The work cycle is triggered in three stages: 1.Pure air is sucked in first. 2.This air is compressed to 30â55 bar â heating it up to. 700â900 Â°C. 3.Diesel fuel is injected into the combustion chamber. The high temperature of the compressed air triggers self-. ignition, the interior pressure rises and the engine. performs its work. Compared to gasoline engines, self-igniters require more. elaborate injection systems and engine structures. The first. diesel engines were not particularly comfortable or fast.