Aviation gas

[heviarti]

Yeah, I think i'll try it in my 105 as soon as i get pieces. There are some faqs on blending too, which I may consider

Wiemedog: how well does that 797 start? 100LL make it more difficult?

Has anyone tried the John Deere synthetic two stroke oil? I'm prolly going to go and get my chain sharpened by Don Stallions as well... he is supposed to have been famous for sharpening competition chains at one time. I really plan on giving that stihl a run for its money.

 

[MacDaddy]

You will build more hp with the lowest octane fuel your saw can handle To much octane will actualy lower your hp And if dont beleave me call VP fuel tech line and they can explain it to you

 

[heviarti]

Somewhere I have to do something to combat vaporlock. I'd run my 1-71 about an hour and it just would not run anymore. everyone attributed that to vaporlock.

 

[bwalker]

YIKES! Almost nothing said in this thread is even remotley factual. Do a google search....the thruth is out there.

 

[rb_in_va]

plus I have a last name that means something around here.

What does it mean?

 

[jimbo1490]

Lead and two strokes

The primary reason for adding lead to fuels is to lubricate the exhaust valve on Otto cycle engines. No two-stroke gasoline engines that I know of are using poppet style exhaust valves, so this just is not needed in a two-stroke engine. Lead potentially could be bad since the two-stroke oil may not cope well with lead; it was never designed to do so. Some of you in aviation may remember the Mobil 1 AV fiasco. Some oils handle lead well, some definitely do not.
That being said, 100LL is awesome fuel; it never spoils (I've used 100LL that sat for ~8years with no problems), is of very consistent quality, runs cooler and of course reduces pinging. Avgas is awesome for putting up equipment for storage.
If weimedog has had good experience with 100LL and certain oils, then those oils should be good-to-go with 100LL. Mo gas conversions are for those who fly small planes from remote airfields not served by an avgas provider. There are many thousands of these little airfields in the US.
Auto fuels are all 'pooled', that is, all the fuel owned by all the sellers is stored together in huge tanks, so despite their commercials trying to convince you to the contrary, their additive packages are all the same (by region). They have to be; they're all stored in the same tanks!
There is one exception to this practice; Amoco Ultimate. I wrote a letter to Amoco circa 1994 inquiring if they reserved the right to make unannounced changes to Ultimate the way they do with other grades of auto gas. Amoco answered with a form letter which implied a promise to keep Ultimate both unchanged and seperate from 'pooled' automotive premium fuels. This was being done, the letter explained, as part of an agreement (non-binding?) with the people who owned the mo-gas conversions for light aircraft. These 'conversions' were granted based on test data from using Amoco ultimate.
If all you want is higher octane, you can simply add 10% toluene to your fuel to gain about 3 points. Virtually all toulene began to be refined out of gasoline by the mid nineties to reduce emissions. Toluene is an economical octane boost as it can be had for about $200 a drum. The last drum I bought (not for fuel additive) cost about $175, but that was a few years back.

Jimbo

 

[heviarti]

If two stroke oil and lead do not co-exist, why is it leaded was the only thing available for a long time? what did most people run their saws on in the 60s and 70s?

I know all about valves and lead, so let me just re-reiterate, I'm not in it for tjhe octane so much as I am the anti vaporlock additive. it really sucks when your saw just stops running, and everything is mechanically ok. I've worked my 10-10 that hard once or twice, but the 1-71 and super 44 A are really bad about it. They just sit there and smoke. Two hours later you can work again. kinda sucks some days.

 

[heviarti]

btw, do you mean tolulene?

 

[Lakeside53]

If two stroke oil and lead do not co-exist, why is it leaded was the only thing available for a long time? what did most people run their saws on in the 60s and 70s?

I know all about valves and lead, so let me just re-reiterate, I'm not in it for tjhe octane so much as I am the anti vaporlock additive. it really sucks when your saw just stops running, and everything is mechanically ok. I've worked my 10-10 that hard once or twice, but the 1-71 and super 44 A are really bad about it. They just sit there and smoke. Two hours later you can work again. kinda sucks some days.

Are you sure it's even vapor lock, and not just a bad tank vent? Have you torn down the carb or pressure tested it to make sure it's working o.k.?

 

[jimbo1490]

It's spelled toluene, pronounced tall-you-ween (sorry for the mis-spellings :^). You are talking about the two-stroke stone age when you mention the 60's. Purpose made two-stroke oil was uncommon back then. Mostly people used motor oil (four stroke, OK with lead) at a fairly rich ratio, like 16:1 as recommended, or castor oil. By the late 60's and into the 70's, purose-made two-stroke petroleum and synthetic oils were available, firstly to the boat insustry. At that time, Amoco developed a lead-free high octane fuel marketed primarily to the boat crowd. All the boat engine manufacturers recommended it. We used to call it 'Amoco white gas' as it had no dye color. With the exception that it's now 93 instead of 95 octane, that fuel is essentially Amoco Ultimate, which was always lead-free, even before gov't mandates.
It's worth mentioning that 100LL is rated for octane number by 'research octane' only while all auto fuels are rated by the average of research ond motor octane numbers. This makes the octane rating of 100LL 3-4 points higher than it would be if the R+M/2 method was used. So Amoco Ultimate is actually within a couple of points of 100LL, both measured by the same method.

Jimbo

 

[WRW]

jimbo 1490,
If I'm not mistaken, octane in the US was once measured in RON only. Somewhere in the early 70's was when I seem to remember it converted to an average. That 95 octane number you gave for AMOCO (used to be AMERICAN), was that pre-70's.

 

[bwalker]

Avgas isnt rated by the Research Octane method. Its rated by the ASTM rich/lean scale. Big differance.
I am not aware of any two cycles oils that have issues with lead. Most race fuels used for mx, jet ski and snowmobile racing are leaded and standard oils work fine.
the issue with Mobil AV-1 and lead had as much to do with the engine design as anyhting else. Also keep in ming that the additive packages for avation oils are vastly differant than two cycle oils. Not only that the oils function in much differant ways. I flyout camp owners that use avcgas in outboards and have for years with good results.
And one last thing. Tolulene is a piss poor octane booster for a two stroke. About the only application where it works ok would be a turbo charged four stroke.

 

[Chopwood]

I used to run 110 sunoco unleaded in my gas race saws. I tried AV gas in them and picked up power and they started easier (we cold start around here). I've been running it for about three years now. Stihlman can attest to the speed of my gas saws vs how they used to run.

 

[jimbo1490]

I was riding dirt bikes regularly by the late 70's and distinctly remember Amoco rated at 95 octane circa '78-'79. As long as I can remember (I'm only 40 ;^) the pumps have been marked "R+M/2".
Interestingly, as late as the mid 90's, Amoco made a special grade of their 'Ultimate' available in selected markets(?) which was rated 95. The pumps were specially marked with some cute name which escapes me now. I was driving a Buick GN and used to go to this one station on North Miami Beah Blvd (I lived doen there back then) which carried it. Have not seen it in years.

Jimbo

 

[jimbo1490]

Avgas isnt rated by the Research Octane method. Its rated by the ASTM rich/lean scale. Big differance...

It's worth mentioning that 100LL is rated for octane number by 'research octane' only...


Looks like we're both wrong on this one (though I think you were a bit closer to the mark than I was):

http://www.prime-mover.org/Engines/GArticles/octane.html

I'm not aware of any two-stroke oils that don't like lead, either. But if there was going to be a problem, it would be a bad interaction 'tween lead and the oil. Small two-strokes don't have an oiling 'system', so plugging up small pressure orfices will obviously not be an issue.
BTW, If toluene is so "piss poor", then you must have been really unhappy with fuels refined twenty years ago, back before they went to the extra refining steps to remove the last of it to reduce NOx emissions. As I recall, the fuels back then ran just fine in two strokes, toluene and all.
The fact is, most commercial octane boosters of the 'lead free' variety are nothing more than toluene or toluene/xylene blends. The big article on octane boosters in Motorcross Action a while back mentioned this. (MXA also raised the objection that some additives in avgas are incompatible with two-stroke oils) No mention that toluene is a "piss poor" octane boosters for two-strokes, which were the subject of the article. If you want to bump up octane cheaply, try toluene. It's only a couple of bucks a gallon, and was in the gas for years anyway, so you're not really in uncharted territory.
MXA probably publishes their old mag articles online, as do a lot of rags lately, so if you search a bit, you can prob'ly find the full text of the article I'm referring to.

Jimbo

 

[Sylvatica]

Since my friend is a pilot, I have had the opportunity to run 100 LL in all of my off-road gas engines, 2 & 4 cycle.

It is simply superior. Why?

Regulated quality. It is frowned upon to have perfectly good airplanes dropping out of the sky due to a refiner cutting corners on aviation fuel.

No dubious additives. It is designed to perform, not make people "feel" good.

Extreme resistance to decomposition and varnishing. Excellent tank life.

No, it will not contribute to exhaust valve erosion. I am not dealing with 30 year old engine components in this case.

Excellent resistance to detonation. Unless you are using it in a racing engine with according spark advance, the octane is more than adequate.

Main reasons 100 LL is great: Runs strong, smooth, and clean, and it practically doesn't go stale.

 

[jimbo1490]

Though I have never tried avgas in any two-strokes, I use it in all of my small four stroke engines as a matter of practice. It keeps forever; I've never seen it varnish. Smells good before and after it burns, too. A two stroke engine will probably not know the difference 'tween lead and no-lead, as long as all other things are equal.
Back in 1999, I bought a 7Kw generator for Hurricane i-can't-recall, which was threatening, and filled the tank with avgas.. That storm was a no-show, and the generator languished for five years in my garage. In August of 2004, Charlie knocked out our power. In the middle of the night, I dug out the generator and it started in two pulls. It had not been looked at since '99, God is my witness.
I work with small airplanes, so have constant access to free avgas from all the 'de-fuel' gas at work. All of my co-workers have late-model cars. Since avgas is a definite no-no in those, I'm generally the only taker. Additionally the recent storms gave me a windfall of about 300 gallons which was destined for the fuel dump(!) since the aircraft salvage people are not at all interested in the tanks full of fuel, only the wrecked airplanes. Go figure...

Jimbo

 

[bwalker]

Jimbo, First off MXA is the biggest bunch of losers and couldnt right a real technical article to save there life.
Tolulene is found in some of the cheaper octane boosters. The majority of the over the counter boosters however contain MMT.


BTW I said "avation fuel is rated by the ASTM rich/lean scale". Go read the link you posted and it says the same thing.

Check these links out. All you ever wanted to know on tolulene.

http://www.dirtrider.net/forums3/showthread.php?t=56918&highlight=octane+boosters

http://ericgorr.com/techarticles/Fuel_Basics.htm

 

[jimbo1490]

The link says that aviation fuels are octane rated as the average of motor rated octane and ASTM Aviation Lean scale rated, NOT simply by the ASTM aviation lean scale. Toluene is present in todays fuels as well, more so in higher octane rated fuels, which is the main reason toluene is not extrraordinarily effective at boosting octanein these fuels; they've alread got a bunch of toluene in them. However it is still pretty cheap to get two points of octane boost out of 93 by using $2-3/gal toluene, and it's a very safe additive, heving been in the fuel all along. PJ-1 and other cheap octane boosters are mainly toluene. They cost $3 for a pint and some people still buy them. Just what is your argument?

Jimbo

 

[bwalker]

Re-read this jimbo. Its not a average. And Tolulene stinks as a octane booster for many reasons. Did you care to check out the links I posted and read the links within those threads?
In case you didnt a few thing s againsttolulene. Attacks rubber seals and hoses, doesnt vaporise in a NA engine whcih leaches heat from the combustion chamber and decreases hp, Doesnt mix in a linear matter with gasoline.
BTW I would be very supprised if modern pump fuels have very much tolulene or other aromatics in them. Can you say unburnt HC emmisions?



"Once again, you start with your trusty ASTM-CFR engine. First you set up the ASTM-CFR for the motor method and use that method to determine the motor rating of your fuel. You then correct that rating to the "Aviation Lean" rating using a conversion table. Below about 110 motor octane (a performance number of 110), the aviation lean and motor octane numbers will differ by only about 1 or 2 points. Above 110 motor octane the differences can be significant. Next you pull out another version of the ASTM-CFR engine. This one has a fixed compression ratio but allows you to supercharge the intake manifold. You pressurize the intake to higher and higher values until the onset of knock. Other than that, the parameters are the same as for the motor method used for automobiles. The supercharge method is then used to assign the Aviation Rich value of the fuel. Supposedly the pressurization method (as opposed to changing compression ratios) is a throwback to the 1950s and 60s when supercharging was common in aircraft engines. The engineers were particularly concerned with the fuel's behavior under boost".