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In gasoline direct injection (GDI) systems, various injection types are needed to reduce emissions and improve fuel consumption. This requires high-precision injection in the region in which the amount of injection is small. Achieving injection of a small amount of fuel using GDI solenoid injectors requires the use of the half-lift region. In this region, however, the variation in the injection amount tends to increase due to the variation in the lift behavior of the injectors, posing the problem of how to achieve high-precision injection. To reduce the variation, we analyzed the lift timing out of the injector current and voltage signal with the ECU in an attempt to adjust the amount of injection.

Recently, the electronic fuel injection systems have been widely applied to small motorcycles including scooters. In the high pressure fuel lines, plastic hoses have been increasingly used instead of conventional rubber hoses. As the plastic hose is less elastic than the rubber hose, the fuel pressure pulsates more in the plastic hose. To cope with this issue, we have conducted researches on how the fuel pressure pulsation in the plastic hose affects the accuracy of fuel injection. Keeping our eyes on the pulsation damping effects derived from the changes of volume due to the expansion and contraction of hose when the pressure changes, we have established the analysis method for optimization of the inner diameter and the thickness of the hose utilizing CAE analysis. The newly-developed plastic hose is applicable to motorcycles having a single cylinder 250 cm3 engine using an injector of a high static flow rate.

Recently, the use of ethanol blended fuel is growing worldwide. Therefore, there is increasing needs for addressing issues relating to ethanol blended fuel use in gasoline engine fuel supply systems. In this paper, we focused on one of such issues, which is the reduced life of a multi-layered fuel filter used at inlet side of a fuel pump when it is used with ethanol blended fuel. In this study, we clarified that ethanol blended fuel tends to disperse dust particles contained in fuel to a greater extent than gasoline, and that it has a mechanism to accelerate clogging by concentrating the clogging only on the finest layer of the multi-layered filter. Also, in the process of clarifying this principle, we confirmed that dust particles dispersed by ethanol are coagulated when passing through the filter layers.

A flexible-fuel system for small motorcycles has been developed that can utilize both gasoline, and ethanol as an alternative to fossil fuel. For practicality, we aimed to develop a system that uses a minimum of additional parts. As a method to make both ethanol and gasoline available with the system, a control algorithm that estimates the ethanol concentration by utilizing the output voltage of an OXYGEN SENSOR and selects the appropriate injection quantity is employed. Usually, in automotive flexible-fuel vehicles (FFV), sub-tanks are mounted to ensure engine startability in cold temperatures. However, in small motorcycles, limitations of mounting space must be addressed. In this system, by clarifying the control logic and determining the difficult cases for cold temperature starts due to high ethanol concentration, configuring the indicator to promote gasoline mixture when the start is difficult enabled the elimination of the sub-tanks.

As we developed Ion Current Combustion Control system (ICCS), we began to discover some issues of the ion current system. Depending upon combustion scenarios, the noise contributed to weak output characteristics and output variations making the combustion unstable. This paper intends to present methods developed to overcome these issues: SYSTEM HARDWARE In the previous report(1), we described the issues on the detection sensitivities and noise proof characteristics. In this study, we further reviewed the system component designs to address those challenges. SYSTEM SOFTWARE We have reported(1) a learning method for the stable knock control for varying output characteristics. However, there was a limitation in the application. Hence, we further analyzed the ion current characteristics, then developed a new algorithm to resolve this issue. This new system with the knock control and the misfire detection was introduced in 2000 MY.