A Study of Injector Deposits, Combustion Chamber Deposits (CCD) and Intake Valve Deposits (IVD) in Direct Injection Spark Ignition (DISI) Engines II

The effects of Injector deposits, Combustion Chamber Deposits (CCD), and Intake Valve Deposits (IVD) on exhaust emissions, fuel economy and vehicle performances have long been recognized in engine and fuel/detergent design. Because important elements of engine design such as injector position, exhaust gas recirculation (EGR) ratio, and air fuel ratio (AFR) differ from those of port fuel injection (PFI) engines, current existing test methods are not applicable. Therefore, the demand has been increasing year by year for specific evaluation methods for vehicles with direct injection spark ignition (DISI) engines which have spread rapidly worldwide.

Oil and Auto Cooperation for International Standards (OACIS) of Japan selected the Mitsubishi DISI engine (4G93-1.8L) [1] and conducted engine bench tests to investigate the effects of deposits on operating conditions at 40km/h, 70km/h, 140km/h and WOT. The effects of combinations of these operating conditions including the shifting of the test sequence and short cyclic tests. Tests were conducted at different facilities in Japan to check repeatability. According to these test results, OACIS determined several key factors for the evaluation of deposits in DISI engines. These considerations are expected to be helpful in the development of worldwide accepted test methods by the Coordinating European Council (CEC), Coordinating Research Council (CRC) and OACIS.

Note: Abbreviations are defined at the end of this paper.