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Motorcycle engines are required to have high output levels but low exhaust gas emission levels. Measuring the combustion condition proves useful for understanding the engine's operating condition. We developed a compact, high-performance combustion analyzer for measuring the combustion condition of motorcycle engines. This newly developed combustion analyzer is capable of analyzing the indicated mean effective pressure at each engine cycle at the engine speeds exceeding 10,000 rpm required of a high-performance motorcycle engine. Its compact size makes it easily applicable for onboard use, allowing measurement in any operating condition, including circuit travel, which has never been possible with conventional combustion analyzers. We used this new combustion analyzer to measure combustion condition not only on a chassis dynamo but also during circuit travel, when the motorcycle and engine are subjected to much harsher operating conditions.

There is an unceasing demand for motorcycle operating performance levels to rise higher and for exhaust gas emission levels to fall lower. And decreasing the development term is also important demand. Therefore in the development of motorcycles that can satisfy that demand, the ability to carry out measurements under actual driving conditions is of enormous importance. In particular, if the pressure inside the engine cylinder can be measured, a broad range of information can be obtained. The authors are engaged in the development and improvement of combustion analyzers that can be mounted on motorcycles, thereby making it possible to conduct measurements even while driving on a circuit. This paper is the authors' second report on the background to and the latest results of that development effort.

In many cases of the development of motorcycle engines, the combustion analysis has been of the engine in laboratory, not of the one onto actual motorcycles. It is mainly because the combustion analyzer in the market is too large to load onto a motorcycle. Pressure sensor, crank angle detector, arithmetic unit and data record device are necessary to analyze the combustion. The arithmetic unit is to process detected signals and generally needs the largest space among them. Needless to say, more reliable results of the combustion analysis could not be obtained under such limited experimental conditions. Therefore, we developed a compact combustion analyzer, which is possible to be loaded onto a motorcycle. The width of the arithmetic unit is 91mm, the depth 98mm and the thickness 20mm. The core chip has the calculation ability of 78MIPS at a clock speed 60MHz, and it has AD converter, DA converter and high-speed counter.

A new engine of which the fuel is injected directly into the has been developed cylinder as an environmental-friendly engine for personal watercraft(PWC). This new engine surpasses the conventional carbureted engine in performance, yet achieves 75% reduction of THC+NOx emission and 30% improvement of fuel consumption in the ICOMIA mode. This paper describes the system characteristics of this newly developed DI engine, with reference to its combustion and exhaust gas emission properties. This newly developed engine employs a fuel injection system that injects the fuel directly into the cylinder without a high-pressure fuel pump. To analyze the reliability of its unique fuel injection system, the cyclic injection rate is measured the Bosch method.

From a view point of reducing exhaust emission level on a small utility 4-stroke spark-ignition engine, this paper describes the exhaust emission materials analysis and the affect against California Air Resources Board (CARB) specified testing mode on a new prototype while applying very lean mixture burning. The combustion chamber shape and the intake air passage of a production model (Displacement 286 cc, 4-stroke, air cooled, over head valve (OHV), single cylinder) was modified and optimized on the prototype to achieve a stable run up to a lean air-fuel ratio of 20 : 1. When the air-fuel ratio was changed, the highest density of NOx was a little higher than 3,000ppm at an air-fuel ratio of 16 : 1 and the lowest was about 300 ppm at an air-fuel ratio of 19 : 1. The emission level of THC was a little higher than 2,000ppm at an air-fuel ratio of 12 : 1 and less than 1,000 ppm at an air-fuel ratio of 15 : 1 and higher.

A single diesel spray of n-decane which was miscible with a small quantity of exciplex dopants was injected from a hole nozzle into a quiescent high-temperature and high-pressure atmosphere of nitrogen, and was impinged in a normaldirection upon a flat wall with elevated temperature. This experiment was to serve as a simplified model of the actual state in a combustion chamber of diesel engines. When a thin sheet of laser light from Nd:YAG laser is passing through the cross section of this spray containing its central axis, it is able to generate fluorescent emissions from vapor and liquid phases in this evaporating spray. Then, clear 2-dimensional images concerning the concentration distributions of vapor and liquid phases were obtained simultaneously, by an exciplex fluorescence method using an image-intensifier and a CCD camera system. The dispersion processes of vapor and liquid phases in this impinging spray near the wall were analyzed with an image analyzer.