COMBUSTION STABILITY OF FOUR-VALVE ENGINE AT LOW SPEEDS

An investigation was made of the degree to which low-speed combustion performance of a four-cylinder engine is improved by throttling one of the two intake ports of the four-valve cylinder head. It was found that such throttling resulted in more rapid flame propagation and less cycle-to-cycle fluctuation, thus improving engine stability. These phenomena were confirmed in a single-cylinder engine equipped with a quartz piston crown, using a high-speed camera. The study further suggested the importance of optimizing fuel spray characteristics of four-valve engines, notably spray angle and atomization.