Stihl MS660 Avgas 100LL
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. . . . . .These newer saws are not designed to run with any lead in the gas, nor are they designed to run on gas with octane higher than 93 (mixed with oil it drops to about 90).[/quote]
Which octane rating system are you referring to? The US uses AKI (Anti-Knock Index) which is about 5 points less than what the rest of the world which uses (RON) Octane ratings
Also none of the user manuals I have read mention anything about max octane rating - all they mention is minimum rating.
Which octane rating system are you referring to? The US uses AKI (Anti-Knock Index) which is about 5 points less than what the rest of the world which uses (RON) Octane ratings
Also none of the user manuals I have read mention anything about max octane rating - all they mention is minimum rating.
psgflier
ArboristSite Member
Your not going to get enough lead from using avgas to harm you, even if you used it 10 hours a day for the next 50 years. These days the only lead poisoning you have to worry about is in pill form delivered from an explosion of black or smokeless powder, and probably not much from black powder.
Most of the gas we get here in the states is crap, even before ethanol was added. In the 70s the refiners started putting ethers, ketones, and other volatiles into the gas that used to go up the stacks. This stuff flashes of pretty fast, that's why if it sits in a container for a couple of weeks, it looses its oomph(technical term) and gunks up fuel tanks and carburetors after a few months.
Ethanol mucked thinks up even more. Not only does it have less energy than gasoline, it attracts water. You might think that"s a good thing, especially if you have used gas dryer to get rid of water in your cars fuel tank, but ethanol attracts water from the air, and when it reaches saturation point, all of the water dumps out of it.
Four stroke engines, like your car, handle this for a while, although it does cause longer term damage, but two strokes bite the dust pretty fast. This has been a big problem in outboard engines, both two stroke and four stroke, and in chainsaws. Some of the saw shops and boat shops are selling special blend two stroke oil that is supposed to help, but they're all making money repairing engines.
Now, avgas is stable, it is the only fuel that has to meet the same standards by all refiners( there are only a few of them left) for stability, volatility and reid vaper pressure. I'd highly recommend using avgas to fill tanks and carbs of any equipment without a catalytic converter for storage.
As far as running equipment on avgas, four strokes, especially modern ones are going to have a shorter life as valves and rings foul up with lead, they just don't run hot enough to keep the lead in suspension and purge it out. The old 80/87 would have been ok, but 100ll has 4 times as much lead.
For chainsaws, they might foul the plug and maybe the rings eventually, but not anymore than running 32:1 or 40:1, or enriching up the carb mixture to make up for modifying the engine beyond its design limits.
If you have a saw that has a carb that can be adjusted, adjust it just the way you would for any fuel, four stroking with no load, two stroking under load.
The idea that avgas will foul the bearings is ludicrous.
Most of the gas we get here in the states is crap, even before ethanol was added. In the 70s the refiners started putting ethers, ketones, and other volatiles into the gas that used to go up the stacks. This stuff flashes of pretty fast, that's why if it sits in a container for a couple of weeks, it looses its oomph(technical term) and gunks up fuel tanks and carburetors after a few months.
Ethanol mucked thinks up even more. Not only does it have less energy than gasoline, it attracts water. You might think that"s a good thing, especially if you have used gas dryer to get rid of water in your cars fuel tank, but ethanol attracts water from the air, and when it reaches saturation point, all of the water dumps out of it.
Four stroke engines, like your car, handle this for a while, although it does cause longer term damage, but two strokes bite the dust pretty fast. This has been a big problem in outboard engines, both two stroke and four stroke, and in chainsaws. Some of the saw shops and boat shops are selling special blend two stroke oil that is supposed to help, but they're all making money repairing engines.
Now, avgas is stable, it is the only fuel that has to meet the same standards by all refiners( there are only a few of them left) for stability, volatility and reid vaper pressure. I'd highly recommend using avgas to fill tanks and carbs of any equipment without a catalytic converter for storage.
As far as running equipment on avgas, four strokes, especially modern ones are going to have a shorter life as valves and rings foul up with lead, they just don't run hot enough to keep the lead in suspension and purge it out. The old 80/87 would have been ok, but 100ll has 4 times as much lead.
For chainsaws, they might foul the plug and maybe the rings eventually, but not anymore than running 32:1 or 40:1, or enriching up the carb mixture to make up for modifying the engine beyond its design limits.
If you have a saw that has a carb that can be adjusted, adjust it just the way you would for any fuel, four stroking with no load, two stroking under load.
The idea that avgas will foul the bearings is ludicrous.
psgflier
ArboristSite Member
I watched mixes go from 16:1 to 24:1 then 32:1, 40:1 and now 50:1, on two stroke outboards with computer controls mixture varies from 50:1 at idle to 100:1 at full power.
Up to the 40:1 mixtures, the only change I know of( common fuels did get better from the early 50s to the late 50s, and that's when mixes went from 16:1 to 24:1) was in the composition of the oil. The old 16:1 and 24:1 mixes were for regular 30wgt crankcase oil, later blends were with special 2 stroke oils. About the time mixes changed from 40:1 to 50:1, modern saws with chrome and especially nickle plated cylinders came out, of course this is also the time gas turned to crap.
If you use a good oil, mix according to what the oil recommends.
That being said, I would mix 40:1 on old big Macs, Homelites, etc. with steel cylinders.
The richer the mix, the lower the octane of the fuel, and the more fouling of plugs, rings, etc.
Air cooled engines depend on vaporization of the fuel for part of the cooling, richer oil mixes(not fuel/air mixes) decrease the efficiency of this cooling.
Up to the 40:1 mixtures, the only change I know of( common fuels did get better from the early 50s to the late 50s, and that's when mixes went from 16:1 to 24:1) was in the composition of the oil. The old 16:1 and 24:1 mixes were for regular 30wgt crankcase oil, later blends were with special 2 stroke oils. About the time mixes changed from 40:1 to 50:1, modern saws with chrome and especially nickle plated cylinders came out, of course this is also the time gas turned to crap.
If you use a good oil, mix according to what the oil recommends.
That being said, I would mix 40:1 on old big Macs, Homelites, etc. with steel cylinders.
The richer the mix, the lower the octane of the fuel, and the more fouling of plugs, rings, etc.
Air cooled engines depend on vaporization of the fuel for part of the cooling, richer oil mixes(not fuel/air mixes) decrease the efficiency of this cooling.
When I read this I realised this may not be completely clear to a newbie.
A richer fuel/air mix will also help cool the saw.
I won't agree or disagree but I will do the math and let you decide
100LL Avgas contains between about 0.15 and 0.5 g/L - lets average that to ~0.3 g/L.
Let's look at this from the point of the saws exhaust gasses.
Using fuel with a lead concentration 0.3 g/L, a saw will exhaust about 15 micrograms of lead per Litre of exhaust.
The maximum EPA standard of exposure 0.15 micrograms of lead per cubic meter of air!
So the saw exhaust is 100,000 times above the EPA limit.
Now lets look at it from an aggregate or all day perspective
Let's say that the saw only burn 1L (~1 tankful) per hour, in a 10 hour day the saw will pump to about 3 g of lead.
At the start of the day there will next to no lead in the air and at the end of the day there will be 3 g of lead so the average is 1.5 g in total
On a still day the saw exhaust will form a half bubble of exhaust gas and dust around the operator.
To meet maximum EPA standards of 0.15 micrograms per cubic meter that 1.5g of lead must fully and immediately disperse into a half bubble that is 555 ft in diameter.
Of course the exhaust/lead does not instantaneously fully disperse into that half bubble but decreases with an inverse square of the distance from the source so where the saw and operator are located the air will contain much more lead in the air than the EPA limit, right up to where it comes out of the saw exhaust where it is 100,000 times above the limit. Experiments on highways in the 1970's showed than most of the lead emitted by motor vehicles was deposited as a dust within a few hundred feet of highways, although small amounts of the very fine dusts were/are blown as far way as Antarctica.
Any potential problem is compounded by the location of the exhaust exiting from most saws because during milling it deflects off the log and blows back up into the operators face.
Like I said , that is just some basic maths - you decide.
For further comments on the phasing out of lead in Avgas, and the "environmental regulation" there of it is worth having a read of the Wikipedia entry on avgas.
http://en.wikipedia.org/wiki/Avgas
BTW Just about everyone thinks that the lead from leaded gasoline, leaded paint scrapings, industrial smelting dusts etc generated during the last century has magically disappeared. It hasn't, massive amounts of lead from this use resides in the top 2-3 ft of soils especially in urban area, river and estuary bottoms and represents an awaiting problem. Every time this is disturbed lead is kicked back up into the atmosphere as dust. The lab I worked in for 30 years can even identify which country a piece of urban soil comes from by the anthropogenically deposited lead isotopes present in these soils. This lead is a serious potential future hazard because all that has to happen to mobilise this lead into our ground water is for precipitation to become more acidic - which we are also slowly doing because we keep pumping more CO2 into the air At the present rate of acidification of the atmosphere it is not clear how much time we have left before our major groundwaters are contaminated. This is a very nasty little time bomb we have left our grandkids that they will not thank us for.
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Sorry Sach, In terms of total exposure, if anyone is an occasional chainsaw user, e.g. a couple of days a month and chooses to use Avgas on a windy day, I doubt it would add much lead to their overall intake. 10 hours a day for 50 years would be something else.
samdweezel05
ArboristSite Guru
Yup 50:1 works great if your bucking 18" logs and it takes you an hour to go through a tank of gas. This bucking is what the oil guys are expecting you to do with your saw. They never intended it to be run for a full tank under load with out a single second of idle time. I can hold my 660 wide open for 12 minutes on the mill under load before it's out of gas. I would rather use an extra 20 cents worth of oil and run 32:1 on the mill and 40:1 on everything else. I also use AV fuel....for storage.
samdweezel05
ArboristSite Guru
I hear your saws are ported by a hack.
Trx250r180
Saw polisher
I heard the same thing too..............don't believe everything you read on the internet ..........
samdweezel05
ArboristSite Guru
I heard the same thing too..............don't believe everything you read on the internet ..........
I was praying it wasn't true as he has one of mine now.
sachsmo
Addicted to ArboristSite
Always figured an ounce o' prevention is worth a pound o' cure.
Milling with a chainsaw has got to be harder on them than almost anything else. .
Perhaps you could get by with 50:1 87 octane, I for one will leave it to someone else to try. (ever try to find a P&C fer a 30+ year old Sachs Dolmar?)
Actually what I put them through I picked one up off the bag (just in case)
Milling with a chainsaw has got to be harder on them than almost anything else. .
Perhaps you could get by with 50:1 87 octane, I for one will leave it to someone else to try. (ever try to find a P&C fer a 30+ year old Sachs Dolmar?)
Actually what I put them through I picked one up off the bag (just in case)
sachsmo
Addicted to ArboristSite
Ain't so much the octane,
It is the e that scares me more.
Although probably not needed the higher octane does help with knock and pre- ignition.
And it keeps for a good while also.
If'n I didn't have it available right in town, I would probably not go out of me way to get it eh?
On the other site is most of them. They'll be more when I get more time at home.
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