stinkbait
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Whether it is synthetic or not? What are the effects?
More oil also means less gas which is a leaner running saw
That depends on how the carb is adjusted.
I run 'em a touch richer, doesn't foul plugs.
Just what we needed, another oil thread!
So can someone explain to me this "more oil means leaner" thing? It seems to violate basic chemistry.
That's the second time I've seen that on these forums and I can't find a way to reconcile that with chemistry. Oil is fuel just as much as gas. It just doesn't burn as easily. Gasoline is more volatile SNIP
You can get a lot of carbon buildup. If the carbon gets too thick you run the risk of a piece(s) eventually breaking loose and scoring the cylinder wall and piston. This was more of a problem with the old saws that used motor oil as 2-cycle mix in extremely high ratios. It can also plug exhaust ports / mufflers. Keep it cleaned out and the problems are negligible. Plugs need to be cleaned or changed out much more frequently too. The extra smoke will help keep the skeeters away.
I learned this the hard way. (pretty good 044 on the to do list because of it). Marine TWC rated oil will cause even more problems in your saws.
That's the second time I've seen that on these forums and I can't find a way to reconcile that with chemistry. Oil is fuel just as much as gas. It just doesn't burn as easily. Gasoline is more volatile so it atomizes better before it gets to the combustion chamber, but the chemistry is fixed. The max amount of oxygen that can be consumed is a function of the chemical bonds available to be broken . 100% efficiency would reduce every molecule of fuel into carbon dioxide and water. As efficiency goes down you get carbon monoxide, carbon dioxide and water. In reality you get a mishmash of other things because of impurities and additives. But it is still a basic chemical equation. C2H4 + 3O2 -> 2CO2 + 2H2O would be ethane burning. Gasoline and oil are simply more complex hydrocarbons but the basic equation is the same.
So can someone explain to me this "more oil means leaner" thing? It seems to violate basic chemistry.
70% ethene and 30% oil is a 2.5:1 mix ratio which makes it a very unrealistic example. How about we stick to realistic ratios?
None of this stuff makes much difference unless you dramatically change operating mix ratios
For example; with 50:1 the gas represents 50/51'ths of the mix, or 98.03% of the mix is gas.
With 40:1 the gas represents 40/41 or 97.56% of the mix
A 0.53% difference in the amount of gas in the mix will not make much difference in terms of leaness. The critical factor in leaness is the "air to mix" ratio - not the "oil to gas" ratio. This has to change by ~5% or more to make a significant difference.
25:1 means gas is 25/26 or 96% is gas
Now look at what else varies the air to fuel mix ratio. The total amount of air getting into the cylinder is influence by the atmospheric pressure which can commonly vary between 1000 to 1020 mb over a few days. This change represents a 2% change in air pressure and means the saw will get ~2% more oxygen at 1020 than 1000 mb.
Does anyone operating at the same elevation read the atmospheric pressure and then retune? - of course not, a stock saw can tolerate at least a +/- 2.5% change in air pressure which corresponds to shifting the mix down from 50:1 to about 25:1.
Even my old dads 2 man saw (Nominally 12:1), could survive with quite a varied mix ratio from ~10:1 to about 15:1 without any problems - and just as well because he used to prepare his mix by eye using dollops and dashes. If not enough smoke was coming out of the saw he would just add another dash to the mix and sometimes even direct to CS fuel tank.
Now completely unrelated is the fact that extra oil provides extra lube which does protect a saw that constantly operates at high RPMs. This is why a slightly lower mix ratio is recommended for example when milling - but the amount it changes the air to gas ratio is trivial.
70% ethene and 30% oil is a 2.5:1 mix ratio which makes it a very unrealistic example. How about we stick to realistic ratios?
None of this stuff makes much difference unless you dramatically change operating mix ratios
For example; with 50:1 the gas represents 50/51'ths of the mix, or 98.03% of the mix is gas.
With 40:1 the gas represents 40/41 or 97.56% of the mix
A 0.53% difference in the amount of gas in the mix will not make much difference in terms of leaness. The critical factor in leaness is the "air to mix" ratio - not the "oil to gas" ratio. This has to change by ~5% or more to make a significant difference.
25:1 means gas is 25/26 or 96% is gas
Now look at what else varies the air to fuel mix ratio. The total amount of air getting into the cylinder is influence by the atmospheric pressure which can commonly vary between 1000 to 1020 mb over a few days. This change represents a 2% change in air pressure and means the saw will get ~2% more oxygen at 1020 than 1000 mb.
Does anyone operating at the same elevation read the atmospheric pressure and then retune? - of course not, a stock saw can tolerate at least a +/- 2.5% change in air pressure which corresponds to shifting the mix down from 50:1 to about 25:1.
Even my old dads 2 man saw (Nominally 12:1), could survive with quite a varied mix ratio from ~10:1 to about 15:1 without any problems - and just as well because he used to prepare his mix by eye using dollops and dashes. If not enough smoke was coming out of the saw he would just add another dash to the mix and sometimes even direct to CS fuel tank.
Now completely unrelated is the fact that extra oil provides extra lube which does protect a saw that constantly operates at high RPMs. This is why a slightly lower mix ratio is recommended for example when milling - but the amount it changes the air to gas ratio is trivial.
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