The purpose of this study is to evaluate the effect of water addition on combustion in a conventional SI engine. The manifold induction method is used for water addition in this study. The exhaust emissions, ignition timing, and exhaust temperature values were measured for different equivalence ratio values by using a naturally aspirated liquefied-petroleum-gas-fueled spark ignition, four-cylinder engine. The water induction is accomplished over a wide range of water to fuel mass ratios of 0.2-0.5. The results showed that water addition worked as a cooling mechanism for the fuel-air charge and slowing the burning rates, yielding a reduction of the peak combustion temperature, which in turn provides a 35% reduction in peak NOx emissions without any significant change in CO and HC emissions. In addition, greater ignition advance is obtained.