ORIGINAL: merugo

Treven,
very few engines work approximating Diesel cycle, since it can performed only partly without very particular arrangements. The Diesel cycle can work with a glow plug, a simple hot head previously heated with ...a blacksmith forge, or simply ignite on the rise of temperature caused by adiabatic compression.
NO commercial engine work following true Diesel cycle, so their efficiency is lower than the exceptional one of Diesel cycle. In practice they all differ from the original idea by approximating the isothermal combustion-expansion phase of the original cycle by means of tricks, more or less efficient and simple.
Model engines, apart from remarkable exceptions to be counted on the fingers of one hand, are the roughest approximation of diesel cycle. They are HCCI engines, (Homogeneus Charge Compression Ignition) The combustion-expansion is in practice left to nature, renouncing to the control of the injection of the fuel DURING the combustion, that is THE ONLY peculiar characteristic of the diesel cycle.
It is a common practice to name "diesel" every engine with compression ignition, as you understand this is only an approximation, but this can lead to considerable disguise when using too far the similitude. WHAT IS THE COMBUSTION OF A TRUE DIESEL WILL NEVER HAPPEN IN A MODEL "DIESEL", so the best thing is to forgot verbal similitudes.