REFLECTOR: High temps

[Jim Sower]

I can't speak to your "octane additives".  Perhaps Jim Agnew or Don 
Royer could speak to that.  I would suspect that it might depend on what 
you coated the inside of your tanks with.

I do know that alcohol is REALLY bad for composite tanks.  Actually, 
alcohol won't hurt them and water won't hurt them, but alcohol and water 
mixed is very damaging and of course if you have alcohol, it's bound to 
end up with some water in it.  That's the bad news.  The good news is 
that it's really easy to test for alcohol.  For the most part, you can 
plan on finding alcohol in the gas stations in [agricultural] states 
that mandate it and in and around metropolitan areas that are not 
meeting EPA air quality standards.  Here in central TN there isn't any.  
LA would be another matter.  MTBE and ETBE do not damage composites. 

I have heard of people taking a coupon of a glass sandwich structure, 
prepped and painted various ways, stored in a jar of Mogas for a 
substantial period with no discernible damage.  The ones I have heard of 
are anecdotal tests.  Haven't heard of anything notably scientific.  Has 
anyone heard of anything systematic research around this issue??  I 
would hope that the factory would look into the issue seriously.

Everyone needs to be looking at Unleaded Avgas since it will certainly 
replace 100LL, and probably sooner rather than later.  For the most 
part, it promises to be a boon to engine life and reliability but there 
are bound to be areas where conversion might be problematic.  Composite 
tanks are potentially one of those areas.

I am personally confident that it will be a manageable problem ... Jim S.

John Dibble wrote:

>Thanks, Jim.  My next question is if the auto gas is compatable with the standard velocity tank?  The octane additive in auto gas is an ether which is in a chemical family close to alcohols and acetone.
>
>John
>
>Jim Sower wrote:
>
>  
>
>><... Has anyone with a Lycoming tried a lower octane fuel ...>
>>I have used hi-test auto gas (93 pump octane =~ 87 motor octane) and did not notice any difference (except on my bank card bills :o).  About 75% of flat aviation engines are designed for 80 octane.  Regular mogas is 82 octane.  There's a lot of interesting reading (about a dozen documents) on mogas on the EAA web site - search on auto gas.  Unleaded regular auto gas IS the unleaded avgas of the near future.
>>
>>Embry Riddle has used nothing else for years ... Jim S.
>>
>>John Dibble wrote:
>>
>>    
>>
>>>I have a Franklin, not a Lycoming and no temp problems.  Has anyone with a Lycoming
>>>tried a lower octane fuel?  My experience with Rotax engines is that using a higher
>>>octane fuel than what the engine requires results in high CHTs (50 F higher, enough to
>>>sieze the engine).  I think 100 LL is higher octane than any normally aspirated engine
>>>should need.  Several Cessnas in my flying club use 50/50 avgas/regular.  In a pinch,
>>>I have topped off my tanks with regular and couldn't see any difference in performance
>>>or other problems.
>>>
>>>John
>>>
>>>Jim Sower wrote:
>>>
>>>
>>>
>>>      
>>>
>>>>I am running a LIO-360-C1E and even after a lot of work on the baffling
>>>>have CHTs around 375 - 400 with occasional excursions to 425 which I try
>>>>to correct for.  From the beginning, my oil temp never ever budged off
>>>>of 180, but more recently I have had oil temps up to 210 - 220 on
>>>>occasion.  I think part of this might have to do with the firewall oil
>>>>cooler which exhausts right into the plenum - the high pressure air for
>>>>cooling the cylinders.  There can't possibly be much air flow through
>>>>that cooler, and I regard it as a significant design defect.  At some
>>>>juncture (after I get the engine running again and the plane annualed) I
>>>>am going to exhaust it to outside air under the cowl.
>>>>
>>>>Glad I'm not the only one with high CHTs ... Jim S.
>>>>
>>>>
>>>>
>>>>        
>>>>
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