The effects of injector deposits, combustion chamber deposits (CCD), and intake valve deposits (IVD) on exhaust emissions, fuel economy and engine performance have long been recognized in engine and fuel/detergent design. Because important elements of the engine design such as injector position, exhaust gas recirculation (EGR) ratio, and air fuel ratio (AFR) differ from those in port fuel injection (PFI) engines, direct injection spark-ignition (DISI) engines require specific evaluation methods. However, little data is available regarding engine deposits in the more recently produced DISI engines.
Oil and Auto Cooperation for International Standards (OACIS) of Japan have conducted engine deposit tests using three representative Japanese DISI engines, from Toyota, Nissan and Mitsubishi (1.8-2.0L Displacement); seven test fuels (including two gasolines commercially available in the European and the U.S. markets, and five domestic gasolines specially blended to reflect the results of surveys of fuels used in the Japanese market); and a typical detergent suitable for specific operating conditions. The effects of the gasolines, detergent and oils on injector deposits, IVD and CCD were investigated in order to select an engine for test method development.
The results and considerations are expected to enhance the first step in the establishment and global application of test methods, which are being developed jointly by the Coordinating European Council (CEC), Coordinating Research Council (CRC) and OACIS.
Note: Abbreviations are defined at the end of this paper