RC Nitro Fuel is one of those subjects that causes a great deal of discussion and misunderstanding when radio control enthusiasts get together. Questions are often asked about how much lubricant should the nitro fuel contain, or how much nitro? Or what about changing to a different brand of nitro fuel, and how much power will I get from a higher nitro percentage? Here’s a summary of some of the basics to try and help you.
Nitro Fuel Essentials
The three main contents of nitro fuel are methanol, nitromethane and lubricant. Methanol is a fuel in its own right, a bit like gasoline but costing more and producing more power. Nitromethane contains both nitrogen and oxygen and is related to propane. It’s a bit like and accelerator, or oxygenator, and without getting too complex with the chemistry it enables more nitro fuel to burn and produce more power in the same volume. The lubricant keeps everything moving smoothly by reducing friction and heat, so preventing wear and prolonging engine life. It can be either synthetic oil or a blend of good old castor oil and synthetic oil. Popular belief is that the synthetic oils are the more effective lubricant but castor oil can be more effective in dissipating heat. The exact blend of oils in nitro fuels is something manufacturers tend to keep to themselves. Flash point is another factor. Lubricants with a relatively low flash point will burn more easily with the fuel and keep the engine cleaner, but fuels with a higher flashpoint will not burn and provide better lubrication.
Nitro Percentages
Nitro engines cannot be designed without the designer taking into account the nitro fuel to be used. Engine timing and compression ration cannot be decided without knowing the fuel to be used in the nitro engine so every engine is designed to use a specific percentage of nitro in the fuel. If the engine is designed to run on 20% nitro then the combustion and power produced will in theory be ideal at that mix. Increasing the nitro content can cause combustion problems, for example, detonation (explosion) of the fuel, rather than burning. But, that said, many rc nitro enthusiast will experiment with up to 5% more or less nitro to see how it affects engine performance. Careful testing and tuning is needed to see if better performance comes from a different nitro mix.
Nitro Engine Care
When changing fuels and experimenting it is important that changes to nitro percentages are made gradually. A sudden large change of nitro percentage combined with full throttle may not give your engine time to adapt to the new running conditions caused by higher temperatures. It is best to play safe - break-in the nitro engine as if it were new and run a slightly rich mixture at first. Frustrating when you just want to compare fuel performance but taking it steady will result in longer engine life and less potential damage.
Nitro Fuel Storage and Safety
Nitro fuel attracts moisture – technically it’s called hygroscopic, and it also evaporates easily, so the cap should be kept on the bottle when not refuelling. Sudden changes in temperature can cause condensation or evaporation, even in a closed container so try and keep nitro fuel in a reasonably cool place but away from direct sources of heat and cold. Heat sources need to be avoided in any case as like all fuels it is combustible and basic fuel safety rules should be used. Keep it away from heat and flames, don’t smoke and avoid any sparking process if accidents are to be avoided.