ABSTRACTModern diesel Fuel Injection Equipment (FIE) systems aresusceptible to the formation of a variety of deposits. Thesecan occur in different locations, e.g. in nozzle spray-holes andinside the injector body. The problems associated withdeposits are increasing and are seen in both Passenger Car(PC) and Heavy Duty (HD) vehicles. Mechanismsresponsible for the formation of these deposits are not limitedto one particular type.

This paper reviews FIE deposits developed in modern PC andHD engines using a variety of bench engine testing and fieldtrials. Euro 4/ IV and Euro 5/V engines were selected for thisprogramme. The fuels used ranged from fossil only todistillate fuels containing up to 10% Fatty Acid Methyl Ester(FAME) and then treated with additives to overcome theformation of FIE deposits.

It was observed that engine performance was significantlyimpacted by the formation of deposits which may lead toincreased fuel consumption, loss in power, poor driveabilityand failure to start.

The selection of appropriate fuel additive technology allowscontrol of all deposit types, either by preventing theirformation or restoring engine performance.

INTRODUCTIONModern-day diesel powered vehicles are subject toincreasingly stringent exhaust emission regulations, whilst atthe same time having to meet end user requirements withrespect to power, torque, fuel economy, good driveability andincreasing levels of refinement. In addition, concerns overclimate change have resulted in measures being taken toreduce CO2 emissions from road transport. For example, in

Europe a target of 120 g/km for passenger cars will be phasedin from 2012 to 2015, with punitive financial penalties forfailure to meet the targets. For light commercial vehicles, thefleet average CO2 limit will be 175 g/km, being phased infrom 2014 to 2016.

Diesel powertrains have already undergone major technicaladvances in order to satisfy regulatory and end userrequirements, and these will continue to be further developed.Advances in Common Rail (CR) FIE have included increasedinjection pressure, multiple injection strategies, smallernozzle holes and high efficiency injector nozzles. Thesemeasures ensure the precise and repeatable metering of eventhe smallest quantities of fuel as well as providing theexcellent fuel atomisation and spray characteristics necessaryacross all engine operating conditions to promote morecomplete combustion. Other recent developments haveincluded direct-acting piezoelectric injectors, which provideimproved atomisation and more accurate fuelling controlresulting in reduced gaseous emissions, higher power andtorque and improved fuel economy [1].

These recent technical advances in fuel injection systemsrequire components to be smaller and lighter to ensure highlydynamic response. They need to be manufactured to veryexacting tolerances and have to operate within very smallclearances to minimise any leakage at the very high pressuresencountered in modern systems. Therefore, it is essential thatthe FIE is kept free from deposits of any kind and is operatedwith fuel which is fit for purpose, otherwise problems ofpower loss, emissions non-compliance, reduced fueleconomy, poor driveability and difficulty in starting are likelyto be observed.

Deposit Control in Modern Diesel Fuel InjectionSystems

2010-01-2250Published

10/25/2010

Rinaldo Caprotti, Nadia Bhatti and Graham BalfourInfineum UK, Ltd.

Copyright © 2010 SAE International

DEPOSIT FORMATION IN OLD,CURRENT AND MODERN FIESYSTEMSInjector spray-hole deposits have been observed for manyyears. Historically, these were most problematical in InDirectInjection (IDI) engines operating with pintle type injectornozzles. This resulted in the development of the CEC-023injector deposit test based upon a Peugeot XUD9 engineintended for passenger car applications. The test defined an“acceptable” level of deposit which would allow satisfactoryengine performance. This enabled the engine manufacturersand FIE companies to develop FIE systems which werespecifically designed to operate with the levels of depositswhich would result from operation with typical market fuels[2]. Mentioned in this reference is that 'complete eliminationof deposits is undesirable as nozzles are ‘designed’ to giveoptimum performance with a certain level of deposit. This isthe only FIE system where complete cleanliness is consideredundesirable. However, the use of this particular type of FIEdesign was discontinued in the late 1990's because if itsinability to meet stringent emission regulations.

Direct Injection (DI) and High Speed Direct Injection (HSDI)engines did not suffer to the same extent, but more recentlythe trend for smaller holes and high efficiency nozzles hasresulted in many more instances of injector spray-holedeposits causing problems [3, 4, 5]. The reasons for thisincrease include:

1. Smaller holes which for a given deposit level will result ina proportionately larger reduction in flow area and thereforelarger flow rate reduction, resulting in loss of torque andpower.

2. High efficiency nozzles with honed entry to nozzle holesand/or tapered nozzle holes resulting in reduction orelimination of cavitating flow within the nozzle. The collapseof cavities in such flow regimes is known to be effective indislodging and preventing the build up of deposits.

3. Combustion and air management trends resulting in highernozzle tip temperatures, which promote nozzle deposits. Thetrend towards downsized engines will tend to exacerbate this.

The FIE systems utilised since the late 1990s, unlike thosedescribed in reference 2, require no or very minor level ofdeposits to perform at their best, hence ensuring the lowestpossible level of noxious emissions and fuel consumption.Therefore, a fuel additive solution to control depositformation is very complex to achieve as the requirements aredependent of the FIE type. It is therefore the remit of theadditive and fuel formulator to develop solutions that areapplicable to such a diverse range of FIE systems. Thischallenging target can however be met as described inreference [6] where the best level of spray-hole deposit isachieved for any FIE system in the market:

I). No deposits in modern FIE systems

II). The level of deposit that the IDI system has beencalibrated to [2]

Internal Injector Deposits (IID) are a relatively newphenomenon, initially reported in PC applications [7, 8], andnow increasingly observed in PC and HD vehicles. Currentlythe problem appears to be particularly acute in HDapplications in North America, and as a consequence theCRC has now formed a working group to look at this issue.In addition, there have been reports of deposits in highpressure fuel pumps causing operational problems.

FUEL ADDITIVE APPROACHThe problems described in the previous chapter are seen in avariety of countries and can occur in PC and HD typeapplications equipped with High Pressure Common Rail(HPCR) systems or with Electronic Unit Injectors (EUI).These problems are not specific to one fuel type as they areseen in markets that have Ultra Low Sulphur Diesel (ULSD)fuel, but also in markets where sulphur (S) level is up to 500ppm. It would seem that the presence of Fatty Acid MethylEster (FAME) can significantly vary the level of deposit,sometimes more, equivalent or lower than that seen in fossilbased diesel fuel. Therefore, the mix of issues is complex andis somewhat difficult to postulate mechanisms that describeall the phenomena experienced. It has been made aware to theauthors that more than 20 companies around the world havereported one or more of these issues related to injectordeposits.

Traditionally, injector deposits have been tackled by the useof detergent/surfactants chemistries developed in the 1980s.Through their life, such fuel additives have undergone avariety of improvements to increase their performance andcost effectiveness. However, studies carried out recently [3,4, 6] have confirmed that these chemistries are no longer thebest option to deal with a type of deposit that is chemicallydifferent from the wholly carbonaceous type deposit seen inIDI type FIE or that which is formed in a completely differentarea of the fuel injector [7,8].

The challenge then becomes the development of an additivesolution which can deal with all these types of deposits. Thiswould then allow any fuel used in the market place toovercome most of the issues that have recently surfaced, andthis is the task that has been addressed in this paper. Newdiesel detergent technology has been tested in a variety ofFIE system applications to understand the potential for thecontrol of different types of injector deposit. In some of thesetests, the results obtained have also been compared withconventional diesel detergents.

The testing carried out used modern engines which are fittedwith the latest FIE systems. As such, the expectation is that

there should not be a large change in engine performanceover the short period of time typical of the deposit test cyclesdescribed in this paper. Therefore, the effects that areobserved in the testing carried out can be largely attributed toFIE deposits being formed.

Engine TestingThe testing undertaken encompassed the use of the CECDW10 bench engine test and field trials using passenger carsfitted with CR Euro 4 engines to assess the performanceregarding spray-hole deposits. HD bench engine tests wereused to confirm additive performance in EUI Euro IVengines, whilst an advanced Euro V engine was used tounderstand the ability to prevent one particular type ofinternal injector deposits.

Test FuelsIn the market today there are a variety of fuel qualities. Theserange from fuels of different S level, to those containingdifferent level of bio-component, typically FAME. In order toconfirm the performance of the additives tested, a variety offossil fuels and BX have been selected (X is the percentage ofbio-component). Today, diesel fuel can contain bio-component. In Europe B7 is now becoming more prevalentand as the level of the bio-component will further increase inthe future, most of the data were developed in European typefuels containing 10% FAME.

Zinc contamination has been used in most testing presentedin this study. Metal contamination has shown to be present infield conditions. Two sources have been described, the firstcontamination occurs prior to fuel delivery into vehicle tanks;the other happens due to the corrosive attack of the fueltoward FIE components [5, 11]. Therefore, there is scope formetal contamination of fuel throughout its pathway fromrefinery to its combustion in the engine. The metalcontamination, together with fuel degradation products, canaccumulate within the FIE system causing deposits that canlead to increased fuel consumption, loss in power and poordrivability. A further study has been conducted to confirmthis potential. Twenty five different ULSD fuel samples havebeen collected from service stations in the same market/country. The level of metal contamination was measured.Several metals were found to be present including Zn, Na.The level of Zn and Na measured is reported in the table 1below. In this market FAME is not yet used. The expectationis that the presence of this bio-component will furtherexacerbate the metal pick up potential.

Table 1. Zn and Na content of 25 ULSD market samples

Passenger CarsWith the plethora of fuel qualities available in the marketplace, there is an increasing incentive for an additivecompany to supply detergent technologies that workeffectively across the board. The CEC F-098-08 PeugeotDW10 engine is widely recognised as the industry standardinjector deposit test for Euro 5 and beyond [3, 6]. Thissection examines the appetite and propensity to form depositsof varying fuel types in this test with and without dieseldetergents.

Infineum's experience with this test has shown that base fuelsof different origin have a varying degree of propensity to foulinjectors resulting in power loss. The CEC procedureprescribes the use of DF-79-07 as the reference fuel for thetest with and without metal contamination, where the metalcontamination is 1 ppm Zinc (Zn). It can be noted that fossilfuels which are not contaminated with metal prior to the testdo not usually show the tendency to foul injectors. However,the fouling levels can be quite substantial with the level ofmetal contamination used in the CEC reference fuel (which isindicative of the level of Zn observed in the field).

Figure 1 demonstrates the level of power loss observed whenusing different fuels over an extended period of time.DF-79-07 at 32 hours has developed up to 6.5% power loss;conversely a standard EN590 fossil fuel (EU 1) achieved upto 12% power loss. Additional tests were then carried out tounderstand what the maximum possible fouling level was forboth fuels. Extending the run time to 64 h did not change thelevel of deposit for the CEC reference fuel, however for EU 1fuel, the deposit level further increased by an additional 5%by 80 h.

Moreover, at the end of this test, this fuel continued to show atrend to develop further deposits. This phenomenon has also

been seen with other fuels from Europe and Asia Pacific intesting recently carried out. The level of fouling shown issimilar to the EU 1 fuel, whilst different batches of the CECreference fuel, tested in different DW10 engines, have onlygiven between 4 and 6% power loss with 1 ppm Zn. Thesedata suggest that the CEC reference fuel, if anything, isrepresentative of market fuels which generate a low level ofinjector deposits. Possibly, the typical market fuel has ahigher degree of fouling as also confirmed in other papers[9].

As previously mentioned, the use of FAME in the DW10 testcan result in varying levels of injector fouling. Numerouspapers, including that presented by the CEC working group,describe extensive studies in this area. There does not seem tobe a clear and agreed position on why different biofuels indiesel generate different level of deposits. The level ofpossible oxidative degradation, as measured by the Rancimattest or inferred from the iodine value, and the level ofimpurities like mono-glycerides do not seem to correlate withthe deposit formation rates observed [10]. Therefore, ourwork focussed on the use of test fuels containing bio-component with 1 ppm Zn in an effort to provide consistencyin deposit generation. The data in table 2 show that:

1. The European BX market fuels tested have a large depositformation propensity when metal contamination occurs.

2. Using the same biofuel batch of RME, the results seen arevery variable and also somewhat confusing. The RME10alone has the highest level of injector deposit. When this testwas repeated with 1 ppm Zn added, the result was better,from 15% to just below 5% power loss. This phenomenonhas been seen in some studies, whilst others have reported theopposite effect [4].

3. The reference fuel and the market fuel treated with thesame batch of RME at different levels of BX gavesubstantially different results, from just below 5% power lossto more than 8%.

4. Different batches of commercial RME give can also givedifferent results

These data confirm that the behaviour of FAME is variableand can not be predicted as yet. Furthermore, the profile at 32hours shows that deposit is still forming and, for some BXfuels, the downward trend is still very pronounced (notreported in this paper). The implication is that any additivetreat rate that is used to control injector coking must take thisinto account. Therefore, any safe level selected for marketuse should be able to cope with fuels as severe as thoseshown. This is further supported by other studies wheresimilarly high levels of deposits were reported for marketfuels [9].

These types of injector deposits can be controlled withappropriate additive technology for entirely fossil and FAMEcontaining diesel as shown in figure 2. The treat rate used (asactive ingredient or as a component) for the new dieseldetergent is substantially lower than the typical treat rate ofconventional diesel detergent used in most standard marketdiesel fuel. The treat rate of the new diesel detergent used todevelop the data in figure 2 is the same for fossil fuel andBX.

For ease of interpretation, new diesel detergent has beenabbreviated to NewD and conventional diesel detergent toConvD in all figures going forward.

Figure 1. DW10 power loss results for B0 reference fuels with 1 ppm Zn.

With the same additive technology it is possible to achievereliable and consistent clean up performance in this type oftest. The injectors are first run on base fuel for 32h, as per theCEC test, or until a certain level of power loss has beenreached. Then, the same fuel treated with additive is used toassess its cleaning ability. Typically, additive treat rates usedare higher than those applied to keep the injector clean.

The ability of the new diesel detergent to remove deposits ata treat rate which is typical for top premium fuel qualities inthe market place today can be seen in figure 3. The powerloss in this engine test is proportional to the deposit level asconfirmed by the findings of the CEC 098 working group.The clean up profile suggests that the vast majority of thedeposit is removed in the first hour, approximately 70%,which corresponds to 2% absolute power loss. This isgenerally considered by the industry to be the maximumacceptable level for modern powertrains. The rate of cleaning

reduces after the first hour and all the deposit is removed witha further 11 hours of running. The data have been obtained ina typical European B7 market fuel.

It has been observed, that by varying the relative treat rates ofthe new diesel detergent technology, the rate/profile of powerrestoration in the first few hours will differ greatly, whilst thesubsequent rate of cleaning is somewhat similar regardless ofthe additive treat rate level, see figure 4. This shows thepotential that, at elevated treat rate, the new detergent canreach the industry target of less than 2% power loss wellwithin a tank full of premium fuel (equivalent to 80%normalised power loss in figure 3).

Several papers report that conventional diesel detergents,usually long chain poly-isobutylene/polar bridge/N richsurfactants, are less effective in this environment [8]. Thisdescribes the typical chemical signature of most diesel

Table 2. DW10 results in BX fuels with and without 1 ppm Zn.

Figure 2. DW10 power loss results of base fuel with 1 ppm Zn and the same fuel treated with NewD, at a treat rate which islower than typical treat rate of conventional detergent for most standard fuel qualities in the market place today.

detergents currently used in the market place. Infineum'slatest data confirms this. These types of detergents areineffective in the DW10 test at typical market treat rates forfossil and for FAME containing fuels. The relative treat ratesof conventional and new diesel detergent to achieve the samelevel of performance in the DW10 test are shown in figure 5.It is worth noting that with the conventional detergent it is notpossible to reach a good level of clean up at market relevanttreat rates. The level of conventional detergent can bereduced by utilising a Metal De-Activator (MDA). However,

this approach is only applicable for maintaining cleaninjectors as MDAs are far less effective in clean up mode.

Field testsIn order to confirm the applicability of the bench engine testresults to real life conditions, some passenger cars were testedin the field to assess their tendency to form injector deposits.This helped further understanding of the impact that fielddeposits can have on the designed engine performance and

Figure 3. Normalised power loss- DW10 clean up performance of new diesel detergent technology at treat rate which is typicalfor premium diesel fuel.

Figure 4. Clean up effects of varying additive treat rates in the first hour and after 32 hours run time in DW10.

the benefits of restoration/prevention when utilising additivetreated fuel.

Test fuelsThe fossil fuels tested were all EN590 compliant. Base fossilfuel was obtained directly from a European refinery, whilstthe FAME (RME- rich) was sourced from a major producerand contained antioxidant. The premium market treated dieselfuel was sourced from the forecourt in a single batch. Zinccontamination was only used in programme 2.

Test VehiclesVehicles selected for this testing programme were twomodern passenger car vehicles that comply with Euro 4emission standards. The vehicles had CR fuel injectionsystems and did not have a diesel particulate filter. This typeof vehicle is highly relevant as it represents 29% of Europeanmarket sales in 2007, a segment known in the industry as B-class. Each vehicle had completed approximately 100,000kmof uncontrolled driving prior to the field trial and, when fieldtested, was loaded to simulate four passengers with luggage.Driving conditions were mostly uncontrolled highwaydriving, with some low speed operations, with driving speeddependant on speed limits and weather conditions. Thevehicles were fully checked before the trial to ensure thatthere were no engine or vehicle problems.

Testing ProgrammesTwo different programmes were completed. For eachprogramme, the vehicles were taken as received and assessedfor the impact of deposits on the engine performance.

Programme one was aimed at assessing the impact of fuelquality. As such, the vehicle was run as received. European

premium market fuel was used for 3,000km followed by anadditional 3,500km with the same fuel top treated with thenew diesel detergent technology (No added Zncontamination).

In programme two, the used vehicle was fitted with newinjectors. The fuel used was contaminated with Zn at 1 ppm,a level used in the reference fuel in the DW10 test and alsofound to be of possible market relevance [11]. Aftersuccessful accumulation of deposits in 10,000 Km, the effectof utilising the new diesel detergent technology was assessedfor a further 5,000 Km.

For each programme, the vehicle was tested at regularintervals to indicate whether deposits were formed and if so,their impact on engine performance. To do this, a variety oftests were carried out. The typical testing regime involved thevehicle being preconditioned with a 12 hour soaking periodfollowed by the New European Driving Cycle (NEDC) foremission testing and fuel consumption (standard and hotconditions). Other cycles were also used to confirm thepresence of deposit via power loss at different engineconditions. When one cycle was showing differences, theother tests were giving similar ratings confirming the validityof the results. The details of the test protocols are describedbelow.

Test protocols11- NEDC - This is the emissions regulatory cycle used inEurope for passenger cars and is well known. Therefore, it isnot described in this paper.

22- Full load acceleration: measured using street loadsimulation and a warm engine, with a coolant temperature ofabout 90°C. The vehicle is driven in gear at idle/low speed

Figure 5. Relative treat rate comparison (as active ingredient or component) of new diesel detergent technology vs. conventionalcurrent detergent in DW10.

(this must be always the same at the start of each test). Then,the throttle is set at 100%. When the engine speed reaches aset rpm, which is vehicle dependent, the throttle is then set to0% to return to the original conditions. This is done threetimes. The average of the higher rpm data is used in thispaper. For the vehicle tested, the gear used for this protocolwas the 4th and the rpm were increased from 1000 to4500rpm.

33- Full load: measured using the mode for constant vehiclespeed and a warm engine, with a coolant temperature ofabout 90°C. A constant vehicle speed is driven and the pedalvalue is set at 100% and maintained for about 3 minutes. Thepower at the roller is measured. From these data, it is possibleto estimate the power provided to the wheel. The speedselected was 90 km/h.

The results of both programmes will be discussed in furtherdetail in the following paragraphs.

Results of Programme One

Programme one consisted of three distinct stages. At no stagewas Zn contamination added to the fuel prior to fuelling thevehicle. The first stage assessed the vehicle as received fromthe field, which had accumulated approximately 100,000kmof uncontrolled driving and fuel source. The vehicle was thenfitted with new injectors and run for 2,000km. This was toassess the potential for power increase, similar to that seen inthe initial phase of most CEC DW10 tests. Figure 6 comparesthe observed power loss across the injector sets. For ease of

interpretation the differences in injector sets are describedbelow:1). Injectors as received from the field with approx100,000km accumulated: Injector set A2). Same vehicle fitted with new injectors: Injector set B at0km3). Same vehicle fitted with new injectors which have beenrun in for 2,000km: Injector set C

Comparing injector set A vs. new injector set B, a 1.6%increase of power was measured with protocol 22. Similarly,a change in power was also observed when testing injector setC and B, a further 2.4% increase. Therefore, the totalpotential power loss between injectors as received from thefield and the best possible with new run in injectors is 3.9%.This is a substantial level of power loss which is very likelyto be experienced by a driver, particularly when accelerating.The loss in engine performance due to fouling is alsoreflected in an increase in fuel consumption as measured byprotocol 11. The penalty was approximately 5.2%. The valueof this initial test is that it indicates the maximum powerachievable by a clean set of nozzles. This defines the truetarget for any test aimed at removing deposits as the valueobtained with new injectors is lower than what achievable inthe field after a running in period.

The second stage involved assessing the impact of a premiummarket fuel on the already fouled injectors, set A. The vehiclewith the old injectors (set A) ran in segments of 750km to atotal accumulation of 3,000km. After each segment, the

Figure 6. Graph to show impact of deposits on power for injector sets A, B and C.

vehicle was assessed in the same way as described above.The fuel utilised in this segment was a European marketpremium diesel fuel. Figure 7 shows the power loss observedover the period of testing in protocol 22. It can be noted thatwhen using premium treated market fuel, the final poweroutput further decreased by approximately 3.6% from thealready fouled injectors or 7.3% power loss from newinjectors after run in (Set C). The power level is seen to bestabilising from 2,250km to 3,000km.

The test was then continued with premium market fuel toptreated with the new diesel detergent additive at a levelsimilar to that used for today's standard fuel. The fueladditive was added to the already treated premium marketdiesel fuel. At the end of an additional 3,500km, there was apower recovery of 1.8%, using the same test protocol. Thisresulted in a fuel consumption benefit of 9.4%; this is a verylarge value. However, whilst the absolute amount may bequestioned as being too high, the trend to better fuel

consumption with lower power loss has been confirmed alsoin the second programme and in other papers [4, 9].

Programme two involved generating deposits in the FIEsystem in a more controlled manner. A second vehicle wasselected as per the criteria described above and fitted with anew set of injectors. The vehicle was fuelled with a B10-RME dosed with 1 ppm Zn contamination and ran for10,000km, after which the new diesel detergent was added atpremium market treat rate. Figure 8 shows the powerresponse over the mileage accumulated in the two phasesusing protocol 22. Within 10,000km a considerable powerloss of 13.4% was observed, however the addition of the newdiesel detergent at market relevant treat rates substantiallyrestores power, almost to the original level achieved withclean injectors. It is worth noting that most of the power isrecovered within 2,500 km. For the vehicle tested, a smallpassenger car, this is equivalent to three tanks full.

Figure 7. Protocol 22- Power curve over time with treated premium market fuel and new diesel detergent technology.’

Figure 8. Protocol 22-Power curve over time with B10 diesel fuel and treated with new diesel detergent technology

Figure 9 shows the comparison of power loss in the full loadacceleration test (protocol 33), where only three results areshown for improved clarity. There is a substantial loss whenthe deposit is formed, see the 10,000 km point vs. start of test.When using treated fuel, the majority of the deposit isremoved and the power restored within 5,000 km. The resultsobtained in protocol 33 show the same benefit as that shownin figure 8.

The fuel consumption data shown in figure 10, mirrors whatis seen in programme one. NEDC data was measured at thestart, after 10,000 km and after a further 5,000 km withtreated fuel (the 15,000 km point). Throughout theprogramme the metal contamination in the fuel wasmaintained at 1 ppm Zn. Fuel consumption penalty with lossin power due to spray-hole deposit is seen both in cold(standard) and hot test conditions. The penalty is substantial.The use of the new diesel detergent restores fuel consumptionto a level similar to that of new injectors/without deposits.

Figure 10. Protocol 11- Fuel consumption in l/100kmmeasured in the NEDC.

This set of results further confirms how contaminated fuelscan lead to power loss and performance debits: particularlycritical is the increase in fuel consumption. The use of thecorrect fuel additive technology can result in part or completerestoration of power. This can re-establish the fuelconsumption to a level which is the lowest achievable by thevehicle.

HDRecent work presented at the SAE World Congress in 2009[12] highlighted the potential for deposit formation in EUIsystems. Here, there is the potential for lubricant to enter thefuel in the high pressure area of the FIE system. Although thelevel of oil leakage is minimal and injector dependent, thiscontaminant is known for its criticality in generating injectordeposits. All engine lubricants contain Zn based componentsto prevent wear. The reference cited earlier demonstrated thatsuch component can lead to spray-hole deposits [3, 4, 5, 9,10, 11, 12].

A programme mirroring the protocol in reference 12 wascarried out to assess the ability of the new diesel detergentadditive technology to prevent or remove deposits in this typeof FIE system. The details of the projects are listed below.The engine used is described in the table 3 below and is thesame as used for the previous work [12].

Figure 9. Protocol 33-Comparison of power loss in full load acceleration test

Table 3. Engine parameters

The inability to control the amount of lubricant leakagemeant that the level of contamination would be very difficultto estimate or measure and highly dependant on the injectorset used. Therefore, it would be meaningless to compareresults from different tests. To overcome this, a metal freelubricant was used. Controlled metal contamination wasachieved via the addition of Zn at 1 ppm in fuel. The benchengine testing protocol used consists mainly of a high loadcycle and is the same as Cycle 1 with the final phaseextended by 14 hours to 34 hours in total. Instead of ZDDP(present in lubricant) a Zn salt was used to ensure consistentlevel of contamination in the fuel, avoiding any potentialuncontrolled precipitate/loss of this component.

Two European market fossil fuels were used for this project.The main fuel, used for all comparison testing and asreference fuel, was than made into RME10. The RME usedwas treated with a high level of antioxidant to ensure that nodegradation occurred over time. This fuel was free of anydetergent additive. The second diesel was a premium fuelwidely sold across Europe. This fuel contains a substantiallevel of conventional diesel detergent.

The results obtained when using the two fuels was surprising.What was interesting was not so much the level of power lossdue to spray-hole deposits, figure 11, but the difference seenbetween the two fuels. The reference fuel was tested threetimes during the project. The result shown is typical of whatwas seen and the difference between the test runs was small,with less than 1% power loss at the end of the tests.Surprisingly, the level of deposit formed with the premiumfuel is substantially more. It was not possible to understandwhy such difference was seen. However, the data reinforcewhat has been seen in the DW10 test: the deposit formationrate is fuel dependent and the presence of conventional dieseldetergent technology, at high market treat in the premiumfuel, is not able to control injector spray-hole depositsformation in modern FIE systems.

The next stage of the project was aimed at understanding,using the RME10 fuel, what could be the impact ofconventional and new detergent technology. The keep cleandata, when trying to prevent deposit formation, aresummarised in figure 12. It is clear that there is a step changein performance when the new detergent technology is used.The control of the injector deposit is significant whencompared to the three runs with the same untreated base fuel.This also confirms that the difference seen in figure 11 is

Figure 11. Response of two European fuels

significant. Conventional detergent can help in controllingdeposits in this environment. However, as per the data shownin figure 5, the level of additive required is much higher thanfor the new detergent additive technology. Several studieshave reported that the use of MDA can help and this studyconfirms this. The use of MDA with conventional dieseldetergent can reduce the overall treat rate, although always ata level well above that used for the new detergent. However,although not tested here, the main limitation of this approachis in the ability to clean up.

The previous data show the ability of the new diesel detergentto control deposit formation. This is further demonstrated infigure 13, where the new diesel detergent, at a typical markettreat for standard fuel quality, is able to remove some of thedeposit. The rate of removal is not large. It suggests that atthis treat rate and at least in this base fuel, the additive mighteventually return power loss to zero. Moreover, it is also verylikely that, similarly to the DW10 test, higher treating levelscould achieve a higher degree of power recovery.

Internal Injector DepositsIn the last two to three years, the industry has seen theoccurrence of a new type of deposit in modern FIE systems,never experienced before, in various regions. The depositshave been analysed and several mechanisms have beenproposed [7, 8]. The authors of this paper have been madeaware of a range of these types of issue in the market. Thesituation is rather complex as these IIDs do not seem tocorrelate strongly to specific types of diesel fuel, fossil or

FAME containing, and occur both in PC and HDapplications. Moreover, the nature of the deposit can be verydifferent, from metal salts to ashless polymeric materials.Another complexity is that it is not clear which are theboundary conditions that can generate such deposits, althoughsome suggestions have been reported in the literature [7, 8].

One of the OEM reporting such problems was able togenerate IIDs in a bench engine test using advanced Euro VHD engines. After some initial testing that showed thepotential of the new diesel detergent, a back to back benchengine test was performed. The test engine, fitted with a CRFIE, underwent a 300 h endurance test. The test was mainlyrun at high load, with fossil fuel meeting EN590. At the endof the test, the engine was showing a variety of problems.The OEM running this test identified IIDs as the cause ofthese problems. They observed deposits on the injectorneedle and on the pushrod which caused sticking of thesecomponents in their guidance. This sticking resulted in someinjectors not injecting at all at low rail pressures, thus causingdifficulties in restarting and poor running at idle due toincomplete combustion or non-firing cylinders. Thephotographs of the critical components are shown in figure14. They show the extent of the deposit after the 300 hourrun. The visual evaluation of the deposits seen suggests thepresence of thick carbonaceous and varnish-like material.

Figure 12. Comparison of power loss in kW between base fuel and detergent treated fuel.

Figure 14. Photographs of critical components after 300hours run with EN590 fossil fuel

The same fuel was then treated with the new diesel detergenttechnology at a typical treat rate for standard fuel qualitiesused in the market today to control injector deposits inmodern PCs. The use of this additive completely overcamethe problem. At the end of the 300 h test with treated fuel, the

injectors were removed and dismantled for inspection. TheOEM observed no evidence of any internal depositwhatsoever, as shown in figure 15. This can only be ascribedto the presence of the new diesel detergent technology.

Figure 15. Photographs of critical components after 300hours run with EN590 fossil fuel and new detergent

Figure 13. Clean up ability of new additive technology in HD applications

It is clear that the new diesel detergent additive technology isalso able to control this type of internal injector deposit seenin this engine group. It must be stressed that the nature ofthese deposits, to the best of our knowledge, is not related tosodium salt deposition. The analysis of the deposit will becarried out in the near future, though its nature is expected tobe due to a mix of different mechanisms/deposit formationpathways.

SUMMARY/CONCLUSIONSModern diesel FIE systems are susceptible to the formationof a variety of deposits that occur in nozzle spray-holes andalso inside the injector body. These problems are increasingin the field and are seen in both PC and HD vehicles.Mechanisms responsible for the formation of these depositsare not limited to one particular type and are sometimes notwell understood.

The data presented in this paper confirms that:

Conventional diesel detergent technology can match theperformance of the new diesel detergent in keep clean(prevention) type testing, although at high treat rates.However, it is impossible to achieve a good degree ofdeposits removal (clean up) even if treat rate is increased wellabove the level acceptable in the market.

The new diesel detergent additive technology can controlthese new types of deposit either by preventing or byremoving them when present on injector components and atinjector spray-holes. Remarkably, increasing additive treatrate, where tested, can achieve full control of spray-holedeposits within a short time. The performance has beenconfirmed in bench engine tests and field trials using avariety of PC and HD configurations. Testing was carried outwith market fuels ranging from fossil to fuels containing upto 10% FAME, confirming the effectiveness of this productin market representative fuels.

Testing has confirmed that removal of injector deposits canrestore the best driving conditions and achieve the lowestsignature fuel consumption.

CONTACT INFORMATIONInfineum UK LTDwww.infineum.com

ACKNOWLEDGMENTSThe authors would like to thank Continental for the supportof carrying out some of the testing presented in this paper.We would also like to thank our colleagues in FuelsTechnology for their contribution, in particular MarkoZupancic.

DEFINITIONS/ABBREVIATIONSFIE

Fuel Injection Equipment

HSDIHigh Speed Direct Injection

HPCRHigh Pressure Common Rail

EUIElectronic Unit Injector

IDIIndirect Injection

IIDInternal Injector Deposits

NewDNew Detergent

ConvDConventional Detergent

REFERENCES1. Dober, G., Tullis, S., Greeves, G., Milovanovic, N.,Hardy, M., Zuelch, S., “The Impact of Injection Strategies onEmissions Reduction and Power Output of Future DieselEngines,” SAE Technical Paper 2008-01-0941, 2008, doi:10.4271/2008-01-0941.

2. Panesar, A., Martens, A., Jansen, L., Lal, S., Ray, D.,Twilley, M., “Development of a New Peugeot XUD9 10Hour Cyclic Test to Evaluate the Nozzle Coking,” SAETechnical Paper 2000-01-1921, 2000, doi:10.4271/2000-01-1921.

3. TAE Symposium, 2005: Injector Deposit Test For ModernDiesel Engines, Graupner, O., Klaua, T.; Siemens VDOAutomotive AG, Caprotti, R., Breakspear, A.; Infineum UK,Schik, A., Rouff, C.; APL Automobil Prueftechnik LandauGmh.

4. Caprotti, R., Breakspear, A., Graupner, O., Klaua, T.,“Detergency Requirements of Future Diesel InjectionSystems,” SAE Technical Paper 2005-01-3901, 2005, doi:10.4271/2005-01-3901.

5. Capriotti, R., Leedham, A., Graupner, O., Klaua, T.,“Impact of Fuel Additives on Diesel Injector Deposits,” SAE

Technical Paper 2004-01-2935, 2004, doi:10.4271/2004-01-2935.

6. TAE Esslingen Symposium 2007: Beyond 2008: Thechallenges for diesel detergency, Caprotti, R, Breakspear, A,Graupner, O, Klaua, Ts, Kohnen, O.

7. TAE Esslingen Symposium 2009: Effects of FuelImpurities and Additive Interactions on the Formation ofInternal Diesel Injector Deposits, Ullmann, J, Geduldig, M,Stutzenberger, H, Caprotti, R, Balfour, G.

8. Ullman, J., Geduldig, H., Stutzenberger, H., Capriotti, R.,Balfour, G., “Investigation into the Formation and Preventionof Internal Diesel Injector Deposits,” SAE Technical Paper2008-01-0926, 2008, doi:10.4271/2008-01-0926.

9. 2007 13th Asia Fuel and Lube Conference: Injectorfouling effects in modern Direct Injection Diesels, Barbour,RH, Macduff, MAJ, Panesar, A, Quiegley, R.

10. JSAE, Injector Workshop Japan, July, 2007:Development of Peugeot DW10 Direct Injection DieselNozzle Fouling Test.

11. TAE Esslingen Symposium 2009: Diesel fueldegradation and contamination in Vehicle Systems, Williams,R, Balthazar, F.

12. Tan, J., Pischinger, S., Tomazic, D., Lamping, M.,Thomas, K., Tatur, M., “Coking Phenomena in NozzleOrifices of DI Diesel Engines,” SAE Int. J. Fuels Lubr. 2(1):259-272, 2009.

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ISSN 0148-7191

doi:10.4271/2010-01-2250

Positions and opinions advanced in this paper are those of the author(s) and notnecessarily those of SAE. The author is solely responsible for the content of the paper.

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