I really like that video. That's awesome...


Keeping on track - How a model airplane engine works:

There are two types of "natural aspiration" for internal combustion engines.
Two Stroke/Cycle and Four Stroke/Cycle.

A two stroke engine intakes and exhausts at the same time.
Try to stay with me...
The piston is travelling upwards, (compressions stroke). The compressions stroke always just precedes fuel ignition.
While moving upwards, a vacuum is created in the crankcase. This vacuum draws air/fuel into the crankcase, (oil in the fuel lubricates the crankshaft, piston, and wrist pin).
The air/fuel mixture that was ingested last time around is ignited, and the piston is forced downward.
In the way down, the air/fuel mixture in the crankcase is compressed. As the piston approaches the bottom of its stroke, ports open on the side of the cylinder wall, (OK, they don't "OPEN", they are always there and open, but the top of the piston passes by them and they are now exposed to the inside of the combustion chamber).
One port allows the burned air/fuel mix to escape the combustion chamber, and the other allows the compressed air/fuel mix to enter the combustion chamber.

Got it so far? Good, 'cause that's it. The cycle starts all over again. Up - Bang! - Down - Intake AND exhaust, repeat

4 cycle engines work much differently.
We'll start with the intake stroke... The piston starts moving downward, and the intake valve opens allowing the air/fuel mixture to be drawn into the combustion chamber.
When the piston reaches the bottom of the stroke, the intake valve closes, and the piston starts to move upward, (Compression).
Once the piston reaches the top, the air fuel is ignited, creating high pressure causing the piston to be pushed down.
Once the piston is at the bottom of this stroke, the exhaust valve opens, and the upward movement of the piston pushes the exhaust out through the valve.
Start over.
This type of engine fires once every two revolutions.
The two stroke fires every one revolution.

Got it? OK, let's move on...

There are 3 types of ignition.
Spark, Diesel, and Semi-Diesel.

Spark is self explanitory. It uses a spark inside the combustion chamber to ignite the fuel/air mixture. Once it starts to burn, (not explode), the gasses expand creating pressure on the top of the piston, pushing it downward in the cylinder. Fuel is mixed with the air outside of the combustion chamber, and pulled into the chamber as a mixture.

Diesel uses compression of the air inside the combustion chamber to create heat. This heat is enough to ignite the fuel by itself, and if the fuel is mixed with the air before the compression cycle, you risk the chance of igniting the air/fuel mixture before it should be ingnitred and damage the engine. In a diesel, the fuel is atomized through an injector that pumps the fuel directly into the combustion chamber at the correct time.

A Semi-Diesel usually mixes the air and fuel before ingesting them into the combustion chamber like the spark ignition engine.
The air/fuel mixture is heated up just below ignition point during the compression cycle. The way it is ignited is with the aid of the glowplug.

OK, so how does the model airplane engine work?
Most model airplane engines are Semi-Diesel, two stroke engines.
There are 4 stroke semi diesel engines like the Sato's.
There are also, (for the gant scale planes), spark ignition two and four stroke engines.

Well, I hope that this long post anwers your questions regarding model plane engines without causing confusion.

Bob