Experiments were conducted on a turbocharged three cylinder automotive common rail diesel engine with port injection of butanol. This dual fuel engine was run with neat butanol and blends of water and butanol (up to 20% water by mass). Experiments were performed at a constant speed of 1800 rpm and a brake mean effective pressure of 11.8 bar (full load) at varying butanol to diesel energy share values while diesel was either injected as a single pulse or as twin pulses (Main plus Post). Open engine controllers were used for varying the injection parameters of diesel and butanol.Water butanol blends improved the brake thermal efficiency by a small extent because of better combustion phasing as compared to butanol without water. When the butanol to diesel energy share was high, auto-ignition of butanol occurred before the injection of diesel. This lowered the ignition delay of diesel and hence elevated the smoke level. Two separated heat release phases along with high rates of pressure rise were thus observed. This limited the maximum butanol to diesel energy share. However, it was also possible to enhance the butanol to diesel energy share from about 28 to 33% through the use of water butanol blends. However, the change in the amount of water in the blend had little impact due to its small quantity. Increase in the amount of butanol decreased the NO emission because of reduced charge temperature. However, the water in the blend had little impact due to its small quantity. Smoke and NO emissions were lower with the water butanol blends. Use of Main plus Post Injection with the blend (W10) was effective in reducing NO (by 10%) and smoke (by 52%) emissions, without any adverse effect on brake thermal efficiency. The optimal main to post offset was 10 deg. CA and the best post quantity was about 10% of the total diesel injected.