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In order to understand and resolve the exhaust valve carbon sticking problem, the engine parameters effective on the phenomenon are shown by bench tests. Based on the results, a new test code which can evaluate the exhaust valve sticking has been developed. And by using the test code, the effects of engine hardware, gasoline properties, and warm-up enrichment are shown. Finally, the detailed mechanism of the exhaust valve carbon sticking is clarified and solution to it is proposed.

This paper discusses the effects of lubricant viscosity on the friction characteristics of engine bearing and cam/tappet which are the typical moving parts of an engine and operate in different lubrication regimes. Based on the measured crankshaft temperatures, we calculated the friction coefficient of the engine bearing according to Sommerfeld number by a simple heat equilibrium equation. The oil film thicknesses between cam and tappet were measured in a motored cylinder head which had a direct acting type overhead camshaft. The boundary and viscous friction components were estimated separately according to a parameter defined as the ratio of the central oil film thickness to the composite surface roughness. These two friction components were added to calculate the friction coefficient. Finally, the motoring friction torque was measured and compared with the estimated friction coefficient.

In order to study the effect of the oil aeration rate on bearing reliability, the minimum oil film thicknesses(MOFT) were measured by the change of oil aeration rate using the total capacitance method(TCM), and at the same time, to study the appropriateness as an index of bearing reliability, crankshaft temperatures were measured. The minimum oil film thicknesses were measured at each of five main bearings and No.1 connecting rod bearing. A scissor type linkage system was employed to measure the minimum oil film thickness of connecting rod bearing. Special techniques were devised to inject air into the oil, and to monitor the aeration rate by an on-line measurement system. The measured aeration rates are proportional to the oil pressure drop. The change of the MOFTs are very slight up to a 30% aeration rate in the test engine. But if the oil aeration rate exceeded 30%, the minimum oil film thicknesses were changed.

The minimum oil film thicknesses(MOFT) in the connecting-rod bearings of a 1.5 liter, L-4, gasoline engine are measured up to 5500 rpm and calculated to study the dynamically loaded engine bearings. Short bearing approximation and Mobility methods are used for theoretical analysis of oil film characteristics. Also cylinder pressure, crank-pin surface temperature and bearing temperature are measured and used as the input data of theoretical analysis. The MOFT are measured by the total capacitance method(TCM). To improve the reliability of the test results, a reasonable determination method of bearing clearance is introduced and used, and the effects of cavitation and aeration on the test results are neglected. Also the crankshaft is grounded by means of a slip ring. A scissor type linkage system was developed to measure the MOFT and bearing temperature.

The minimum oil film thicknesses (MOFT) in the crankshaft main bearings of a 1.5 liter, L-4, gasoline engine are measured and calculated to study the dynamically loaded engine bearing. The MOFT are measured simultaneously at each of the five main bearings using the total capacitance method(TCM). To improve the reliability of the TCM, a reasonable determination method of bearing clearance is introduced and the effects of bearing cavitation and aeration on the test results are analyzed. Also the crankshaft is grounded by means of a slip ring instead of the friction contact method to improve the test precision. The calculation is based on the model of statically determinate beam, short bearing approximation and Mobility method. From the comparison between the measured and calculated MOFT curves, it is found that a qualitative similarity exists between them, but in all cases, measured MOFT are smaller than that of calculated.