Van's Air Force
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rotax engine
- Thread starter lewy
- Start date
Ethanol
Rotax seems to be OK with up to 10% Ethanol. Here in the midwest, where a lot of ethanol comes from, and is promoted a lot, you get it in a lot of your gas, sometimes you are not even told about it. With 5 years of experience with it in a 912S, can't say I noticed any difference.
John Bender
Rotax seems to be OK with up to 10% Ethanol. Here in the midwest, where a lot of ethanol comes from, and is promoted a lot, you get it in a lot of your gas, sometimes you are not even told about it. With 5 years of experience with it in a 912S, can't say I noticed any difference.
John Bender
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There is a lot of info available if you look through the 4 stroke engine service letters, etc. It will explain in detail approved fuels and what is required for maint. depending on which fuel you are using.
If you use avgas rotax spells out what you have to do. For example if you use more than 30% avgas, don't use full synthetic oil, use semisyn. Change it more frequently. Change out your plugs every 25 hours, cruise at a higher RPM, take your oil tank off more often and clean it out, etc. There is also a requirement to take your gearbox off periodically and clean out the lead scum that builds up. The rotax manual spells it out.
Basically, I always use non ethanol mogas when I am near home. Problem is if you go anywhere you most likely will be sticking in avgas. I would use up to 10% ethanol over avgas anytime as long as Vans doesn't say otherwise.
Basically, I always use non ethanol mogas when I am near home. Problem is if you go anywhere you most likely will be sticking in avgas. I would use up to 10% ethanol over avgas anytime as long as Vans doesn't say otherwise.
Geico266
Well Known Member
lewy Welcome to VAF
When traveling cross country you can find mogas available at airports if you do some pre-planning with AirNav fuel search.
http://www.airnav.com/plan/fuel/
Put in your airport and your destination, under "Fuel Types" click mogas.
Under "Where to Refuel" Click a time period, I use the last 6 months.
Under "What Time" click 24 hour service and you will get the airports with credit card readers.
It will list the airports along your route with mogas and prices.
It's a good idea to call ahead to make sure they still have mogas, but I have found this service to be most helpful in getting mogas. If all else fails use 100ll. As soon as you can get to mogas start diluting the 100ll.
When traveling cross country you can find mogas available at airports if you do some pre-planning with AirNav fuel search.
http://www.airnav.com/plan/fuel/
Put in your airport and your destination, under "Fuel Types" click mogas.
Under "Where to Refuel" Click a time period, I use the last 6 months.
Under "What Time" click 24 hour service and you will get the airports with credit card readers.
It will list the airports along your route with mogas and prices.
It's a good idea to call ahead to make sure they still have mogas, but I have found this service to be most helpful in getting mogas. If all else fails use 100ll. As soon as you can get to mogas start diluting the 100ll.
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kell311496
Member
Even though the airport directories indicate mogas, there is no way to know if it is 91 or 87 octane without calling. I am finding mostly 87, which is unacceptable for the 912 ULS. Given the choice of 87 octane or 100LL, you must choose 100LL.
the_other_dougreeves
Well Known Member
From Rotax and others, E10 seems to be Ok if the aircraft's fuel system is up to it (fuel tank, lines, etc). Given the choice between lead and EtOH, you're probably better off using the E10 gas and not putting lead into the engine.
100LL won't harm the aircraft, but it does mean shorter time between oil changes and lead will accumulate in the engine, particularly in the gearbox.
TODR
100LL won't harm the aircraft, but it does mean shorter time between oil changes and lead will accumulate in the engine, particularly in the gearbox.
TODR
Ya'll probably already know this, but just for peace of mind, Rotax officially approved up to 10% eth. in the engine this past spring. The SI is SI-912-016 available at rotax-owner.com.
I've been using 10% premium mogas in my 912ULS since then with no problems, even up to 10,000' MSL...
LS
Geico266
Well Known Member
87 Octane will run just fine in a 912 if that is all you have. If the octane level concerns you mix 87 & 100ll. It is the lead you are trying to avoid, not the octane level.
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I strongly recommend RV-12 owners do NOT use fuel with an octane lower the what is recommended by Rotax (92 octain).
The 912ULS is a high compression engine.
I fact, this summer rotax issued a service letter recommending against any propeller (or pitch adjustment) that results in clime mode RPMs of less than 5200 at takeoff power because of the higher resulting combustion chamber pressures which reduce the separation safety margin from detonation.
Geico266
Well Known Member
The response I made was to a question about going cross country. If 87 octane fuel is available Rotax recommends using that over 100ll.
Rotax Documentation SI-912-016
States in part: "Avgas 100LL places greater stress on the valve seats due to it's high lead content and forms increased deposits in the combustion chamber and lead sediments in the oil system. Thus, it should be only used incase of problems with vapor lock or when other types of gasoline are unavailable."
Other types of gasolene are further described in ASTM D4814.4
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Larry,
I need to disagree with you. There is nothing in SI-912-016 that says it's OK to run 87 in an engine where rotax specifies 91. What the SI is saying is that they want you to run the appropraite grade of mogas if it's available. For the 80 HP that means 87 octane or better but for the 100 HP its 91. If you put 87 in the 100 HP you are going to end up doing damage. This is my opinion. Unless I see something in writing from rotax, I would never put 87 in my 912 ULS. Let us know how your engine is doing after running 87 for about 10 hours, especially on a hot day.
I need to disagree with you. There is nothing in SI-912-016 that says it's OK to run 87 in an engine where rotax specifies 91. What the SI is saying is that they want you to run the appropraite grade of mogas if it's available. For the 80 HP that means 87 octane or better but for the 100 HP its 91. If you put 87 in the 100 HP you are going to end up doing damage. This is my opinion. Unless I see something in writing from rotax, I would never put 87 in my 912 ULS. Let us know how your engine is doing after running 87 for about 10 hours, especially on a hot day.
Geico266
Well Known Member
We are talking about going cross country. If you have a choice between 100ll or 87 Octane I would add 2 gallons to the 87 octane and call it good. You know what the lead will do in the engines.
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Geico266
Well Known Member
I'm no expert on fuel for the Rotax 912S, I just don't want people to get the idea that these engines cannot go cross country due to the lack of mogas. I have made many cross country trips and have never had any problems getting fuel, or causing damage to an engine because of my fuel choices. Most people say just use 100LL and IMHO that is not the way to go. I have seen first hand the deposits lead makes in the gear box, oil tanks, journals having replaced the sprag clutch & spring assembly in a 912S. Use mogas when you can and use 100ll sparingly to avoid lead deposits and sediment in the engine.
JMHO.
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Agreed. In the 200 hours I've put on my CT it has rarely seen 100LL. Having a 34 gallon capacity helps. Check out www.ctflyer.com. CT owners are flying coast to coast. They are not letting fuel issues stop them.
If you have the 912ULS and the choice is between 87 octane mogas and 100LL you MUST use 100LL OR a 50:50 blend of the 87 and 100LL (there's an SI that states blending to get the correct octane rating is OK, can't remeber what it is offhand tho) to get the net octane up to meet the requirements of the motor. With the 80 horse version, tho, 87 is fine.
But at 20 grand a pop for the 912ULS, this is not the motor you want to be experimenting with too low of an octane fuel with. Detonation will knock a whole bunch more off the motor's TBO than a few tanks of 100LL!
100LL is ok in the 912 series (with the maintenance caveats) - this is from Rotax and their dealers. Too low of an octane gas is NOT ok under any circumstances.
Out in the field, the 912 series burns lots of 100LL on cross-countries without any ill effects. One gentleman I know has close to 3000 hours flying 912ULS's across the US burning all 100LL on the trips. He's on his 3rd engine now, the previous 2 having gone to TBO and past it a bit and were still running fine when he pulled them off for replacement.
Don't be paranoid about filling up with 100LL on a trip. Just remember to double the oil change interval if you use a lot of it and run the engine hard. It'll be fine.
It's only when you run 100LL exclusively, all the time, that you eventually run into problems. But if you're out in the wild for a few weeks and can only get 100LL, don't worry about it.
LS
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Geico266
Well Known Member
