How RC Gas Engines Work (Gas and Glow Differences)

by FliteTest | September 12, 2018 | (4) Posted in How To

For people new to the gas-powered side of the RC hobby, engines can be intimidating. Let's unravel some of the mysteries in a short introduction.

These days, electric is king. It's clean, efficient and great for beginners. However, you might still want to dip your toes into the world of gas engines. Here's how they work and what the difference is between Glow and Gas motors. 

How they work

Model airplane engines are usually 2 stroke. This type of engine is different to a 4 stroke in that it completes a power cycle with only two strokes (up and down movements) of the piston whilst running. This makes them small, simple and comparatively powerful when it comes to the thrust to weight ratio. For this reason, they've always been popular in the model airplane world, even before there was Radio Control available. 

4 stroke engines tend to be a little bulkier and more complicated than their 2 stroke counterparts. These engines sometimes use multiple pistons and sound much more like the big versions found in full-scale aircraft. This means they work great in large-scale airplanes. Check out this incredible model of a Reno P-51 Mustang that uses a 4 stroke engine. 

Glow Engines

An RC glow engine uses a glow plug to ignite its fuel and air mixture. Nitro engines are a type of glow engine. The glow plug is heated with electric current during the starting procedure after which the wires disconnected and a combination of residual heat and catalytic action of the plug ignites the fuel. The continual 'glow' of this plug is, subsequently, where the name comes from. 

Earlier this year, I got the opportunity to visit the workshop that creates these kind of engines. It was called Progress Aero Works. This United Kingdom company produces hundreds of these engines a year and distributes them all over the world. Here's an article about that factory tour. 

Gas Engines

A gas engine uses a spark plug to ignite the gasoline it uses as fuel. These have a lower compression than a glow engine. They often look very similar but use different fuel and provide quite a different (generally cleaner) experience. Way back in 2013, Josh and David bought a 38cc 'gasser' and got to grips with their new plane. Here's the video. It should give you a good idea of the process needed to get one of these to fire up and into the air.

Breaking in Gas Engines

When you get a new gas engine, you'll need to run it on the ground to get it to ware in. Often, the manual will have detailed instructions on how long to run it for and at which settings. Here's a video we made back in May to explain this in more detail. 

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Jackson T on September 13, 2018
When are we going to see the big gas Ugly Stick fly?
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How RC Gas Engines Work (Gas and Glow Differences)