Abstract: An ammonia combustion engine, a mobile or stationary system having an ammonia combustion engine, and a method comprise operating an ammonia combustion engine with a combustion chamber and an injection device which is in fluidic connection with the combustion chamber. The ammonia can be metered into the combustion chamber. Ammonia is metered into the combustion chamber such that an exhaust gas stream generated by the ammonia combustion engine has a predetermined molar ratio of ammonia to nitrogen oxides independently of the current operating point of the ammonia combustion engine.