First off the glow plug is heated by an external power source. A glow plug igniter. The igniter heats the element, causing it to glow.



This starts the chain reaction of igniting the fuel on the compression stroke and starting the internal- combustion cycle. The glow plug igniter can be removed and your nitro engine is running at idle.

Now why does nitro engine stay running? Presuming your carburetor is tuned correctly. This is where science comes into play. There is heat generated in the combustion cycle. This heat is called "the catalytic reaction".

A catalytic reaction occurs causing platinum to glow in the presence of "methyl-alcohol," or "methanol". This catalytic reaction will occur on it's own without any outside power source. All of this only comes onto play during low rpm and when there is not enough heat being generated to burn all the fuel vapor. The catalytic reaction changes as rpms and temperature rise. This has just been a very basic explanation of how a glow plug works at low rpm or idle.

Next let us look at what makes up a glow plug. There are five basic parts to a glow plug. We are going to look at a glow plug from the top to the bottom.

1. The post that sticks out of the top of the glow plug, the positive connection.

2. The heating coil is connected to the positive connection making these two items are one piece. The coil is made out of platinum and some makers use rhodium.

3. The post and coil are separated from the plug body by a washer. The washer is called an insulator. The insulator is most often made of "mica", which is a non-conductive material. The insulator prevents electricity from bypassing the coil to find a ground. Plus, it can withstand extreme heat.

4. The plug body, this is the part that screws into the head of the engine. Usually made of steel, for two reasons, it is cheap and makes an ground for the coil.

5. On the top of the body is a crimp washer, this holds all the parts together. Almost all glow plugs use a crimp washer. The only exception is the O'Donnell glow plugs. They have a different design and do not use a crimp washer.

The RC nitro engine glow plug is and can be a mysterious little creature. It can make our rc vehicles run great or be very temperamental beasts. Understanding how and why glow plugs work will make it easier to keep your rc vehicle/s running to their highest potential.