REFLECTOR: High temps

[Jim Sower]

<... 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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