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Motorcycle usage continues to expand globally. Motorcycles use various fuels in different countries and regions, and it is required that they comply with emissions and fuel consumption regulations as specified in UN-GTR No.2 (WMTC). In general, a motorcycle engine has a large bore diameter and a high compression ratio due to demands of high performance. Poor fuel quality may cause damage to the engine, mainly by knocking. Knock control systems utilizing high-frequency vibration detection strategies like knock sensors, which are equipped on several sport-touring motorcycles, are not used widely for reasons of complex construction and high cost. This research aims to develop a new concept of combustion control for common motorcycle as an alternative.

The Drive By Wire (hereafter referred to as DBW) system is the electronically throttle control system. It controls a throttle valve in order to aim at a suitable throttle position according to an engine operating condition and a demand of driver or rider. This system is basically composed of a throttle body with driving motor, an Accelerator Position Sensor (hereafter referred to as APS), and an Electronic Control Unit (hereafter referred to as ECU). The DBW system is spreading to motorcycle field as replacement of existing mechanical intake control system. This is because there are some advantages as the following especially in the large displacement model: capability for installation of several functions, flexibility in adaptation to recent environmental regulations, and effect on reduction of system cost, etc. In general, the motorcycle has some unique features compared with the automobile. Among them, important features for the DBW system are following three points.

A new power control unit (PCU) has been developed for a Honda small hybrid vehicle with a two-motor hybrid system launched in 2020. For small hybrid vehicles, downsizing and reducing costs of hybrid systems are major challenges. As such, there were emphatic requirements for the newly developed PCU to be small and affordable. To satisfy these requirements for the PCU, new technologies and components have been introduced such as an all-in-one type intelligent power module (IPM) with integrated functions and reverse conducting IGBT (RC-IGBT), a new control sequence for voltage control unit (VCU), and revised PCU packaging to improve cooling performance. The new IPM has a printed-circuit board (PCB) equipped with an electric control unit (ECU) and gate drive circuits, 7 current sensors, and a power module with RC-IGBTs. This functional integration led to a reduction in the number of main electrical PCU assembly components from 9 in the previous PCU to 2 in the new PCU.

The performance of Gasoline Direct Injection (GDI) engines is governed by multiple physical processes such as the internal nozzle flow and the mixing of the liquid stream with the gaseous ambient environment. A detailed knowledge of these processes even for complex injectors is very important for improving the design and performance of combustion engines all the way to pollutant formation and emissions. However, many processes are still not completely understood, which is partly caused by their restricted experimental accessibility. Thus, high-fidelity simulations can be helpful to obtain further understanding of GDI injectors. In this work, advanced simulation and experimental methods are combined in order to study the spray characteristics of two different 3-hole GDI injectors.

Spray characteristics of injectors depend on, among other factors, not only the level of turbulence upstream of the nozzle plate, but also on whether cavitation arises. "Bulk" cavitation, by which we mean cavitation which arises far from walls and thus far from streamline curvature associated with salient points on a wall, has not been investigated thoroughly experimentally and moreover it is quite challenging to predict by means of computational fluid dynamics. Information about the effect of the injector geometry on the formation of bulk cavitation and quantitative measurements of the flow field that promotes this phenomenon in gasoline injectors does not exist and this forms the background to this work. Evolution of bulk cavitation was visualized in two gasoline multi-hole injectors by means of a fast camera.

Fuel spray injected by a port injector has significant effects on engine power output and combustion efficiency. For this reason, it is necessary to atomize fuel into fine droplets and accurately supply it without being susceptible to any changes in temperature or negative pressure affected by engine. This document introduces an atomization technique with optimized layout of nozzle holes and drastically reduced pressure loss (energy loss) in the flow under a needle valve seat. It also describes an injector having a short fuel flow path and a small dead volume under the valve seat, which can have good resistance against any changes in temperature and negative pressure.

We have extended application of fuel injectors (hereafter as “injector”) for small motorcycle engines in developing countries by making it compatible with various engine displacements and trims as well as satisfying the needs from a variety of operating and environmental conditions. The motorcycles with a small-displacement engine are mainly for developing countries and often have an uncovered engine. Accordingly, a noise-insulating cover was indispensable to insulate injector noises. Since it was necessary to attain a low cost for the complete motorcycle by eliminationof the noise-insulation cover for extensive application of an electronic fuel injection system (hereafter “FI”) in developing countries, we developed the quiet injector by thorough reduction of mass of the needle valve and lowering of the operation speed.