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The improvement of fuel consumption is the most important issue for engine manufactures from the viewpoint of energy and environment conservation. A piston-cylinder system plays an important role for the reduction of an engine friction. For the improvement of the frictional behavior of the piston-cylinder system, it is beneficial to observe and analyze the frictional waveforms during an engine operation. To meet the above-mentioned demand, frictional waveforms were measured with using the renewed floating liner device. In the newly developed floating liner device, an actual cylinder block itself was used as a test specimen. The measured single cylinder was an aluminum monolithic type made of hypereutectic Al-17%Si alloy using a high pressure die casting process. The combined piston was a light weight forged piston and a DLC coated piston ring was used. For the measurement, 110cc air cooled single cylinder engine was used.

Decrease of engine lubricating oil consumption is necessary to reduce environmental impact. Usually oil consumption is estimated experimentally at the engine development stage, and it is expensive in terms of both time and cost. Therefore it is essential to develop its calculation method. The purposes of this study are clarifying the mechanism of engine lubricating oil consumption and developing the calculation method for the estimation of oil consumption. In this report, oil film on the piston skirt, which affected on oil volume supplied to the oil ring, was observed. Furthermore the effect of piston skirt design on oil consumption was investigated. Findings showed that the splashed oil on the cylinder liner had much effect on the oil film on the piston skirt hence oil consumption. It was suggested that the splashed oil on the cylinder liner affected on supply oil volume and it should be considered in the calculation of oil consumption.

The friction reduction of a piston/piston-ring assembly is effective for fuel economy of an engine, and a friction measurement method is required for developing low friction pistons, piston-rings and lubricants. Most suitable method for friction measurement for piston assemblies is “floating liner method”. It has load sensors between a floating cylinder liner and cylinder block, and the sensors can detect friction force acting on the liner. Many apparatuses using floating liner method are developed. They are roughly divided to two categories. In one of them, floating liner is supported by load-washers which axis is set parallel to the center line of the cylinder liner. In another type, floating liner is supported by three-component force sensors installed on the side face of the cylinder. In this paper, five types of floating liner devices were compared.