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The world's first Variable Cylinder Management (VCM) system for large motorcycles, which will achieve both high power and low fuel consumption, has been developed. The system uses a mass production in-line four-cylinder engine which has a displacement of 1137 cm₃ as the base engine. The VCM system is capable of increasing and decreasing the number of working cylinders between 2-cylinder, 3-cylinder and 4-cylinder operations by modifying some parts of the base engine. Utilizing throttle valves installed on each cylinder, the throttle valves for continuously operating the regularly working cylinders and the on-demand working cylinders are controlled by three motors, which divide them into three independent lines. In order to improve fuel consumption by reducing the pumping loss of the non-working cylinders, the engine is equipped with hydraulically operated intake and exhaust valve deactivating mechanisms.

The world’s first variable cylinder management system, VCM system, for large motorcycles has been developed. The system uses an in-line four-cylinder, 1 137 cm3 engine as the base, and allows changing of the number of working cylinders from 2-cylinder to 3-cylinder to 4-cylinder. To eliminate an abrupt change of power delivery when shifting number of working cylinders, the electronically-controlled throttle valve (Throttle-By-Wire: TBW) is employed. Coupled with the harmonized control of the intake-and-exhaust valve deactivating system, the smooth switching of number of working cylinders suitable for motorcycles has been realized. As a result, while maintaining the same power output characteristics of the conventional engine, EURO 3 exhaust emission regulations are satisfied while attaining approximately 46% better fuel economy in the New European Driving Cycle mode (NEDC mode).

In reciprocating internal combustion engines, the Otto cycle indicates the best thermal efficiency under a given compression ratio. To achieve an ideal Otto cycle, combustion must take place instantaneously at top dead center, but in fact, this is impossible. Meanwhile, if we allow slower piston motion around top dead center, combustion will be promoted at that period; then both the in-cylinder pressure and degree of constant volume will increase, leading to higher thermal efficiency. In order to verify this hypothesis, an engine with slower piston motion around top dead center, using an ideal constant volume combustion engine, was built and tested. As anticipated, the degree of constant volume increased. However, thermal efficiency was not improved, due to increased heat loss.

The government has been imposing a stricter diesel engine efficiency standard to reduce carbon dioxide, NOx and other particulate emissions. Diesel combustion improvement is a major concern, and many researchers have examined diesel combustion and its sprays. One possible method to solve the technical problems is applying the Variable Orifice Nozzle (VON) to fuel injection systems. The VON, which nozzle cross-sectional area is changed continuously, has been developed for direct injection (DI) diesel engines. The orifice changing mechanism is composed mainly of a rotary valve, drive shaft and small pulse motor. The VON's standard deviation (SD) of injection quantity in injection pump operation range is the same as the conventional hole nozzle's due to the rotary valve that is fixed by a spring. The smaller orifice of the VON has produced a higher injection pressure and produced a longer injection duration than that of a larger orifice.

Due to the present demand for further improved emissions and performance of diesel engines, there is a growing need to improve the control of fuel injection quantity and timing, as well as spray properties. We have developed a Micro Turbine Sensor that can measure transient injection rate and timing using micro machining technology. This sensor realizes volumetric flow measurement using a tangential turbine as the sensing element which has an outside diameter of 1mm, and which is located next to the inlet connector of the injection nozzle. The measured results are compared with a Bosch type injection rate meter. Since the tendency of measured injection rate shows fair agreement with results of the reference system, this sensor has potential as a fuel flow meter which is able to measure the injection rate and timing directly and continuously during engine operation.