Development of Combustion Technology for Improving Scavenging Process and for Reducing Catalyst Warm-Up Time in a High-Compression-Ratio Gasoline Engine

The high compression ratio is effective in improving the thermal efficiency for a spark-ignition gasoline engine. However, the exhaust emissions are deteriorated by the increased catalyst warm-up time, which results from (1) the reduced exhaust gas temperature caused by the elevated expansion ratio and (2) the elongated exhaust pipe for better scavenging efficiency. To meet the stringent emission regulations, the technology development was conducted for retarding the combustion phasing and for improving the scavenging process in a high-compression-ratio engine. The results show that both high environmental performance and high engine torque are achieved.高圧縮比エンジンは熱効率が向上する一方，高膨張比による排ガス温低下とトルク向上を狙ったロング排気系により触媒昇温時間が増加する．このため従来技術では排気ガス規制への適合が困難である．そこで，新たなリタード燃焼技術を掃気性の改善と合わせて開発し，優れた環境性能と高トルクの両立を実現した．