Abstract Ethanol as a renewable fuel has been used widely in vehicles. Dual fuel injection which is one of the new techniques in development was adopted to enhance the engine’s thermal efficiency and reduce the emissions. This paper reports an experimental investigation to the ethanol direct injection plus ethanol port injection (EDI+EPI) fuel system with a focus on the effect of spark timing on the engine performance at different ratios of fuel directly injected to fuel port injected (EDI/EPI). Experiments were conducted on a single cylinder 250 cc spark ignition engine at two engine loads, and 3500 RPM. The volumetric ratio of EDI/EPI was varied between EPI (100% port injection) to EDI (100% direct injection) at approximately 25% of the interval. Experimental results showed that the indicated mean effective pressure (IMEP) was improved significantly by up to 20.88% over the entire dual ethanol injection strategy and spark timing. At the minimum spark advance for the best torque (MBT) timing of 30o bTDC of a light load, the IMEP at 56% of EDI/EPI was 4.4% greater than that at GPI only, and that the combustion duration (θ10-90%) was 8.91% less than that at GPI only. These could be attributed to the reduction in heat loss through the combustion chamber walls due to low-temperature combustion and the greater ethanol combustion speed. On the other hand, the HC and CO emissions were increased by up to 2.03% and 25.38% respectively compared to GPI only. These could be attributed to local rich mixture regions formed by fuel impinged to the wall and the ethanol’s slow vaporization process. However, as a result of the charge cooling effect of EDI the NOx emission was reduced significantly. The greatest reduction in the NOx emission was 68.34% at 100% EDI condition.