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The effects of lubricating oil on friction and engine-out emissions in a light-duty 2.2L compression ignition direct injection (CIDI) engine were investigated. A matrix of test oils varying in viscosity (SAE 5W-20 to 10W-40), friction modifier (FM) level and chemistry (MoDTC and organic FM), and basestock chemistry (mineral and synthetic) was investigated. Tests were run in an engine dynamometer according to a simulated, steady state FTP-75 procedure. Low viscosity oils and high levels of organic FM showed benefits in terms of fuel economy, but there were no significant effects observed with the oils with low MoDTC concentration on engine friction run in this program. No significant oil effects were observed on the gaseous emissions of the engine. PM emissions were analyzed for organic solubles and insolubles. The organic soluble fraction was further analyzed for the oil and fuel soluble portions.

The effect of engine oil aging on the fuel economy of two matched 1998MY Buick Centuries equipped with 3.1L engines but operating on different GF-3 prototype engine oils (one SAE 5W-20 engine oil and a second SAE 5W-30 oil) has been determined in EPA FTP testing. Combined FTP Fuel Economy for these vehicles was reduced at a rate of 0.06-0.12% per 1,000 miles of accumulation. The data for the various parts of the FTP test indicated differences in the loss of FE with use for the two vehicles. The vehicle with the SAE 5W-20 oil containing a Mo-type FM additive showed a lower decrease in FE with use during the cold transient than the vehicle with the SAE 5W-30 oil. On the other hand, the vehicle with the SAE 5W-30 oil containing an organic type FM additive and a balanced detergent/dispersant package showed a lower rate of decrease of combined FE with use than the vehicle with the SAE 5W-20 oil. These differences may be indicative of the different additive chemistry in these oils.

This paper discusses the compression ratio influence on maximum load of a Natural Gas HCCI engine. A modified Volvo TD100 truck engine is controlled in a closed-loop fashion by enriching the Natural Gas mixture with Hydrogen. The first section of the paper illustrates and discusses the potential of using hydrogen enrichment of natural gas to control combustion timing. Cylinder pressure is used as the feedback and the 50 percent burn angle is the controlled parameter. Full-cycle simulation is compared to some of the experimental data and then used to enhance some of the experimental observations dealing with ignition timing, thermal boundary conditions, emissions and how they affect engine stability and performance. High load issues common to HCCI are discussed in light of the inherent performance and emissions tradeoff and the disappearance of feasible operating space at high engine loads.

Homogeneous Charge Compression Ignition (HCCI) has been proposed for natural gas engines in heavy duty stationary power generation applications. A number of researchers have demonstrated, through simulation and experiment, the feasibility of obtaining high gross indicated thermal efficiencies and very low NOx emissions at reasonable load levels. With a goal of eventual commercialization of these engines, this paper sets forth some of the primary challenges in obtaining high brake thermal efficiency from production feasible engines. Experimental results, in conjunction with simulation and analysis, are used to compare HCCI operation with traditional lean burn spark ignition performance. Current HCCI technology is characterized by low power density, very dilute mixtures, and low combustion efficiency. The quantitative adverse effect of each of these traits is demonstrated with respect to the brake thermal efficiency that can be expected in real world applications.

Natural gas quality, in terms of the volume fraction of higher hydrocarbons, strongly affects the auto-ignition characteristics of the air-fuel mixture, the engine performance and its controllability. The influence of natural gas composition on engine operation has been investigated both experimentally and through chemical kinetic based cycle simulation. A range of two component gas mixtures has been tested with methane as the base fuel. The equivalence ratio (0.3), the compression ratio (19.8), and the engine speed (1000 rpm) were held constant in order to isolate the impact of fuel autoignition chemistry. For each fuel mixture, the start of combustion was phased near top dead center (TDC) and then the inlet mixture temperature was reduced. These experimental results have been utilized as a source of data for the validation of a chemical kinetic based full-cycle simulation.

Gains in fuel economy with modern technology, SAE 5W-20 engine oils (GF-3 quality) in two identical 1998 MY Buick Centuries equipped with the 3.1L engine were measured in the EPA FTP test. These oils resulted in 1.0-2.2% gains in combined fuel economy (average 1.5%) over a typical GF-2 quality SAE 5W-30 oil. No significant gains in FE were observed during the cold transient portion of the FTP test. Engine oil temperatures were also reduced by 1-2°C with the SAE 5W-20 oils compared to the SAE 5W-30 oil. Of the two test oils, the one formulated with a Mo-type friction modifier additive was about 0.5% more fuel-efficient than the one formulated with an organic-type FM additive. Of the two vehicles, the one with the inherently poorer FE performance showed higher gains (expressed as percent improvement in FE) with the SAE 5W-20 oils than the other vehicle. Potential carry-over FE effects were observed with the oil containing the organic-type FM additive, but these effects were not verified.

Engine design and tribology engineers are constantly challenged to develop advanced products with reduced weight, reduced friction, longer life, and higher engine operating temperatures. The resulting engine systems must also meet more demanding emissions and fuel economy targets. Advanced energy-conserving lubricants and surface coatings are concurrently evolving to meet the needs of new engine materials. Because of the enormous cost and time associated with engine testing, much interest is being focused on the development of representative and repeatable bench tests for evaluation of engine materials and lubricants. The authors have developed a bench test employing reciprocating motion for evaluating friction and energy-conserving characteristics of lubricants.

This paper presents an overview of techniques for measuring friction using bench tests and fired engines. The test methods discussed have been developed to provide efficient, yet realistic, assessments of new component designs, materials, and lubricants for in-cylinder and overall engine applications. A Cameron-Plint Friction and Wear Tester was modified to permit ring-in-piston-groove movement by the test specimen, and used to evaluate a number of cylinder bore coatings for friction and wear performance. In a second study, it was used to evaluate the energy conserving characteristics of several engine lubricant formulations. Results were consistent with engine and vehicle testing, and were correlated with measured fuel economy performance. The Instantaneous IMEP Method for measuring in-cylinder frictional forces was extended to higher engine speeds and to modern, low-friction engine designs.

Eight engine oils were evaluated in four GM vehicles in standard EPA fuel economy (FE), vehicle-dynamometer tests. The results were compared with the FE obtained with a standard ASTM reference oil (BC). The viscosity and the friction modification effects of engine oil on vehicle FE were quantified. Combined FE performance in the vehicles ranged from almost 2 percent improvement for an SAE 0W-10 oil, to over 1.5 percent poorer FE than the reference oil for an SAE 10W-40 oil. FE in three engines (3.1L, 3.8L, and 2.3L) showed a strong dependence on the viscosity of the oil (HTHS at either 100° or 150°C). This dependence was stronger during the city portion of the EPA test (lower temperatures) than the highway portion (higher temperatures). For the 5.7L engine no significant effect of oil viscosity on FE was observed although the highest FE seemed to be obtained at an HTHS (at 150°C) viscosity near 3.1 cP.

Nine engine oils were evaluated in two GM vehicles: a 1993 Pontiac Grand Am with a 2.3L Quad4 engine and a 1993 Buick LeSabre with a 3.8L (3800) V-6 engine. Standard EPA (Environmental Protection Agency) fuel economy (FE), vehicle-dynamometer tests were conducted. The results were compared with the fuel economy obtained with a standard ASTM reference oil (BC). The vehicle data from this program were used in evaluating the new engine-dynamometer ASTM Sequence VI-A test designed to predict “real world” fuel economy in vehicles. EPA 55/45 combined fuel economy performance in the GM vehicles ranged from almost 2 percent improvement (over the BC oil) for an SAE 5W-20 oil, to over 2 percent poorer fuel economy than the reference oil for an SAE 20W-50 oil. The two different engines responded similarly to the different oils and showed similar trends.

Gasoline-derived deposits in modern automobile engines can plug fuel injectors and impair engine performance. The deposits (which originate from gasoline oxidized at moderate temperatures) contain higher sulfur concentration than the fuel. We used laboratory tests to study the effect of organic sulfur on the formation of solid deposits in an uninhibited gasoline oxidized at 100°C. Gravimetric studies showed that the effect of sulfides on deposit formation was strongly dependent on the structure of the sulfur compound. Disulfides and thiophenes showed little or no effect. Thiols enhanced the formation of insoluble deposits; but 1-dodecanethiol decreased the amount of deposits formed after long oxidation times. Analysis of thin deposit films with XPS(ESCA) showed that sulfur in the deposits was primarily bound to oxygen. When the fuel was blended with thiols, non-oxidized sulfur also appeared in the deposits.

Fuel-derived deposits on injectors and elsewhere in engines can severely impair engine performance. A laboratory test procedure was developed to produce thin deposit films from oxidized fuel on steel. The deposit films were analyzed using ESCA (XPS) and depth profiling with Ar i-ons. The deposits were carbonaceous in nature with lesser amounts of oxygen, and small amounts of sulfur and nitrogen. The total sulfur concentration in the deposits was approximately five-ten times higher than the concentration of sulfur in the original gasoline. Ion bombardment preferentially removed oxygen from the deposit layer, revealing that sulfur in the deposits was in the form of oxygenated compounds (RSO2 R, RSO2OR, RSO2OR, RSO2OSO2 R) and removal of oxygen converted them to lesser or non-oxygen-containing compounds (RSR, RSOR, RSSR, RSSO2 R). Fuel samples were spiked with two sulfur-containing chemicals, thioanisole and thianaphthene.

A laboratory test procedure was developed, and used to evaluate the deposit-forming tendencies of liquid fuels on a metal surface, and to identify deposit precursors in fuel. The impetus for this work was deposit formation in multiport fuel injection(MPFI) systems. Results from our laboratory test correlated well with those from engine dynamometer tests. Deposit formation is shown to be caused by the oxidation, condensation, and precipitation of unstable hydrocarbon species in the fuel. The immediate precursors for deposit formation were determined, based on liquid chromatographic separation and GC/MS analysis, to be oxygenated hydrocarbons included in the fuel.