High-pressure engines can achieve fuel self-ignition in hot air, so there is hardly any difference in operation between them and non-supercharged diesel engines. In glow plug engines, there is also a brief combustion of the entire fuel quantity, resulting in a significant pressure increase. The glow plug engine is almost exclusively designed as a two-stroke engine with port exhaust and port scavenging. The scavenging and intake air is generated by the engine itself, as the crankcase is sealed airtight and equipped with intake valves, allowing the rising piston to draw in air, which it compresses to about 0.3 bar during its descent. The scavenging air enters the cylinder through the scavenging ports after the combustion gases escape through the exhaust ports. The operation is illustrated by the included diagrams of the engine.