Rc Fuel Faq
The RCU Administrator felt it would be a good idea to have a Frequently Asked Questions area in this forum. What I will attempt to do is make this particular FAQ area somewhat of a refrence page to some of the more often asked questions I've heard concerning fuel. I will do this without intent to insult, inflame or otherwise upset anybody. Quite a bit of mis-information, half truths and incomplete information about glow fuels circulates at the flying fields. Much of this information does little more than confuse the modeler trying to learn about the fuel their engines need. Regardless of what the "club guru" says, I will present the facts as best I can and when necessary contact other experts concerning a particular subject. I will not bash one product or praise another- please do not supply the administrator with questions in which a side has to be taken in order to answer.
Q: What makes my glow fuel go bad?
A: A couple of things can and will contribute to a glow fuel "going bad" First, lets talk about how you should store it; Fuel should never be opened untill you're ready to start using it, and after its opened it should have its exposure to the atmosphere limited as much as possible. This is because the methanol (alcohol) in our fuel is hygroscopic, which means it will soak up water like a sponge- even out of the air! To help limit the exposure, especially in warmer humid climates, once open and at the field, devise a system to block off or cap your vents to the bottle. Don't leave the vents open if you use a pump or something similar, air (and humidity) will pass through an open vent and the fuel is more exposed. Water in the fuel is not a good thing, if it gets exposed to air, it can get water in it.
Next, while storing fuel, it is important to limit the sunlight it is exposed to. During storage, for obvious reasons a cool dry DARK place is the best way to go. Nitromethane, one component that most of us have in our fuel, will for the lack of a better term degrade when exposed to sunlight. I'm not going to get technical here with the chemical reaction specifics, but limit the sunlight exposure to fuels containing nitro. But what about a trip to the field? Yes, it gets exposed to moisture (through the air) and to sunlight! So lets keep it simple: keep the lines pluged and toss a light colored cloth over the bottle so that it is shaded.
If your are a large glow fuel user, say a gallon per weekend or day, is this something to get concerned about- probably not. However if you are a less frequent flier and that gallon of fuel will last you many trips to the field, all this may help you keep your fuel as fresh as possible.
As a sidebar to this question, I have been asked numerous times if glow fuel has a shelf life. The answer is that I can not find any evidence to support weather it does or does not when it is kept unopened and tightly capped in a cool dry place. Once opened it can be a whole new ball game.
Below is a post that I will address one line item at a time. This may take a day or two to get it all together, so come on back and we'll have some answers for you.
A few more (taken from an e-mail by a new modeler)
Q: Can I add xxWxx motor oil to the fuel?- Why or why not?
A: Update to the previous answer; I actually tried mixing up a test blend and found that the generic motor oil will not stay in solution with the methanol and nitromethane. I called up Dave Geirke and he verified the fact.
Q: How come my fuel doesn't contain 2 stroke oil for my 2 stroke engine.
A: IT DOES!!! your glow fuel is designed with 2-stroke oils- the best ones out there for use in an alcohol based fuel. They are Castor oil and Synthetic Castors. Castor oil has been lubricating gasoline and alcohol based fuels since the internal combustion engine became viable. Widely used in WW I as the 2 stroke oil of choice in the rotary engines of the biplanes of the day. The 2-stroke oils you see on the shelf at the store for weed eaters and such will not work for our applications: that oil is designed to be used in gasoline in engines designed a little bit differently.
Q: Since I already left an open container of fuel out for two days in my garage should or could I use a commercial fuel stabilizer, say like the ones available to boat owners for winter storage?
A: Once glow fuel has absorbed water, its there for good for all practical purposes. The only way I know of getting absorbed water out of methanol is to use a molecular seive, something I have very little experience with. As far as fuel stabilizers go, they are designed to keep the gasoline from breaking down and turning into varnish and gumming up your boat, mower etc during long term storage. They will not absorb water, that is not the intended purpose of the stabalizer. This will not solve a glow fuel problem. If you are in a very humid area, the fuel will absorb much more water than in a dry arid climate. Run your fuel in your engine and decide if the fuel has been contaminated enough to warrant purchasing a new bottle. Keep your containers caped and in a cool dry dark place when not in use.
Q: If I add more castor oil to the fuel, will it reduce the fuels octane? or overall energy output?
A: If you add more anything to your jug of fuel, it will change the ratios of all other ingredients. For instance, you add 3 oz of castor to a new gallon of fuel, now that gallon is 131 oz, not 128. Your other ingredients are not added in proper proportion so they actually drop as a percentage of the whole. Will it hurt anything- probably not. The energy out put as you term it will be affected but if you even can notice it, it'll be a negledgable amount and not worth worring about especially since the engine will be happier.
Q: Why is it PINK?
A: Most fuel manufacturers use a dye in the finished product for a number of different reasons: Product Identity, different blends such as different uses or nitro contents. Allow the user to see how much is in his tank (important for heli's)
Q: What is the best oil ratio (castor to synthetic) mix for breaking in my xxx type engine.
A: I can see this question opening up a can of worms. Seems everybody has an opinion on the great ongoing debate of castor or synthetics.
In days of old, castor was the oil of choice with the lapped iron piston and sleeve engines and still is. Today, not as many engines are of that piston and sleeve metalurgy. Most today are either ringed piston in a steel or chrome sleeve or of an interference fit type commonly called ABC/ABN or AAC. In either type of the most modern offerings, too much oil will never hurt anything. I have, and always will recommend a minimum of 20% oil to all my customers with airplane or boat engines. Now too much castor will not hurt anything during the first gallon in any engine (break in period), after that feed your engine according to type. Ie: You're going to feed a ringed engine or an ABC type engine and in some cases a lapped iron engine.
In the ringed engines after break in (both two and four stroke) use 20% total oil with a little bit of castor (2% works great) and 18% synthetic. This is my prefered choice for any ringed engine since it is enough castor to help protect the rod journals and rust prevention on the bearings without being too much to gum up the ring after many many gallons. This holdes true for 4-strokes as well.
In ABC type engines, use more castor to offer greater scuff protection, I recommend 20% total oil with 4% of that being castor and 16% synthetic.
In lapped iron type engines such as the lapped Fox control line engines and the Fox 40 lapped engine, I recommend a very high content of castor for break in such as 29% all castor. After a thorough break in, some guys like to back down to 20% to 22% total oil with at least 50% of the oil content being castor.
Q: What is the best recipie for speed/ reliability?
A: Speed and reliability are two totally different subjects if you're refering to racing.
Obviously if you cut down on oil, your burnable components are increased, namely the methanol. Some racing fuels on the market contain less than 16% total oil and some racers have mixed up fuel with very little oil such as 4-6%, all in an effort to get the extra edge. Fuel with low oil is great for speed but longevity will diminish rapidly. All out competition racers expect to win races at the cost of racing engines.
If you want to run your sport XX46XX engine with a competition type low oil fuel in an effort to gain more performance, you may in fact ruin it. If you want a high performance engine, buy a Nelson, Jett, Rossi, MVVS or a couple others. Most these engines makers offer a sport style engine that is very high in performance. But keep in mind that even these high performance "sport" engines require a higher oil content that what competition fules usually have.
The overall answer is if you want to go faster, buy a faster engine, but you still need to properly feed it. No such sport recipies exist.
I have made fuel to compare the performance gain by cutting down the oil content. On a Super Tiger 75, my traditional 20% ringed engine oil blend at 15% nitro only turned 40 rpms less than a fuel with 17% oil. Is that a significant amount?- definatly not! however, the down side was that the lower oil fuel ran 38 degrees hotter at the maximum rpm. That's Significant!!!!
Q: What type of glow plug works best with xx% of fuel.
A: General rule of thumb:
High nitro fuels need a colder plug and,
Lower nitro fuels need a hotter plug.
4-strokes need 4-stroke plugs, they are very hot.
Heli's usually fly hot plugs.
I have compiled a list of some common plugs and catagorized it by heat range as specified by the manufacturer. e-mail me if you want a copy.