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1 High precision high pressure diesel common rail fuel injection systems play a key role in emission control, fuel consumption and driving performance. Deposits have been observed on internal injector components, for example in the armature assembly, in the slots of the piston and on the nozzle needle. The brownish to colourless deposits can adversely impact driveability and result in non-compliance with the Euro 4 or Euro 5 emission limits. The deposits have been extensively studied to understand their composition and their formation mechanism. Due to the location of these deposits, the influence of combustion gas can be completely ruled out. In fact, their formation can be explained by interactions of certain diesel fuel additives, including di- and mono-fatty acids. This paper describes the methodology used and the data generated that support the proposed mechanisms. Moreover, approaches to avoid such interactions are discussed.

Diesel fuel is a major grade in the Thai market used in transportation of goods and in most light duty vehicles. Over the last fifteen years the quality of this fuel has continuously increased. This is one of the major factors that have allowed a substantial improvement in air quality. The improvement in diesel fuel quality has been achieved by using a mix of measures, some well known like reduction in sulphur content, whilst others are unique to this market. Since 1993, in Thailand it has been mandatory to use a diesel detergent. This has ensured best driveability and lowest emissions due to the control of injector deposits. This measure was unique in the world and although not mandatory any longer, this market has a large proportion of automotive diesel treated with this type of additive. Another action has been the evaluation of Palm Oil Methyl Ester (PME) and its potential impact in the market. However, experience with PME is limited.

The use of a diesel particulate filter (DPF) is one of the most flexible methods of reducing particulate emissions from diesel engines, and has the advantage of controlling both the number and mass of particulate emissions. To maintain engine performance over time, the soot accumulated in the filter needs to be removed by oxidation. This paper describes the development of a novel iron based fuel-borne additive that controls soot deposit build-up in DPFs. This technology controls soot accumulation at significantly lower treat rates than those of previously reported [1] additives at temperatures well below those previously required for soot combustion. Ash accumulation testing and the chemical characterisation of the ash are also described. Any successful solution to the problem of soot accumulation in the filter needs to be harm free in the field.

Internal Diesel Injector Deposits (IDIDs) have been known for some time. With the latest powertrains becoming ever more sophisticated and reliant on efficient fuel delivery, the necessity for a continued focus on limiting their formation remains. Initial studies probed both carbonaceous based/ashless polymeric and sodium salt based IDIDs. The reported occurrence of the latter variety of IDID has declined in recent years as a result of the removal of certain additives from the diesel distribution system. Conversely, ashless polymeric based deposits remain problematic and a regular occurrence in the field.

The use of Diesel Particulate Filters (DPFs) as a means to meet ever more stringent worldwide Particulate Matter/ Particle Number (PM/ PN) emissions regulations is increasing. Fuel Borne Catalyst (FBC) technology has now been successfully used as an effective system for DPF regeneration in factory and service fill as well as retrofit applications for several years. The use of such a technology dictates that it be stable in long term service and that it remains compatible with new and emerging diesel fuel grades. In order to ensure this, neat additive stability data have been generated in a very severe and highly transient temperature cycle and a large selection of current (Winter 2012) market fuels have been evaluated for stability with this FBC technology. Results indicate that FBC technology remains suitable. The incidence of Internal Diesel Injector Deposits (IDIDs) is increasing, particularly for advanced FIE systems.

Retrofitting current and legacy diesel vehicles with Diesel Particulate Filters (DPFs) and associated aftertreatment technology has long been an option to enable vehicles with older engines to meet specific regional emissions legislation. A major positive is the ability for enforced vehicle retrofitting to have an immediate impact on the local air quality in urban environments without vehicle owners having to purchase new vehicles. Retrofit in China in comparison to Europe, for example, is in its relative infancy as China's emission legislation rapidly moves towards adopting European like limits whilst available diesel fuel continues to have variable sulphur concentrations. This paper details the results from a two phase retrofit-study conducted to investigate the ability for Fuel Borne Catalyst (FBC) technology to regenerate DPFs in retrofitted Light Duty (LD) vehicles in China.