Page 3 of 5
Re: Question about gas
Posted: Mon Aug 02, 2021 9:44 am
by PhilipRueker
ibgarrett wrote: ↑Sun Aug 01, 2021 6:52 pm
I'm assuming the Rotax can handle the 100 unleaded?
Very likely, since it can also handle 100LL and other fuels and this one is supposed to be a direct replacement 100LL.
But I guess to be safe we'll have to wait for a service letter from Rotax that says as much.
Re: Question about gas
Posted: Thu Oct 28, 2021 9:00 am
by SlingDriver
I am planning to fuel the TSi the same way I do my boat. I use a 1" siphon self priming shaker and 4 5Gal VP racing 5 gallons jugs, It is a breeze. I guess each jug takes around 20 to 30 seconds. Just a few quick shakes and it starts flowing fuel. The VP racing 5 gallons actually takes a bit more, for all 4 jugs I get around 23 gallons. At least in FL, the 91 ethanol free is pretty easy to find, there is a gas station in the corner of my home airport.
Re: Question about gas
Posted: Tue Nov 02, 2021 6:56 am
by msejourne
Well, read the following article and IMHO Cessna (Textron) has finally given the go ahead to provide what I believe will create a need for Unleaded fuel at airports. Since there are so many 172 & 182s out there, I would think that we might start seeing more availability of 91UL and/or 94UL.
"Cessna 172 Skyhawk and the 182 Skylane are now compatible with 91-octane unleaded (91UL), 94UL, or 100VLL (very low lead) fuel. Also, the Cessna 206 Turbo Stationair HD is compatible with 100VLL fuel."
https://www.autoevolution.com/news/cess ... 73092.html
Re: Question about gas
Posted: Tue Nov 02, 2021 11:03 am
by ibgarrett
Wouldn't the final say for the fuel type fall to the engine manufacturers (lycoming/continental/Rotax)? I mean I get Textron might have a say in it, but not the final say.
I wasn't making many friends here as the airport managers were like "no one would use it" when I asked why they weren't putting in Mogas... my response was "it's tough to use if you aren't providing it"... they didn't like my answer for some reason... ¯\_(:/)_/¯
Re: Question about gas
Posted: Tue Nov 02, 2021 11:11 am
by Skepilot
ibgarrett wrote: ↑Tue Nov 02, 2021 11:03 am
Wouldn't the final say for the fuel type fall to the engine manufacturers (lycoming/continental/Rotax)? I mean I get Textron might have a say in it, but not the final say.
Textron owns Lycoming.
Re: Question about gas
Posted: Tue Nov 02, 2021 12:41 pm
by ibgarrett
Oh good grief... how did I not know that...
Thanks for setting me straight..
Re: Question about gas
Posted: Tue Nov 02, 2021 12:50 pm
by PhilipRueker
It's actually two-fold for certified airplanes.
Both the engine, as well as the airframe need to be certified for specific fuel types, since some parts like fuel pumps are considered part of the airframe.
So for example for the flight club I'm part of, we can use Mogas in our C172 because both the engine and airframe are approved for it, but can't use it in our Cardinal C177, because the airframe doesn't have an AD for it, while the engine does.
Re: Question about gas
Posted: Wed Mar 23, 2022 7:33 am
by scout
Can our rotax 915is use 93 with ethanol ? If so what would the down side be ? anything more than the increased oil change interval that we already expect ?
Re: Question about gas
Posted: Wed Mar 23, 2022 7:56 am
by Skepilot
scout wrote: ↑Wed Mar 23, 2022 7:33 am
Can our rotax 915is use 93 with ethanol ? If so what would the down side be ? anything more than the increased oil change interval that we already expect ?
Yes, it can use unleaded mogas 91AKI or better with up to 10% ethanol. There is no increase oil change interval associated with unleaded mogas. The increased oil change interval is when using leaded fuel (e.g. 100LL) more than 30% of operation.
Downsides with ethanol:
1.) Decreased lifespan of rubber fuel lines. This can be addressed by using aluminum or teflon fuel lines. I used teflon in my TSi.
2.) Shelf life of mogas with ethanol is about half that of ethanol free mogas.
3.) Mogas with Ethanol has lower vapor pressure, which could cause vapor lock or low fuel pressure, especially on hot days or at high altitudes.
All that said, I understand N135WT uses 91 mogas with 10% ethanol all the time with no problems, including many hours at 17,500' and that one run up to 27,000'. (They used 100LL for the run up to 30,000'.)
On my plane, I have noticed slightly lower fuel pressures when flying in the high teens using even ethanol-free mogas. Sometimes I've had to keep both fuel pumps on to maintain fuel pressure in the green, whereas one pump will suffice with 100LL.
Another issue is using winter blend mogas in the spring/summer. Winter blend has lower vapor pressure and can be a problem in warm temperatures and/or high altitudes. This issue remains with or without ethanol, but ethanol makes it worse. Fuel suppliers must change to summer blend by May 1, but retailers have until June 1 to switch over to summer blend. They make the switch back to winter blend around September 15.
Re: Question about gas
Posted: Wed Mar 23, 2022 10:54 am
by scout
Skepilot wrote: ↑Wed Mar 23, 2022 7:56 am
scout wrote: ↑Wed Mar 23, 2022 7:33 am
Can our rotax 915is use 93 with ethanol ? If so what would the down side be ? anything more than the increased oil change interval that we already expect ?
Yes, it can use unleaded mogas 91AKI or better with up to 10% ethanol. There is no increase oil change interval associated with unleaded mogas. The increased oil change interval is when using leaded fuel (e.g. 100LL) more than 30% of operation.
Downsides with ethanol:
1.) Decreased lifespan of rubber fuel lines. This can be addressed by using aluminum or teflon fuel lines. I used teflon in my TSi.
2.) Shelf life of mogas with ethanol is about half that of ethanol free mogas.
3.) Mogas with Ethanol has lower vapor pressure, which could cause vapor lock or low fuel pressure, especially on hot days or at high altitudes.
All that said, I understand N135WT uses 91 mogas with 10% ethanol all the time with no problems, including many hours at 17,500' and that one run up to 27,000'. (They used 100LL for the run up to 30,000'.)
On my plane, I have noticed slightly lower fuel pressures when flying in the high teens using even ethanol-free mogas. Sometimes I've had to keep both fuel pumps on to maintain fuel pressure in the green, whereas one pump will suffice with 100LL.
Another issue is using winter blend mogas in the spring/summer. Winter blend has lower vapor pressure and can be a problem in warm temperatures and/or high altitudes. This issue remains with or without ethanol, but ethanol makes it worse. Fuel suppliers must change to summer blend by May 1, but retailers have until June 1 to switch over to summer blend. They make the switch back to winter blend around September 15.
Wow! thank you. that is very informative. I didn't know about winter vs summer blends.