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Supercub and Mogas

giangab

giangab

Registered User
Hello,
My PA18/95 project is getting close to paint job

This supercub is powered by a C90 which, I understand has an STC combined with the plame type, for Mogas.

How to get the STC?

The fuel system of the PA18/95 works essentially on gravity (no fuel pump). Eould it be worth to install an electical booster pump (say a Facet one) at the lowest point near the gascolator to prevent vapor-lock?

Thanks for your comments.


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You're never going to have a vapor lock issue with a carbureted Continental on a Cub, and a pump is just one more mechanical contrivance to fail.
 
How to get the STC?

STCs. One STC for the airframe. A separate STC for the engine.
 
Yes, there are separate STCs for the airframe and the engine. You buy the STCs from either Peterson or EAA (they are each slightly different) once you have them, you them get your IA to fill out a 337 to “install” the STCs on your airplane and engine. Both STCs require Mogas without ethanol, so depending on where you live you may not be able to find non-ethanol Mogas.


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Had good luck running alcohol free regular in my O-320. Might be my imagination, but runs better than on a gas.
 
don d said:
Had good luck running alcohol free regular in my O-320. Might be my imagination, but runs better than on a gas.
Click to expand...
Mogas has the octane/burn rate it was designed for. It probably DOES run better. 100 LL burns slow and causes somewhat elevated CHT's and EGT's. For a low compression Lyc. 100 LL I recommend bumping the timing 2-3 degrees.
 
Last edited:
One of the big differences between mogas and avgas is the filtration. If you use mogas, fill a tank that has a filter between it (the tank/jug your filling)and your plane (a fine one!). Dont go from the gas pump to a portable, then to the plane. Just my $2 cents. Do we still use pennies?
 
Mr funnel is a must for using car gas. It filters out the water and solids.


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The STC is going to call for 87 octane or higher and NO E10 the alcohol destroys rubber fuel lines and attracts water it is very bad in an airplane. I know a guy that couldn’t find straight gas so he used E10 was flying at night the alcohol ate the diaphragm in the fuel pressure gauge gas started running on his legs he had to find a place to land at night with gas in the cabin not cool


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I have found just the opposite. I have burned over 21,000 gallons of mogas in the last 25 years in my airplanes. Almost all of it hauled in cans. I almost never have water in my fuel with mogas. The only times I discover water while sumping is when I stop to buy 100LL once in a while. I used a funnel for awhile but not with the last 20K gallons. YMMV

Glenn
 
I've found the same thing. The mogas is cleaner. My mogas goes into a tank where I have a filter/water block downstream of the pump. There's never anything in the filter or the tanks and no lead fouling.
 
Me too. If there was trash or water in mogas you would see a lot more cars disabled on the freeway. Do you know why cars no longer have gascolators?

We use 75% mogas, 25% avgas, giving us roughly the equivalent of 80 octane lead content. We never see trash or water.
 
Vehicals have whats called fuel filters. I guess im the only one whos ever seen plugged fuel filters in autos. Different gas stations have different quality fuel filtration. Either way, its your ass and your $30k engine. Do what you want. Its not that big of a deal to run your mogas through another filter to be safe.
 
I haul gas for a living. Filter it. Like cub special ed said not all stations filter systems are the same and the gas that comes down the pipe lines are not clean


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Peterson STC http://www.autofuelstc.com

EAA STC https://www.eaa.org/en/eaa/aviation-communities-and-interests/pilot-resources/auto-fuel-stc

I like the Peterson if you ever go to a 160 hp O-320 they cover it. The problem is finding high octane ethanol free mogas. I have one local station here in my home town that has ethanol free mogas but no high octane. I have run mogas in my Super Cub almost exclusively in my stock fuel system 150 hp Super Cub for the last 4 years except on cross countries with no issues.
 
Funny how here in Iowa non ethanol 87(all gas stations) and 91 octane is plentiful. We also have 10,15,20,30 and 85% ethanol blends. Here at Paullina Avgas is $4 per gallon,E0 91 is $3.50, 87 E0 is $3.10 and E10 87 is $2.80. E85 is $1.90
 
180Marty said:
Funny how here in Iowa non ethanol 87(all gas stations) and 91 octane is plentiful. We also have 10,15,20,30 and 85% ethanol blends. Here at Paullina Avgas is $4 per gallon,E0 91 is $3.50, 87 E0 is $3.10 and E10 87 is $2.80. E85 is $1.90
Click to expand...

I don't find it funny. I find it criminal especially since I live in Texas where we produce more oul than any other state.
 
I deliver fuel to stations in Nebraska, Wyoming, South Dakota and most all stations carry at least one straight gas product . This time of the year 91 is used for mowing and boating and they go through a lot.


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A side note: the Peterson STC for my C-90 requires that I mix 10% avgas with auto gas to provide adequate lead to valve train.

MTV
 
I'm thinking when they did the STC for 88% ethanol (AGE 85) for the big Continentals in 180/182's with hardened valve seats no lead is fine. Little ones don't have seats like that?????

Here is another interesting tidbit on fuel use from the Iowa Dept of Revenue. For 2017 87.2% of all gas sold had ethanol in it.

Gasoline Fuel Sales
During 2017, the reported amount of E10 gasoline sold equaled 1,314.9 million gallons.
E85 gasoline sold equaled 20.6 million gallons, E20 gasoline sold equaled 1.2 million
gallons, and E15 gasoline sold equaled 27.6 million gallons, with 94.1 percent sold
through registered pumps. Combined, the five ethanol blends represented 87.2 percent
of total reported gasoline fuel sales during the year. Of the 2,053 locations that sold
gasoline, 1,999 (97.4%) sold one or more ethanol blend.
Click to expand...
 
Ethanol is largely corn fed. It was hugely subsidized, and perhaps still is. Corn farmers and large crop growers love the ethanol market, it's a cash cow.

And while I support farmers probably more than the next guy as I've been there, ethanol is a product of the EPA, which is by and large has created (produced?) more cost and problems for the public in the last 20 years than any other group of people that I'm aware of.

On the flip side, Marvel Mystery oil should have ramped up their marketing on the same scale as ethanol has been introduced. Combat dryness by lubricating. lol... yup, I just went there. There's a thousand slogans MMO could be using right now, with sales through the roof.
 
I put a cap full of marvel mystery oil in each tank fill up with car gas


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Started using MMO after I stuck a valve in a c-85 . I have never had a problem since


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I was taught to use 2.5 ounces per 5 gallons, which I did. Even heard from the armchair experts that the engines torn down after running MMO were in excellent condition compared to those that did not.

My lawnmower just had a stuck ring _and_ stuck float dumping all the fuel into the crankcase. Entire neighboorhood went IFR in smoke in about 2 minutes. Why? Because of Ethanol.

Drained out the oil/fuel, added fresh oil with a healthy dose of MMO, added another good dose to the fuel tank with some gas, and Voilà! the ring freed itself, the carb worked. Freaking cub cadet never ran so good.

pb
 
I did a little research, it is all driven by EPA National; Air Standards. They take air readings and if the emissions are high in a certain county they adjust the formula. Unfortunately I am in in a county with low emissions (low population and emission producing industry) but the infrastructure in place to deliver ethanol fuels to the big metropolitan areas make it not cost effective to deliver non-ethanol fuel to my area even though it is far cheaper to manufacture non-ethanol fuel. Still makes no sense to me to put something in my airplane to lower the power but I am not on the ethanol dole.
 
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