Rotax 912ULS Fuels

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Rotax 912ULS Fuels

Postby FredHoffman » Wed Jun 06, 2018 10:41 pm

Wow never though feeding the Rotax would be such a problem ! I too just lost access to 93 ethanol free fuel. So now only 90 is available locally. I thought mixing 1/3 100LL avgas and 2/3 ethanol free.

I have slight green tint fiberglass tank, anyone been using 10% ethanol premium in them with out trouble? Would really like to do this but worried the epoxy might dissolve out and cause major trouble.

The options as I see it now are :

1) Use the 90 octane ethanol free................. detonation /engine failure/ land in field !
2) Use the 93 10% ethanol premium gas.......... epoxy dissolves clogs fuel filters and carbs/ engine failure/ land in field !
3) Use 100LL.......................................... rebuild gearbox after 400 hours and engine gets early overhaul from lead buildup !
4) Mix 100LL / 90 octane ethanol free............ rebuild gearbox after unknown recommended hours ? / slow down lead build up?

Option 4 seems like the best way to go but it is going to be a major headache, especially as not even 100LL is avail at the airport I'm flying from !
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Re: Rotax 912ULS Fuels

Postby SuperFly » Thu Jun 07, 2018 8:26 am

Fred,

Look into getting Swift Fuels UL94. I am really liking it. I cant prove it, but I swear my EGTs have come down 70-80* burning it. But no one can explain why that would be the case, even the Swift engineers. SO perhaps its coincidental, but it sure seems to follow the fuel use (I have in no way documented to track, just observation)
It is not terribly expensive if you buy enough of it, the only real hurdle is storage and perhaps transportation depending on your proximity to Lafeyette Indiana.
I am really happy with it. Its clean, doesnt stain if spilled, smells ok/smell doesnt linger like gas, has good longevity in the tank (so far so good), is high enough octane to prevent detonation problems, girls dig it.

Ok. I cant prove ALL of the above, but I stand by all but the last claim.
Best,
Ben Schneider
Highlander #263 converted to SuperSTOL
N45FT Now Flying!
http://www.stolairplane.com
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Re: Rotax 912ULS Fuels

Postby gkremers » Thu Jun 07, 2018 10:54 pm

Fred,
What year did your kit deliver. My tanks are the fiberglass variety, not really slight green. I had the same issue but decided on running 93 Ethanol. So far after 4 years and 325 hrs I see no problem with the fiberglass. If I could get ethanol free higher than 90 octane I would have gone in that direction, no such luck finding it near me. If I ever have an issue I'm going to have a friend weld up some aluminum tanks and never think about it again.


My serial number is 249.

Gary
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Re: Rotax 912ULS Fuels

Postby FredHoffman » Thu Jun 07, 2018 11:30 pm

My kit number is 234 delivered in May 2011 but I sent back the tanks that came with the kit which were more yellow and was shipped new tanks late 2011. They were much better quality than the first ones. Here is a photo of them just before fitting them in the wing.
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IMG_5502.jpg
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Re: Rotax 912ULS Fuels

Postby z987k » Sat Jun 09, 2018 3:10 am

We have no ethanol in our gas, but the highest I can get at the pump is 90. I have an 80 gallon tank for getting fuel to the airport and to get 90 to 91, I mix 75 gallons of 90 with 5 gallons of avgas, which gives me 91.55.
The lead in the fuel after that kind of dilution goes from 2ppm in Avgas to .125ppm in the mix. Not much. I haven't noticed any lead build up on the plugs like I do in in my IO-360 which runs 100% avgas.
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Re: Rotax 912ULS Fuels

Postby AV8R Paul » Sun Jun 10, 2018 10:44 am

I had a Kitfox with fiberglass tanks. In Texas it’s ethanol or 100LL, I only know of 2 stations that have 90 octane ethanol free. I was told the tanks were ethanol resistant tanks. I used 2 or 3 tanks of ethanol, and I was out flying when I cam to my home Airport. As I cam in for a landing, I noticed when I tried reduced throttle, it wouldn’t. I broke out of pattern and head out to see what was the cause. I could get the throttle to reduce below 4700 rpm. I went back to pattern, told the tower I would be doing a dead stick landing. When I got back to the hanger, I Started checking to see what the problem was. There was a very sticky brownish tan substance in the air box, on the carb sliders. I spent the next few weeks trying to fix it. To make a long story short. A number of teardowns cleaning. I finally sent the carbs off 2 different time for rebuilding to Florida. I scoped the tanks the tanks were ethanol resistant tanks, but the bulkheads in the tanks were not. For a while I tried mixing the 90 octane ethanol free with 100LL. However, the 65 mile round-trip drive to go get the ethanol free was a problem. I was told by a flight instructor that had a Kitfox SLSA as long as you use Decalin [spelling?], He never had any problems with the lead build up. So I started using it. At about 500 hours I have to send the heads in to clean up the valves because of the lead build up. The moral of the story, I’m putting 180 hp Titan in my SuperSTOL

FredHoffman wrote:Wow never though feeding the Rotax would be such a problem ! I too just lost access to 93 ethanol free fuel. So now only 90 is available locally. I thought mixing 1/3 100LL avgas and 2/3 ethanol free.

I have slight green tint fiberglass tank, anyone been using 10% ethanol premium in them with out trouble? Would really like to do this but worried the epoxy might dissolve out and cause major trouble.

The options as I see it now are :

1) Use the 90 octane ethanol free................. detonation /engine failure/ land in field !
2) Use the 93 10% ethanol premium gas.......... epoxy dissolves clogs fuel filters and carbs/ engine failure/ land in field !
3) Use 100LL.......................................... rebuild gearbox after 400 hours and engine gets early overhaul from lead buildup !
4) Mix 100LL / 90 octane ethanol free............ rebuild gearbox after unknown recommended hours ? / slow down lead build up?

Option 4 seems like the best way to go but it is going to be a major headache, especially as not even 100LL is avail at the airport I'm flying from !
AV8R Paul
SuperSTOL XL - N357TX - Titan 180 HP
S/N JA498-11-16
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Re: Rotax 912ULS Fuels

Postby danerazz » Sun Jun 10, 2018 3:28 pm

I don’t have a rotax, but I looked at them, and others, and the issues 100ll caused, and the fact that this asinine ethanol issue causes so many other problems, led me to pick an engine that doesn’t have a 100ll restriction.

Ethanol is a stupid idea, and it causes so many issues. If I could get ethanol free gas it would change a lot of things I do, even if I had to pay more (which would be subsiding the subsidies on ethanol that I am already paying for with my tax dollars).
Dane

Paralysis by analysis
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Re: Rotax 912ULS Fuels

Postby gkremers » Sun Jun 10, 2018 7:22 pm

Dane,
I'm with you on the stupidity of Ethanol. If I could get higher octane non ethanol fuel I'd buy it in a heartbeat. Since that isn't an option in my area I'm running 93 octane fuel with up to 10% ethanol. There are thousands of Rotax 912 and 912S engines running this. The engine is fine with it, the fuel delivery system is the issue on some installs. I did the best I could with everything in the system ethanol friendly. The biggest unknown are the fuel tanks. I've been watching them over the years and so far so good. I've got about 325 hours or so over the past 4 years. Luckily I get to fly fairly often all year long.

I do run Ethanol free 90 octane in my 1978 Goldwing, 1991 Honda Nighthawk and a 1978 VW Super Beetle.

As I said earlier. If I have fuel tank issues down the road I'll be having a friend build some nice aluminum tanks.

Gary
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Re: Rotax 912ULS Fuels

Postby danerazz » Sun Jun 10, 2018 8:47 pm

Some of the issues with ethanol also include its short shelf life, and the fact it readily absorbs water. This can lead to all of the problems you would expect water to cause (especially where it may stagnate for long periods such as valves and float bowls). Plus it deteriorates faster than non-ethanol gas, and over long periods the absorbed water will separate and stratify in the fuel tank. We work hard to avoid water in our fuel systems and ethanol absorbs it and puts it in there. Alcohol can also be corrosive to fuel system components on its own.

Not to mention your consumption will be higher for a given horsepower.

So, even if the engine and the tanks can handle the ethanol, over time it can cause problems with nearly every component of the fuel system.
Dane

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Re: Rotax 912ULS Fuels

Postby gkremers » Sun Jun 10, 2018 10:01 pm

True on all fronts. As I said I fly often which means the fuel is never sitting for very long. I've been to the Rotax class and have torn down several high time engines that all ran exclusively on 93 octane with Ethanol. No issues and much cleaner than you can imagine. Again these were all engines out of trainers that flew often.

If you don't fly that often and let the engine sit for weeks on end, anything with Ethanol wouldn't be a good choice.


Gary
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Re: Rotax 912ULS Fuels

Postby FredHoffman » Mon Jun 11, 2018 8:47 am

I read a research paper on ethanol and water. Good news is it absorbs water which may let it pass through engine without trouble, but the bad part is it can precipitate back out just like the air we fly though. I read each gallon of 10% ethanol fuel can suspend over a tablespoon of water but it can precipitate out depending on temperature collecting in the low spots of your fuel system. Each tank full could add more water, eventually making it to the carbs in one big slug with bad results. I put a second sump drain under my seats with all fuel lines leading down to this point in a level three point attitude. The header tank sump drain is not the lowest point.
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