. As can be seen, there is nosingle excess-air factor which cansimultaneously generate the mostfavorable levels for all three factors. Airfactors of = 0.9...1.1 produceconditionally optimal fuel economy withconditionally optimal power generationin actual practice.Once the engine warms to its normaloperating temperature, precise andconsistent maintenance of = 1 is vitalfor the 3-way catalytic treatment ofexhaust gases. Satisfying this re-quirement entails exact monitoring ofinduction-air mass and precise meteringof fuel mass.Optimal combustion from current en-gines equipped with manifold injectionrelies on formation of a homogenousmixture as well as precise metering of theinjected fuel quantity. This makeseffective atomization essential. Failure tosatisfy this requirement will foster theformation of large droplets of condensedfuel on the walls of the intake tract and inthe combustion chamber. These dropletswill fail to combust completely and theultimate result will be higher HCemissions.Gasoline-engine management 8Effects of excess-air factor on power P andspecific fuel consumption be.a Rich mixture (air deficiency),b Lean mixture (excess air).UMK0033EFig. 1Effect of excess-air factor on untreatedexhaust emissionsUMK0032EFig. 20.8 1.0 1.2a bPbePower P,Specific fuel consumption beExcess-air factor 0.6 1.0 1.4Relative quantities ofCO; HC; NOXExcess-air factor 0.8 1.2COHC NOXMixtureformation9Adapting to specificoperating conditionsCertain operating states cause fuelrequirements to deviate substantially fromthe steady-state requirements of an enginewarmed to its normal temperature, thusnecessitating corrective adaptations in themixture-formation apparatus. The follow-ing descriptions apply to the conditionsfound in engines with manifold injection.Cold startingDuring cold starts the relative quantity offuel in the inducted mixture decreases: themixture goes lean. This lean-mixturephenomenon stems from inadequateblending of air and fuel, low rates of fuelvaporization, and condensation on thewalls of the inlet tract, all of which arepromoted by low temperatures. To com-pensate for these negative factors, and tofacilitate cold starting, supplementary fuelmust be injected into the engine.Post-start phaseFollowing low-temperature starts,supplementary fuel is required for a briefperiod, until the combustion chamberheats up and improves the internalmixture formation. This richer mixturealso increases torque to furnish asmoother transition to the desired idlespeed.Warm-up phaseThe warm-up phase follows on the heelsof the starting and immediate post-startphases. At this point the engine stillrequires an enriched mixture to offset thefuel condensation on the intake-manifoldwalls. Lower temperatures are synony-mous with less efficient fuel proces-sing (owing to factors such as poor mix-ing of air and fuel and reduced fuel va-porization). This promotes fuel precip-itation within the intake manifold, with the formation of condensate fuel that willonly vaporize later, once temperatureshave increased. These factors make itnecessary to provide progressive mixtureenrichment in response to decreasingtemperatures.Idle and part-loadIdle is defined as the operating status inwhich the torque generated by the engineis just sufficient to compensate for frictionlosses. The engine does not providepower to the flywheel at idle. Part-load (orpart-throttle) operation refers to therange of running conditions between idleand generation of maximum possibletorque. Todays standard concepts relyexclusively on stoichiometric mixtures forthe operation of engines running at idleand part-throttle once they have warmedto their normal operating temperatures.Full load (WOT)At WOT (wide-open throttle) supple-mentary enrichment may be required. AsFigure 1 indicates, this enrichmentfurnishes maximum torque and/or power.Acceleration and decelerationThe fuels vaporization potential is stronglyaffected by pressure levels inside theintake manifold. Sudden variations inmanifold pressure of the kind encounteredin response to rapid changes in throttle-valve aperture cause fluctuations in thefuel layer on the walls of the intake tract.Spirited acceleration leads to highermanifold pressures. The fuel respondswith lower vaporization rates and the fuellayer within the manifold runners expands.A portion of the injected fuel is thus lost inwall condensation, and the engine goeslean for a brief period, until the fuel layerrestabilizes. In an analogous, but inverted,response pattern, sudden decelerationleads to rich mixtures. A temperature-sensitive correction function (transitioncompensation) adapts the mixture tomaintain optimal operational responseand ensure that the engine receives theconsistent air/fuel mixture needed forefficient catalytic-converter performance.Trailing throttle (overrun)Fuel metering is interrupted during trailingthrottle. Although this expedient savesfuel on downhill stretches, its primarypurpose is to guard the catalytic converteragainst overheating stemming from poorand incomplete combustion (misfiring).Carburetors and gasoline-injection sys-tems are designed for a single purpose:To supply the engine with the optimal air-fuel mixture for any given operatingconditions. Gasoline injection systems,and electronic systems in particular, arebetter at maintaining air-fuel mixtureswithin precisely defined limits, whichtranslates into superior performance inthe areas of fuel economy, comfort andconvenience, and power. Increasinglystringent mandates governing exhaustemissions have led to a total eclipse of thecarburetor in favor of fuel injection.Although current systems rely almostexclusively on mixture formation outsidethe combustion chamber, concepts basedon internal mixture formation with fuelbeing injected directly into the combustionchamber were actually the foundationfor the first gasoline-injection systems. Asthese systems are superb instruments forachieving further reductions in fuelconsumption, they are now becoming anincreasingly significant factor.OverviewSystems withexternal mixture formationThe salient characteristic of this type ofsystem is the fact that it forms the air-fuelmixture outside the combustion chamber,inside the intake manifold.Multipoint fuel injectionMultipoint fuel injection forms the idealbasis for complying with the mixture-formation criteria described above. In thistype of system each cylinder has its owninjector discharging fuel into the areadirectly in front of the intake valve.Representative examples are the variousversions of the KE and L-Jetronic systems(Figure 1).Mechanical injection systemsThe K-Jetronic system operates byinjecting continually, without an exter-nal drive being necessary. Instead ofbeing determined by the injection valve,fuel mass is regulated by the fueldistributor.Combined mechanical-electronicfuel injectionAlthough the K-Jetronic layout served asthe mechanical basis for the KE-Jetronicsystem, the latter employs expandeddata-monitoring functions for moreprecise adaptation of injected fuelquantity to specific engine operatingconditions.Electronic injection systemsInjection systems featuring electroniccontrol rely on solenoid-operated injectionMultipoint fuel injection (MPI)1 Fuel,2 Air,3 Throttle valve,4 Intake manifold,5 Injectors,6 Engine.Gasoline-injection systems325641Fig. 1UMK0662-2YGasoline-injectionsystems10valves for intermittent fuel discharge. Theactual injected fuel quantity is regulatedby controlling the injector's opening time(with the pressure-loss gradient throughthe valve being taken into account incalculations as a known quantity).Examples: L-Jetronic, LH-Jetronic, andMotronic as an integrated engine-manage-ment system.Single-point fuel injectionSingle-point (throttle-body injection (TBI))fuel injection is the concept behind thiselectronically-controlled injection systemin which a centrally located solenoid-operated injection valve mountedupstream from the throttle valve spraysfuel intermittently into the manifold. Mono-Jetronic and Mono-Motronic are theBosch systems in this category (Figure 2).Systems for internal mixture formationDirect-injection (DI) systems rely onsolenoid-operated injection valves to sprayfuel directly into the combustion chamber;the actual mixture-formation process takesplace within the cylinders, each of whichhas its own injector (Figure 3). Perfectatomization of the fuel emerging from theinjectors is vital for efficient combustion.Under normal operating conditions, DIengines draw in only air instead of thecombination of air and fuel common toconventional injection systems. This is oneof the new system's prime advantages: Itbanishes all potential for fuel condensationwithin the runners of the intake manifold.External mixture formation usuallyprovides a homogenous, stoichiometric air-fuel mixture throughout the entirecombustion chamber. In contrast, shiftingthe mixture-preparation process into thecombustion chamber provides for twodistinctive operating modes:With stratified-charge operation, only themixture directly adjacent to the spark plugneeds to be ignitable. The remainder of theair-fuel charge in the combustion chambercan consist solely of fresh and residualgases, without unburned fuel. This strategyfurnishes an extremely lean overall mixturefor idling and part-throttle operation, withcommensurate reductions in fuelconsumption.Homogenous operation reflects theconditions encountered in external mixtureformation by employing uniformconsistency for the entire air-fuel chargethroughout the combustion chamber.Under these conditions all of the fresh airwithin the chamber participates in thecombustion process. This operationalmode is employed for WOT operation.MED-Motronic is used for closed-loopcontrol of DI gasoline engines.Overview11Throttle-body fuel injection (TBI)1 Fuel,2 Air,3 Throttle valve,4 Intake manifold,5 Injector,6 Engine.325641UMK0663-2YFig. 2Direct fuel injection (DI)1 Fuel,2 Air,3 Throttle valve (ETC), 4 Intake manifold,5 Injectors,6 Engine.325641UMK1687-2YFig. 3The story offuel injection12The story of fuel injectionThe story of fuel injection extendsback to cover a period of almost onehundred years.The Gasmotorenfabik Deutz wasmanufacturing plunger pumps for in-jecting fuel in a limited productionseries as early as 1898.A short time later the uses of the ven-turi-effect for carburetor design werediscovered, and fuel-injection systemsbased on the technology of the timeceased to be competitive.Bosch started research on gasoline-injection pumps in 1912. The firstaircraft engine featuring Bosch fuel in-jection, a 1,200-hp unit, entered seriesproduction in 1937; problems with car-buretor icing and fire hazards had lentspecial impetus to fuel-injection devel-opment work for the aeronautics field.This development marks the begin-ning of the era of fuel injection atBosch, but there was still a long pathto travel on the way to fuel injection forpassenger cars.1951 saw a Bosch direct-injection unitbeing featured as standard equipmenton a small car for the first time. Sev-eral years later a unit was installed inthe 300 SL, the legendary productionsports car from Daimler-Benz.In the years that followed, develop-ment on mechanical injection pumpscontinued, and ...In 1967 fuel injection took anothergiant step forward: The first electronicinjection system: the intake-pressure-controlled D-Jetronic!In 1973 the air-flow-controlled L-Jetro-nic appeared on the market, at thesame time as the K-Jetronic, which fea-tured mechanical-hydraulic control andwas also an air-flow-controlled system. In 1976, the K-Jetronic was the firstautomotive system to incorporate aLambda closed-loop control.1979 marked the introduction of a newsystem: Motronic, featuring digital pro-cessing for numerous engine func-tions. This system combined L-Jetro-nic with electronic program-map con-trol for the ignition. The first automo-tive microprocessor!In 1982, the K-Jetronic model becameavailable in an expanded configura-tion, the KE-Jetronic, including anelectronic closed-loop control circuitand a Lambda oxygen sensor.These were joined by Bosch Mono-Jetronic in 1987: This particularly cost-efficient single-point injection unitmade it feasible to equip small vehicleswith Jetronic, and once and for all madethe carburetor absolutely superfluous.By the end of 1997, around 64 millionBosch engine-management systemshad been installed in countless types ofvehicles since the introduction of the D-Jetronic in 1967. In 1997 alone, thefigure was 4.2 million, comprised of 1 million throttle-body injection (TBI)systems and 3.2 million multipoint fuel-injection (MPI) systems. Bosch gasoline fuel injection from the year 1954K-JetronicSystem overviewThe K-Jetronic is a mechanically and hydraulically controlled fuel-injection sys-tem which needs no form of drive andwhich meters the fuel as a function of theintake air quantity and injects it contin-uously onto the engine intake valves.Specific operating conditions of the engine require corrective intervention inmixture formation and this is carried outby the K-Jetronic in order to optimizestarting and driving performance, poweroutput and exhaust composition. Owingto the direct air-flow sensing, the K-Je-tronic system also allows for enginevariations and permits the use of facilitiesfor exhaust-gas aftertreatment for whichprecise metering of the intake air quantityis a prerequisite.The K-Jetronic was originally designedas a purely mechanical injection system.Today, using auxiliary electronic equip-ment, the system also permits the use oflambda closed-loop control.The K-Jetronic fuel-injection system covers the following functional areas: Fuel supply, Air-flow measurement and Fuel metering.Fuel supplyAn electrically driven fuel pump deliversthe fuel to the fuel distributor via a fuel accumulator and a filter. The fuel distribu-tor allocates this fuel to the injectionvalves of the individual cylinders.Air-flow measurementThe amount of air drawn in by the engineis controlled by a throttle valve and measured by an air-flow sensor.Fuel meteringThe amount of air, corresponding to theposition of the throttle plate, drawn in bythe engine serves as the criterion for metering of the fuel to the individual cylinders. The amount of air drawn in bythe engine is measured by the air-flowsensor which, in turn, controls the fueldistributor. The air-flow sensor and thefuel distributor are assemblies whichform part of the mixture control unit. Injection occurs continuously, i.e. withoutregard to the position of the intake valve.During the intake-valve closed phase, thefuel is stored. Mixture enrichment iscontrolled in order to adapt to variousoperating conditions such as start, warm-up, idle and full load. In addition, supple-mentary functions such as overrun fuelcutoff, engine-speed limiting and closed-loop lambda control are possible.K-Jetronic13Functional schematic of the K-JetronicFig. 1Electricfuel pumpFuelaccumulatorAir-flowsensorFueldistributorFuel filterAir filterThrottle valveIntake portsCombustionchamberMixtureFuelAirInjection valvesMixturecontrol unitUMK0009EFuel supplyThe fuel supply system comprises Electric fuel pump, Fuel accumulator, Fine filter, Primary-pressure regulator and Injection valves.An electrically driven roller-cell pumppumps the fuel from the fuel tank at apressure of over 5 bar to a fuel accu-mulator and through a filter to the fuel distributor. From the fuel distributor thefuel flows to the injection valves. Theinjection valves inject the fuel con-tinuously into the intake ports of theengine. Thus the system designation K(taken from the German for continuous).When the intake valves open, the mixtureis drawn into the cylinder.The fuel primary-pressure regulatormaintains the supply pressure in the system constant and reroutes the excessfuel back to the fuel tank.Owing to continual scavenging of the fuelsupply system, there is always cool fuel available. This avoids the formation offuel-vapor bubbles and achieves goodhot starting behavior.Electric fuel pumpThe electric fuel pump is a roller-cellpump driven by a permanent-magnet electric motor.The rotor plate which is eccentrically mounted in the pump housing is fittedwith metal rollers in notches around itscircumference which are pressed againstthe pump housing by centrifugal forceand act as rolling seals. The fuel is car-ried in the cavities which form betweenthe rollers. The pumping action takesplace when the rollers, after havingclosed the inlet bore, force the trappedfuel in front of them until it can escapefrom the pump through the outlet bore(Figure 4). The fuel flows directly aroundthe electric motor. There is no danger ofexplosion, however, because there is never an ignitable mixture in the pumphousing.Gasoline-injectionsystems14Fig. 2Schematic diagram of the K-Jetronic system with closed-loop lambda control1 Fuel tank, 2 Electric fuel pump, 3 Fuel accumulator, 4 Fuel filter, 5 Warm-up regulator, 6 Injection valve,7 Intake manifold, 8 Cold-start valve, 9 Fuel distributor, 10 Air-flow sensor, 11 Timing valve, 12 Lambda sensor, 13 Thermo-time switch, 14 Ignition distributor, 15 Auxiliary-air device, 16 Throttle-valve switch, 17 ECU, 18 Ignition and starting switch, 19 Battery.1234576 8131214151718161019911BOSCHUMK0077YThe electric fuel pump delivers more fuelthan the maximum requirement of the engine so that compression in the fuelsystem can be maintained under all oper-ating conditions. A check valve in thepump decouples the fuel system from the fuel tank by preventing reverse flow offuel to the fuel tank.The electric fuel pump starts to operateimmediately when the ignition and start-ing switches are operated and remainsswitched on continuously after the enginehas started. A safety circuit is incorpor-ated to stop the pump running and, thus,to prevent fuel being delivered if the ig-nition is switched on but the engine hasstopped turning (for instance in the caseof an accident).The fuel pump is located in the imme-diate vicinity of the fuel tank and requiresno maintenance.Fuel accumulatorThe fuel accumulator maintains the pressure in the fuel system for a certaintime after the engine has been switchedoff in order to facilitate restarting, parti-cularly when the engine is hot. The spe-cial design of the accumulator housing (Figure 5) deadens the sound of the fuelpump when the engine is running.The interior of the fuel accumulator is divided into two chambers by means of adiaphragm. One chamber serves as theaccumulator for the fuel whilst the otherrepresents the compensation volumeand is connected to the atmosphere or tothe fuel tank by means of a vent fitting.During operation, the accumulatorchamber is filled with fuel and the dia-phragm is caused to bend back againstthe force of the spring until it is halted bythe stops in the spring chamber. Thediaphragm remains in this position, whichcorresponds to the maximum accumu-lator volume, as long as the engine isrunning.K-Jetronic15Fuel accumulatora Empty, b Full. 1 Spring chamber, 2 Spring, 3 Stop, 4 Diaphragm,5 Accumulator volume, 6 Fuel inlet or outlet, 7 Connection to the atmosphere.Operation of roller-cell pump1 Suction side, 2 Rotor plate, 3 Roller, 4 Roller race plate, 5 Pressure side.Electric fuel pump1 Suction side, 2 Pressure limiter, 3 Roller-cellpump, 4 Motor armature, 5 Check valve, 6 Pressure side.43 56121 52 3 41 2 3 4 567abFig. 3Fig. 4Fig. 5UMK0120-2Y UMK0121-2YUMK1653YFuel filterThe fuel filter retains particles of dirtwhich are present in the fuel and whichwould otherwise have an adverse effecton the functioning of the injection system.The fuel filter contains a paper elementwith a mean pore size of 10 m backedup by a fluff trap. This combination ensures a high degree of cleaning.The filter is held in place in the housingby means of a support plate. It is fitted inthe fuel line downstream from the fuel accumulator and its service life dependsupon the amount of dirt in the fuel. It isimperative that the arrow on the filterhousing showing the direction of fuel flowthrough the filter is observed when the filter is replaced.Primary-pressure regulatorThe primary-pressure regulator main-tains the pressure in the fuel system constant.It is incorporated in the fuel distributorand holds the delivery pressure (systempressure) at about 5 bar. The fuel pumpalways delivers more fuel than is requiredby the vehicle engine, and this causes aplunger to shift in the pressure regulatorand open a port through which excessfuel can return to the tank.The pressure in the fuel system and theforce exerted by the spring on the pressure-regulator plunger balance eachother out. If, for instance, fuel-pumpdelivery drops slightly, the plunger is shifted by the spring to a correspondingnew position and in doing so closes offthe port slightly through which the excessfuel returns to the tank. This means thatless fuel is diverted off at this point andthe system pressure is controlled to itsspecified level.When the engine is switched off, the fuelpump also switches off and the primarypressure drops below the opening pres-sure of the injection valves. The pressureregulator then closes the return-flow portand thus prevents the pressure in the fuelsystem from sinking any further (Fig. 8).Fuel-injection valvesThe injection valves open at a given pres-sure and atomize the fuel through oscilla-tion of the valve needle. The injectionvalves inject the fuel metered to them intothe intake passages and onto the intakevalves. They are secured in specialGasoline-injectionsystems16Primary-pressure regulator fitted to fuel distributora In rest position, b In actuated position. 1 System-pressure entry, 2 Seal, 3 Return to fuel tank, 4 Plunger, 5 Spring.a b132 4 51 2 3Fig. 7UMK1495YFuel filter1 Paper element,2 Strainer, 3 Supportplate.UMK0119YFig. 6holders to insulate them against the heatradiated from the engine. The injectionvalves have no metering function them-selves, and open of their own accordwhen the opening pressure of e.g. 3.5bar is exceeded. They are fitted with avalve needle (Fig. 9) which oscillates(chatters) audibly at high frequencywhen fuel is injected. This results in ex-cellent atomization of the fuel even withthe smallest of injection quantities. Whenthe engine is switched off, the injectionvalves close tightly when the pressure inthe fuel-supply system drops below theiropening pressure. This means that nomore fuel can enter the intake passagesonce the engine has stopped.Air-shrouded fuel-injection valvesAir-shrouded injection valves improve themixture formation particularly at idle.Using the pressure drop across thethrottle valve, a portion of the air inductedby the engine is drawn into the cylinderthrough the injection valve (Fig. 20): Theresult is excellent atomization of the fuelat the point of exit (Fig. 10). Air-shroudedinjection valves reduce fuel consumptionand toxic emission constituents.K-Jetronic17Pressure curve after engine switchoffFirstly pressure falls from the normal system pressure (1) to the pressure-regulator closingpressure (2). The fuel accumulator then causes it to increase to the level (3) which is below theopening pressure (4) of the injection valves.Fuel-injection valvea In rest position, b In actuated position. 1 Valve housing,2 Filter,3 Valve needle,4 Valve seat.msbarPressure pTime t12341234baFig. 8Fig. 9UMK0018EUMK0069-2YUMK0042YUMK0041YFig. 10Spray pattern of an injection valve without air-shrouding (left) and with air-shrouding (right).Fuel meteringThe task of the fuel-management systemis to meter a quantity of fuel corre-sponding to the intake air quantity.Basically, fuel metering is carried out by the mixture control unit. This com-prises the air-flow sensor and the fueldistributor.In a number of operating modes however,the amount of fuel required deviatesgreatly from the standard quantity and itbecomes necessary to intervene in themixture formation system (see sectionAdaptation to operating conditions).Air-flow sensorThe quantity of air drawn in by the engineis a precise measure of its operatingload. The air-flow sensor operates ac-cording to the suspended-body principle,and measures the amount of air drawn inby the engine.The intake air quantity serves as themain actuating variable for determiningthe basic injection quantity. It is the appropriate physical quantity for derivingthe fuel requirement, and changes in theinduction characteristics of the enginehave no effect upon the formation of theair-fuel mixture. Since the air drawn in bythe engine must pass through the air-flowsensor before it reaches the engine, thismeans that it has been measured andthe control signal generated before it actually enters the engine cylinders. Theresult is that, in addition to other measures described below, the correctmixture adaptation takes place at alltimes.Gasoline-injectionsystems18Updraft air-flow sensora Sensor plate in its zero position,b Sensor plate in its operating position.1 Air funnel,2 Sensor plate, 3 Relief cross-section, 4 Idle-mixture adjusting screw,5 Pivot,6 Lever,7 Leaf spring.Principle of the air-flow sensora Small amount of air drawn in: sensor plate onlylifted slightly, b Large amount of air drawn in: sensor plate is lifted considerably further.abhh1 2 3 4 567abFig. 11Fig. 12UMK0072YUMK1654YThe air-flow sensor is located upstreamof the throttle valve so that it measures allthe air which enters the engine cylinders.It comprises an air funnel in which thesensor plate (suspended body) is free topivot. The air flowing through the funneldeflects the sensor plate by a given amount out of its zero position, and thismovement is transmitted by a lever sys-tem to a control plunger which deter-mines the basic injection quantity re-quired for the basic functions. Consider-able pressure shocks can occur in theintake system if backfiring takes place inthe intake manifold. For this reason, theair-flow sensor is so designed that the sensor plate can swing back in theopposite direction in the event of misfire,and past its zero position to open a reliefcross-section in the funnel. A rubber buffer limits the downward stroke (the upwards stroke on the downdraft air-flowsensor). A counterweight compensatesfor the weight of the sensor plate and lever system (this is carried out by an extension spring on the downdraft air-flow sensor). A leaf spring ensures thecorrect zero position in the switched-offphase.Fuel distributorDepending upon the position of the platein the air-flow sensor, the fuel distributormeters the basic injection quantity to theindividual engine cylinders. The positionof the sensor plate is a measure of theamount of air drawn in by the engine. Theposition of the plate is transmitted to thecontrol plunger by a lever.K-Jetronic19Barrel with metering slits and control plungera Zero (inoperated position), b Part load, c Full load. 1 Control pressure, 2 Control plunger, 3 Metering slit in the barrel, 4 Control edge, 5 Fuel inlet, 6 Barrel with metering slits.Barrel with metering slits1 Intake air, 2 Control pressure, 3 Fuel inlet, 4 Metered quantity of fuel, 5 Control plunger, 6 Barrel with metering slits, 7 Fuel distributor.457642311a b c23645Fig. 13Fig. 14UMK1496YUMK1497YDepending upon its position in the barrelwith metering slits, the control plungeropens or closes the slits to a greater orlesser extent. The fuel flows through theopen section of the slits to the differentialpressure valves and then to the fuel injection valves. If sensor-plate travel isonly small, then the control plunger is lifted only slightly and, as a result, only asmall section of the slit is opened for thepassage of fuel. With larger plunger travel, the plunger opens a larger sectionof the slits and more fuel can flow. Thereis a linear relationship between sensor-plate travel and the slit section in the barrel which is opened for fuel flow.A hydraulic force generated by the so-called control pressure is applied to thecontrol plunger. It opposes the movementresulting from sensor-plate deflection.One of its functions is to ensure that thecontrol plunger follows the sensor-platemovement immediately and does not, forinstance, stick in the upper end positionwhen the sensor plate moves down again.Further functions of the control pressureare discussed in the sections Warm-upenrichment and Full-load enrichment.Control pressureThe control pressure is tapped from theprimary pressure through a restrictionbore (Figure 16). This restriction boreserves to decouple the control-pressurecircuit and the primary-pressure circuitfrom one another. A connection line joinsthe fuel distributor and the warm-up regulator (control-pressure regulator).When starting the cold engine, the control pressure is about 0.5 bar. As theengine warms up, the warm-up regulatorincreases the control pressure to about3.7 bar (Figure 26).The control pressure acts through a damping restriction on the controlplunger and thereby develops the forcewhich opposes the force of the air in theair-flow sensor. In doing so, the restric-tion dampens a possible oscillation of thesensor plate which could result due topulsating air-intake flow.The control pressure influences the fueldistribution. If the control pressure is low,the air drawn in by the engine can deflectthe sensor plate further. This results inthe control plunger opening the meteringslits further and the engine being allo-cated more fuel. On the other hand, if thecontrol pressure is high, the air drawn inby the engine cannot deflect the sensorplate so far and, as a result, the enginereceives less fuel. In order to fully seal offthe control-pressure circuit with absolutecertainty when the engine has been switched off, and at the same time tomaintain the pressure in the fuel circuit,the return line of the warm-up regulator isfitted with a check valve. This (push-up)valve is attached to the primary-pressureregulator and is held open during oper-ation by the pressure-regulator plunger.When the engine is switched off and theplunger of the primary-pressure regulatorreturns to its zero position, the checkvalve is closed by a spring (Figure 17).Differential-pressure valvesThe differential-pressure valves in thefuel distributor result in a specific pres-sure drop at the metering slits.The air-flow sensor has a linear charac-teristic. This means that if double thequantity of air is drawn in, the sensor-Gasoline-injectionsystems20Barrel with metering slitsThe slits are shown enlarged (the actual slit is about 0.2 mm wide).Fig. 15UMK0044Yplate travel is also doubled. If this travel isto result in a change of delivered fuel inthe same relationship, in this case doublethe travel equals double the quantity,then a constant drop in pressure must be guaranteed at the metering slits (Figure 14), regardless of the amount offuel flowing through them.The differential-pressure valves main-tain the differential pressure between theupper and lower chamber constant re-gardless of fuel throughflow. The differ-ential pressure is 0.1 bar.The differential-pressure valves achievea high metering accuracy and are of theflat-seat type. They are fitted in the fuelK-Jetronic21Primary pressure and control pressure1 Control-pressure effect (hydraulic force),2 Damping restriction, 3 Line to warm-up regulator, 4 Decoupling restric-tion bore,5 Primary pressure (delivery pressure),6 Effect of air pressure.Primary-pressure regulator with push-up valve in the control-pressure circuita In zero (inoperated) position,b In operating position.1 Primary pressure intake,2 Return (to fuel tank), 3 Plunger of the primary-pressure regulator,4 Push-up valve,5 Control-pressure intake (from warm-up regulator).6 53214b12 3 45aFig. 17Fig. 16UMK1498YUMK1499Ydistributor and one such valve is allo-cated to each metering slit. A diaphragmseparates the upper and lower chambersof the valve (Figures 18 and 19). The lower chambers of all the valves are con-nected with one another by a ring mainand are subjected to the primary pres-sure (delivery pressure). The valve seatis located in the upper chamber. Eachupper chamber is connected to ametering slit and its corresponding con-nection to the fuel-injection line. Theupper chambers are completely sealedoff from each other. The diaphragms arespring-loaded and it is this helical springthat produces the pressure differential.Gasoline-injectionsystems22Differential-pressure valvea Diaphragm position with alow injectedfuel quantityb Diaphragmposition with a large injectedfuel quantityFig. 18UMK1656YIf a large basic fuel quantity flows into theupper chamber through the metering slit,the diaphragm is bent downwards andenlarges the valve cross-section at theoutlet leading to the injection valve untilthe set differential pressure once againprevails.If the fuel quantity drops, the valve cross-section is reduced owing to the equilib-rium of forces at the diaphragm until thedifferential pressure of 0.1 bar is againpresent.This causes an equilibrium of forces toprevail at the diaphragm which can bemaintained for every basic fuel quantityby controlling the valve cross-section.Mixture formationThe formation of the air-fuel mixturetakes place in the intake ports andcylinders of the engine.The continually injected fuel coming fromthe injection valves is stored in front ofthe intake valves. When the intake valveis opened, the air drawn in by the enginecarries the waiting cloud of fuel with itinto the cylinder. An ignitable air-fuel mixture is formed during the inductionstroke due to the swirl effect. Air-shrouded fuel-injection valves favormixture formation since they atomize the fuel very well at the outlet point (Figures 10, 20).K-Jetronic23Fuel distributor with differential-pressure valves1 Fuel intake(primarypressure),2 Upper chamber ofthe differential-pressure valve,3 Line to the fuel-injection valve(injectionpressure),4 Control plunger,5 Control edge andmetering slit,6 Valve spring,7 Valve diaphragm,8 Lower chamber ofthe differential-pressure valve.Mixture formation with air-shrouded fuel-injection valve1 Fuel-injection valve, 2 Air-supply line, 3 Intake manifold, 4 Throttle valve.2 3 4 5 67811 2 3 4@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@Fig. 19Fig. 20UMK1602YUMK0068YAdaptation to operating conditionsIn addition to the basic functions de-scribed up to now, the mixture has to beadapted during particular operatingconditions. These adaptations (correc-tions) are necessary in order to optimizethe power delivered, to improve theexhaust-gas composition and to improvethe starting behavior and driveability.Basic mixture adaptationThe basic adaptation of the air-fuel mix-ture to the operating modes of idle, partload and full load is by appropriately shaping the air funnel in the air-flowsensor (Figures 21 and 22).If the funnel had a purely conical shape,the result would be a mixture with a con-stant air-fuel ratio throughout the wholeof the sensor plate range of travel (meter-ing range). However, it is necessary tometer to the engine an air-fuel mixturewhich is optimal for particular operatingmodes such as idle, part load and fullload. In practice, this means a richer mixture at idle and full load, and a leanermixture in the part-load range. This adaptation is achieved by designing theair funnel so that it becomes wider in stages.If the cone shape of the funnel is flatterthan the basic cone shape (which wasspecified for a particular mixture, e.g. for = 1), this results in a leaner mixture. Ifthe funnel walls are steeper than in thebasic model, the sensor plate is lifted further for the same air throughput, morefuel is therefore metered by the controlplunger and the mixture is richer. Conse-quently, this means that the air funnel canbe shaped so that it is poss-ible to metermixtures to the engine which have dif-ferent air-fuel ratios depending upon thesensor-plate position in the funnel (whichin turn corresponds to the particularengine operating mode i.e. idle, part loadand full load). This results in a richermixture for idle and full load (idle and full-load enrichment) and, by contrast, aleaner mixture for part load.Cold-start enrichmentDepending upon the engine temperature,the cold-start valve injects extra fuel intothe intake manifold for a limited periodduring the starting process.In order to compensate for the conden-sation losses due to condensation on thecold cylinder walls, and in order to facil-itate starting the cold engine during coldstarting, extra fuel must be injected at theinstant of start-up. This extra fuel is in-jected by the cold-start valve into theintake manifold. The injection period ofthe cold-start valve is limited by athermo-time switch depending upon theengine temperature.This process is known as cold-start en-richment and results in a richer air-fuel Gasoline-injectionsystems24Influence of funnel-wall angle upon the sensor-plate deflection for identical air throughputa The basic funnel shape results in stroke h,b Steep funnel walls result in increased stroke h for identical air throughput,c Flatter funnel shape results in reduced deflection h for identical air throughput.A Annular area opened by the sensor plate (identical in a, b and c).Adaptation of the air-funnel shape1 For maximum power, 2 For part load, 3 For idle.hhhAAAabc123Fig. 21Fig. 22UMK0071YUMK0155Ymixture, i.e. the excess-air factor istemporarily less than 1.Cold-start valveThe cold-start valve (Figure 23) is a solenoid-operated valve. An electro-magnetic winding is fitted inside thevalve. When unoperated, the movable electromagnet armature is forced againsta seal by means of a spring and thus closes the valve. When the electro-magnet is energized, the armature whichconsequently has lifted from the valveseat opens the passage for the flow offuel through the valve. From here, the fuelenters a special nozzle at a tangent andis caused to rotate or swirl.The result is that the fuel is atomized veryfinely and enriches the mixture in the manifold downstream of the throttlevalve. The cold-start valve is so posi-tioned in the intake manifold that good distribution of the mixture to all cylindersis ensured.Thermo-time switchThe thermo-time switch limits the dur-ation of cold-start valve operation, de-pending upon temperature.The thermo-time switch (Figure 24)consists of an electrically heated bimetalstrip which, depending upon its tempera-ture opens or closes a contact. It isbrought into operation by the ignition/starter switch, and is mounted at aposition which is representative of enginetemperature. During a cold start, it limitsthe on period of the cold-start valve. Incase of repeated start attempts, or whenstarting takes too long, the cold-startvalve ceases to inject.Its on period is determined by thethermo-time switch which is heated byengine heat as well as by its own built-inheater. Both these heating effects are necessary in order to ensure that the on period of the cold-start valve is limited under all conditions, and engineflooding prevented. During an actual coldstart, the heat generated by the built-inheater is mainly responsible for the on period (switch off, for instance, at 20 C after 7.5 seconds). With awarm engine, the thermo-time switch has already been heated up so far by engineheat that it remains open and preventsthe cold-start valve from going into action.K-Jetronic25Cold-start valve in operated state1 Electrical connection, 2 Fuel supply with strainer, 3 Valve (electromagnet armature), 4 Solenoid winding, 5 Swirl nozzle, 6 Valve seat.Thermo-time switch1 Electrical connection, 2 Housing, 3 Bimetal, 4 Heating filament, 5 Electrical contact.35126412543Fig. 23 Fig. 24UMK0118YUMK0125-1YWarm-up enrichmentWarm-up enrichment is controlled by the warm-up regulator. When the engineis cold, the warm-up regulator reducesthe control pressure to a degree depen-dent upon engine temperature and thus causes the metering slits to open further(Figure 25).At the beginning of the warm-up periodwhich directly follows the cold start, someof the injected fuel still condenses on thecylinder walls and in the intake ports.This can cause combustion misses to occur. For this reason, the air-fuel mix-ture must be enriched during the warm-up ( < 1.0). This enrichment must becontinuously reduced along with the risein engine temperature in order to preventthe mixture being over-rich when higherengine temperatures have been reached.The warm-up regulator (control-pressureregulator) is the component which carriesout this type of mixture control for thewarm-up period by changing the controlpressure.Warm-up regulatorThe change of the control pressure is effected by the warm-up regulator whichis fitted to the engine in such a way that itultimately adopts the engine tempera-ture. An additional electrical heating sys-tem enables the regulator to be matchedprecisely to the engine characteristic.Gasoline-injectionsystems26Warm-up regulatora With the engine cold,b With the engine at operating temperature.1 Valve diaphragm, 2 Return, 3 Control pressure (from the mixture-control unit),4 Valve spring,5 Bimetal spring,6 Electrical heating.6 5 41a2 3bFig. 25UMK1567YThe warm-up regulator comprises aspring-controlled flat seat (diaphragm-type) valve and an electrically heated bimetal spring (Figure 25).In cold condition, the bimetal springexerts an opposing force to that of thevalve spring and, as a result, reduces theeffective pressure applied to the under-side of the valve diaphragm. This meansthat the valve outlet cross-section isslightly increased at this point and morefuel is diverted out of the control-pres-sure circuit in order to achieve a lowcontrol pressure. Both the electrical heating system and the engine heat thebimetal spring as soon as the engine iscranked. The spring bends, and in doingso reduces the force opposing the valvespring which, as a result, pushes up thediaphragm of the flat-seat valve. Thevalve outlet cross-section is reduced andthe pressure in the control-pressure circuit rises.Warm-up enrichment is completed whenthe bimetal spring has lifted fully from thevalve spring. The control pressure is nowsolely controlled by the valve spring andmaintained at its normal level. The con-trol pressure is about 0.5 bar at cold startand about 3.7 bar with the engine at operating temperature (Figure 26).Idle stabilizationIn order to overcome the increasedfriction in cold condition and to guaranteesmooth idling, the engine receives moreair-fuel mixture during the warm-upphase due to the action of the auxiliaryair device.When the engine is cold, the frictional resistances are higher than when it is atoperating temperature and this frictionmust be overcome by the engine duringidling. For this reason, the engine is allowed to draw in more air by means ofthe auxiliary-air device which bypassesthe throttle valve. Due to the fact that thisauxiliary air is measured by the air-flowsensor and taken into account for fuelmetering, the engine is provided withmore air-fuel mixture. This results in idlestabilization when the engine is cold.Auxiliary-air deviceIn the auxiliary-air device, a perforatedplate is pivoted by means of a bimetalspring and changes the open cross-section of a bypass line. This perforatedplate thus opens a correspondingly largecross-section of the bypass line, as a function of the temperature, and thiscross-section is reduced with increasingengine temperature and is ultimately closed. The bimetal spring also has anelectrical heating system which permitsthe opening time to be restricted de-pendent upon the engine type. The in-K-Jetronic27Warm-up regulator characteristics at various operating temperaturesEnrichment factor 1.0 corresponds to fuel metering with the engine at operating temperature. 30 60 90 120 150 sEnrichment factorTime after starting+20C0C20C432100 30 60 90 120 150 sControl pressureTime after startingbar+20C0C20CFig. 26UMK1658Estallation location of the auxiliary-air de-vice is selected such that it assumes theengine temperature. This guaranteesthat the auxiliary-air device only functionswhen the engine is cold (Figure 27).Full-load enrichmentEngines operated in the part-load rangewith a very lean mixture require an en-richment during full-load operation, in addition to the mixture adaptation result-ing from the shape of the air funnel.This extra enrichment is carried out by aspecially designed warm-up regulator.This regulates the control pressure de-pending upon the manifold pressure(Figures 28 and 30).This model of the warm-up regulatoruses two valve springs instead of one.The outer of the two springs is supportedon the housing as in the case with thenormal-model warm-up regulator. The inner spring however is supported on adiaphragm which divides the regulatorinto an upper and a lower chamber. Themanifold pressure which is tapped via ahose connection from the intake manifolddownstream of the throttle valve acts inthe upper chamber. Depending upon themodel, the lower chamber is subjected toatmospheric pressure either directly orby means of a second hose leading to theair filter.Due to the low manifold pressure in theidle and part-load ranges, which is alsopresent in the upper chamber, the dia-phragm lifts to its upper stop. The innerspring is then at maximum pretension.The pretension of both springs, as a result, determines the particular controlpressure for these two ranges. When thethrottle valve is opened further at fullload, the pressure in the intake manifoldincreases, the diaphragm leaves the upper stops and is pressed against thelower stops.The inner spring is relieved of tensionand the control pressure reduced by thespecified amount as a result. This resultsin mixture enrichment.Gasoline-injectionsystems28Auxiliary-air device1 Electrical connection, 2 Electrical heating, 3 Bimetal spring, 4 Perforated plate.Dependence of the control pressure on engine loadAcceleration responseBehavior of the K-Jetronic when the throttle valveis suddenly opened.1 2 3 4Control pressureEngine loadFull loadIdle and part loadOpenClosedThrottle-valveopeningSensor-plate travelEngine speed0.10 0.2 0.3 0.4 sTime tFig. 28Fig. 29Fig. 29UMK0127YUMK0019EUMK1659EAcceleration responseThe good acceleration response is a re-sult of overswing of the air-flow sensorplate (Figure 29).Transitions from one operating conditionto another produce changes in the mix-ture ratio which are utilized to improvedriveability.If, at constant engine speed, the throttlevalve is suddenly opened, the amount of air which enters the combustion chamber, plus the amount of air which isneeded to bring the manifold pressure up to the new level, flow through theairflow sensor. This causes the sensorplate to briefly overswing past the fully opened throttle point. This overswingresults in more fuel being metered to theengine (acceleration enrichment) and ensures good acceleration response.K-Jetronic29Warm-up regulator with full-load diaphragma During idle and part load,b During full load.1 Electrical heating,2 Bimetal spring,3 Vacuum connection (from intake manifold), 4 Valve diaphragm,5 Return to fuel tank, 6 Control pressure (from fuel distributor),7 Valve springs,8 Upper stop,9 To atmospheric pressure,10 Diaphragm,11 Lower stop.a21 3 4 5 67891011bFig. 30UMK1660YSupplementary functionsOverrun fuel cutoffSmooth fuel cutoff effective during over-run responds as a function of the enginespeed. The engine-speed information isprovided by the ignition system. Inter-vention is via an air bypass around thesensor plate. A solenoid valve controlledby an electronic speed switch opens thebypass at a specific engine speed. Thesensor plate then reverts to zero positionand interrupts fuel metering. Cutoff of thefuel supply during overrun operationpermits the fuel consumption to bereduced considerably not only whendriving downhill but also in town traffic.Engine speed limitingThe fuel supply can be cut off to limit themaximum permissible engine speed.Lambda closed-loop controlOpen-loop control of the air-fuel ratio isnot adequate for observing extremely low exhaust-gas limit values. The lambdaclosed-loop control system required foroperation of a three-way catalytic con-verter necessitates the use of an elec-tronic control unit on the K-Jetronic. Theimportant input variable for this controlunit is the signal supplied by the lambdasensor.In order to adapt the injected fuel quantityto the required air-fuel ratio with = 1, theAdditional components for lambda closed-loop control1 Lambda sensor, 2 Lambda closed-loop controller, 3 Frequency valve (variable restrictor), 4 Fuel distributor, 5 Lower chambers of the differential-pressure valves, 6 Metering slits, 7 Decoupling restrictor (fixed restrictor),8 Fuel inlet, 9 Fuel return line.Gasoline-injectionsystems30Fig. 31UMK1507Y42175610 10738 9pressure in the lower chambers of thefuel distributor is varied. If, for instance,the pressure in the lower chambers is reduced, the differential pressure at themetering slits increases, whereby the injected fuel quantity is increased. In order to permit the pressure in the lowerchambers to be varied, these chambersare decoupled from the primary pressurevia a fixed restrictor, by comparison withthe standard K-Jetronic fuel distributor. A further restrictor connects the lowerchambers and the fuel return line.This restrictor is variable: if it is open, thepressure in the lower chambers can drop.If it is closed, the primary pressure buildsup in the lower chambers. If this restrictoris opened and closed in a fast rhythmicsuccession, the pressure in the lowerchambers can be varied dependent uponthe ratio of closing time to opening time.An electromagnetic valve, the frequencyvalve, is used as the variable restrictor. Itis controlled by electrical pulses from thelambda closed-loop controller.K-Jetronic311 Fuel accumulator, 2 Electric fuel pump, 3 Fuel filter, 4 Warm-up regulator, 5 Mixture-control unit with air-flow sensor and fuel distributor, 6 Cold-start valve, 7 Thermo-time switch, 8 Injection valves, 9 Auxiliary-air device, 10 Electronic control relay.Components of the K-Jetronic system10987654321Fig. 32UMK0040YExhaust-gas treatmentLambda sensorThe Lambda sensor inputs a voltagesignal to the ECU which representstheinstantaneous composition of the air-fuel mixture.The Lambda sensor is installed in theengine exhaust manifold at a point whichmaintains the necessary temperature forthe correct functioning of the sensor overthe complete operating range of theengine.OperationThe sensor protrudes into the exhaust-gas stream and is designed so that theouter electrode is surrounded by exhaustgas, and the inner electrode is connectedto the atmospheric air.Basically, the sensor is constructed froman element of special ceramic, the sur-face of which is coated with microporousplatinum electrodes. The operation of thesensor is based upon the fact thatceramic material is porous and permitsdiffusion of the oxygen present in the air(solid electrolyte). At higher tempera-tures, it becomes conductive, and if theoxygen concentration on one side of theelectrode is different to that on the other,then a voltage is generated between theelectrodes. In the area of stoichiometricairfuel mixture ( = 1.00), a jump takesplace in the sensor voltage output curve.This voltage represents the measuredsignal.ConstructionThe ceramic sensor body is held in athreaded mounting and provided with aprotective tube and electrical connec-tions. The surface of the sensor ceramicbody has a microporous platinum layerwhich on the one side decisively influ-ences the sensor characteristic while onthe other serving as an electrical contact.A highly adhesive and highly porousceramic coating has been applied overthe platinum layer at the end of theceramic body that is exposed to the ex-haust gas. This protective layer preventsthe solid particles in the exhaust gas fromeroding the platinum layer. A protectivemetal sleeve is fitted over the sensor on the electrical connection end andcrimped to the sensor housing. Thissleeve is provided with a bore to ensurepressure compensation in the sensor in-terior, and also serves as the support forthe disc spring. The connection lead iscrimped to the contact element and is ledthrough an insulating sleeve to the out-side of the sensor. In order to keepcombustin deposits in the exhaust gasaway from the ceramic body, the end ofthe exhaust sensor which protrudes intothe exhaust-gas flow is protected by aspecial tube having slots so designedthat the exhaust gas and the solid par-ticles entrained in it do not come intodirect contact with the ceramic body.In addition to the mechanical protectionthus provided, the changes in sensortemperature during transition from oneoperating mode to the other are effec-tively reduced. The voltage output of the sensor, andits internal resistance, are dependentupon temperature. Reliable functioningof the sensor is only possible withexhaust-gas temperatures above 360 C(unheated version), and above 200C(heated version).Gasoline-injectionsystems32Control range of the lambda sensor andreduction of pollutant concentrations inexhaustWithout catalytic aftertreatmentWith catalytic aftertreatment0.9 0.95 1.0 1.05 1.1Excess-air factor Exhaust emissions, sensor voltageNOxNOx-control rangeHCCOCOHCVoltage curveof sensorFig. 33UMK0004-2EHeated Lambda oxygen sensorTo a large extent, the design principle ofthe heated Lambda sensor is identical tothat of the unheated sensor.The active sensor ceramic is heated in-ternally by a ceramic heating elementwith the result that the temperature of theceramic body always remains above thefunction limit of 350 C.The heated sensor is equipped with aprotective tube having a smaller opening.Amongst other things, this prevents thesensor ceramic from cooling down whenthe exhaust gas is cold. Among the ad-vantages of the heated Lambda sensorare the reliable and efficient control at lowexhaust-gas temperatures (e.g. at idle),the minimum effect of exhaust-gas tem-perature variations, the rapid coming intoeffect of the Lambda control followingengine start, short sensor-reaction timewhich avoids extreme deviations from theideal exhaust-gas composition, versatilityregarding installation because the sensoris now independent of heating from itssurroundings.Lambda closed-loop control circuitBy means of the Lambda closed-loopcontrol, the air-fuel ratio can be main-tained precisely at = 1.00.The Lambda closed-loop control is anadd-on function which, in principle, cansupplement every controllable fuel-management system. It is particularlysuitable for use with Jetronic gasoline-injection systems or Motronic. Using theclosed-loop control circuit formed withthe aid of the Lambda sensor, devia-tions from a specified air-fuel ratio can bedetected and corrected. This controlprinciple is based upon the measurementof the exhaust-gas oxygen by theLambda sensor. The exhaust-gas oxy-gen is a measure for the composition ofthe air-fuel mixture supplied to the en-gine. The Lambda sensor acts as a probein the exhaust pipe and delivers theinformation as to whether the mixture isricher or leaner than = 1.00.In case of a deviation from this = 1.00figure, the voltage of the sensor outputsignal changes abruptly. This pronouncedchange is evaluated by the ECU which isprovided with a closed-loop control circuitfor this purpose. The injection of fuel to the engine is controlled by the fuel-management system in accordance withthe information on the composition of theair-fuel mixture received from the Lambdasensor. This control is such that an airfuelratio of = 1 is achieved. The sensorvoltage is a measure for the correction ofthe fuel quantity in the air-fuel mixture.K-Jetronic33Location of the lambda sensor in the exhaustpipe (schematic)1 Sensor ceramic, 2 Electrodes, 3 Contact,4 Electrical contacting to the housing,5 Exhaust pipe, 6 Protective ceramic coating(porous), 7 Exhaust gas, 8 Air. U voltage.43U216587Positioning of the lambda sensor in a dual exhaust systemFig. 34 Fig. 35UMK1684YUMK0151YThe signal which is processed in theclosed-loop control circuit is used tocontrol the actuators of the Jetronic in-stallation. In the fuel-management systemof the K-Jetronic (or carburetor system),the closed-loop control of the mixturetakes place by means of an additionalcontrol unit and an electromechanicalactuator (frequency valve). In this manner,the fuel can be metered so precisely thatdepending upon load and engine speed,the air-fuel ratio is an optimum in alloperating modes. Tolerances and theageing of the engine have no effect what-soever. At values above = 1.00, morefuel is metered to the engine, and atvalues below = 1.00, less. This con-tinuous, almost lag-free adjustment of theair-fuel mixture to = 1.00, is one of theprerequisites for the efficient after-treatment of the exhaust gases by thedownstream catalytic converter.Control functions at various operating modesStartThe Lambda sensor must have reacheda temperature of above 350C before itoutputs a reliable signal. Until this tem-perature has been reached, the closed-loop mode is suppressed and the air-fuelmixture is maintained at a mean level bymeans of an open-loop control. Startingenrichment is by means of appropriatecomponents similar to the Jetronicinstallations not equipped with Lambdacontrol.Acceleration and full load (WOT)The enrichment during acceleration cantake place by way of the closed-loopcontrol unit. At full load, it may be neces-sary for temperature and power reasonsto operate the engine with an air-fuel ratiowhich deviates from the = 1 figure.Similar to the acceleration range, a sen-sor signals the full-load operating modeto the closed-loop control unit which thenswitches the fuel-injection to the open-loop mode and injects the correspondingamount of fuel.Deviations in air-fuel mixtureThe Lambda closed-loop control oper-ates in a range between = 0.81.2 inwhich normal disturbances (such as theeffects of altitude) are compensated forby controlling to 1.00 with an accuracyof 1%. The control unit incorporates acircuit which monitors the Lambdasensor and prevents prolonged marginaloperation of the closed-loop control. Insuch cases, open-loop control is selectedand the engine is operated at a mean -value.Gasoline-injectionsystems34Heated lambda sensor1 Sensor housing, 2 Protective ceramic tube, 3 Connection cable, 4 Protective tube with slots, 5 Activesensor ceramic, 6 Contact element, 7 Protective sleeve, 8 Heater, 9 Clamp terminals for heater.1 2 34 5 6 7 8 9 10Fig. 36UMK0143YK-Jetronic35Lambda closed control-loopThe Lambda closed control-loop is superimposed upon the air-fuel mixture control. The fuel quantity to be injected, as determined by the air-fuel mixture control, is modified by the Lambda closed-loop control in order to provide optimum combustion. U Lambda-sensor signalView of the unheated (front) and heated lambda sensorsDifferential pressure(manipulated variable)Sensor-plateposition(mechanical)Engine (controlled system)Intake airAir-flowsensorCatalyticconverterLambda closed-loop controlin the Motronic ECUFuelUFuel-injectionvalvesFueldistributorExhaust-gas oxygen(controlledvariable)LambdasensorFrequency valve(final controllingelement)Fig. 38Fig. 37UMK0282YUMK0307EElectrical circuitryIf the engine stops but the ignition re-mains switched on, the electric fuel pump is switched off.The K-Jetronic system is equipped with a number of electrical components, suchas electric fuel pump, warm-up regulator,auxiliary-air device, cold-start valve andthermo-time switch. The electrical supplyto all of these components is controlled bythe control relay which, itself, is switchedby the ignition and starting switch.Apart from its switching functions, thecontrol relay also has a safety function. A commonly used circuit is described below.FunctionWhen cold-starting the engine, voltage isapplied to the cold-start valve and thethermo-time switch through terminal 50of the ignition and starting switch. If thecranking process takes longer thanbetween 8 and 15 seconds, the thermo-time switch switches off the cold-startvalve in order that the engine does notflood. In this case, the thermo-timeswitch performs a time-switch function.If the temperature of the engine is aboveapproximately +35C when the startingprocess is commenced, the thermo-timeswitch will have already open-circuitedthe connection to the start valve which,Gasoline-injectionsystems36Circuit without voltage applied1 Ignition and starting switch,2 Cold-start valve,3 Thermo-time switch, 4 Control relay, 5 Electric fuel pump, 6 Warm-up regulator, 7 Auxiliary-air device.Starting (with the engine cold) Cold-start valve and thermo-time switch are switched on. The en- gine turns (pulses are taken from terminal 1 of the ignition coil). The control relay, electric fuel pump, auxiliary-air device and warm-up regulator are switched on.3012 3 4 5 6 7305015 15 8730W1 31G5013012 3 4 5 6 7305015 15 8730W1 31G501Fig. 39Fig. 40UMK0196YUMK0197Yconsequently, does not inject extra fuel.In this case, the thermo-time switch functions as a temperature switch.Voltage from the ignition and startingswitch is still present at the control relaywhich switches on as soon as the engineruns. The engine speed reached whenthe starting motor cranks the engine ishigh enough to generate the engine running signal which is taken from theignition pulses coming from terminal 1 ofthe ignition coil. An electronic circuit inthe control relay evaluates these pulses.After the first pulse, the control relay isswitched on and applies voltage to the electric fuel pump, the auxiliary-air device and the warm-up regulator. Thecontrol relay remains switched on as longas the ignition is switched on and the ignition is running. If the pulses from terminal 1 of the ignition coil stop be-cause the engine has stopped turning,for instance in the case of an accident,the control relay switches off approxi-mately 1 second after the last pulse is received.This safety circuit prevents the fuel pumpfrom pumping fuel when the ignition isswitched on but the engine is not turning.K-Jetronic37OperationIgnition on and engine running. Control relay, electric fuel pump, auxiliary-air device and warm-up regulator are switched on.Ignition on but engine stoppedNo pulses can be taken from terminal 1 of the ignition coil. The control relay, electric fuel pump, auxiliary-air device and warm-up regulator are switched off.3012 3 4 5 6 7305015 15 8730W1 31G5013012 3 4 5 6 7305015 15 8730W1 31G501Fig. 41Fig. 42UMK0198YUMK0199YWorkshop testing techniquesBosch customer serviceCustomer service quality is also a mea-sure for product quality. The car driver hasmore than 10,000 Bosch Service Agentsat his disposal in 125 countries all over theworld. These workshops are neutral andnot tied to any particular make of vehicle.Even in sparsely populated and remoteareas of Africa and South America thedriver can rely on getting help very quickly.Help which is based upon the samequality standards as in Germany, andwhich is backed of course by the identicalguarantees which apply to customer-ser-vice work all over the world. The data andperformance specs for the Bosch systemsand assemblies of equipment are precise-ly matched to the engine and the vehicle.In order that these can be checked in theworkshop, Bosch developed the appropri-ate measurement techniques, test equip-ment, and special tools and equipped allits Service Agents accordingly.Testing techniques for K-JetronicApart from the regular replacement of thefuel filter as stipulated by the particularvehicles manufacturer, the K-Jetronicgasoline-injection system requires nospecial maintenance work. In case of malfunctions, the workshopexpert has the following test equipment,together with the appropriate test specs,at his disposal: Injector tester Injected-quantity comparison tester Pressure-measuring device, and Lambda closed-loop control tester (onlyneeded if Lambda control is fitted).Together with the relevant Test Instruc-tions and Test Specifications in a variety ofdifferent languages, this uniform testingtechnology is available throughout theworld at the Bosch Service Agent work-shops and at the majority of the work-shops belonging to the vehicle manufac-turers. Purposeful trouble-shooting andtechnically correct repairs cannot be per-formed at a reasonabe price without thisequipment. It is therefore inadvisable forthe vehicle owner to attempt to carry outhis own repairs.Injector testerThe injector tester (Fig. 43) was devel-oped specifically for testing the K- andKE-Jetronic injectors when removedfrom the engine. The tester checks all thefunctions of the injector which are essen-tial for correct engine running: Opening pressure, Leakage integrity, Spray shape, Chatter.Those injectors whose opening pressureis outside tolerance are replaced. For theleak test, the pressure is slowly in-creased up to 0.5 bar below the openingpressure and held at this point. Within 60 secs, no droplet of fuel is to form at theinjector. During the chatter test, theinjector must generate a chatteringnoise without a fuel droplet being formed.Serviceable injectors generate a fullyatomized spray pattern. Pencil jets andbundled jets are not to form.Injected-quantity comparison testerWithout removing the fuel distributor fromthe vehicle, a comparitive measurement ismade to determine the differences in thedelivered quantities from the various fuel-distributor outlets (this applies to all en-gines of up to maximum eight cylinders.Gasoline-injectionsystems38Injector testerFig. 43UMK1494YFig. 44). And since the test is performedusing the original injectors it is possible toascertain at the same time whether anyscatter in the figures results from the fueldistributor itself or from the injectors.The testers small measuring tubes servefor idle measurement and its larger measuring tubes for part-load or full-load measurement. Connection to the fuel distributor is bymeans of eight hoses. The injectors arepulled out of their mountings on the engine and inserted in the automatic couplings at the ends of the hoses. Eachautomatic coupling incorporates a push-up valve which prevents fuel escaping onhoses which are not connected (e.g. on6-cylinder systems. Fig. 44). A furtherhose returns the fuel to the tank.Pressure-measuring deviceThis is used to measure all the pressureswhich are important for correct K-Jetronicoperation: Primary (system) pressure: Provides information on the performance of thefuel-supply pump, on fuel-filter flowresistance, and on the condition of the primary-pressure regulator. Control pressure: Important for as-sessment of all operating conditions(for instance: Cold/warm engine; partload/full load; fuel-enrichment func-tions, occasionally pressure at highaltitudes). Leakage integrity of the complete system. This is particularly importantwith regard to the cold-start and hot-start behavior. Automatic couplings inthe hoses prevent the escape of fuel.Lambda closed-loop-control testerOn K-Jetronic systems with Lambda closed-loop control, this tester serves tocheck the duty factor of the Lambda-sen-sor signal (using simulation of the rich/lean signal), and the open-loop/closed-loop control function. Special adapterlines are available for connection to theLambda-sensor cable of the various ve-hicle models. Measured values are shownon an analog display.Injected-quantity comparison tester (connected to a 6-cylinder installation)1 Fuel-distributor injection lines, 2 Injectors, 3 Automatic couplings, 4 Comparison-tester hoses, 5 Small measuring tube, 6 Large measuring tube, 7 Return line to fuel tank.1 2 3 4 5 6 7 81742 35 6Fig. 44UMK1493YK-JetronicWorkshoptestingtechniques39(4.0)1 987 722 159KH/PDI-02.00-EnThe Program Order NumberGasoline-engine managementEmission Control (for Gasoline Engines) 1 987 722 102Gasoline Fuel-Injection System K-Jetronic 1 987 722 159Gasoline Fuel-Injection System KE-Jetronic 1 987 722 101Gasoline Fuel-Injection System L-Jetronic 1 987 722 160Gasoline Fuel-Injection System Mono-Jetronic 1 987 722 105Ignition 1 987 722 154Spark Plugs 1 987 722 155M-Motronic Engine Management 1 987 722 161ME-Motronic Engine Management 1 987 722 178Diesel-engine managementDiesel Fuel-Injection: An Overview 1 987 722 104Diesel Accumulator Fuel-Injection SystemCommon Rail CR 1 987 722 175Diesel Fuel-Injection SystemsUnit Injector System / Unit Pump System 1 987 722 179Radial-Piston Distributor Fuel-InjectionPumps Type VR 1 987 722 174Diesel Distributor Fuel-Injection Pumps VE 1 987 722 164Diesel In-Line Fuel-Injection Pumps PE 1 987 722 162Governors for Diesel In-Line Fuel-Injection Pumps 1 987 722 163Automotive electrics/Automotive electronicsAlternators 1 987 722 156Batteries 1 987 722 153Starting Systems 1 987 722 170Electrical Symbols and Circuit Diagrams 1 987 722 169Lighting Technology 1 987 722 176Safety, Comfort and Convenience Systems 1 987 722 150Driving and road-safety systemsCompressed-Air Systems for CommercialVehicles (1): Systems and Schematic Diagrams 1 987 722 165Compressed-Air Systems for CommercialVehicles (2): Equipment 1 987 722 166Brake Systems for Passenger Cars 1 987 722 103ESP Electronic Stability Program 1 987 722 177Automotive electric/electronic systemsSafety, Comfort andConvenience SystemsTechnical InstructionAutomotive Electric/Electronic SystemsLighting TechnologyTechnical InstructionVehicle safety systems for passenger carsESP Electronic Stability ProgramTechnical InstructionEngine management for diesel enginesRadial-Piston DistributorFuel-injection Pumps Type VRTechnical InstructionElectronic engine management for diesel enginesDiesel Acumulator Fuel-InjectionSystem Common RailTechnical InstructionEngine management for spark-ignition enginesEmission ControlTechnical InstructionGasoline-engine managementME-MotronicEngine ManagementTechnical InstructionEngine management for spark-ignition enginesSpark PlugsTechnical InstructionBrake systems for passenger carsBrake SystemsTechnical Instruction


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