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  #11  
Old 06-21-2012, 04:42 AM
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Geico266 Geico266 is offline
 
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Running a mixture of 87 octane and 100ll works fine. I would tend to use less of the 100ll though, the 912 does not like the lead. A 25% 100ll and 75% 87octane works well.

Earlier, a post talked about a very clean engine running a mixture and that make sense to me. Good info BTW.

Stay away from continually 100ll use no matter what the manual says. Fying cross country burning 100ll is fine, but mix it with non leaded as much and as often as you can. Change oil every 25 hours for two or three times after that to clean out the lead. Get back to a diet of non leaded fuel as soon as you can.
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  #12  
Old 06-21-2012, 07:04 AM
Randy Randy is offline
 
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Default Octane Calculator

Search on octane calculators and many are available on the net. This calculator says that mixing 20 Gal. 87 regular with 10 Gal. 100 LL will result in 91.3 Octane.

http://www.serioussolutions.com/evo/octcalc.htm

I have read that there are no magic additives that somehow chemically react to increase octane, rather it is strictly a matter of ratios of the fuels that are mixed.
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  #13  
Old 06-24-2012, 06:14 AM
HDDAHL HDDAHL is offline
 
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I would think that lead in the avgas would kick the octane level higher than the arithmatic average. Any thoughts?

Doug Dahl
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  #14  
Old 06-24-2012, 10:38 AM
NASA515 NASA515 is offline
 
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It would seem that production and marketing of UL 91 (100LL without the lead) would solve all of our Avgas/MoGas/Octane/Ethanol problems in one fell swoop. This fuel is beginning to appear in Europe.

Maybe Lycoming's recent actions will act to spur activity in this country - but don't count on it.

Announcement here:

http://www.aopa.org/aircraft/article...WT.mc_sect=gan

and a good discussion of the technicals and problems here:

http://www.generalaviationnews.com/2...l91-explained/

Bob Bogash
N737G
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  #15  
Old 06-28-2012, 03:37 PM
dick seiders dick seiders is offline
 
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Bob et al, thanks for the info. Referring to your (Bob's) comment about importing ul91 to the states I just read in Aviation News that the FAA is demanding fuelers come up with an unleaded avfuel promptly and they're only getting till 2018 to do it. Wow! What pressure. Given the fact fuel creators have been alledgedly working on that goal for yrs already I am underwhelmed with the target date.
I discussed as I said I would earlier the 90ul ethanol free fuel at Madison (ga) with the City Mgr. He was very interested and stated he would look into it. I informed him that I, nor any other rotax100 drivers could use the stuff, and also mentioned the fact that Marathon Oil says the fuel is NOT to be used in aircraft. I suspect that got his attention as it did mine given the position of Marathon the use of the fuel in aircraft suggests a transfer of liability in the event of fuel issues arising. So that's it for now. I will follow up in a few weeks to see if any conclusions and/or changes are made as to what fuel would be offered. It doesn't appear that anything else (other than 100ll) will be available, but I am still curious to see whether the 90 E0 Rec. Fuel will be offered. When I learn more I will post it here.
Dick Seiders
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  #16  
Old 06-28-2012, 04:41 PM
MLock MLock is offline
 
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Larry,

You gotta come talk to the engine in New Blue and tell it that it doesn't like 100LL. It doesn't know.

The engine has over 600 hours on it, the last 410 has been nothing but 100LL with decaline. I have seen no ill effects. I maintain the engine as per the maintenance schedules and it's just a purring right along.

On second thought, please don't come and tell it. Apparently what it doesn't know won't hurt it.
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  #17  
Old 06-28-2012, 04:55 PM
MLock MLock is offline
 
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As an additional note, next week New Blue is going down for annual. We'll be changing oil, plugs, wiping out the oil tank, rebuilding the carbs, changing coolant, and everything our Rotax mechanic out here says we need to do.

Believe me, if I see something that can attributed to the steady diet of 100LL it gets, I'll be certain to let everyone know.
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  #18  
Old 06-28-2012, 05:56 PM
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Jetguy Jetguy is offline
 
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Thumbs up How about this one!

Well, there is that one thing. "rebuilding the carbs". Would you have to do this if you were running pure Unleaded? Could you share what the cost is to send them off to get them rebuilt? Just finished another set of happy trainees.Thanks
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  #19  
Old 06-28-2012, 06:40 PM
dick seiders dick seiders is offline
 
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John. I believe carb rebuild is a Rotax requirement at 500 hours.

Mitch , sounds like you are doing fine on 100ll. Please keep us posted on what you find. Thanks.
Dick Seiders
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  #20  
Old 06-28-2012, 07:16 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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There are only two maint. interval differences, caused by the (majority of the time) use of 100LL that I am aware of.

1. Plug replacement is supposed to be done every 100 hrs instead of every 200.

2. The first gear box internal inspection is due at 600 hours instead of 800 hours (This is from memory, someone correct me if I have it wrong).
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