Glow Engine Tuning

Carburetor

The carburetor mixes the fuel and air in exact proportions and passes it on to the engine through the vacuum intake. The engine naturally causes the flow of the gases to pass through the engine and out a pipe or muffler.

It is important for you to know that the air and fuel pass into the engine because of the carburetor, so you can adjust how much of the gas and air mixture reaches the engine. If you reduce the amount of fuel per volume of air, you are making the mixture lean, and by increasing the amount of fuel you are making the mixture rich.

There are two types of carburetors, and they are slide and barrel. The barrel style has been around since the first glow engines, and are still used. They control the gas and air flow by rotating a barrel with a hole cut in either side that allows varying amounts of the gas and air mixture to flow through the carburetor as the hole opening enlarges to the venturi.

Adjustments

The next glow engine tuning adjustment that can be done is the low-end mixture adjustment. This will adjust the fuel mixture at, or almost near idle. This adjustment on barrel carburetors is located where the throttle-arm pivots. If you have a slide carburetor, they are generally found on the opposite side of the carburetor from the throttle slide shaft next to, but below the fuel-inlet and high-end mixture valve.

The final adjustment in glow engine tuning is called the high-end mixture adjustment. This is the primary fuel mixture adjustment, and is most important. This adjustment can be usually found next to the fuel line on top of the engine.

Basic Tuning Information

The first step to take is to properly dial in your engine. Before you do that, you have to make sure of a couple things on your engine. First, your idle-speed must be properly adjusted. The instructions that came with your engine should give you specific instructions on setting the aperture gap to the minimum size. This is important because if your engine can't get enough air and gas flow, then it won't start or run properly. If you turn the adjustment in a clockwise rotation, then that will open the aperture and increase the idle speed. If you rotate it counterclockwise, the idle speed will slow down.

Secondly, make sure the low-end mixture valve is correct. You must do this before you adjust the high-end mixture valve, because it can be affected by the low-end mixture valve. Just like most mixture valves, a clockwise rotation will make the mixture lean, and a counterclockwise turn will richen the mixture.

To find out whether the low-end mixture valve requires tuning, allow the engine to warm up completely, and then idle it for one full minute. If the engine continues to run properly after a minute, then your low-end mixture valve is correct and you can start to adjust your high-end mixture valve. If your glow engine stops running after a minute, then you are either running on to lean or to rich of a setting.

To find out which it is you need to listen when the engine stops running during the test. If the engine's speed increases at the last second and then the engine dies, than you are running on too lean of a setting. To fix this, turn the low-end mixture screw counterclockwise 1/8 of a turn and test it again.

Now if the engine sort of just slows down when it stops running, then you are running on to rich of a setting. This can be fixed by turning the low-end mixture screw clockwise 1/8 of a turn and then retry the test again.

When your engine can run for a full minute, you can continue on with your glow engine tuning. You may have to repeat the above process a few times until all adjustments are set properly.

Now that you have properly set your low-end mixture valve, any problems can be isolated to the high end mixture valve. Now, too properly set your high-end mixture adjustment. First, if you give your engine throttle and it goes for a second, but then suddenly dies, then your high-end mixture is set to lean.

Try turning the high-end mixture needle counterclockwise 1/8 of a turn and retry. If it chokes immediately when you hit the throttle, then it's most likely running too rich. Try making the mixture leaner by turning the valve clockwise 1/8 of a turn.

Another good way to properly dial in your engine is taking its temperature. A properly tuned engine should run between 210° and 220° Fahrenheit. If the temperature is more then that, you’re your mixture is to lean and needs to be richened. If the temperature is lower then that, then your engine is running to rich and needs to be leaned out.

Some useful tips

• When setting the lean adjustment during your glow engine tuning, make sure the engine runs on the rich side. That basically makes sure there is a good amount of lubrication going on.
• Make all engine adjustments in 1/8 turns
• The temperature outside can affect your engine. If you are going to fly, and the temperature outdoors is different then the last time you flown, then you will need to tune it. Warm temperatures require a leaner setting, and cold temperatures require a richer setting.
• After you complete your adjustments, make sure you give them time to take effect. Run the engine for at least a minute with your new adjustment in affect.

Glow Engine Tuning Books