Red Scholefield

My Feedback: (9)

I just read Joe Wagner's article in Model Aviation (July 04). He is claiming a small actual gain in performance on fuel containing 20% water. SAY WHAT????

All these years we have done everything possible to keep moisture OUT of our fuel. Whenever we can't find some other reason for engine problems we always fall back to "Try some fresh fuel, you may have gotten some moisture in the stuff you are using".

If this was the April 1 issue I could understand, but this appears to be legit . . . hard to believe. Has anyone tried it?

Red S.

XJet

Whenever I've found myself using damp fuel it usually manifests itself as difficult starting, RPMs drop when the plug lead is disconnected and very poor idle (usually just stopping instead of idling).

While it may be true that in a suitably tuned engine, you might get a bit of extra power from a small amount of water in the fuel, it's been my experience that on the average RC engine it's just bad news.

I also suspect you wouldn't need too much water in the fuel before the oil began to separate -- which would cause a whole lot of new problems.

If you want more power, get a bigger engine or add some nitro :-)

Hobbsy

My Feedback: (102)

Fuel contaminated with water also makes engines run hot, I think the guy lost a great deal of credibility with most folks when he wrote that. If what he said was true fuel manufacturers would make a blend of wet fuel for the believers and I wouldn't be one of them.

Jim Thomerson

I think you would have a hard time keeping the oil in solution with 20% water. I personally think the 'fuel contaminated with water' problem is a myth because I am not aware I've ever had a problem with it. On the other hand, people whose judgment I respect have said otherwise. I think the major thing happening when fuel is exposed to air is methanol evaporating. (You notice all the 'I think' rather than 'I know'.) And I suggest you do not expose your fuel to the air unnecessarily; couldn't hurt.

Jim

Sport_Pilot

Only if you don't readjust the needle. Adding water to the fuel is an old hot rodders racing trick. On the alky cars if the compression ratio is just a mite bit high on the hot days, you add water to the fuel and richen up the mixture. I have left model fuel jugs open in the ran for a short time, no problem except the needle had to be opened a bit. I have argued that water in the fuel was not as serious a problem as others have claimed. Downunder also ran water in the fuel with no problems till he added enough water that the oil seperated out.

Sport_Pilot

Good point. Methanol has a much higher vapor pressure than water, so on a hot day the methanol would evaporate faster than air and water moisture can get in. But then the percentages of oil and nitro get larger. This could effect the fuel to a much greater degree than adding water to it.

sopwith

I started mixing my own fuel a few months ago trying all kinds of wacky things. I have settled on 10 percent synthetic oil and 5 or 10 percent water (depending on temperature). It works great in all engines except a few that need nitro to run properly (like the FX series of OS Engines). I don't have starting problems or overheating. It is much cleaner than regular oil mixes, but the engines feel like they would need after run oil in humid locations. The latent heat of vaporization of water is very high, so I suspect it greatly helps in keeping the engine cool, but that is just my opinion with no instrumentation to verify such claims.