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Previous research in our laboratory has shown that NOx emissions can be sharply reduced by PREDIC (PRE-mixed lean DIesel Combustion), in which fuel is injected very early in the compression process. However some problems still remain, such as higher fuel consumption, a lack of ignition timing control, and a large increase in THC and CO, compared to conventional diesel combustion. Appropriate mixture formation is necessary to solve these problems. In this paper, the influence of mixture formation on PREDIC was investigated. It was found that the pintle type injection nozzle was shown to be suitable for PREDIC, because it produced a comparatively uniform mixture in the combustion chamber and avoided collision of the fuel spray with the cylinder liner. Modeling by the KIVA-II software package was carried out to improve our understanding of the mixture formation process.