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A test was developed by the Cummins Engine Company to evaluate Diesel fuel quality and potential additive effects. This test utilizes a Cummins L10 Diesel engine with a PT fuel system and stepped plunger injectors. A modified CRC rating system is used to quantify deposit levels. This paper further investigates the L10 Injector Depositing Test and will focus on Diesel fuel and additive variables. In the original work, the bulk of the data was collected on an industry standard reference fuel, Cat 1-H, as opposed to commercially available Diesel fuels. Commercially available Diesel fuel varies in composition with regard to sulfur level, percent aromatics, final distillation end point, and cetane number. To evaluate these fuel properties and their possible effects on injector deposit formation, two test matrices were designed. The first experiment is a 12-run fractional factorial design with four factors: additive level, sulfur, aromatics, and 90 percent distillation point (T90).

A test method has been developed which provides for the rapid measurement of the scuffing performance of diesel fuel using the Ball-On-Cylinder Lubricity Evaluator (BOCLE). A test can be completed in less than one hour. Data has been generated indicating that the method achieves good discrimination between fuels of varying lubricity and correlates well with fuel performance as measured in pump tests.

This paper describes the development of a image analysis system that can be used to rate injectors from the Cummins L10 Injector Depositing Test. In the procedure, injectors are mounted on a computer controlled turntable and scanned using a CCD camera focused on the labyrinth flow area of the injector. The scanned monochrome images are processed and assigned an average gray scale rating. Results from the image analysis system are compared to the modified CRC Piston and Ring Rating method currently used within the Cummins test procedure. To do this, a series of injectors that have been rated by trained raters at a recent workshop were also rated via the image analysis system. The image analysis system ratings demonstrated a strong correlation (R = 0.85) to the CRC ratings. Using these same injectors, the image analysis method shows improvements in repeatability and reproducibility of approximately 50% over the current procedure.

Two prominent trends are facing diesel engine builders and their customers, environmental regulations and cost containment. Increasingly stringent exhaust emissions regulations have necessitated major changes in diesel engine design. Combustion temperatures and fuel injection pressures continue to rise. This and other factors, such as lower oil consumption for exhaust particulate reduction, place greater demands on crankcase lubricating oils. Another prominent environmentally related cost factor facing fleet operators is that of waste oil management. The inventory and disposal of used lubricants must now be handled in accordance with regulated guidelines and their associated costs. To compensate, new lubricant categories have been designed in both North America and Europe, such that 1994 and later emission controlled engines will perform as reliably as their earlier counterparts.

The use of a copper diesel fuel additive in an emission control system improves particulate oxidation. This expands the operability of available systems by reducing the particulate mass loading and related external energy consumption required during regeneration. Easier, more frequent regenerations improve overall engine/system efficiency and reduce thermal stress on filtration media. Procedures for optimizing additive use are presented. In addition, the results from a health study are reviewed.

Viscosity Modifiers (VM's) are commonly sold as polymer in oil concentrates. Thus, the handling (pumpability and mixability) characteristics of these systems are important practical considerations. These VM's normally are characterized only by kinematic viscosity, although they are handled at a range of shear rates/stresses which kinematic viscosity does not describe. New polymer types and structures and the desire to make the modifier level as high as possible requires more than a single point kinematic viscosity measurement. The rheological behavior of the concentrate is required to make economical systems that can be handled in a practical manner. This paper represents an initial study of viscosity modifier concentrates by rheological techniques.

The technology has been developed which will allow manufacturers to produce cars capable of running on methanol/gasoline blends with a methanol content up to 85% (i.e., M85). These cars will operate on varying methanol/gasoline ratios without any adjustments from the driver. The dual-fuel capability is attractive since vehicle use will not be handicapped by a restricted fuel distribution system. In addition, it provides the option of running on an environmentally “cleaner” fuel where it is available. The advent of fuel-flexible vehicles encourages the development of lubricants which will satisfy the demands of both fuels. The unique properties of methanol, however, increase the challenges of meeting the lubricant performance needs. Field and engine dynamometer testing have been aimed at understanding the response of key lubricant variables with M85. Short-trip, cold-weather conditions have been of particular concern.

There is concern over water-in-oil emulsion formation in passenger cars in the field. Crankcase pressure measurements in the ASTM Sequence IID rust test have been used to indicate possible emulsion formation tendencies of lubricants. This paper presents the development of a short duration emulsion fleet test procedure which demonstrates low car-to- car variability and correlates well with a previous fourmonth winter emulsion fleet test. Physical emulsion characteristics and used oil analyses are described. Evaluation of both Sequence IID reference oils and commercial oils in this field test reveals a lack of correlation between Sequence IID crankcase pressure results and field performance. The new procedure has been applied to investigate the impact of additive and base oil variations on the emulsion-forming tendencies of lubricants in the field. Base oil variables such as viscosity grade, composition, and volatility were evaluated.

The regenerative characteristics of a diesel particulate filter have been experimentally examined. The effect of particulate accumulation on system backpressure was of primary interest. To improve particulate regeneration, a copper compound was added to the fuel. The test results demonstrate that copper-containing fuel additives improve the regeneration characteristics of the filter, maintaining system backpressure at an acceptable level. Improved regeneration performance is expected to extend the operating range and life of the filter system. A model describing regeneration characteristics was developed to indicate the benefits of fuel copper concentration in controlling system backpressure.