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Here is a good review of 2 cycle chain saw E10 fuel concerns

 

S + C12Hhttp://www.forestnet.com/TWissues/August08/chainsaw.pdf

 

The 2 cycle engine people have a definite concern with ethanol mixtures. Not, that E10 can’t be a fuel, just these engines often at the edge of destroying themselves and any little bit of extra heat or lean mix will tank them. These engines run to limit of lubrication to satisfy the Clean Air regs. Since ethanol runs so clean less contaminates left over to insulate combustion chamber or piston from heat with the usual insulating carbon soot layer.  Gasoline pollution helps the engine to maintain itself from destruction.

 

My advice learned the hard way, even before the ethanol issue came up, run 32:1 or richer oil mix on all your 2 cycles. I destroyed boat motors, cycles, chainsaws, snow blowers, etc. until giving up on the strict instructions of owners manual. My guess the EPA threatens manufacturers unless they write such advice. Nowadays, upon long history, never a problem with 2 cycle engines, even with E10.

 

The small engine technology should get review, not to exist with ethanol, but fueled by ethanol. Ethanol with a bio diesel additive could be the perfect fuel. First the low biological impact of pollutants and fuel spills, but also the fuel more capable to remove heat and avoid pre-ignition. It’s a fuel for high rpm motors running on edge of engine destroying heat. The vegetable oil lubricants are proving themselves superior, note the use in metal cutting and race engines. Currently, a blending problem with ethanol. We do need new technology to make mixtures or solutions of ethanol and vegetable oils.

 

Marine engine manufactures should look hard at pure ethanol. Could become the fuel of choice.   

 

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The key point is that they should be slightly enriched-unless they were already rich on gas. There were a few inaccuracies in the "report" such as "ethanol does not cool as well as gas", and the detonation/preignition statement was also incorrect in part- detonation and preignition are quite different, yet they lumped them together as one.

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Enriching fuel a notch definitely. I do question the claim of  detonation and pre-ignition increase with E10? It should be less?

 

The claim of ethanol not cooling....it's confusing. As I understand the exhaust temps of ethanol fuel or blended fuel is lower. Also, the ability of fuel to absorb latent heat of vaporization btu (cool combustion chamber) before ignition greater. Yet, many reports out their mentioning valves getting hotter as no insulating blanket of thermally protective soot. Remember lead was used to insulate valves in bygone era. It seems ethanol cleans up combustion chamber and valves subjected to more heat? Now the 2 cycle has no valves, yet they usually fail at piston dome. May the piston get hotter with ethanol and create pre-ignition possibility with lean burn? The report mention burn from spark plug down and piston up. This may be the detonation?

 

Anyways I bet the small engine technology would benefit with a fuel switch to E85. Two cycle chain saws would benefit even more, but with need of new vegetable oils for fuel mix. This E85 fuel would improved small engine technology resulting in cooler engines, less pollution, and more power. Under old technology better off with plain gas. 

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Enriching fuel a notch definitely. I do question the claim of  detonation and pre-ignition increase with E10? It should be less?

 

The claim of ethanol not cooling....it's confusing. As I understand the exhaust temps of ethanol fuel or blended fuel is lower. Also, the ability of fuel to absorb latent heat of vaporization btu (cool combustion chamber) before ignition greater. Yet, many reports out their mentioning valves getting hotter as no insulating blanket of thermally protective soot. Remember lead was used to insulate valves in bygone era. It seems ethanol cleans up combustion chamber and valves subjected to more heat? Now the 2 cycle has no valves, yet they usually fail at piston dome. May the piston get hotter with ethanol and create pre-ignition possibility with lean burn? The report mention burn from spark plug down and piston up. This may be the detonation?

 

Anyways I bet the small engine technology would benefit with a fuel switch to E85. Two cycle chain saws would benefit even more, but with need of new vegetable oils for fuel mix. This E85 fuel would improved small engine technology resulting in cooler engines, less pollution, and more power. Under old technology better off with plain gas. 

 

Detonation would be far more likely to occur on a lean engine tune. The enleanment factor of the E10 could lead to that or hotter exhaust only if the carb was not adjusted back to correct AFR. If running on gas vs E10 at the correct AFR for that fuel would give the E10 a theorectical cooler engine advantage.

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Ah, the lean burn. Probably a bigger concern with chain saws full throttle operation.

 

Compounding the problem....I was reviewing a presentation for auto engineers entitled ethanol a small molecule with complex combustion.  The fuel burn is not linear relationship with increasing concentrations of ethanol within gas. They described it as a "new" fuel i.e. E10 vs E30 vs E85. Mixing ethanol within gas creates a complex fuel, but the complexity and variables minimal with E85. May E85 be blended more accurately? Also, the engine controls technology was the easiest with E85 fuel. 

 

Since E10 fuel is not particularly an accurate blend, may that be a problem with the dumb and crude 2 cycle engine that barely works with gas without burning up? May the 2 cycle engine operate more consistent, powerful and reliable with E85 only fuel? That is if the engine was designed to the fuel and only for E85.  But again that fuel changes concentrations for cold or hot temperatures, too.   

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I've converted 2 cycles to E85 before.  It works great!  I can't see how E10 would be a problem if, as you say, the carb is adjusted at the same time.

 

Here's one...

http://e85vehicles.com/e85/index.php/topic,2779.0.html

 

"May the 2 cycle engine operate more consistent, powerful and reliable with E85 only fuel?"

 

Yes, that's what I've found.  2-strokes work much better with E85.  I've run lean mixtures in that weed wacker, sometimes unintentionally, that would have destroyed it if running gas.  Instead, no harm was done at all.

 

I do need to mess with the chain saw at some point this summer.  I understand they're a little different, where you directly control the throttle, and if run lean can overspeed.  Is that correct?

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Quote:"I do need to mess with the chain saw at some point this summer.  I understand they're a little different, where you directly control the throttle, and if run lean can overspeed.  Is that correct?"

 

Rusty- about 32 years ago I raced 2 stroke asphalt track carts. These generally ran Mac 91 chainsaw engines that were blueprinted. We ran them on unleaded but the idea would be similar for E85. We had to run on the lean edge for speed (about 12-15,000 rpm at 70 mph on the backstretch). Track was Grand Prix style with backstretch, hairpin, reverse half loop, short stretch, turn, then backstretch again. We tuned exhaust then tuned AFR so that we would only 4 stroke (get pop, pop) two times going into the hairpin. Two pops in the whole circuit. The purpose of the pop/4 stroke was for extra cooling and lube. Anything leaner and it would sieze in 2-3 seconds-anything richer and you were not competitive. High speed needle was set by ear- a fine edge of sound tone diffference between too lean and slightly rich- since we all ran the same motor all one had to do was stand trackside and listen- soon enough someone would go lean and stick a piston- you remembered that sound and did not go there. A motor lasted one 60 mile race plus the qualification runs leading to it-after that it needed to be bored and reblueprinted. We started these things with a pull cart loaded with a six volt tractor starter on a 12 volt battery with a belt over the flywheel pully- we needed speed at crank for them to even fire.

 

If you think about the saw then I would want more life and would tune for constant "pops" (4 stroking) at every throttle release/chain decel- also listen to your high speed- if it is too fast and super clean it may be to lean for long life if something wears or goes wrong. When one thinks of all the things that can wear there is no wonder on old saws why they can fail. Reed valves, fuel pump diaphram, metering lever and pin, tiny fuel/air passageways clogging with fuel deposits or bits of sawdust finer than the filter, plugging filter (enleanment), carbon deposits all over (detonation and preignition), changing oil mixes, fuel changes due to lack of agitation, sticking rings, cooling fins plugged with oily sawdust, yada, yada. So is there any doubt why on gas or low ethanol blends these things need to be tuned rich for safety-- all the while spewing oily smoke full of partially burnt gas throughout the entire woods? ;) Not only is it safe so rich but your top end rpms are cut down- as is power so you cant blow it up unless several stars are aligned.

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That's interesting...torturing engines for max speed. A good testing ground to push reliability performance. How about going back to that track with 5 gallons of E85? See what that does to the race?

 

Outlaw's post reminded me of watching loggers as a youth. They carried a small screw driver for tweaking the carb. The reason most chainsaws have an external accessible screws for low speed and high speed adjustment. Usually the logger would find a big log and get the saw buzzing at full throttle, holding at full throttle with one hand, then reaching for vest pocket screwdriver. Adjusting to high speed lean, then open up to the first decline in rpm. Low speed adjustment was to improve idling, but if changed would require another high speed adjustment. Then the idle speed sometimes had to be tweaked. And the constant sharpening and cleaning of filter and removal of saw dust chips for proper engine cooling/air flow. These loggers had two or three chain saws in the truck box and a reel of new chain.  They always had a saw in the shop to get straightened out. So, they had their hands full even with regular gas. As the weather changed, oil concentrations, and yes the fuel does change per those automotive engineers. Also, the saw a vibrating screw loosening machine very capable of knocking itself out of tune. Cheap saws will leak air at the seals and potentially cause saw failure if the operator doesn't quickly adjust carb to accommodate. I remember the fuel was a concern when snowing as the moisture in fuel or air would lean out the engine and make it fail. Don't know the chemistry or mechanics of such, but this was before ethanol mixes.

 

One problem with continuous max power 2 cycle engines.....the piston never gets a break. Every stoke a high heat compression or extremely hot power stroke, at 20,000 plus stokes per minute. Ouch, no break.  Four cycle engines gets two easy cooling strokes in between to vent some heat to cooler gases or convect to cylinder wall.

 

Doesn't E85 fuel per Rusty make sense for these engines? I think these engines so vulnerable to change, that they had to go through a learning curve. The more they learn of ethanol, they all may realize a friend and a better fuel for their purposes?

 

Rusty, how did you handle the oil mix problem?

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Rusty, how did you handle the oil mix problem?

 

Simple.  I went to Klotz Benol.  The Redline 2-stroke Allsport I was using would leave a small amount of sludge on the bottom of the fuel tank when used with E85.  The Benol does not do this, and stays mixed.  I left some Benol mixed E85 outside all winter.  I went to start up the converted Lawnboy mowers this spring, and the fuel was still mixed when I poured it in the tank!

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