Development of Automatic Calibration System for PFI Engines

This report summarizes the research findings on fuel injection calibration methods, aiming to improve engine performance and reduce environmental impact. In PFI (Port Fuel Injection) engines, the injected fuel adheres to the port walls and mixes with air as it vaporizes, then flows into the combustion chamber. Traditionally, the fuel injection quantity is determined by the base map, which is calibrated for a steady state, and corrections for transient conditions. During steady-state operation, the air-fuel ratio of the mixture is uniquely determined by the amount of fuel injected, allowing for reproducible calibration. However, during transient conditions, the amount of fuel adhering to the walls and the amount vaporized do not balance, necessitating transient compensation to achieve the desired air-fuel ratio. Traditional transient compensation has been adapted for each engine model based on experience to accommodate differences in port shapes and injector placements. This approach has not always resulted in optimal calibration and often required significant time. To address this issue, a new transient compensation logic and an automated calibration system have been developed, enabling efficient and optimal calibration. The implementation of this system eliminates variations due to the skill level of the calibration engineer　and reduces time requirements. Furthermore, optimal calibration contributes to improved engine performance and reduced environmental impact.