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Real-Time Measurement of Camshaft Wear in an Automotive Engine - a Radiometric Method

Research Laboratories, General Motors Corp.-Eric W. Schneider, Daniel H. Blossfeld
Published 1990-10-01 by SAE International in United States
A radiometric method has been developed for the determination of camshaft wear during engine operation. After a radioactive tracer is induced at the tips of one or more cam lobes by the technique of surface layer activation, calibration procedure are performed to determine the amount of radioactive material remaining versus the depth worn. The decrease in γ-ray intensity measured external to the engine is then directly related to cam lobe wear. By incorporating a high-resolution detector and an internal radioactive standard,measurement accuracy better than ±0.2 μm at 95% confidence has been achieved. Without the requirement of engine disassembly, this method has provided unique measurements of break-in wear and wear as a function of operating conditions. Because this approach requires only low levels of radiation, it has significant potential applications in wear control.
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Control of the Homogeneous–Charge Passenger–Car Engine — Defining the Problem

Research Laboratories, General Motors Corp.-Charles A. Amann
Published 1980-11-01 by SAE International in United States
The evolution of increasingly stringent standards for passenger-car exhaust emissions has increased the need for more sophisticated engine controls. In the era prior to emissions control, the dependent variables were fuel economy, driveability, and convenience and cost to the customer. The principal independent variables were spark advance and air-fuel ratio. With the tailpipe emissions of unburned hydrocarbons, carbon monoxide, and oxides of nitrogen now added to the list of dependent variables, a number of additional concepts have been introduced on production automobiles. Among these are exhaust-gas recirculation (EGR), the oxidizing catalytic converter, and the three-way catalytic converter. These developments, in combination with tighter emission standards and new fuel-economy mandates, have complicated the engine control problem.This presentation focuses on the definition of that problem. The effects of spark advance, air-fuel ratio, and EGR on emissions and fuel economy are reviewed. The needs for considering system deterioration, combustion knock, drive-ability, the cold start, dynamic effects, and control-system anomalies are delineated. The presentation thus provides an understanding of the challenges presented to the controls engineer by the modern…
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Diesel Combustion Chamber Sampling - Hardware, Procedures, and Data Interpretation

Research Laboratories, General Motors Corp.-James E. Bennethum, James N. Mattavi, Richard R. Toepel
Published 1975-02-01 by SAE International in United States
In-cylinder sampling appears to be the only available means for obtaining detailed information of the diesel combustion process. This information is necessary to understand pollutant formation because of the intimate relationship between formation rates and local cylinder conditions.This paper discusses efforts to (1) examine and improve sampling valve design, (2) evaluate potential effects of the valve and the sampling system on sample composition, (3) find methods to extract useful information from sampling data.Sampling hardware is currently being used to study combustion in engines, but further work is needed to quantify the influence of hardware and procedures on sample composition and to design experiments to provide data containing maximum information.
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Deposits, Wear, and Catalyst Performance with Low Ash and Ashless Engine Oils

Research Laboratories, General Motors Corp.-Loren G. Pless
Published 1975-02-01 by SAE International in United States
To meet exhaust emission standards, nearly all 1975 model U. S. passenger cars use catalytic converters in conjunction with unleaded gasoline. While it has been established that lead and phosphorus from gasoline are deleterious to catalyst performance, much less is known about any similar effect of elements normally present in conventional engine oils. In addition, the ability to protect engines from excessive deposits and wear is essentially unproved for engine oils in which the phosphorus and metals contents have been either reduced (low ash oils) or eliminated (ashless oils).To obtain catalyst and engine performance information on such oils, tests were run using 95, 1972-1973 model passenger cars, operated with unleaded gasoline in several types of service. Forty cars were equipped with 1975 production-prototype underfloor catalytic converters containing pelleted oxidation catalysts.Neither exhaust emissions nor catalyst conversion efficiency were affected by using either a low ash or an ashless oil instead of a conventional oil. However, oil consumption was less than typical for such service, so the effect of oil additives on catalyst durability may have been…
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Wind Tunnel Development of the Dragfoiler - A System for Reducing Tractor-Trailer Aerodynamic Drag

Research Laboratories, General Motors Corp.-William T. Mason
Published 1975-02-01 by SAE International in United States
Dragfoiler II, an effective and practical add-on aerodynamic drag reducing system for tractor-trailers, has been developed. Wind tunnel tests with 1/16- and 1/7-scale tractor-trailer models were used to determine empirical design guidelines for the Dragfoiler II's side elevation and planform shapes. Optimum designs for various combinations of tractor roof height and length, trailer height, and tractor-to-trailer gap length gave zero-yaw drag reductions between 30 and 35%. At a yaw angle of 10°, the percentage drag reductions were about half those at 0°. Off-design performance and the effects of trailer side-edge geometry were investigated. Several full-scale Dragfoiler II's are currently undergoing proving ground and commercial fleet evaluation tests.
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Digital Data Aquisition with Emphasis on Measuring Pressure Synchronously wih Crank Angle

Research Laboratories, General Motors Corp.-Russell V. Fisher, James P. Macey
Published 1975-02-01 by SAE International in United States
A general purpose data acquisition system has been developed which converts analog data to scaled, tabulated, and graphical output. A scanning synchronization unit ensures that each input channel is sampled synchronously with input data pulses. System input can be either direct from the test area or from an analog tape recorder, in which case time expansion is possible by the use of high record-low play/back speeds.A computer program controls the analog to digital conversion process. The on-line control of the program minimizes the subsequent data reduction, and through the use of input parameters, flexibility is attained in data formatting. The data reduction error is less than 1% and statistical programs included in the system provide estimates of the quality of the input data. The entire system including all associated hardware and software is described in detail, using acquisition of pressure data synchronously with crank angle as an example.
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Automobile Radar Signature Studies

Research Laboratories, General Motors Corp.-Robert M. Storwick, Louis L. Nagy
Published 1975-02-01 by SAE International in United States
One of the prime requisites for automobile radar systems is obstacle hazard evaluation, the extent needed being dependent upon the particular system application. Much of the information necessary for a radar system to assess the degree of hazard of a target must come from characteristics which can be measured by the radar itself. While the hazard evaluation capacity has not yet been developed for automobile radar systems, research to provide this capability is in progress.Continuous wave (CW) scattering measurements have been made in a manner which is consistent with automobile radar operation. Various aspects of simple targets and of an automobile were measured in a microwave anechoic chamber. Both horizontal and vertical linear polarizations were transmitted and their co-linear and cross polarizations received.These data have been used to confirm the existence of and to understand certain scattering mechanisms. They have also been subjected to analyses in order to determine the ability to discriminate among the various simple targets. It is demonstrated that even a simple analytical method shows discrimination capability among the targets tested. Other…
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Vehicle Evaluation of Synthetic and Conventional Engine Oils

Research Laboratories, General Motors Corp.-John J. Rodgers, Richard H. Kabel
Published 1975-02-01 by SAE International in United States
A five-vehicle, 64 000-km test with 7.45 litre V-8 engines was conducted to determine if synthetic engine oils provided performance sufficiently superior to that of conventional engine oils to permit longer oil change intervals. The results show better performance in two areas of deposit control; inferior performance with respect to wear protection; and essentially equivalent performance in the areas of fuel and oil economies. Based on these data, it was concluded that synthetic engine oils do not provide the necessary performance required to safely recommend their use for extended oil change intervals. In addition, a cost analysis shows that the use of synthetic engine oils, even at a change interval of 32 000 km, will essentially double the customers' cost compared with conventional engine oils at GM's current 12 000-km change interval.
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The Influence of Polymer Additives on Journal Bearing Performance

Research Laboratories, General Motors Corp.-Richard C. Rosenberg
Published 1975-02-01 by SAE International in United States
The temporary viscosity loss experienced by non-Newtonian lubricants, operating in a simulated engine bearing, has been determined. Included in the study were; lubricant blends containing 13 commonly-used viscosity index improvers and six commercial multigraded engine oils. Bearing friction and minimum oil-film thickness data were used to determine the temporary viscosity loss. For the 13 viscosity index improvers, this temporary loss ranged from 20-96% of the polymer contributed viscosity. Results indicate that low shear rate viscosity determinations, such as the currently used ASTM D445, should not be used to characterize the behavior of these lubricants in high-speed engine bearings.
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Lubricant Viscosity Effects on Passenger Car Fuel Economy

Research Laboratories, General Motors Corp.-E. D. Davison, M. L. Haviland
Published 1975-02-01 by SAE International in United States
As part of General Motors effort to improve fuel economy, the effects of engine and power train lubricant viscosities were investigated in passenger car tests using either high- or low- viscosity lubricants in the engine, automatic transmission, and rear axle. Fuel economy was determined in both constant speed and various driving cycle tests with the car fully warmed-up. In addition, fuel economy was determined in cold-start driving cycle tests.Using low-viscosity lubricants instead of high-viscosity lubricants improved warmed-up fuel economy by as much as 5%, depending upon the differences in lubricant viscosity and type of driving. Cold-start fuel economy with low-viscosity lubricants was 5% greater than that with high-viscosity lubricants. With such improvements, it is concluded that significant customer fuel economy gains can be obtained by using the lowest viscosity engine and power train lubricants recommended for service. To determine if currently recommended engine oil, automatic transmission fluid, and rear axle lubricant viscosities can be reduced, extensive performance and durability testing will be required.
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