Fuel/Oil mix

[Stumper]

Ralph, Your arguments are so logical that it amazes me that you missed our point. Yes, 32/1 will always deliver less gas and more oil to the combustion chamber than 50/1 at any given jet setting. That is what some of us actually desire. If the jets were not changed then the 32/1 would indeed be leaner in the fuel/air mixture entering the cylinder. HOWEVER, when we richen the fuel/air mixture by slightly opening the jet we can now deliver the same ratio of gasoline to air to the combustion chamber while also delivering a greater quantity of oil. If this greater quantity of oil is truly a bad thing then "we done messed up big time" but if it is beneficial-"Yippee". If it makes little difference then we spent a little extra and blew a little more out the exhaust.

 

[begleytree]

Justin, extremaly well written and logical post. Were finally down to it now. I gotcha that you richen up a little, to keep the same air/fule ratio, but adding a little more oil with it. I get it, BUT, how does that equate with the test results showing more oil=more heat?
-Ralph

 

[begleytree]

Sitting here, pulled out the first stihl owners manual I found, copyrt1990, for 009L
Quote: (talking about fuel octane, min87) lower octane ratings may cause 'pinging' which is accompanied by a rise in engine temp. This increases the risk of piston seizure, and damage to the engine-unquote
SO,..... too much oil does what to raise temp? does it lower the octane rating of the gas being used (I know, higher grade fuels would negate this, bear with me)
would too much oil, mixed with minimum octane (87) gas decrease the octane rating enough to cause saw failure? would min octane fuel, mixed 32:1 be as bad to a saw engine as no mix? or not enough mix?
I know straight mixing oil barely burns. Is this the reason for 50:1 mix rates? because most homeowners would use 87 octane fuel?
More questions (edit in) the book talks about pinging, or preignition. Now, I know the plug isn't going to fire any sooner, so is the mixing oil creating a condition like a diesel engine, whereas the fuel is ignited by compression, and if its per-igniting, then the fuel is on fire, longer, in the bore, before allowing release through the exhaust. Seems that would allow for more heat transfer to the cylinder walls and piston, by virtue of being in the area, on fire, for a (however) slightly longer time period than if it waited to be lit by the plug
-Ralph

 

[klickitatsacket]

New wrinkle here guys. If you read my post back aways you will notice that we build saws. If you are running under 14K you do not need to change your mix ratio from 50:1. With that said, if you are leaning out your saw to achieve higher RPM then making your mix thicker to compensate for the lack of oil in a lean mix is needed to protect your saw. Your saw needs a certain amount of oil per revolution no matter what the mix ratio is. It is all a balancing act. Some guys like more oil in a lean air / fuel mix; most of these guys are RPM speed freaks. Then you get the guy who likes to have a rich air/fuel mix; he generally is looking for brute torque. It is all in what you like, what you are cutting and the way you approach the puzzle. The munufacturers have set their saws up for the average with a margin of error built in. Guys who tweek them for speed wear them out faster but get the cut done quicker. The guys who tweek their saws for torque get the job done faster but pounds on them harder. To the extremes come greater punishment to the saw but with the rewards of More time to play, to work on saws (my favorite) and BRAGGING RIGHTS.

 

[Stumper]

Ralph, I don't know about the test results-I remember someone posting that they recorded higher exhaust temperatures with 32/1 that 50/1 but I dont know if they had readjusted the carburetor jetting with each different mix ratio( I think the answer was no but cannot swear to it). I also do not know of a source for temerature comparisons of internal parts (the question that most of us are most concerned with). If yu have long, trouble free saw life with 50/1 I can understand no interest in changing. It is interesting to me that many non-Stihl mechanics and just about all of the saw/motorcycle racers/builders recommend richer oil mixes. The argument can be made that the manufacturers know best about their products and we should leave it alone. Two questions always arise: 1. Are they instructing us on what is best for optimum useful life of their product?2. Is their recommendation based on an accomodation of EPA mandates that will still provide reasonable service life? It is ffair toquestion the entire saw modification field also. Do they really think they know better than STihl, Husky, Dolmar, Echo,etc. engineers? Most will say tht they improve saws in a couple of ways.1. Polishing/fitting parts that the factories can't spend the extra time on and keep their prices competitive.2. Undoing design features that were mandated by arbitrary emissions regulations rather than peak performance. When they modify port timing they enter the arena of making a saw perform best for a specific purpose rather than the general, broad spectrum that factory port figures are designed to perform adequately in. I don't think this makes them greater experts than the factory engineers but it does mean that they know more about what is going on inside the saw's engine than I do. Since they think 32/1 is wise and my own experience with that ratio has been good in a plethora of equipment I am inclined to continue using 32/1

 

[Stumper]

Ralph,Interesting question about octane. FWIW I choose midgrade fule(which meets the makers octane recommendations generally) most of the time in winter. When summer comes around I switch to 'premium'. I learned a long time ago that their are fewer vaporlock problems when running hard in hot weather using premium fuel. Someone posted here that this has nothing to do with octane but is because of the "10% rate" of the fuel blends. Be that as it may, I get the results I desire with higher octane fuel.

 

[bwalker]

Ralph, Yes, 32/1 will always deliver less gas and more oil to the combustion chamber than 50/1 at any given jet setting. That is what some of us actually desire. If the jets were not changed then the 32/1 would indeed be leaner in the fuel/air mixture entering the cylinder. HOWEVER, when we richen the fuel/air mixture by slightly opening the jet we can now deliver the same ratio of gasoline to air to the combustion chamber while also delivering a greater quantity of oil. If this greater quantity of oil is truly a bad thing then "we done messed up big time" but if it is beneficial-"Yippee". If it makes little difference then we spent a little extra and blew a little more out the exhaust.

BINGO!

 

[bwalker]

Sitting here, pulled out the first stihl owners manual I found, copyrt1990, for 009L
Quote: (talking about fuel octane, min87) lower octane ratings may cause 'pinging' which is accompanied by a rise in engine temp. This increases the risk of piston seizure, and damage to the engine-unquote
SO,..... too much oil does what to raise temp? does it lower the octane rating of the gas being used (I know, higher grade fuels would negate this, bear with me)
would too much oil, mixed with minimum octane (87) gas decrease the octane rating enough to cause saw failure? would min octane fuel, mixed 32:1 be as bad to a saw engine as no mix? or not enough mix?
I know straight mixing oil barely burns. Is this the reason for 50:1 mix rates? because most homeowners would use 87 octane fuel?
More questions (edit in) the book talks about pinging, or preignition. Now, I know the plug isn't going to fire any sooner, so is the mixing oil creating a condition like a diesel engine, whereas the fuel is ignited by compression, and if its per-igniting, then the fuel is on fire, longer, in the bore, before allowing release through the exhaust. Seems that would allow for more heat transfer to the cylinder walls and piston, by virtue of being in the area, on fire, for a (however) slightly longer time period than if it waited to be lit by the plug
-Ralph

This is what i meen by clueless.

 

[bwalker]

BTW engineers said the Titanic was unsinkable and that the Tacoma narrows bridge was a masterpiece.

 

[begleytree]

Walker, do you have any insight to add? Clueless? Are you iliterate? or do you just not understand whats being said?
As far as your examples, they only made one of them, each, whereas there are millions of saws made, using the same specs and recommendations. something must be right.
-Ralph

Does mixing oil lower the octane rating of gasoline? if yes, is the wrong mix ratio causing the problems via preignition, or if not, is the unburnt oil staying under the rings, pushing them out harder, causing more heat buildup, or is it both?
-Ralph

 

[Molecule]

Roz ?

Apparently the Dolmar specification of 91 ROZ for gas is NOT the same as 91 octane, which is RON + MON/2. RON = Research Octane Number. MON = Motor Octane Number. Octane = RON+MON/2.

Does anyone know what ROZ stands for. I can't find anything but web pages in German and Russian? One Google-translated page for BMW suggested that a 91 ROZ was the same as 87 octane-USA, because of a chip which can retard timing to decrease ping ("increase virtual octane")

 

[rupedoggy]

begleytree "illiterate" is what I think you meant. "Unburned oil pushing out on the rings causing more heat" Wow! That is the one I don't believe had much thought behind it. Mike

 

[begleytree]

Rupe, thanks for the spelling, I choose to be me, verses me with a spell check. What you see, is what you get, so to speak.
The oil under the rings was brought up by a friend of mine who called, owns a stumper, and nothing else, he does my stumps, borrows my 036 to cut some off, and builds motors on racing 2 stroke 4 wheelers. He suggested that to me, thought I'd throw it out to see what anyone thought. I only feel that extra oil (unburnt) may collect on the rings, causing sticking, as I've seen on 2 stroke outboards, using premixed fuel, mixed around 32:1. Something I mentioned (ring sticking) a few post back, or so. I didn't totally buy that either, But, the pre-ignition part intrigues me, as it can answer questions I have. Does mix oil affect the octane rating of gasoline? I don't know myself, but knowing pure mix is very hard to burn, when mixed with gas, I tend to think it would lower the octane rating. I know that 50:1 mixed gas and a match produces little results by way of combustion, but don't know if pressure exerted on the mixture would have any better result. I understand boiling points of water when placed under pressure, or in a vacuum. I just don't know about gas.
I know mixed (50:1) gas when run in a 4 stroke auto engine, like a chipper someone didn't fuel up, causes pre-ignition also, at compression ratings of 8.5:1, and thereby, more heat on the cylinders, although probably not as serious a problem when dealing with liquid cooled engines as opposed to air cooled.
-Ralph

 

[klickitatsacket]

Diesel won't hardly light with a match either. I wouldn't get caught up with that line of reasoning.

 

[bwalker]

Begley, I wouldnt let your freind near any of your engines,lol. MORE OIL DOES NOT CAUSE RING STICKING? I will bet you money my engines ran at 32:1 are cleaner than yours. Wanna wager?
As for saying that pre mix causes pre igntiion. I own a fishing lodge. We have a 1500 gallon bulk tank that fuels all of our boats, 2 Yamaha Rhinos,3 kawasaki mules a 82 chevy and a 94 chevy. They all run on 50:1 premix out of neccessity and have for years with out issue. Havent even had to change a plug or anything in any of them in the three years i have owned the place. The older chevy has been running on 50:1 since new and its has 80,000 miles on it!

 

[bwalker]

BTW Begley, I think in order to be taken seriously in regards to this thread you need to do some more studying? Most of your points are bizzaare and have no technical merit. I dont type fast enough or have the energy to go through it point by point with you, but if you PM me I will give you my phone #.

 

[begleytree]

Oh yeah, now I remember why I quit comming to this place. Must be bored with 3 straight days of rain, had a re-lapse.
Whatever.
Don't need your #, probably wouldn't do much good anyway. For not being able to type, you sure figured out how to try to troll. Another good discussion, and site, gone to 5hit.
Do what you want, I'll run mine 50:1, and sleep well knowing no-one here could possibly explain why 32:1 would be any better, they just always did it that way, and couldn't figure out how to change.
later

 

[rupedoggy]

"Rupe, thanks for the spelling, I choose to be me, verses me with a spell check. What you see, is what you get, so to speak."
This is a little off topic Ralph but when I look at your avatar it seems difficult to reconcile the above quote. Don't you think? Mike

 

[Al Smith]

I must be mistaken

I don't quite get what you meant,Ben,when you said you have an 82 Chevy,with 80,000 miles,ran on 50 to 1 mix .Did I miss understand?This is Chevy,like in the famous"57,or is this a 2 cycle I have never heard of?

 

[bwalker]

Al, you read it right. A 82 chevy that has ran its entire life on 50:1 premix.