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With emergence of fuel cells which have much better thermal efficiency than internal combustion engines (later abbreviated as ICE), ICE has to improve its thermal efficiency to the level of 50%. One of the ways to improve the thermal efficiency of ICE is to utilize ultra-lean combustion and several technical papers have been published. But it seems the thermal efficiency has not been improved as the theory predicts. The test data of these technical papers were re-examined and it was concluded that the thermal dissociation of burned gas and NOx formation is the key factor of a discrepancy between the theory and the actual test data. In order to prevent an occurrence of thermal dissociation, emulsified fuels (mixture of carbonaceous fuels with water) was proposed.

In the past, the performance of motorcycle engines has improved quite rapidly through intensive competition in racing and in the marketplace. Motorcycle engines have contributed to the technological progress of internal combustion engines (hereafter abbreviated as ICE). Today's environmental concerns require motorcycle engines to improve fuel economy and exhaust emission pollutants. After examination of potential measures to improve the thermal efficiency of small engines, it was concluded that if engineers of motorcycle engines fail to take on new ideas such as those being developed in cold fusion, it is foreseen that motorcycle engines will be replaced with new power plants as was seen on locomotives in the past.

A multi-layer catalyst comprising of a core of oxides of transition metals, an intermediate layer of an alumina- based silicate covering the core, and an outer layer of a noble metal alloy covering the intermediate layer was developed and was evaluated as to the reforming performance and its effects on fuel economy. The test results showed that the catalyst, with help of water contained in gasoline, can crack higher molecular hydrocarbons especially such a less combustible substance like aromatics to a lower molecular weight components, resulting in better combustion efficiency.

Increasing consumption of petroleum fuels will eventually force us to utilize synthetic fuels made from renewable sources. This paper, after reviewing the trends of the ways how to make synthetic fuels and new combustion technologies, discusses ideas to raise the thermal efficiency of internal combustion engines (later abbreviated as ICE) to the range of 50%, so that ICE can be competitive with fuel cells whose technologies have been progressing much faster than expected. These ideas include: 1) Active radical combustion 2) Utilization of endothermic reaction of fuels in compression stroke 3) Reduction of thermal dissociation of gases in expansion stroke by lowering combustion gas temperature 4) Emulsified fuels (mixture of carbonaceous fuels with water) 5) Fuel reforming catalysts. The emerge of stable emulsified fuels and catalyst which can reform less combustible species of hydrocarbon to a better combustible one, gave a hint to keep ICE competitive with fuel cells.

YAMAHA Motor has developed and marketed a hybrid bicycle with an electric supplemental power source which generates assist power in proportion to the pedal torque by riders. The key function required for this assist power control system is that the variation of the assist ratio should be as small as possible over wide range of riding conditions. The assist power control system consists of mechanical and electrical components and requires a very tight quality control of each component if the design fails to be robust to disturbances such as pedal torque or vehicle speed. We applied the Taguchi method to this development and succeeded in selecting the optimum combination of component levels in the system.

Two ways to attain low emission diesel combustion, which are capable of meeting future regulations, are the so-called two-stage “rich and lean” combustion and ‘lean” diesel combustion. To actually achieve these types of combustion, homogeneous lean air-fuel mixture formation is very important In this study, two methods of producing a desirable air-fuel mixture axe investigated experimentally by observing fuel sprays from several unique injection nozzles in a high-pressure vessel. One was a slit shaped hole nozzle, which might result in increased air entrainment into the spray because of the larger surface area. The other was impinging flow nozzle, which generated a more homogeneous mixture by its high turbulence. It was observed that with the slit shaped hole nozzle, the cross-sectional shape of the spray was unexpectedly circular, which was attributed to a greater dispersion of the spray perpendicular to the lengthwise slit axis.

When a clutch pedal is operated, the clutch pedal vibration and interior noise are mostly affected by the dynamic characteristics of the clutch cover assembly. We achieved a high correlation between vehicle test data and results using this method when exciting not only clutch system but also the engine system. Finally, we developed an excitation method to evaluate the dynamic characteristics of the clutch cover assembly.

Based on a 1982 model passenger car powered by a 1490 cm3 4-cylinder engine, a concept car has been designed to achieve a substantial fuel economy improvement without sacrificing vehicle performance. The deisgn factors affecting the fuel efficiency of the engine and the vehicle were picked up and improved via experimental analyses. As the cumulative effects of the modifications implemented, the concept car has virtually achieved a fuel economy improvement goal of 40%. A simulation program was carried out to determine the fuel economy contribution of each design factor modified for incorporation in the concept car, thereby identifying the areas to be concentrated on for practical application.

Computer aided systems for performance evaluation of functional devices for passenger cars, such as engines or transmissions, have been applied for ten years. These systems generally consist of a large main frame computer or minicomputers for conducting a large number of complicated analyses. In the past, these computer aided systems were used for vehicle research and development since they were too expensive and sophisticated for use on the production line. Today, microcomputers with mass memory or personal computers are available at very low cost in comparison to conventional minicomputers. With many distributed microcomputers, we have developed a new test and control system for the engine production line. This system consists of (1) a microcomputer with a disk system for test data storage, (2) five personal computers for the man-machine system and data processing, and (3) microcomputers for real time control and data acquistion.