Water was inducted with the intake air and injected emulsified with the fuel, in a conventional single cylinder D.I. diesel engine. The major effects of inducted water were an increase in ignition delay, and reduction in the oxides of nitrogen and smoke at a constant fuel/air ratio. When the water was emulsified with the fuel, the ignition delay increased so much that no benefits were obtained except for a reduction in smoke.The results are compared to a similar study on an engine with the “M” combustion system. The major differences between the results obtained with the two combustion systems are attributed to the differences in the ignition delay caused by the water addition.