BIGRCR
Veteran
Location: Easley, South Carolina
| Correct.
Unfortunately, too much oil can also "ruin" an engine. In the older days of the Webra Bully (needle bearinged engine), it ran on only 5% oil in the fuel mix (on glow). If you added more oil and did not pay attention to the instructions, the engine would soon burn up. This is because when there is more oil in the total fuel package, there is less fuel in it to mix with the volume of air being pulled into the engine, this is called being lean. Of course you can open the needles up to get the fuel mixture right, but then the oil package is way too rich then again. This can stick a ring or most importantly cause poor running conditions. Gee, now what happens, HHMM...it seems to be running rich, so...let's lean it down a bit....get the picture?????? The engine may be getting enough lubrication, but soon leans out from a lack of fuel and quicky burns up. This will even start to burn up the additional oil and further hurt the engine.
The fuel in our two cycle gas engines does TWO things. It provides the fuel for combustion in which there is a definite "window" that is controlled by the needle to provide a fuel flow that mixes with a given amount of oxygen for combustion. The "fuel" part of this must stay within a given amount to support combustion, too much is too rich... too little is too lean.
The second part of our fuel "Package" that is fed to the engine is oil or a combination of lubricants and possibly conditioners. If there is not enough of these, then the engine will not get the proper lubrication. If there is too much, then the motor is getting enough lubrication but the additonal amount can and does effect how the fuel burns. Most of our lubricants today are designed not to burn in the cylinder so that they can lubricate. Some of this oil does however burn in the cylinder, but the rest is still inside of the engine and to get out must pass through the cylinder. Oil is pretty much non compressable (this is the part that does not burn) so it does one thing after it lubricates the engine and captures some heat to carry away. What's that,??? It increases the compression in the cylinder and this in turn greatly effects what the engine is doing. If the compression goes up, so does the cylinder temperature and the added heat excites the fuel more and will make the mixture LEANER and can cause detonation, all bad things. And then we richen it up to get rid of the lean condition (or the engine just runs like crap) and it is even richer.......... a viscious cycle that is not good for performance or the engine.
This is why someone who knows these engines will start with a good safe oil mix ratio and run it for a while with the proper needle settings so that they can read the plug. This is done every 1/2 to 1 gallon or so and is done with a plug that is clean each time ( if not new). Reading the plug is very important for the above reasons to analize the oil ratio ( promarily) and the fuel ratio (secondary- over a longer period of time). After reading the plug and getting a good idea of what is going on by looking at it, you can make a oil ratio change (or not) and zero in on the proper oil ratio and plug. The manufacturers have already done this for the most part and give you recommended plugs, oil ratios and initial needle settings to use. Unfortunately, the ratios for the engines recommended for helicopter use (in Zenoah's case anyway) are way off base and are most likely taken from the airplane applications and do not usually work well in the heli engines. I just don't think that they have done the research for helicopter applications. All of us know that helicopter engines are much more specific than airplane counterparts.
Bill Meader (and others) has done a bunch of field research over the years and has come up with recommendations due to this, as the manufacturer has not it seems (well, maybe so, the carbs are getting better). His methods and recommendations are from experience and knowledge of what these engines need and how they actually operate...in a helicopter, not in theory, not on a bench and not from what the airplane guys get by with!!
The new G231 is partly due to research and input from field research by several folks ( thanks Carey, Tim, and Blois) and these motors are getting better every day and becoming more user friendly at that. It's a great time to be fooling around with the gas helicopters, just hold on tight and watch what happens!!!
Hope this helps!!
BIGRCR- John Garst |
I'm sure I would have been tared, and feathered if there had been problems...Its pretty well proven now, and if one burns up, its probally because someone didn't stay in the guidelines, which is a pretty broad window I might add...I ran 85 :1 with the old engines because that was the only way I could get them to run the way I wanted...I have since put new guidlines on the net that I run 64:1 with the new engines...that is way more than enough, believe me.
