hi,

i've been looking around for a while and i see that
a lot of people here use pretty high nitro% in their
fuel, like 15% to even 30%? Sometimes even heli-fuel?

Why is that?
I run 5% at max in my Saito .91 and it runs super!
But now i'm gonna put it in a 3D-plane so i wondered
if i would need higher nitro...

Thanks,
Wouter

buy some higher nitro and tach it and see. Saito's especially will gain significant rpm from higher nitro, so it depends on the plane if you want/need more nitro.

Nitro helps to gain power and often helps cooling the engine since you will most certainly have to open needles for the engine to perform well. More fuel in the engine gives more power and more oil in the engine gives less heat, even if the engine produces more power.

I like to run on 20% nitro and 20% oil but more nitro is good also.

I don't know if 15 to 30% is even considered high anymore. Thats pretty much average now-a-days. I see very few people running 5% nitro at the field, but the warbird racers are running 65 and sometimes even 80% nitro. Now that's high content.

I run 20/20 full synthetic in my Saito .91 I would use 18/30 Heli fuel but It's too expensive. Heck the 20/20 is too much... Anyone got an RCS 140 to sell?

I've never tried it, but I've heard some of the guys at the field saying the Saito .91 runs a little blubery on 5%. You might want to try something like Powermaster YS 20/20 fuel or an 18% Heli mix. Just as long as the oil content is high for those YS and Saito engines, you can run some pretty high nitro numbers on those engines.

Hi Wouter

I would stick with the 5% in the saito unless the plane/ engine combo turns out a little marginal for power. I run 15% in most every thing except Webras and 1.2 or larger 2 strokes just because I get it cheap by the case. My Saitos DO respond well to more nitro when I need more power. My Saito 72 especially likes 30% heli which has 23% low viscocity oil. Good for 600 rpm on a 13/6 apc. That's real helpful if your vertical acceleration is marginal. But if your performance is good I wouldn't bother with the high nitro

Denis

Higher nitro will aid in engine cooling because it attracts more oxygen.

The engine will be used in a .46 3D plane (Robbe diamant no limit)
so it allready has plenty of power for it. I'll stick with the
5%.

Actually, most of the local flyers here, use 0% nitro. It works
just fine.
I also was told that nitro makes the engine rust a lot faster?

I use 10%. we dont use higher nitro in england, apart from YSs, cos its expencive. higher nitro throttles alot better. but 80% nitro! thats berserk

You are right about the rusting. Nitromethane attracts water from the air and thus water gets into your engine. But as long as you don't forget to run it out when your done flying for the day, rust won't be a problem.

I think I'm going to avoid all the rust and cost problems by switching to gas anyhoo... Can anyone say U-Can-Do-3d-With-an-RCS-140?

Or maybe an Mvvs 160....Hmmm. :devious:

80% nitro... about 18-20% oil. There's no alcohol in that fuel


SInce nitromethane attracts oxygen, it will cause oxidation (rust) if not taken care of properly.

Americans seem to use a heck of a lot more nitro than brits and europeans!
Ive never gone over 10%nitro!
Luke

It's because we're all nuts. :bananahea

We also supercharge and turbocharge our gasoline engines in our automobiles.

I have a 5.3 Litre engine in my 5500 lbs (2495 Kilos) truck that gets about 12 Miles per gallon (or 5.1 Kilometers per litre.)

What the heck is wrong with me?!?! :drowning:

Uh, nitro IS an oxidizer. It's kind of like running no2 in your car. Think of it this way, the higher the nitro the less burnable fuel is in the mix. The nitro adds O2 to the mix and causes a faster burn and sometimes more power. Some engines don't respond well to higher nitro. Was running my OS 160 on 15% and got 8500 rpm in an 18x8. I went to 3% nitro and reduced the oil to about 12% and now getting 8700 on the same prop. More fuel to burn. I also believe the cooling comes from the methanol not the nitro.

i like the hummer v2, 1 mpg i saw on the dial once

This is a write up by PowerMasterFuels. It pretty much mirrors MHO and experience. I pretty much run 15% except for certain engines as a matter of convenience. I get it for only a dollar more than 5% (12.50 /gallon), it's aways immediately available by the case (4 gallons), and I don't have a bunch of different fuels laying around the garage. I run all my engines on 15% including YS 2 and 4 strokes unless the engine shows me it doesn't like it. My Webra 120s almost always indicate they don't like anything over 5%. I could go to the slight pain of ordering 10% or 5% but then my YSs wouldn't like or some of my little .15s might act like I was being a little skimpy. So!!! 15% is the happy medium.

I follow a couple of German forums and what I don't understand is why some of you folks over on that side of the pond skimp on the oil. 12 to 15 percent oil will get more power but at what risk. The oil carrys away a significant amount of heat and is real important for that roll in the smaller high powered engines

The real hygroscopic in your fuel is the alcohol. It is true that nitro is water solueable but getting rid of it won't do anything to prevent water from getting in your fuel. As stated run the engine dry.

PowerMaster write up

Nitromethane…..everybody knows it's there, but few, it seems, really know much about it. Although most seem to know - at least vaguely - that's its primary purpose is to add power, we still get an occasional call or letter asking, "Why do you use it in model fuel?" At best, there is much misinformation regarding this somewhat exotic ingredient. Let's see what we can do to clear some of it up.

Nitromethane is just one of a family of chemicals called "nitroparaffins." Others are nitroethane and 1-nitropropane and 2-nitropropane. Nitroethane can be used successfully in small quantities. (Top fuel drag racers, which generally run on straight nitromethane, sometimes add a little in hot, humid weather to prevent detonation.) At one time, nitroethane was only about half as expensive as nitromethane, but its cost now is so nearly the same, using it to lower cost is hardly worth the trouble. Neither of the nitropropanes will work in model engine fuel. Incidentally, nitromethane is made of propane, in case you didn't know (and I'll bet you didn't).

Yes, NITRO = POWER! But….there are conditions and contingencies. First of all, it doesn't add power because it's such a "hot" chemical. Not at all. This may come as a surprise to most readers, but the methanol (methyl alcohol) in the fuel is by far the most flammable ingredient….nearly twice as flammable as nitromethane. As a matter of fact, if nitro were only 4 degrees less flammable, it wouldn't even have to carry the red diamond "flammable" label!

In actuality, nitromethane must be heated to 96 degrees F. before it will begin to emit enough vapors that they can be ignited by some sort of spark or flame! (I demonstrated this not long ago to a friend by repeatedly putting a flaming match out in a lidful of nitro. I might add that he insisted on standing about 20 feet away during the demonstration.)

So….how does it add power? We all know (I think) that although we think of the liquid part substance we put in fuel tanks (in our automobiles or model airplanes) as the fuel, in truth, there is another "fuel," without which the liquid part would be useless. Remember what it is? Right….just plain old air (in reality, the oxygen in the air).

Every internal combustion engine mixes air and another fuel of some sort….in our case, a liquid…glow fuel. The purpose of the carburetor is to meter those two ingredients in just the right proportions, and every individual engine has a requirement for a specific proportion of liquid fuel and air. Try to push in too much liquid without enough air, and the engine won't run at all. That's the purpose of the turbocharger on full-size engines….to cram in a lot more air than a simple carburetor or fuel injection system can handle.

Now…..suppose we were to find a way to run more liquid through our model engines without increasing the air supply? That would add power, wouldn't it? Well, guess what….we can! An internal combustion engine can burn more than 2 ½ times as much nitromethane to a given volume of air than it can methanol. Voila! More Power! That's how it works, and it ain't all that complicated. Nor do we have to spend a lot of time thinking about it in the course of a normal day's sport flying.

However, there are some factors we do need to consider. As a practical matter, virtually all our everyday sport flying can be done on model fuel containing from 5% to 15% nitromethane. If you're flying something like a trainer or a Cub or similar model, there's probably no reason why 5% won't work perfectly well. Need a little more power? Move up to 10% or 15%. In most of our sport engines today, I really wouldn't recommend going any higher than that. It probably won't hurt anything, but it won't do you much good, either.

We sell more 15% fuel than any other single blend, and for good reason. Most of the popular engines on the market today are built to run on something very near that blend. Typically, European engines will successfully run on lower nitro blends, because they are built to do so. Why? In Europe, nitro can cost between $150 to $200 a gallon! Reason enough?

Nitro does more than just add power. It also helps achieve a lower, more reliable idle. One good rule of thumb for checking to see if a particular engine needs a higher nitro blend is to start the engine, let it warm up for a few seconds, set throttle to full idle and remove the glow driver. If it drops rpm, move up to a 5% higher nitro blend. If there is no discernible drop, you should be fine right where you are.

One of the most popular misconceptions is that by adding substantial nitro, the user will immediately achieve a huge power jump. Just ain't so. Most will be surprised to learn that in the 5% - 25% nitro range, you will probably only see an rpm increase of about 100 rpm static (sitting on the ground or on a test stand) for each 5% nitro increase. In the air, it will unload and achieve a greater increase, and it will probably idle better, too.

My pet rule is this: If you have a model that's doing well, but just isn't quite "there" powerwise, go up 5% in nitro. If that doesn't do it, you need a bigger engine, not more nitro!

Most of our popular sport engines in use today aren't set up to run on much more than 15% or 20% nitro. Increasing the nitro has the effect of increasing the compression ratio, and each specific engine has an optimum compression level. Exceed it and performance will probably suffer, not gain, and the engine will become much less "user friendly."

High performance racing engines, for example, are tuned entirely differently….compression ratio, intake and exhaust timing etc….and are usually intended to run on much higher nitro blends. One exception, of course, are racing engines used in certain international and world competition (FAI). By the rules, these engines are not allowed to use any nitro at all, and they go just as fast as those that run on 60 or 65%! The first question that comes to mind, then, is, "Why aren't all engines designed to run on no nitro, so we can all save a lot of money?" Ask any of the world-class competitors. Those engines are a serious ***** to tune and run, and are definitely not user-friendly! In fact, they are well beyond the skill levels of most average flyers. There's a price to everything.

Another statement we read or hear frequently is that nitromethane is acidic and causes corrosion in engines. It isn't acidic, and the manufacturers say it doesn't happen…..can't happen. However, at least one noted engine expert and magazine writer insists that it does. Flip a coin. (I once asked Dave Shadel, 3-time World Pylon Champion, and a fellow who works on more high performance engines than anyone I know, how frequently he encounters rust in engines that have been using high nitro blends. His answer? "Never.")

Why does nitro cost so much? While I have no clue as to the cost of manufacturing, other than it takes a multi-million dollar investment in a large refinery to produce it, there is one pretty good reason: There is only one manufacturer of nitromethane in the Western Hemisphere. Figure it out for yourself.

Also (and this will come as a big surprise), our hobby industry only consumes about 5% of all the nitromethane produced; and full-size auto racing about another 5% or so. This means we have no "clout" whatever, and simply must pay the asking price. Where does the rest of it go? Industry. It's used for a variety of things - a solvent for certain plastics, insecticides, explosives (yes, it was an ingredient in the Oklahoma City bombing) and I'm told it's an ingredient in Tagamet, a well-known prescription ulcer medication (no wonder that stuff is so expensive!). Please note that while nitromethane is an ingredient in making some explosives, under normal use, it in itself, is not exploseve. (Remember….the guy used fertilizer, too.)

Hardly a month passes that someone doesn't call to ask, "I hear more nitro will make my engine run cooler. Is that true?" Nope. The higher the nitro content, the higher the operating temperature. Fortunately, in most of our sport engines, the difference in operating temps between 5% and 10% is negligible, and there are lot of other factors (proper lubrication, etc.), that are much more important.

Finally, remember in the beginning of this, we said that nitro adds power because we can burn more of it than we can methanol, for a given volume of air? This also means that the higher the nitro content of the fuel, the less "mileage" (or flying time) we will get. In a typical .40 size engine using 15% nitro, we can usually get a minute to a minute and a half flying time for every ounce of fuel. The Formula 1 guys are lucky to get 2 minutes out of an 8 oz. tank!

What's the practical side of this? If you go to a higher nitro blend, be sure to open your needle valve a few clicks and reset before you go flying. Otherwise, you'll be too lean, and could hurt your engine. Conversely, if you drop to a lower nitro blend, you'll have to crank 'er in a little.

thanks a lot for the input.

That's some good info.

12% is not skimping on oil. A flier at my field has been runing 12% oil in everything he flys for decades and without a problem. Model engine engineers, like all engineers will make recommendations based on a margin of safety. Like "Change your motor oil every 3000 miles." Huh? A lot of Moki and ST owners run as low as 9% and say it's fine.
If your'e not comfortable running lower oil then don't, not trying to push it. My engines run fine. I guess I should say I run this blend in my big bore ringed engines. 12% oil-zero nitro.