Fuel STC (AEIO-360)

N

n303sb

New member
Good Morning,
I recently purchased a 2001 Decathlon and am very happy with it - it's a fun and forgiving plane. I have noticed that there's a placard next to the fuel filler caps that states "91 & 96" octane fuel. I've been using 100LL since purchasing the aircraft. Does anyone know if there's an STC that allows use of a lower octane fuel? My operating manual states that only 100LL should be used and I can't find any paperwork in the aircraft logs that refer to an STC.
I'm mostly interested because of lead fouling; it can be quite a serious problem when I'm doing pattern work (low power, full rich). I've ordered some new plugs that are less prone to fouling and am thinking about GAMI fuel injectors to even out fuel flow among the cylinders. THis should help but probably won't eliminate the fouling problem.
If the plane can use 91 octane fuel, would ordinary automotive fuel (91 or 92 octane) work?
Sincerely,
Mark
N303SB
 
I looked at Peterson and Eaa's list and I don't see your engine, in fact none of the injected Lycomings have an STC. Peterson does have some of the Cont. 470's that are injected.



Woodie
N29763
 
I too am wondering if there is anything out there in existence. My decathlon is a 76 and the caps say 87 octane, i was wondering if i could even get an auto gas stc.
Herm
 
Additives in Autogas may or likely may NOT be friendly to the rubber in the Fuel Servo in Lycomings. If the diaphrams that regulate the fuel pressure recieve much contamination at all, the engine has issues.

This is how it was stated to me anyway.
Its consistant with why the STC does not cover injected Lycomings.

"That's my story and I'm sticking to it."
:)
 
Another big factor in the question of auto fuel in the injected engines is the possibility of vapor lock. In the injection systems vapor lock is a real possibility. Any time you have metal lines that are exposed to the heat that these engines give off and it under pressure you can get vapor lock.


Woodie
N29763
 
woodie,
i am new to aviation and ignorant to the chemical differences in auto fuel vs aviation.
why would auto fuel be more likely to vapor lock than avgas?
thanks in advance.
Herm
 
I can't give you the exact reason. Some of the other guy's here can probably give the chemical reason. I do know that auto fuel is oxygenated along with different additives. Someone at Peterson or the EAA would probably be happy to explain the reason none of the injected engines have an STC.

Woodie
N29763
 
One of the differences between av and auto gas is that auto gas is blended to different vapor pressures for varying times of the year in your location. Avgas is more consistant. If a fuel has more vapor pressure (which makes atomization throught the venturi easier) then it will also vapor lock easier. The colder the outside temperature (time of year) the higher the vapor pressures will be in auto fuel (to help it atomize).

This is an oversimplification, of course, but it does give the 'gist' of the story.


Blair
 
wjwilson2000 said:
Another big factor in the question of auto fuel in the injected engines is the possibility of vapor lock. In the injection systems vapor lock is a real possibility. Any time you have metal lines that are exposed to the heat that these engines give off and it under pressure you can get vapor lock.


Woodie
N29763
Click to expand...

Woodie,

Are you talking about the fuel being under pressure? Pressure REDUCES the chance for vapor lock. Vapor lock occurs when the fuel boils, and increasing the pressure on a liquid raises the boiling point.

Michael
 
That is true, that's the reason for your car having a pressure cap,but also remeber that a vapor will compress where it takes a "great" deal more presure to compress a liquid. What would happen would be the fuel vapor could compress rather that the fuel being moved possibly. That being said I really don't know how much faster auto fuel would turn to a vapor vs 100LL. I do see some fuel injected engines that have available STCs for the use of auto fuel, I think it calls for 93 Octane. That would make me think that on these engines it's possibly a detination problem that keeps them from using reg. unleaded. It would be worth a call to Peterson just to get some answers on this topic. Hey maybe you can get an STC for injected 320's & 360's you'd make a killing!!! My O320A2D dosen't even know what 100LL taste like anymore!!!


Woodie
N29763
 
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