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A new method for the determination of antioxidant capacity in lubricants has been utilized for the analyses of new and used engine oil samples. The results derived from these analyses were used for monitoring the antioxidant decay during laboratory and long drain fleet testing and in various correlation studies. The application of the method provided new insights into the nature of the oxidative deterioration of engine oils as a function of type and initial concentration of antioxidant additives, of type of base oil and of test or engine severity.

The trend to longer oil drain intervals for passenger cars has hastened in the last few years. Most earlier studies on the effects of extended drains on oil and engine performance were conducted prior to 1973 when significant engine modifications were made to reduce exhaust emissions. This paper describes several taxi and other road tests, supplemented by laboratory programs, conducted since 1973. The total field program included approximately 225 cars over sixteen million kilometers. All of the work reported is with 5W and 10W multigrade engine oils. Taxi test results have shown sludge build-up and oil thickening to be the most significant failure modes as drains are extended beyond approximately 12 000 km. This occurs even with oils giving excellent Sequence IIIC and VC results. Oil thickening and particularly engine sludge and filter plugging were more severe in winter driving and with leaded gasoline.

Acquiring and recording real-world vehicle operating and environmental conditions is becoming increasingly important for determining techniques to reduce fuel consumption and other operating costs. The operational characteristics of vehicles has been the object of considerable study, which has included component and vehicle tests under controlled conditions, and computer simulation. The selective gathering of pertinent information under in-service conditions has heretofore not been practicable nor reliable. This paper describes the use of Rockwell International's Tripmastertm on-board Instrumentation System applied to obtaining this information for use in the DOT/SAE Fuel Economy measurement study.

This paper examines the benefits and problems associated with extended oil drain intervals in diesel truck engines. Performance comparisons were made on two-drain periods in three different engines using both mono and multi grade oils. Three typical customer operations were also monitored. Laboratory evaluations were made on typical and severely stressed used oils. Oil filter life and durability were assessed. The economics of extending oil and filter change intervals are reviewed. Efficient combustion and well-filtered air are essential. Potential operational problems, filter durability and economics suggest 40 000 km as being the maximum change interval even under most optimum conditions.

The use of an on-board microprocessor to acquire data on truck and bus performance during in-service operation enables the information transmitted by measurement sensors to be examined, processed, compacted or aggregated, and stored in memory by the on-board computer software. The system development requires a careful balance of the tradeoffs between hardware and software concepts which is quite different from considerations applied with normal “laboratory” type data acquisition systems.

A line of high quality multigrade diesel engine oils suitable for long drain applications has been developed using hydrotreated basestock. Laboratory and engine dynamometer tests indicated that lubricating oils using hydrotreated basestock have superior control of diesel piston deposits and oxidative viscosity increase. Excellent performance of multigrade diesel engine oils using both hydrotreated and solvent refined basestock over extended oil change intervals has been demonstrated in extensive field trials. Cold weather benefits for multigrade diesel engine oils were defined by cold room studies and outdoor trials.

Tests on a single-cylinder engine have shown that the flame speed and lean extinction limir may be increased by the fitment of a “vortex generator” in the engine intake. This consists of a nest of delta wings which generates a vortex system in the inlet air flow. The results show that this vortex generator should be of variable geometry and replace the conventional throttle. The main instrumentation on the engine consists of a flame logger which accepts amplified signals from ionisation probes set in the engine combustion chamber. The logger is gated to count those flames which travel across the combustion chamber during a set crank angle period. Information from this instrumentation is presented in the form of graphs describing the effect of vortex generator blockage ratio, mixture strength, engine speed, load and spark timing upon the percentage number of flames which cross the chamber and apparent flame speed.

In an effort to improve the trade-off between fuel economy and emissions in the rotary combustion engine, research was undertaken to provide a better understanding of the sources of unburned hydrocarbons in the exhaust. Flame photography was used in conjunction with extensive time-resolved exhaust gas sampling. Examinations were made of the effects of air-fuel ratio, engine load, residual gas, and engine speed on combustion and hydrocarbon emissions using the two experimental techniques. These studies identified two major sources of hydrocarbon emissions: flame extinction and, not surprisingly, apex seal leakage. Conclusions were the following: (1) at lean air-fuel ratios (i.e., ≥18.0 to 1), flame extinction in the trailing portion of the chamber was a major source of exhaust hydrocarbons, and (2) at richer air-fuel ratios (i.e., ≤16.5 to 1), apex seal leakage was a major source of exhaust hydrocarbons.

Legislated fuel economy standards have necessitated investigations to determine the cost-effectiveness of “low-friction” engine lubricants to assist in attaining these goals. Preliminary testing indicated friction reduction engine oil additives may provide potentially significant improvements in fuel economy over conventional and low viscosity engine oils. Vehicle test programs were undertaken to evaluate the effects of molybdenum disulfide, graphite and soluble additives on fuel economy, engine cleanliness and wear, as well as exhaust emission levels and engine and emission component durability. The significant fuel economy improvements and effects on all aforementioned variables are detailed in the paper.

Today's commercial transport service vehicle owner is being confronted with increasingly complex problems in his vehicle operation. As a means of solving one of his problems, methods of evaluating power train components and their effect on obtaining optimum vehicle performance and efficiency have been developed. Vehicle vocation variables and the different types of power trains and power components have been analyzed. Utilization of the techniques described should bring the vehicle engineer closer to providing an optimum match of vehicle, engine, transmission, axle, and tires for a given vocation.

Results from a numerical investigation of one-dimensional, laminar flame quenching with constant and time-dependent pressure variations are reported herein. A description of flame quenching and post-flame oxidation processes for the global reaction A + B → C is obtained from a solution of a simplified form of the non-linear conservation of mass, momentum and energy equations in a planar flow field. These equations were reduced to finite difference form and the time-dependent pressure was input via either an integrated form of the energy equation or a third-order polynomial law. Numerical calculations were performed at constant pressure, combustion bombtype conditions and under rapid decompression during quenching. One-dimensional head-on quenching distances, hydrocarbon concentration levels and gas properties were obtained for a variety of stoichiometric values in a propane/airtype mixture.

The effect of bore-to-stroke ratio (B/S) on indicated specific fuel consumption (ISFC) and emissions of a gasoline-fueled, spark-ignited, single-cylinder engine was studied while holding compression ratio and bore diameter constant. As B/S was increased from 1.1 to 3.3, both ISFC and hydrocarbon emissions increased significantly. Increased cylinder heat loss and, to a lesser extent, increased combustion duration were the principal causes of the ISFC increase. Increased surface-to-volume ratio was the principal cause of the increase in hydrocarbon emissions. The influence of combustion chamber modifications on these effects was investigated.

Measurements of engine cylinder pressure have become routine at the General Motors Research Laboratories. EDPAC, an Engine Diagnostic Package, was designed and developed to process these data automatically from single-and multi-cylinder engines in order to provide engine performance and combustion information. EDPAC consists of several self-contained, independent software modules, each having a different analysis function. These include engine performance calculations, pressure-volume graphics, engine simulation for residual gas estimates, and heat release analysis. After each module is executed, computed results are stored automatically, providing input to subsequent software modules as well as providing a data base for future interrogation. Routine use of EDPAC to process pressure data results in reductions of costs, effort, and turn-around times. A data base containing performance, emissions, and combustion data is established automatically.

This paper describes the results of experimental and computer simulation studies of the combustion process in the prechamber three-valve stratified-charge engine. Prechamber and main-chamber pressure data and matched computer simulation calculations are used to determine the effects of variations in overall air/fuel ratio, engine speed and load, and prechamber volume and orifice diameter on the parameters which define the combustion process (spark advance for optimum torque, ignition delay, combustion duration), on cylinder pressure diagrams (mean main-chamber pressure, mean pressure difference across the orifice, and cycle-by-cycle pressure fluctuations) and on exhaust emissions. General correlations are derived from the data for the shape of the combustion rate profile and the extent of the combustion duration.

A method for monitoring the wear of engine parts without engine disassembly is described. Low level radiation sources implanted in the wearing surfaces serve as a tracer for material loss. Prior to engine testing, controlled wearing of an identical part determines a calibration curve relating wear depth to externally measurable radiation. The results of engine testing show that the method is useful in measuring small amounts of wear in individual engine parts such as piston rings and connecting rod bearings simultaneously without engine disassembly. These tests were performed to evaluate the effectiveness of filters in reducing engine wear. The wear measurements showed that both air and oil filters are highly effective in reducing wear throughout an engine.

Today's diesel engine lubricating oils are highly dispersant and typically carry several pounds of solid combustion contaminant in suspension - little of which is filterable. Since the average full flow filter is capable of holding less than a pound of solids, filter life and capacity are no longer directly related. Field experience has demonstrated at least six distinct methods by which filters plug. This data indicates that filter life is simply a function of the type and amount of contaminant present in the crankcase and the oil's ability to handle or tolerate the contamination. However, oils differ greatly in their ability to do this. Field experience also suggests that the current API Classification tests may be inadequate in some areas to determine lubricating oils' suitability for diesel engine service. Finally, filter plugging should be looked at as a symptom of engine or oil problems, but not as a problem itself.

Experimental Brake Specific Fuel Consumption (BSFC) data are presented for two engines as a function of engine speed, load, outlet coolant temperature and inlet oil temperature. The engines used in the study were the Cummins VT-903 (turbocharged) and the Caterpillar 3208, both being direct-injection and four-cycle. The data were taken for the Cat 3208 engine using a fractional factorial statistical method which reduced the total test matrix from 256 to 64 data points. The experimental data are used in the development of BSFC regression equations as a function of load, speed, outlet coolant temperature and inlet oil temperatures. A mathematical parameter for expressing quantitatively the change of BSFC per 10°F change in coolant and oil temperature is presented. It was found that an increase in the coolant and/or oil temperatures had the effect of reducing BSFC in both engines.

This investigation dealt with the experimental determination of a select chemical specie - the hydroxyl radical - present in the non-flamed end gases ahead of the flame front in a spark-ignited engine operating under conditions of both normal and knocking combustion. Concentration measurements of the hydroxyl radical present in the end gases were obtained with the technique of resonance absorption spectroscopy utilizing a broadband-output, frequency-tunable, flashlamp-pumped, organic-dye laser. The dye laser and a photographic spectrometer were placed on opposite sides of a single cylinder research engine and the combustion chamber of the engine was fitted with quartz windows that allowed the dye-laser light pulse to pass through the end gas region and into the spectrometer. The dye laser was pulsed once at a present crankangle during the combustion cycle recording the 2∑+-2∏ electronic transition absorption spectrum on film.

The State-Of-The-Art of automotive corrosion testing is reviewed with particular emphasis on testing related to the exterior environment. The generally poor correlation of laboratory tests with field performance is reviewed and the factors affecting both laboratory and field tests are discussed. Recommendations for the conduct of field tests are presented.

A brief review of the basic theory of the electrochemical corrosion of metals is presented, with emphasis given to the mixed-potential theory. Currently accepted electrochemical corrosion mechanisms of several major forms of corrosion are reviewed. Galvanic, crevice and pitting types of corrosion are considered. The presently held theories on the atmospheric corrosion of steel is also discussed.