Recent studies concluded that the use of ammonia in SI engines is possible thanks to an ignition booster or promoter. In this paper, the improvement of premixed ammonia/air combustion for internal combustion engines is studied as a function of performance and exhaust pollutants in a Spark-Assisted Compression Ignition single-cylinder engine, which supports a higher compression ratio (CR). For the first time, pure NH 3 combustion was performed over a large range of engine operating conditions. The study concludes that neat ammonia can be used over a large operating range, here driven by the intake pressure, using a classical ignition device with a CR of 14-17 at 1000 rpm. The comparison with previous data obtained in a current single-cylinder SI engine clearly shows the potential of this engine mode, even for very low loads and various engine speeds (650, 1000, 2000 rpm), in spite of an initial aerodynamic that is not optimized to enhance flame-turbulence interaction. Kinetic simulations provide some explanations about exhaust emission behaviour, especially unburnt NH 3 , H 2 , NO x and N 2 O.