Fuel Concerns

Posted this on the Auto Fuel thread, but seems to have been ignored.

I started running some 91 octane E Free auto gas this year in my 65 Hp Continental. $2.50 compared to $5.18 for 100LL was the main reason. I found that when running on auto gas the engine does not respond as well to the throttle, stumbles and slower to accelerate. Little rougher at idle too. Other pilots running the same gas say they see no difference. Also the carb will leak fuel when on Mogas, but not on 100LL.

Do I need to change timing or adjust the carb? Different needle for the carb?

My experience was also that car gas gave me higher egt's for the same power settings, I presume because of the lower octane.

sj

17,000+ gal of car gas and still going strong in 6 different engines. Try backing the big screw at the back of your carb out 1/4 turn.

Glenn

Float sinking/melting?

Also remember that if gas is dripping out, air is getting in and maybe where you don't want it...

Most of the Stromberg carbs on little Continentals leak gas when parked if it is left on. Original needles were steel and neoprene tipped. No longer legal.

Glenn

cubdriver2 said:

17,000+ gal of car gas and still going strong in 6 different engines. Try backing the big screw at the back of your carb out 1/4 turn.

Glenn

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Thanks, will give it a try.

cubdriver2 said:

Most of the Stromberg carbs on little Continentals leak gas when parked if it is left on. Original needles were steel and neoprene tipped. No longer legal.

Glenn

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Only happens when running Mogas, stops when I go back to Avgas. Will check the needle, don't see anything in the logs about it being changed, and I have all the logs back to 1944.

ulpilot said:

Only happens when running Mogas, stops when I go back to Avgas. Will check the needle, don't see anything in the logs about it being changed, and I have all the logs back to 1944.

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Interesting, when I ran MoGas I had problems too. The indicator balls in the stock site gauges would discolor, swell up and stick and once you've been through that embarrising indignation of funny colored, swollen, sticky balls I can assure you that I'll only practiced safe fueling from then on!

delete since pic was sideways

swell up

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Kirby, did you ever see this before?

Marty, Is there any information that "O" rings made from "Buna N" are effected one way or another by either ethanol or 100LL? My local "O" ring supplier seems to think that "Buna N" rings are useful across a wide range of chemicals.

I remember years ago that the "O" rings in the Cessna fuel selector were very specific in their composition. The wrong ones would cause the troubles described in your above bulletin.

Marty, Is there any information that "O" rings made from "Buna N" are effected one way or another by either ethanol or 100LL?

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Not sure on that but nitrile rubber is good for both fuels. Eagle Fuel Cells backs that up too. Not sure if o-rings can be made with nitrile or not.

180Marty said:

Kirby, did you ever see this before?
View attachment 21901

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Yes I have. The issues was in the cub4 years ago.

ulpilot said:

Only happens when running Mogas, stops when I go back to Avgas. Will check the needle, don't see anything in the logs about it being changed, and I have all the logs back to 1944.

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Does the mogas leak/dripping stop after a short while?

Not sure on the science behind it (i.e., why mogas does it and 100LL doesn't), but it is a "well known deal" that when you shut an
aircraft engine down that is running mogas, the remaining mogas in the induction system (intake tubes, etc.) will condense on the
walls of the intake tubes and run down to the carb, out the bottom of the airbox and drip onto the ground. I've heard the amount
of fuel that will drip out can vary from a teaspoon to a cup (I suppose depending upon the size of the engine).

Aircraft mechanics / IAs who are unfamiliar with running mogas will at times get fooled & point at the "fuel leak" and go searching
for the problem/fix when there is none!

1954C180 said:

.....the remaining mogas in the induction system (intake tubes, etc.) will condense on the
walls of the intake tubes and run down to the carb, out the bottom of the airbox and drip onto the ground. .....

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I think that that is the answer. The 100LL will evaporate quicker than the car gas so it does not condense and collect in the induction system. I have noticed that engines which are using car gas seem to accumulate yellow/brown stains where the 100LL engines do not accumulate stains at all. Wondered why, perhaps this is the reason?

1954C180 said:

Does the mogas leak/dripping stop after a short while?

Not sure on the science behind it (i.e., why mogas does it and 100LL doesn't), but it is a "well known deal" that when you shut an
aircraft engine down that is running mogas, the remaining mogas in the induction system (intake tubes, etc.) will condense on the
walls of the intake tubes and run down to the carb, out the bottom of the airbox and drip onto the ground. I've heard the amount
of fuel that will drip out can vary from a teaspoon to a cup (I suppose depending upon the size of the engine).

Aircraft mechanics / IAs who are unfamiliar with running mogas will at times get fooled & point at the "fuel leak" and go searching
for the problem/fix when there is none!

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Actually it drips when I turn on the gas before first start of the day. Only with Mogas, and not every time. Never had it drip with Avgas, or when the fuel mix is more Avgas than Mogas.

ulpilot said:

Actually it drips when I turn on the gas before first start of the day. Only with Mogas, and not every time. Never had it drip with Avgas, or when the fuel mix is more Avgas than Mogas.

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Probably a bad/worn needle/seat assembly then. I have noticed that when there is (mostly) mogas in my 180, the primer is slightly easier to use (draws & depresses easier) than
when there is mostly 100LL in the tanks. Per the aforementioned o-ring swelling symptoms in 100LL fuel, maybe that is why.... These carburetors are fairly simple (same as
what you might find on the farm tractor, lol). Take it to someone who knows what they're doing and have them pull it apart. A new float, seat, needle & gaskets (~$100 worth of parts) + setting the thing up per the manual will likely fix the problem.

The benefits of running mogas make it worthwhile to have a peak inside the carb (not only are you saving money by running mogas, but your plugs will stay cleaner).
The flip-side of that is if you run 100LL exclusively in a small-bore engine, you are *going* to get a stuck valve at some point (it is just a matter of time/hours...). 100LL
has 4Xs the lead in it that your engine was designed to run with, and that excess lead will build up on the valve stems/guides over time until their is insufficient clearance
for them to keep moving. The large-bore engines seem to scavenge the excess lead better (more heat/pressure in the combustion chambers I suppose). Also, the lead
scavenging agents you can pour into the fuel tanks (i.e., TCP) only prevent the lead deposits from forming - they won't remove the lead deposits that are already there...

My J3-C65 is the other way around. Leaks fuel if you run 100LL and doesn't on car gas.

I came across the followings on another forum:

http://www.lycoming.com/Portals/0/OurInnovation_Fuels_UnleadedFuels_Part_1.pdf

http://www.lycoming.com/Portals/0/OurInnovation_Fuels_UnleadedFuels_Part_2.pdf

http://www.lycoming.com/Portals/0/OurInnovation_Fuels_Unleaded_Fuels_Part_3.pdf

I've basically been running on Mogaz, 91 oct. ethanol free, with the STC for a few years now, always under the impression I was OK with the "pump gaz" from the corner gaz station...... Seems I might have been kind of wrong, but my engine loves the stuff. Plugs are always clean, oil consumption remains low and most importantly compression stays high.

The way I read these 3 Lycoming info letters, Mogas should only be bought from airport aviation fuel suppliers who handle, store and check quality similarly to 100LL..

I think I'll fish out my A/C's STC and re-read slowly, maybe I jumped over details. Feels like someone just threw sand in a well greased bearing......

Any thoughts ???

Any thoughts ???

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I'd say if what you're doing works, why change.

180Marty said:

I'd say if what you're doing works, why change.

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Well, I'm completely at ease with "the way it's working now". I was more or less wondering if these info letters had gotten around on a large scale, if there were reactions to them.

As previously stated, first time I heard of them yesterday. They are not dated, so would they weigh heavily if something unfortunate, even if not fuel related, happened??

Just food for thoughts, nowadays people are sueing for just about any reason wether it's logical or not.....