Carbureted compression ignition model engine

These are quite similar to the typical glow-plug engine that runs on a mixture of methanol-based fuels with a hot wire filament to provide ignition.

Full-size diesel engines, such as those found in a truck, are fuel injected and either two-stroke or four-stroke.

Apart from sharing the diesel's use of compression ignition, their construction has more in common with a small two-stroke motorcycle or lawnmower engine.

This variable compression is achieved by a "contra-piston," at the top of the cylinder, which can be adjusted by a screwed "T-bar".

Smaller propellers reduce the load, and therefore the compression pressure build up, which changes the ignition timing to earlier.

The fuel used contains Diethyl ether, which is highly volatile and has an extremely low flash point, combined with kerosene and a lubricant plus a very small proportion (typically 2%) of ignition improver such as Amyl nitrite or preferably Isopropyl nitrate nowadays.