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Technical Paper

Development of an Engine Noise Evaluation Meter

A new noise evaluation meter has been developed, which provides a new index for the noisiness of idling engines. In this research, auditory sensations of motorcycle engine noises have been analyzed using multidimensional scaling techniques. As a result, it has been found that the principal hearing factors are loudness, impulsiveness, and frequency characteristics of noise. These factors are quantified with an A-weighted sound level, a fluctuation level, and a high frequency level, respectively. An engine noise evaluation meter has been made, on the assumption that a total evaluation level is obtained by a linear combination of the physical quantities. The functions of the meter are to measure the physical quantities of noise, to calculate the total evaluation level, and to indicate the results. Then, actual engine noises have been evaluated by the meter, and there is a high correlation between the sensory evaluation values and the total evaluation levels.
Technical Paper

Improvement of Fuel Consumption with Variable Exhaust Port Timing in a Two-Stroke Gasoline Engine

In this study, an improvement of fuel consumption by changing the exhaust timing of a two-stroke engine has been made. The study results revealed that a remarkable improvement of fuel economy is possible by controlling the exhaust timing according to the engine speed. The reason for the better fuel economy was clarified through an analysis of exhaust gases, theoretical cycle calculations, and an analysis of combustion pressure. As an example of actual application, the results of tests made on an engine equipped with Yamaha power Valve System (YPVS), which is a variable exhaust timing mechanism using a tabor-shaped valve, will also be discussed.
Technical Paper

Optimization of Multi-Valve Four Cycle Engine Design-The Benefit of Five-Valve Technology

THE MULTI-VALVE FOUR STROKE CYCLE engine design trend is Coward increased engine power and higher fuel efficiency. While a four-valve system is the most common direction, problems occur when the valve area is widened by increasing the cylinder bore for a higher engine output. The layout of four larger valves causes the combustion chamber shape to flatten and the combustion time period to increase. In pursuit of the optimum multi-valve engine we have studied four, five, six and seven-valve per cylinder design. Performance targets and design constraints led us toward the successful five-valve engine technology. This technology develops high engine torque and efficient combustion over a wide range of engine speeds.