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Organic acid degradation products and other anions in engine oil were speciated by capillary electrophoresis (CE) and liquid chromatography-mass spectrometry (LCMS) with electrospray ionization. The sample preparation procedure involved selectively extracting the acids and other water soluble salts into 0.05M aqueous potassium hydroxide. Samples of engine-aged mineral oil and synthetic engine oil contained formic acid, acetic acid, and complex mixtures of fatty acid degradation products. CE analysis of formic acid, acetic acid and selected fatty acids is proposed as a new chemical analysis method for evaluating the condition of engine oil and for studying the effects of high temperature-high load (HTHL) oxidation. Because the overall pattern of CE peaks in the electropherogram changes with oil age or condition, CE-fingerprint (i.e., pattern recognition) techniques may also be useful for evaluating an aged oil's condition or remaining service life.

Electrical ac impedance measurements were used for tracking the time dependence of the electrical properties (resistivity and permittivity) for 18 fully formulated engine oils during two types of engine dynamometer tests: high-temperature high-load (HTHL) and postal cycle (PC). The signatures in the time dependence of the electrical resistivity of engine oil at beginning-of life (BOL) and during early service differentiate both oil service classifications and test/driving conditions. The air content in engine oils can be determined quantitatively from the permittivity with a detection limit of 0.2 vol%. The significance of our results and their consequences for on-board monitoring of engine oil through sensing technology based on electrical ac impedance measurements are discussed.

The time dependence of the electrical properties for several fully formulated engine oils was tracked during engine dynamometer tests. The pattern for the resistivity indicates the existence of two types of processes (fast ion-depleting and slow ion-releasing) whose existence cannot be inferred through standard engine oil analysis. After these processes have subsided, the change in the resistivity correlates with the change in oil viscosity. We show that the peak value of the resistivity at early test times correlates with oil performance longevity as determined from conventional oil analysis parameters. In addition, the permittivity can provide an early warning of a dangerously low oil level. The significance of the results and their consequences for on-board monitoring of oil life through sensing technology based on electrical ac impedance measurements are discussed.

A radiotracer method was developed to measure real-time wear rates of piston rings and cylinder bores in spark-ignition engines. Initial work determined baseline wear rates during break-in and steady-state operating conditions. This work examines the effects of lubricant properties on wear rates of the ring/bore interface. Results show that engine oil service classification, the level of antiwear additives, severe engine aging, synthetic formulations, and viscosity classification have little or no impact on wear rates. These results suggest that concerns of wear between the rings and cylinder bore may not be a roadblock to extended oil-change intervals. Engine operation under cold temperatures appears to be a very important factor in ring/bore wear.

An engine dynamometer test was developed to simulate the effects of high-temperature, high-load driving conditions on the rate of engine oil degradation. The test engine, a 3.4-L 60° V6, is operated at 3000 r/min and 103 Nm load for 125 h at elevated oil and coolant temperatures and without oil additions. Oil samples are collected at regular intervals and analyzed for chemical and physical properties. Results show that five different chemical and physical properties exhibit regular, predictable changes with operating time. By fitting all data to appropriate functional forms, a very precise fit is obtained (r2 typically > 0.97) for the rate of change in each parameter. When these changes are normalized and corrected for oil consumption, their average can be used to calculate an overall Performance Factor.

A radiotracer method has been developed to measure piston ring and cylinder bore wear rates in spark-ignition (SI) engines. The method has sufficient sensitivity to measure ring and bore wear rates in real time during normal operating conditions. This work reports measurements on the rates of break-in and steady-state wear of piston rings and cylinder bores during a variety of engine operating conditions. Results show that piston ring break-in is minimal and that ring wear rates are constant at steady-state engine operation. The key factor affecting ring wear is engine brake mean effective pressure (BMEP). Ring wear behavior is repeatable for a given engine type and between two different engine designs. Cylinder bore wear is dominated by initial break-in, cold-start wear, and changes in operating conditions. Wear of the cylinder bore during steady-state operating conditions is very low when compared to break-in and changes in conditions.

Radiometric wear measurement techniques have been applied to determine the effect of journal surface finish on journal bearing load capacity. Bearing load capacity was measured by using a test machine that applies a linearly increasing unidirectional load to a radioactive test bearing. The onset of bearing wear provides a direct measurement of fluid-film breakdown, which is used to define hydrodynamic bearing load capacity. By use of a journal that can be located at two different positions on the shaft, the relative difference in load capacity between two journal surface finishes can be measured without the need to disturb the geometry of the bearing. The effect of journal surface finish on bearing load capacity was thereby quantified. In this study, nodular iron journals were prepared to have test surfaces with different levels of surface roughness.

A radioactive tracer method was used to measure the contribution of engine oil to deposits on exhaust system components and particulates in the exhaust gas of a gasoline engine. The technique involves the use of an oil molecule labeled with radioactive 14C. By measuring the 14C concentration in engine deposits, the fraction of carbon derived from the lubricating oil can be determined. Results show that depending on the location of the deposit, oil contributes from 1 to 8% of the carbon deposited, and is independent of engine operating conditions. Oil contribution to particulate filtered from the exhaust gas ranges from 2 to 30% of the carbon, which increases in proportion to engine speed.

Excessive cylinder bore out-of-roundness (OOR) can adversely affect the sealing functionality and durability of the piston-ring pack in an engine. This work reports the effects of changes in cylinder bore OOR on: (i) the rotation of the top and second compression rings, and (ii) oil consumption in an open-deck 4.5-L V-8 engine. A method was devised for altering the level of OOR in one cylinder of the engine without engine disassembly. Radiometric techniques were then applied to measure both piston ring rotation and oil consumption of that cylinder at three different levels of bore distortion. Results of these measurements are of value in determining the range of acceptability of production specifications for cylinder bore OOR.

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.

A radiotracer technique has been developed to monitor the rotational movement of piston rings during engine operation. Each ring to be monitored is modified by incorporating two different radiotracers at an angular separation of ∼120°. After engine assembly, a high-resolution detector is mounted outside the engine block to measure the γ-ray emission rates of each of the isotopes. Gamma-ray intensities monitored during engine operation provide information to determine the angle of ring-gap orientation in real time. The radiotracer method for ring-rotation measurement can be applied to any ring in the engine and may be modified to monitor the simultaneous movement of two rings in a given cylinder. Because the radioactive sources are confined and are of low intensity, radiation safety precautions are minimal.

The radiotracer technique of surface layer activation was used to study piston ring wear rates in the Detroit Diesel Allison “Series 60” engine. Radioactive 54Mn was induced in the chromium surface of the ring face by bombardment with an α beam from a particle accelerator. Wear of the piston ring surface was determined by measuring the accumulation of radioactive debris in the oil during engine operation and by measuring the radiation intensity of the rings from outside the engine between intervals of engine operation. Information was obtained on the wear rate of the top compression ring during break-in and as a function of engine speed and power output. In addition, piston rings activated around their entire circumference were used to determine wear as a function of angle from the ring gap. The collection efficiency of the oil filtration system, for ring wear debris was also determined by measuring radioactivity in the oil filters.

Radioisotopic methods have been applied to nondestructive measurements on experimental automotive catalytic converters. These converters consist of thin corrugated metal foil which supports an alumina coating impregnated with noble metals. A radiogauging system, using γ radiation from a gadolinium-153 source, was developed to determine the total quantity and distribution of alumina coating applied to the foil substrate. The radiogauging apparatus was also used to provide axial and radial profiles of lead deposited in the catalytic converter when leaded fuel was used. During dynamometer aging, iron-59 was used as a radiotracer in the alumina to monitor the coating attrition as a function of operating time. These studies demonstrate the capability of radiotracer and radiogauging techniques for rapid, nondestructive measurements on prototype catalytic converters during performance testing.

Radiometric wear techniques have been applied to determine the effect of fuel-saving engine oils on journal bearing load capacity. A test machine which applied a unidirectional load to a radioactive test bearing was used to evaluate bearing load capacity. The onset of bearing wear with increasing load provided a direct measurement of fluid-film breakdown, which defined hydrodynamic bearing load capacity. From this, an “effective” lubricant viscosity was calculated by comparing the performance of non-Newtonian lubricants to the performance of Newtonian lubricants. Results show that for the oil formulations tested that employ either a low viscosity or a soluble friction modifier to reduce engine friction, there is a high correlation between high-shear viscosity and hydrodynamic load capacity. The use of an insoluble friction modifier resulted in a higher bearing load capacity than expected based on high-shear viscosity.

Radiometric techniques have been developed and successfully applied to journal bearing studies in a unidirectional bearing test machine. These techniques, which involve the detection of wear debris from a radioactive (113Sn) test bearing, were used to determine bearing load capacity with both Newtonian and non-Newtonian lubricants. Results indicate that the radiometric method can rapidly provide information that correlates with other laboratory and engine test data.