Our Direction for ICE (Internal Combustion Engine) - Consideration of Engine Displacement

摘要

Based on the availability of high octane gasoline fuel as standard fuel in Europe the worldwide trend of turbocharging and reduction of engine displacement is deduced to increase engine efficiency (downsizing).The primary factor of fuel consumption reduction through downsizing is the reduction of engine mechanical friction losses and pumping losses. At the time, the compression ratio must be reduced. To compare the reduction of compression ratio against downsizing rate while keeping same engine power by turbocharging and same knock resistance by compression ratio reduction finally the trade-off among engine mechanical friction, pumping losses and compression ratio requirement need to be considered versus the efficiencies at each engine load. The result is as follows: In the low load range, downsizing engines with turbocharging have advantages in comparison to large displacement and naturally aspirated engines with high compression ratio. In the medium and high load range, large displacement and naturally aspirated engines with high compression ratio have advantages. In future, lean burn is mandatory to improve dramatically engine efficiency regarding internal combustion engines. The concept of lean burn in small displacement engines can offer little advantages due to little reduction of pumping losses. Breathing ability thanks to large displacement can increase torque without cost increasing such as turbocharger and be used as means to enlarge lean burn area which provides high efficiency. Due to above reasons, the trend of downsizing will be changed.