Glow Plugs

All That You Wanted To Know

So what are glow plugs?

They provide ignition to the air-fuel mixture in an rc car engine. Same like what a spark plug does in a real life gasoline engine.

The way this works is quite interesting. Every plug has a coil inside it which must be heated to a certain extent to get the process rolling. This is why you connect it to a battery before starting. After a certain optimum stage is reached the battery can be disconnected while the glow plug continues to glow to ignite the fuel air mixture.

One question that might come to you is how come the plug glows even after the battery is disconnected?

This is an excellent case of change of form of energy. As we all know energy can neither be created nor be destroyed. It can however be converted from one form to another. In this case the magic lies in the potential energy of the fuel being converted to heat energy.

The coil inside the plug is made of an alloy that can tolerate extreme conditions of heat and vibration. More often than not Platinum is used in such cases. The fuel on the other hand contains methanol.

When Platinum comes in contact with methanol present in fuel a chemical reaction between the two occurs. This reaction is exothermic in nature. This causes the Platinum coil to heat up and helps ignite the alcohol thereby the air fuel mixture.

Let’s get into a little more detail now…

The catalytic reaction that was mentioned earlier depends upon some parameters like coil temperature and the fuel pressure. Higher the temperature or pressures, greater are the chances of reaction.

Thus to control the temperature of the coil you have hot and cold plugs. There may be some heat ranges in between the extreme ends for specific temperatures of the coil. If you use a hotter than required plug then the fuel air mixture will pre ignite whereas use of a colder plug will delay the process of ignition. In either case there will be loss of efficiency.

While working you must remember that higher percentage of nitro fuel in the mixture demands a colder plug. Similarly a less nitro content mixture will need a hotter plug.

Hopefully this article addressed your pressing issues regarding glow plugs. So have fun rc racing.

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