Compressed Natural Gas (CNG) is considered as a source of clean fuel and have large reservation to use as alternative fuels for internal combustion engines. In particular, the research interest for using dual-fuel in engines is considered to be feasible, cost savings and suitable for CNG gas supply infrastructure. However, when CNG gas is burned in compression ignition engines with high compression ratio, it is easy to cause detonation phenomenon therefore reduce ability to use CNG. The CNG - Diesel mixed system is electronic controlled, including CRDI with injection for initial ignition and the CNG injection system into the intake manifold, with various injection timing and ignition pressure to prevent of detonation, increase the maximum rate of CNG/diesel. Test results on VIKYNO RV125-2 engine, showed that the engine work stably at different speeds. This result is the fundamental for the funther reseach to control supply CNG for compression ignition engines.