This study aims to provide full knowledge about the different steps to optimize ammonia/ethanol blends as fuel for Spark-Ignition engine in terms of injection, laminar flame speed, engine performances and pollutant emissions. From the experimental study of the liquid spray of different ammonia/ethanol blends, at low air density, it was concluded that the spray shapes are correlated to the Liquid-Vapor equilibrium diagram. Sprays located in the liquid region in the diagram have similar weak plumes-to-plumes interactions due to slow vaporization and a liquid phase state. For the liquid-vapor region, a transient phase is observed and, when the vapor region is reached, plumes-to-plumes interaction is stronger with a collapsing effect due to a drop of the temperature inside the spray creating a low-pressure zone. From the experimental study of laminar flame speed, using two spherical expanding flame techniques under constant pressure and volume conditions, it was concluded that the addition of 25% of ethanol doubles the laminar flame speed of ammonia and enhances its reactivity. Last by performing experiments in Spark ignition engine, as a function of liquid blend direct injection strategy, it was concluded that high stability is obtained whatever the content of ethanol in the blends. Even if for pure ammonia it was also possible, the operating conditions are more restrictive for pure ammonia. The thermal efficiency is improved in the case of 75% of ethanol in the blend but with consequence on NOx emissions. It can be concluded that trade-offs between performances and pollutant emissions have to be addressed for ammonia/ethanol blends as a function of ammonia and ethanol availabilities.