BadBart

My Feedback: (1)

Started pouring when I was at the field yesterday and my flying partner left the cap off the fuel. No doubt a few drops of rain entered. Today, my engine cut out twice while flying and I couldn't reach a high RPM. My questions is...is the fuel contaminated now? No good? Would this result in my engine having problems all of a sudden?
Pat

jessiej

There is a good chance the fuel is the problem. Borrow a tank of known "good" fuel for a comparison.

Aside from raindrops falling into the container the methanol would also have absorbed moisture from the humid air.

jess

FLYBOY

My Feedback: (11)

How much rain got in? If it was a light sprinkle and there was a full gallon of fuel, you didn't hurt it, if it was almost empty and a downpour, you may have a problem. It would really depend on how much water is in the fuel. A few drops isn't going to hurt it any.

BadBart

My Feedback: (1)

There was only about a 1/3 left of the gallon which is what concerned me. I'll try a new gallon and see what happens.
Thanks!
Pat

Geistware

My Feedback: (16)

Get rid of the fuel. You should NEVER leave the cap off of the jug.
The nitro will evaporate and the alochol will absorb moisture.

rc-sport

My Feedback: (12)

A few months ago one of the RC publications did some testing on the effects water has on fuel and motors. They poured water into glow fuel to the point that the water comprised 10% of the mix. After extensive testing they concluded that the water had no ill effect on the fuel or the motor, they did find that the motor ran about 200 RPM's higher and at the same temperature as previously. The motor suffered no damage aside from normal use. I don't plan on adding water to my fuel but it makes me wonder just how true this moisturing absorbtion theory is.

Cactus.

My Feedback: (1)

i have a nipple in my lid that vents when I'm filling or draining, so effectively it's constantly open, if only by 2mm sq at most. I've never noticed a difference from the start of a gallon to the end other then my fuel changes colours the more its in the sun.

it sounds more like your mixtures have changed maybe due to a change in the weather since you last flew.

Goinstraightup

My Feedback: (26)

Yeah, I think they even ended up with 20% water. They had a pic of a .40/.46 size engine purring along at 11,500 RPM's with that mix. I think it was Model Aviation. Blew the lid off of everything I used to think.

Jeff

Montague

That MA "test" was actually rather bogus, and I was really disappointed that no one caught on at the magazine.

Did you notice that they used an old CL engine?

Try the same tests with a modern ABC .46 (the most common engine out there). Be sure to test the idle and mid-range, espeically the transition. I suspect you'll get "slightly" different results.

Water in the fuel isn't a huge deal at full throttle, but will affect the engine in real world RC useage, espeically reliable operation in the low and mid-ranges. CL also engines have better fuel draw than RC engines due to the clean venturi working better than an RC carb at getting a good fuel/air mixture in to the engine, making it easier to compensate with the needle for changes in the fuel.

In the case above, before I tossed the fuel, I'd try a fresh gallon and see if the problems went away. I'd also check the engine's needle. It's pretty common for a storm front to result in a big temperature/humidity change, and that can really mess with how the engine runs. Also, be sure to check the "normal" things, like the plug and so on.

Sport_Pilot

Did you retune the engine? You can put up to 25% water in the fuel and it will still run if the oil doesn't seperate. But you will have to open the needles up as the water will cause it to run leaner.

Sport_Pilot

The methanol evaporates not the nitro. Nitro has a flash point of 98 degrees methanol is 50 something.

Sport_Pilot

If the idle needle will open far enough it should work fine with some water in the fuel. It is only limited by how much your needles can adjust for the higher fuel flow required, and if the oil can stay mixed with the water.

3DFanatic

My Feedback: (5)

Not to mention that the fuel/water that MA used was no doubt mixed VERY well. If left to stand, the fuel will float on the water and you'll probably be drawing mostly water to the engine...

Imac Kiwi

One thing that has not been mentioned is the corrosion with water contamination. I had a batch of methanol contaminated with water and it cost me engine bearings in 4 engines not to mention pitting inside the crank case and crankshaft.

Sport_Pilot

You can mix any combination of water and alcohol you want and they won't seperate. At some point the oil will seperate and fall to the bottom of the jug.

joeb102072

My Feedback: (9)

I dont think the water getting into the can would be as much of an issue as leaving the can opened for an extended period of time. I actually add water to my fuel mixture if I want to tweek my engine. The purpose? it retards the firing giving you a richer setting so you can lean it a bit more. Its not bad for the engine provideing you dont pre detonate the engine you have to listen carfully. 2 ozs of water per gal of fuel I believe thats the proper ratio. I use a dropper and inject it right into the tank 12 oz fuel tank 5 ml of water. 30% heli fuel. Its an old engine and the power boost is needed.