LeSving wrote:
Theoretically it should work just fine, but in practice the 91UL has lower octane than 95 mogas for some reason.
Why should it not… You can’t directly compare the octane rating of AVGAS and MOGAS as they’re measured in different ways. The 91 octanes in AVGAS are measured as MON, while the 95 octanes in MOGAS are measured as RON. For the same fuel the MON number is lower than the RON number.
Airborne_Again wrote:
But that will happen eventually. Lead is a really nasty substance and the efforts in the US to find a replacement for 100L wouldn’t have happened if there wasn’t a real risk for a ban on 100LL.
Yes but when is the big question… could be many decades. Of course a developer of a fuel like this must have an idea/hope for something to happen otherwise they wouldn’t put in the investment. However so many things in aviation are just ideas with a huge development pricetag, that never really take off. But maybe a state like California could do its own thing here? EU as well but price would be a major issue with all the taxes added on top of the base price…
Airborne_Again wrote:
The 91 octanes in AVGAS are measured as MON, while the 95 octanes in MOGAS are measured as RON
Yes, and mogas 95 is 85 MON. Obviously something very fishy about this 91 UL. When I was at the ULPower factory a couple of years back, they simply said don’t use 91UL.
I can’t wait for unleaded fuel to be widely available to the market. I’ve had 3 stuck exhausts valves so far this year and I would like to think this will be reduced if we had the option to run on unleaded fuels.
LeSving wrote:
When I was at the ULPower factory a couple of years back, they simply said don’t use 91UL.Exactly, I heard it also in some German aircraft maintenance shops. Rotax even officially banned 91UL for the 914 engine, so our Super Dimona with the turbo engine may only refuel Mogas 95/98 RON or Avgas 100LL from now on.
It sounds strange though. UL91 is reportedly 100LL without lead. So if 100LL and 95/98 RON are ok, then UL91 should be as well, as octane is higher than 95/98 RON fuel and there is nothing in there which isn‘t in 100LL.
Is the 10% alcohol car fuel OK in the Rotax? (And in the various tanks – for sealant.)
Absolutely: https://legacy.rotaxowner.com/si_tb_info/serviceinfo/si-914-019-r11.pdf
si_914_019_r11_pdf
UL91 is also not at all a problem for ALL Rotaxes (including the 916 iSc Turbo). All it takes is a look at the appropriate documents….
“And in the various tanks – for sealant.” – That is a whole different story.
It is still a question of availability too. There are some UL91 airports in Switzerland, I am not quite sure how many. We have made a point of fuelling UL91 whenever we can on the Mooney and so far we had no problems, I expect that if we could fuel 100% with UL91 we would certainly have a cleaner engine.
GAMI makes a very strong case here and it should be looked at. The obvious advantage of getting rid of lead are more than enough to really make an effort to get the fuels more distributed. It would already be great if UL91 gets available more for those engines who can use it (which are quite a lot seeing that all O360/O320 and many more lower hp engines e.t.c can use it).
europaxs wrote:
UL91 is also not at all a problem for ALL Rotaxes (including the 916 iSc Turbo). All it takes is a look at the appropriate documents….Our mechanics received a service bulletin from Rotax, where UL91 was banned for use with our Rotax 914 engine. It might not be banned for other engines, but it was a clear statement. In addition, our engine runs with 95/98 RON or 100LL quite a bit smoother, even though the use of 100LL requires an oil change every 50 hours, instead of every 100 hours. This finding was also confirmed by our maintenance shop and mechanics.
