Definition: Nitro or glow engines use nitro fuel but it's actually a mixture of fuel and air that goes into the engine. When there is more air and less fuel it is referred to as a lean mixture. When tuning a nitro engine, leaning means adjusting the air/fuel mixture to have more air.
When you lean out a nitro engine you are adjusting the mixture so that there is more air going into the nitro engine than there is fuel. This lean mixture provides a little more horsepower but can result in very high engine temperatures. If you are not careful leaning out a nitro engine you could run it too lean. This will wear out the glow plug prematurely or cause engine failure such as vapor lock.
A lean mixture may be called for when:
- too much blue smoke (more than a light stream) comes from the exhaust;
- a lot of unburned fuel comes from the exhaust;
- your RC has no "get up and go" and can't reach top speeds.
You may be running too lean if:
- the engine gets so hot that a drop of water on the engine immediately starts sizzling and popping;
- the engine dies while idling;
- you don't see a light stream of blue smoke from the exhaust.
Learn how to lean or richen the air/fuel mixture for your nitro RC.