So you’re interested in using nitro fuels, but how much do you actually know about them? Whether you’re a beginner, or have just been using your factory settings and recommended products for a long time, you could well have the interest but not the facts. If you feel there might be gaps in your knowledge, it’s time to wise up! What do nitro fuel percentages mean, what difference do they make in reality, and which is right for your nitro-powered vehicle/craft? We have the answers.
We’ll start off by stating the obvious: the listed ‘nitro percentage’ is literally the proportion of nitromethane contained in the fuel mixture. This can be anything from 10% to 40% or even higher, depending on what type of machine you’re running and why. There are upsides and downsides to all the levels, which we’ll go into in a minute. The other basic information that you’ll need to know concerns the other components of nitro fuel, which make up anything between 90% and 40% of the fuel mixture. These are methanol and oil, which are used to cool and lubricate the engine, alongside any other additives such as anti-corrosion or degumming agents that the manufacturer might choose to include.
So what difference do these different fuel compositions make? Increasing the nitromethane content of a fuel has a range of consequences, the most significant being that there will be more combustible matter and also more oxygen passing into the engine, so the fuel is burned up faster. This creates more power per second but also more heat and a shorter run time per tank of fuel. The other important point is that the fuel will contain proportionally less of the components that help to cool it down and protect it from damage, meaning still greater heat and a shorter healthy lifespan for the engine. Lowering the level of nitro content, by comparison, means reducing the engine’s power (due to a lesser amount of combustible matter being burned at any one time), but increasing the running time of a tank (due to this slower combustion rate) and usually improving the health of the engine as a result of proportionally more ‘space’ in the fuel being devoted to oils and other additives.
There are exceptions to these rules, of course. Different manufacturers have developed different ways of combating the engine damage and increased heat caused by higher nitro percentage fuels, and high-quality (read: expensive) racing fuels often contain ‘concentrated’ synthetic oils that produce sufficient lubrication using a smaller volume of liquid. So you can potentially up your nitro content while avoiding many negative side effects. Conversely, engines specifically designed for lower nitro percentage fuels can run just as fast, using the fuel efficiently rather than relying on the sheer amount of nitromethane.
Well, how does this all affect you? You can probably guess your ‘general’ ideal level (i.e. the lower or higher end of the spectrum) already. For example, a serious RC racer reading this would realise that, due to their interest in the fastest possible speed and power for limited amounts of time, using a fuel with a relatively high nitro content combined with lots of pre- and post-race care would be their best bet. Your average Joe, on the other hand – who doesn’t earn race winnings, needs fun but not world-beating speeds, and wouldn’t mind saving some money on replacement parts and fuel – might be tempted by a lower nitromethane mix.
‘High’ and ‘low’ are relative terms, however, and what would run a water-cooled nitro boat engine quite happily would be a death sentence for a .12 size car engine. Wildly inappropriate nitromethane levels can even cause the fuel to ‘detonate’ (exploding all at once rather than burning) and destroy your model! So how do you make sure that any tinkering you do will be suitable for your vehicle/craft?
The first thing to do is check the level of your current or recommended fuel. Really you shouldn’t stray more than 10% from that (although, as we’ve mentioned, different brands with different compositions can let you push it further). Another general rule is to stick between 10% and 20% nitromethane with a .12 – .18 size engine (say 15% as a common level), or between 20% and 40% with a .21 size or larger. The second thing to do is make sure you know your stuff about tuning! Even small percentage differences – heck, even switching brands of the same listed nitro percentage – can require some radical retuning of your RC engine. Learn a good tuning routine (we have some on our website) and apply it, or you’ll be wasting your time!
So now you’re well on your way to understanding nitro fuels, and the difference they can make to the performance of a vehicle/craft. Experiment carefully if you’re going to try it – you’ll be using the model differently from how it was designed to be used, after all – but play it safe and you should be rewarded! Have fun out there, and ask us if you have any more questions; we’re here for you all the way.