Fuel/Oil mix

[Crofter]

Ben I have not been consistant enough in what oil I run to say it was such and such. I had some Husk, some Stihl, some odds and ends of motorcycly stuff of my sons and some Castrol I bought and yes even some Easymix (like the nice dark blue colour) They are all good (reputedly) oils and when my saws run, they run pretty hard, so was surprised to see the spoonge and buildup.
Any thoughts about the higher oil (32:1) re bearings and high rpm. When you get your hands on that 260 ehp you won't be running it much BELOW about 13,000 rpm.
For the average user who is not trying to push rpm limits and flirting with too lean, I am sure that whatever the maker recommends is 100 % adedquate

 

[bwalker]

In regards to bearing and High rpm. There is no doubt that more oil would be of help. A older two cycle tuner once told me that the higher the rpm and the higher the load the more oil you must run. Thats why a arbitrary 50:1 mix is laugable. Sspecially since no major changes in cylinder material, piston composition or bearing type have been made since the days when 40 and 32:1 where the factory mix ratio.
I guess in short that one would be wise to match your mix ratio to the most sever operating condition you are likely to encounter. 20:1 wouldnt be out of the question for the guys that mill alot.

 

[bwalker]

In regards to bearing and High rpm. There is no doubt that more oil would be of help. A older two cycle tuner once told me that the higher the rpm and the higher the load the more oil you must run. Thats why a arbitrary 50:1 mix is laugable. Sspecially since no major changes in cylinder material, piston composition or bearing type have been made since the days when 40 and 32:1 where the factory mix ratio.
I guess in short that one would be wise to match your mix ratio to the most sever operating condition you are likely to encounter. 20:1 wouldnt be out of the question for the guys that mill alot.
btw they changed easy mix to nasty green now

 

[Stumper]

Regarding 'spooge'. I have a Craftsman hedger that I bought several years ago when my other hedger was in the shop and I needed one for a job. This particular model is just a Weedeater in different colors. It actually works pretty well(not nearly as well as my Stihl shears though). That Hedger Spooges like a drooling snuff dipper. The manual actually calls for 32/1 if I remember correctly. The carb can be (and has been adjusted for proper running but the thing runns black oil out of the muffler. My saws don't do that-but they are kept sharp and run far faster than the hedger. When I recently had the muffler off my Dolmar 120si.- It was marvelously clean. A Poulan 330 that recently vibrated its muffler off had a very light build up of brown gray ash on the screen and inner exhaust surfaces. That one had been being run on Poulan synthetic as sort of an experiment. I haven't seen spooge on a chainsaw since I quit running 16/1-it only happened then on a saw with a one screw carb that wouldn't run lean enough.

 

[Marky Mark]

"illiterate" is what I am you meant. "Unburned oil pushing out on the rings causing more heat" Wow! That is the one I do believe I've had much thought behind it. Mike

Is that true???

I might have to side with you on this one 32/1 makes for a nice running saw. EH

 

[max2cam]

Its a fact that oil or fuel for that matter has to vaporise in order to combust.

I'm no expert, but I've always thought that the fuel charge is "atomized" in the carb or fuel injector, and does NOT undergo a "change-of-state" into a vapor.

Can anyone clarify this?

 

[bwalker]

The fuel or a very large portion of it most undergo a phase change(IE vaporise) in order to combust. Ever wonder why when you first start a two cycle it tends to smoke alot. This is simply because the engines internal temp hasnt risen to a level hot enought to vaporise the fuel before it enters the combustion chamber. This results in poor combustion and is the reason for the lazy feeling and smoke at start up.
No with that said. Even when a engine is up to normal operationg temperatures its not uncommon to have a portion of the fuel pass right through the motor un vaporised and unburnt. This can be attributed to the very high boiling point fractions that can be found in todays poor quality fuel. The same goes for oil. castor bean or high molecular weight ester oils often pass through the engine intact or partially burnt. you can imagine what effect this has on deposits.

 

[glens]

Remember your fire training at work and the burning tray of diesel you had to extinguish?  Did you pay attention to how the vapors above the fuel were burning and heating the fuel below, making more vapors to burn, and that there was a barrier between them?  Maybe you didn't see a cross-section, but that's what happens.  The liquid fuel doesn't burn.

Glen

 

[bwalker]

Wood actually doesnt burn unless vaporised also.

 

[Pioneer]

Use the oil manufactures recommended mix ratio. This will change as to the brand and type you are using. My Uncle has been using Optimol (Optimal?) in his Stihl 024 av super for years at 100-1 and has had no problems with it. If you do make a change in the oil-fuel ratio, make sure to reset your mixtures because they will change when this is done.

 

[glens]

Wood actually doesnt burn unless vaporised also.

I don't know if it's proper to say the <i>wood</i> "vaporizes", but I'll never forget 7th-grade science for the day old "Fruity Knuty" stuck a piece of popsicle stick in a test tube, put a rubber stopper in with a glass "chimney", and suspended the tube over a burner.&nbsp; Pretty soon the smoke started coming out the tube, which he then lit to prove the point that it's not the wood itself which burns.&nbsp; Sometimes I sit too long at the door of the wood stove and watch the flames follow the streams of smoke back down to the wood...

Glen

 

[DanMan1]

Ever wonder why when you first start a two cycle it tends to smoke alot. This is simply because the engines internal temp hasnt risen to a level hot enought to vaporise the fuel before it enters the combustion chamber. This results in poor combustion and is the reason for the lazy feeling and smoke at start up.

Ben, Don't know if I buy that one 100%, or at least the way you worded it. How come a 4 stroke on a -10 degree morning doesn't' smoke? As far as I know, as fuel/air exits a carb, the fuel is not in a gaseous state, it is still in the liquid state, as small particles suspended in the air stream. But you say it should be in the gaseous state BEFORE entering the combustion chamber.

But then again, I'm not sure how far I know.

 

[WRW]

Ben, Don't know if I buy that one 100%, or at least the way you worded it. How come a 4 stroke on a -10 degree morning doesn't' smoke? As far as I know, as fuel/air exits a carb, the fuel is not in a gaseous state, it is still in the liquid state, as small particles suspended in the air stream. But you say it should be in the gaseous state BEFORE entering the combustion chamber.

But then again, I'm not sure how far I know.

DanMan1,
That's not what he said. He said that it has to vaporize to burn. Nice thing about gasoline is that it vaporizes very fast at temperature...even in the combustion chamber as the flame spreads. VERY FAST.

As for the 4-stroke not smoking at -10...the 4-stroke valves stay closed on the power stroke till the mix is better consumed.

 

[timberwolf]

atomization and vaporization are two different things. atomization in it's self does not require energy beyond the mechanical energy to spray the fuel. It's the state change from liquid to gas that soaks up the heat energy. The same quantity of energy is implicated wether it is a pool of liquid or an equal quantity of liquid particles, the difference is however that the finer the particals the faster this process can hapen. I would thinik this is why the auto manufactures continue to go to higher and higher preasures in fuel injection systems, higher preasure = finer atomization = faster and more complete vaporization to the end of more power higher efficiency and lower polution.

The fuels we are talking about here must be vaporized before they will burn, the simple proof is flash point, when it is too cold (below flash point) the fuel simply can not be ignighted without adding heat or changing atmoshpheric conditions..

As far as wood the process is called pyrolysis, this process is a bit different, in that heat energy breaks down solid fuel into combustable biproducts wich inturn burn as gasses. A simple exercise to see this is with a match light the match and then look closly at the base of the flame, you should be able to see a small gap < 1/16" between the fuel of the match it's self and the flame.

 

[timberwolf]

Another thing to keep in mind is fuel is almost never totaly in one state or another, with the exeception of at absolute zero.

A 100% vaporized fule charge would be theoryetical because state changes are not total or instant. Take for example a pot of water on the stove. at 100 C (normal preasure) the water begins to boil. However it does not instantly change to steam because as some of the water changes state it pulls heat energy from the remaining water hence cooling the remaining water ever so slightly below the boiling point. Also at the same time vapor particals loose heat energy above the pool and drops back to a liquid state (the reason that steam is visible).

The burning of carbon as mentioned above gives the orange flame color, this is why fuels like hydrogen or methane burn with a very light white blue flame and higher order hydrocarbons like diesel or other heavy oils ect give off orange flames and sooty smoke.

 

[DanMan1]

DanMan1,
That's not what he said. He said that it has to vaporize to burn. .

No Bill,
thats not what he said. His exact words that I was questioning were:

"vaporise the fuel before it enters the combustion chamber"

'BEFORE'

Where in my post do you see me questioning the fact that the fuel has to be vaporized to burn?.

Anyways,
I looked up 'vaporize' on the net dictionarys and found even they are in dispute:

Here is one:
"The action of converting a liquid into a mist or vapor by breaking it into small particles and mixing it with air"

And here's another:
"gasify: turn into gas; "The substance gasified""

You can see these are 2 totaly different things.

I was treating the wording vaporize to mean 'vapor' as in the gaseous state. In which I believe you don't want the fuel to be in the gaseous state until it is IN the combustion chamber.

I just hope the oil passing through my needle bearings in the crankcase are still in liquid form at that point.

 

[WRW]

Yer right. Shame on me for not being thorough enough.

 

[WRW]

Maybe that's why Ben underestimates the cooling effect of the gasoline...if it were already vaporized prior to entering the cylinder.

 

[glens]

I looked up 'vaporize' on the net dictionarys and found even they are in dispute:

The best online dictionary, bar none:
http://www.dict.org/bin/Dict?Form=Dict2&Database=*&Query=vaporize

This thread has become "Firebug 101" &nbsp; <tt>:</tt>)

 

[max2cam]

If I understand this right, the fuel charge is "atomized" (combined with air) as it goes thru the carb or injectors, but at the same time a small portion of the fuel also begins to "vaporize" (undergoes a change-of-state), enough, at least, to provide an igniteable fuel-charge for the spark. Or maybe its the higher temp created during the compression stroke that initiates the change-of-state. Maybe it's both. The process becomes more efficient as the engine begins to run and heat up and the higher temperatures facilitates vaporization (change-of-state).

It seems to me that most of the change-of-state takes place within the cylinder where the chance of harm from excess heat is greatest. The incoming fuel-charge undergoing this change-of-state (a process that sucks up heat) is what Dagger claimed cooled the piston.

The percentage or ratio of oil in the incoming fuel charge changes the dynamics of this process.

According to this thinking, more oil in the mix, not tending to vaporize as easily, doesn't allow the incoming fuel charge to cool the piston as effectively.

But the BIG question is: How much is too much? Or how little is too little?

I ran 50:1 for years, but you guys convinced me to go over to 40:1. That's not a huge percentage change, but it is somewhat psychologically reassurring in these already seizure-prone baby 2-strokes with their toy-like pistons and high RPM because you can't teach an old dog new tricks.