Method for injecting a fluid into the exhaust system of a four-stroke internal combustion engine and internal combustion engine for carrying out the method

Injecting a liquid into the exhaust system of a four-stroke internal combustion engine comprises injecting the liquid through a nozzle at regular intervals corresponding to a crank angle of 720[deg] for each cylinder. An independent claim is also included for a four-stroke internal combustion engine comprising a nozzle for injecting a liquid into the engine's exhaust system and an engine control system that receives a position signal from a crankshaft sensor that serves to control the nozzle so that the nozzle is opened or closed at regular intervals corresponding to a crank angle of 720[deg] for each cylinder.