Fuel for model engines
Updated: 10.03.2021 | Reading time: 3 minutes
This text is machine translated.
The actual fuel for glow ignition model engines is methanol (methyl alcohol). This is why these engines are also referred to as methanol engines. Castor oil or synthetic oil is added to the methanol in varying quantities as a lubricant. Castor oil is a natural product and is therefore subject to biological ageing. During combustion, oil carbon is produced, which is deposited on the inside and, due to leaks, also on the outside of the engine.
As the oil carbon has a polishing effect, fuel with castor oil is often used when starting up new engines. Once the moving parts are optimally embedded in each other, you can switch to fuel with synthetic oil.
Various additives are often added to synthetic oils to stabilize the oil film, reduce wear and neutralize aggressive combustion residues.
Nitromethane
As an oxygen carrier, nitromethane has a positive effect on the running behavior of the engines and is the reason why nitro fuel is also referred to in the scene. In principle, two-stroke model glow igniters also run without nitromethane in the fuel. However, the ratio between the intake air and the fuel content must be perfect from idling to full throttle.
However, this is not always guaranteed with the model engine carburetors, some of which are quite simple in design. For this reason, a proportion of approx. 5 % to 12 % nitromethane is added to the fuel. The addition of nitromethane allows the mixture to ignite cleanly even if the proportion of fuel in the intake air is higher. The engines then run reliably at idle and increase the speed quickly when accelerating.
This is particularly important for four-stroke model engines, which are known to ignite only every second revolution.
With higher admixtures of up to approx. 30%, nitromethane primarily has a performance-enhancing effect. Another positive effect is the additional internal cooling. As the proportion of fuel is very high in relation to the intake air (rich carburetor setting), a lot of evaporative cooling is also generated when the fuel droplets evaporate inside the engine. However, the combustion of nitromethane produces extremely acidic and aggressive residues. These must be neutralized by additives in the oil and regular engine care with after-run oil.
Selecting the right composition
The composition of the different fuel components depends on the engine used and the application. A high-displacement model aircraft engine, which is well cooled by the propeller wind, requires a completely different fuel composition than a small glow engine in a model car.
But the quality of the individual components also plays a decisive role. A fuel of inferior quality and unsuitable composition not only leads to poor engine running behavior. In conjunction with a carburetor setting that is too lean, it can very quickly lead to major engine damage. For this reason, inexperienced users should always seek advice when selecting the right fuel.
This was one of the reasons why we decided to offer our high-quality fuels exclusively in the store.
In addition, model building fuel is a hazardous substance that is subject to certain trade restrictions. The fuel may not be sent by post and may only be supplied to persons aged 18 and over.
It is therefore necessary for customers to be able to present proof of age at the store when making a purchase.
Competent specialist advice is particularly important in order to make the right choice from the wide range of different fuel mixtures.
EU ban on fuels with a high nitromethane content
To ensure public safety, the European Union wants to prevent the illegal manufacture of explosives. For this reason, the sale of propellants with a nitomethane content of over 16% to end consumers in Germany is prohibited from February 1, 2021.
Existing residual stocks may still be sold until January 31, 2022.
However, as this fuel is urgently needed especially for helicopter models with combustion engines as well as for car models, the German Model Aviation Association (DMFV) and the German Minicar Club e.V. (DMC) are trying to obtain an exemption for the model building sector.