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Technical Paper

A Comparison of Modified Elevated Temperature HFRR Test Data With Scuffing BOCLE Results

Evolving diesel engine design trends are expected to include fuel systems operating at significantly higher pressures and temperatures than in the past. Accordingly, meaningful laboratory tests are needed to help guide this development. Two candidate test methods were evaluated in this exploratory study. Scuffing Load Ball-on Cylinder Lubricity Evaluator (BOCLE) and Modified High-Frequency Reciprocating Rig (HFRR) test results covering a range of operating temperatures were compared with fuel property data. Correlations of the Modified HFRR test data with BOCLE results were also made.
Technical Paper

A Copper-Lead Bearing Corrosion Test Replacement

The Cooperative Lubrication Research (CLR) Oil Test Engine, usually called the L-38, has been used for nearly 25 years to evaluate copper-lead journal bearing protection of gasoline rnotoroils under high-temperature, heavy-duty conditions. The test is sensitive to aggressive surface active additives that may encourage bearing corrosion. The L-38 also provides an estimate of oil durability, assessing the resistance of an oil to the accumulation of acidic by-products of combustion that could attack copper-lead bearings. However, the L-38 engine dynamometer test uses a heavily leaded gasoline that is no longer representative of the commercial fuels available in North America, Europe, or Japan. Rather than discard the L-38, this paper describes work to modify the L-38 procedure to run with unleaded gasoline.
Technical Paper

A Vegetable Oil Based Tractor Lubricant

Increased awareness of preserving the environment has motivated the development of a wide variety of environmentally compatible products. Such products include environmentally compatible lubricants. Sale and use of these types of lubricants illustrates diligence by the lubricant manufacturer, original equipment manufacturer (OEM), and the consumer in contributing to a cleaner environment. The use of this type of lubricant could enhance the image of the lubricant manufacturer and vendor as well as the equipment manufacturer who employs such a fluid. To base such a lubricant on a vegetable oil creates a product environmentally friendly by its farming origin and its ability to readily biodegrade if released. No machinery is so uniquely suited to using vegetable oil based lubricants as agricultural equipment. Since this equipment is particularly close to the environment, the lubricant can easily come in contact with the soil, ground water, and crops.
Technical Paper

Advanced Power-Cylinder Tribology Using A Dynamically Loaded Piston Ring on Cylinder Bore Tribometer

It has long been understood that the piston assembly of the internal combustion engine accounts for a significant proportion of total engine friction. Modern engines are required to have better fuel economy without sacrificing durability. The pursuit of better fuel economy drives trends like downsizing, turbocharging and direct injection fuelling systems that increase cylinder pressures and create a more arduous operating environment for the piston ring / cylinder bore tribocouple. The power-cylinder lubricant is therefore put under increased stress as modern engine technology continues to evolve. The conventional approach to investigating fundamental power-cylinder tribology employs bench-tests founded on assumptions which allow for simplification of experimental conditions.
Technical Paper

Anatomy of an L-37 Hypoid Gear Durability Test Ridging Failure

The ASTM D6121 (L-37) is a key hypoid gear lubricant durability test for ASTM D7450-08 (API Category GL-5) and the higher performance level SAE J2360. It is defined as the ‘Standard Test Method for Evaluation of Load-Carrying Capacity of Lubricants Under Conditions of Low Speed and High Torque Used for Final Hypoid Drive Axles’. Pass/fail is determined upon completion of the test by rating the pinion and ring gears for several types of surface distress, including wear, rippling, ridging, pitting, spalling and scoring. Passing the L-37 in addition to the other tests required for API Category GL-5 credentials, as well as the more strenuous SAE J2360 certification, requires in-depth formulating knowledge to appropriately balance the additive chemistry. This paper describes the results of ASTM D6121 experiments run for the purposes of better understanding gear oil durability.
Technical Paper

Development of a Bench Test to Detect Oils Corrosive to Engine Components

Corrosive wear of non-ferrous engine components by lubricants is a concern of all major heavy duty diesel engine manufacturers since warranty on key engine components has been extended to 500,000 miles. Several commercial lubricants have been linked to premature cam and rod bearing failures induced by corrosion in certain fleets. Although the overall failure rate is low, specific fleets have experienced significantly higher failure rates due to the lubricants used. These failures usually occur at high mileages but less than 500,000 miles. This kind of slow corrosion easily escapes detection of engine tests contained in current oil specifications, and it represents a serious issue in long term warranty cost to diesel engine manufacturers. A comprehensive fleet database has been established to identify the most corrosive lubricants. These lubricants have served as reference oils to develop a corrosion bench test.
Technical Paper

Development of a Laboratory Hypoid Gear Spalling Test

The laboratory tests used to define API GL5 have been the cornerstone of gear oil development for well over thirty years. In that time they have served the market very well. Lubricants developed with these test methods have provided adequate protection of axle components from severe wear, scuffing, corrosion, and oxidation. Recently, however, there has been an increasing trend toward extended drain intervals which changes the picture. Coupled with longer oil drain intervals there is a continuing increase of power throughput in the equipment. The combination of increased power and extended service life places significant stress on the oil such that the load carrying ability and thermal and oxidative stability could be greatly diminished under these conditions. During the past ten years the industry has been actively working toward a new gear oil specification that will address the performance needs of today's vehicles.
Technical Paper

Effects of Exhaust Gas Recirculation on the Degradation Rates of Lubricating Oil in a Heavy-Duty Diesel Engine

The specific goal of this project was to determine if there is a difference in the lube oil degradation rates in a heavy-duty diesel engine equipped with an EGR system, as compared to the same configuration of the engine, but minus the EGR system. A secondary goal was to develop FTIR analysis of used lube oil as a sensitive technique for rapid evaluation of the degradation properties of lubricants. The test engine selected for this work was a Caterpillar 3176 engine. Two engine configurations were used, a standard 1994 design and a 1994 configuration with EGR designed to meet the 2004 emissions standards. The most significant changes in the lubricant occurred during the first 50-100 hours of operation. The results clearly demonstrated that the use of EGR has a significant impact on the degradation of the engine lubricant.
Technical Paper

Electronic Diesel Fuel Controls

The continuing advances being made in microcomputer technology have resulted in its application to an ever increasing range of control systems. The improved performance and flexibility that would be achieved by a microcomputer based diesel engine fuel system cannot be matched by hydromechanical controls of the type currently used. Before an electronic system can be successfully introduced in the harsh heavy-duty truck environment, however, it must meet stringent reliability and durability goals at reasonable cost. This paper outlines some of the problems encountered and solutions implemented in the design of an electronic fuel pump for this market.
Technical Paper

Exploring PVD Coatings for Cylinder Liner Applications

A number of wear resistant coatings has been developed using physical vapor deposition(PVD) process. However this coating process has not yet been widely used in the automotive industry. The purpose of this work was to evaluate thin PVD coatings such as diamond like carbon doped with tungsten (W-DLC), molybdenum-disulfide doped with aluminum (MoS2-Al), and chrome nitride (CrN). Some of these coatings were previously found to have low friction, high wear resistance, or both when tested in unlubricated conditions. In the present work, the experiments were conducted using a Cameron-Plint apparatus in lubricated conditions. The ring counterfaces used were Cr-plated and gas-nitrided compression rings. Our data also indicated that some PVD coatings with thicknesses in the same order of magnitude as the surface roughness of the liners did show some improvement in liner wear resistance. The suitability of thin coatings for liner applications needs additional study.
Journal Article

Extending SAE J300 to Viscosity Grades below SAE 20

The SAE Engine Oil Viscosity Classification (EOVC) Task Force has been gathering data in consideration of extending SAE J300 to include engine oils with high temperature, high shear rate (HTHS) viscosity below the current minimum of 2.6 mPa⋅s for the SAE 20 grade. The driving force for doing so is fuel economy, although it is widely recognized that hardware durability can suffer if HTHS viscosity is too low. Several Japanese OEMs have expressed interest in revising SAE J300 to allow official designation of an engine oil viscosity category with HTHS viscosity below 2.6 mPa⋅s to enable the development of ultra-low-friction engines in the future. This paper summarizes the work of the SAE EOVC Low Viscosity Grade Working Group comprising members from OEMs, oil companies, additive companies and instrument manufacturers to explore adoption of one or more new viscosity grades.
Technical Paper

HVOF Cermet Coatings for High Horse Power Diesel Engines

High Velocity Oxygen Fuel sprayed face coatings have shown great promise for piston rings used for High Power Density Diesel Engines. Various coatings have been tested on both wear test rigs and in engines. A highly dense HVOF cermet coating was developed with reasonable crack resistance during service. The HVOF coated piston rings wore three to six times lower than chrome plating. Cylinder liner (counter face) wear was found to be one to three times higher than chrome. However, engine oil consumption and blow by were within normal values. The HVOF coating is considered to be an excellent replacement for chrome plating. The coating process is more environmentally friendly than the chrome plating process. Also, the coating has potentially lower or equivalent production cost when compared to chrome.
Technical Paper

High Temperature Liquid Lubricant Development Part I: Engine Tests

A high horsepower, low heat rejection diesel engine is being developed to meet future Army heavy combat vehicle requirements. This engine features high power output in a compact design that is oil-cooled allowing for a significant reduction in radiator size. This design requires a lubricant which can survive a sump temperature of 160°C, for 300 hours with transient sump temperature surges to over 177°C. A comprehensive high temperature lubricant development program has been initiated to address the need for this new design. A modified Cummins 10 liter diesel engine was used to simulate the operating condition of this low heat rejection engine. The premium commercial lubricant that was tested survived only 58 hours before completely losing oxidative stability. Several of the experimental lubricants completed the 200-hour peak torque endurance test.
Journal Article

Impact of Viscosity Modifiers on Gear Oil Efficiency and Durability: Part II

This paper outlines the second part in a series on the effect of polymeric additives commonly known as viscosity modifiers (VM) or viscosity index improvers (VII) on gear oil efficiency and durability. The main role of the VM is to improve cold temperature lubrication and reduce the rate of viscosity reduction as the gear oil warms to operating temperature. However, in addition to improved operating efficiency across a broad temperature range compared to monograde fluids the VM can impart a number of other significant rheological improvements to the fluid [1]. This paper expands on the first paper in the series [2], covering further aspects in fluid efficiency, the effect of VM chemistry on these and their relationship to differences in hypoid and spur gear rig efficiency testing. Numerous VM chemistry types are available and the VM chemistry and shear stability is key to fluid efficiency and durability.
Technical Paper

Improved Lubricants Extend Diesel Engine Life

Diesel engine oils containing a balanced additive package composed of oxidation, corrosion, wear, rust and foam inhibitors plus ashless dispersants and metallic detergents provide long engine life. The major factor is metallic detergent component which contributes alkalinity to the oil and has a direct effect on engine cleanliness and durability. Increased detergent alkalinity reduces deposits and wear, resulting in improved oil control and longer engine life. Careful selection of detergent components is required to control cylinder-bore polishing in diesel engines to assure optimum antiwear and oil control performance.
Technical Paper

Investigations of Lubricant Sludge Formation in the Field: Development of an Effective New Fleet Test Technique

A new field test procedure for evaluation of the sludge formation tendencies of lubricants has been developed. The procedure has the benefits of short running time, reduced variability, and dramatic separation of API SF vs API SG oils. This paper discusses development of the operational procedure and evaluation of four lubricants, including commercial-type API SF and API SG oils as well as experimental future oils. Significantly improved sludge ratings were obtained with an experimental API SG oil. The sludge formation process was studied using infrared spectroscopy, TAN, dielectric measurements, viscosity, quasielastic light scattering particle size, and transmission electron microscopy techniques. These analyses show production of contaminants which form insoluble particles that build up and precipitate out of suspension as sludge. Certain drain analyses can be used as tools for predicting field sludge deposition time.
Technical Paper

Lubricant Technology for Hybrid Electric Automatic Transmissions

The automotive vehicle market has seen an increase in the number of hybrid electric vehicles (HEVs), and forecasts predict additional growth. In HEVs, the hybrid drivetrain hardware can combine electric motor, clutches, gearbox, electro-hydraulics and the control unit. In HEV hardware the transmission fluid can be designed to be in contact with an integrated electric motor. One transmission type well-suited to such hybridization is the increasingly utilized dual clutch transmission (DCT), where a lubricating fluid is in contact with the complete motor assembly as well as the DCT driveline architecture. This includes its electrical components and therefore raises questions around the suitability of standard transmission fluids in such an application. This in turn drives the need for further understanding of fluid electrical properties in addition to the more usually studied engineering hardware electrical properties.
Technical Paper

Measurement and Analysis of the Effect of Wall Temperature on Instantaneous Heat Flux

Measurements of instantaneous temperature were made at three locations on the cylinder head of a direct injection diesel engine. Changes in calculated instantaneous heat flux with changes in cylinder head surface temperature were assessed. The results were used in an assessment of various approaches to the description of instantaneous heat transfer incorporated in diesel cycle simulations. It was concluded that changes in the thermal boundary layer thickness throughout the cycle could account for some of the observed phenomena. A close correlation was seen between the heat transfer measured here and earlier published studies of measured boundary layer thickness. Some additional indications from the measurements point to a significant thermal capacitance of the boundary layer. Additional work is needed to further understand the potential ramifications of this effect.
Technical Paper

Plastic Oil Rings for Diesel Engines: A Preliminary Evaluation

The ability of a piston oil ring to conform to liner distortions during engine operation is directly related to its radial stiffness. The ability to conform is also very important for controlling lubricant oil consumption and emissions. This paper describes the procedure utilized to investigate the technical feasibility of using flexible high performance engineering plastics to replace metal as base material for oil rings. Bench tests and engines were used to select and evaluate different types of plastics for wear resistance and structural integrity. Engine test results indicated no structural failures but wear levels were found to be unacceptably high for use in durable heavy duty diesel engines.
Technical Paper

Simulating the Lubrication System of a Diesel Engine

The entire engine lubrication system has been represented by a series-parallel network of flow passages and flow elements. The pressure distribution and flow rates in the network were computed according to pressure-flow characteristics of each element. The pressure-flow relationship for each network element was estimated using empirical pipe friction, expansion, and bend loss coefficients, as well as by using test rig results and a steady-state journal bearing model. The journal bearing model is basically that of the classical short bearing model with provision for heat transfer to the oil and the relative thermal growth of the journal and bearing system. When compared with diesel engine tests, the simulation predicted the pressure distribution throughout the engine and the flow rate through each branch within 10%.