Auto Fuel STC

[rcarson]

Does anyone know if the O320 has an STC for autofuel. If 110LL goes away it may be advantageous to look at a lower horsepower engine with that capability. Has anyone checked into this and if so what were the results?

[flytoboat]

If it's for an experimental, you don't need an STC

[asav8tor]

STC would not apply to an experimental.

[Garage Guy]

EAA's autogas STC list is here: http://www.eaa.org/autofuel/autogas/approved.asp, and Petersen's is here: http://www.autofuelstc.com/autofuels...d_Engines.html

You will see that several versions of O-320's are on those lists.

But as noted above, since RV's don't have a TC, they don't have a way to attach a STC.

--Paul

[carguy614]

I too am wondering if this will be an issue in out NEAR future, and did some investigation into the usability of auto fuels. My Superior 160 HP engine is OK for 93 octane unleaded auto gas. The 150 HP with the 7 to 1 is also OK, and you can run a lower octane fuel in that engine, but I am not sure of the Minimum octane. A long discussion with Superior a couple of years back confirmed this, and the general rule of thumb was no auto fuel if you have compression ratio greater than 8.5 to 1. for the 160, Superior also recommends retiming to 22 degrees BTDC if you will be using Mogas. I thought a lot about the 160 HP 8.5 to 1 engine that I have going into my RV9 project. I decided not to derate it to 150, based on the hope that there will be 93 octane auto fuel sans the ethanol. So far, that has been available here on the NC coast at most of the marinas.
I am sure others will chime in on the subject with vastly differing opinion, as there seems to be much current discussion on the subject.

Hope this helps,
Chris

[rcarson]

The idea about finding an STC is the person who filed it had to have specific information about what mogas will do to the engine and the reasons it will work. I am aware that it requires lower compression and different timing. My concerns are lead is also a lubricant on valves and while I was using mogas in a previous aircraft I had an exhaust valve stick on take off. Often times information is available from the holder of an STC about such concerns. Thank you all for your replies and keep them comming.

[Garage Guy]

So far as the STC's go, lack of lead is not as big an issue as presence of ethanol. Both EAA and Petersen STC's say "DO NOT burn fuel with ethanol in your airplane".

--Paul

[rcarson]

Originally Posted by carguy614

I too am wondering if this will be an issue in out NEAR future, and did some investigation into the usability of auto fuels. My Superior 160 HP engine is OK for 93 octane unleaded auto gas. The 150 HP with the 7 to 1 is also OK, and you can run a lower octane fuel in that engine, but I am not sure of the Minimum octane. A long discussion with Superior a couple of years back confirmed this, and the general rule of thumb was no auto fuel if you have compression ratio greater than 8.5 to 1. for the 160, Superior also recommends retiming to 22 degrees BTDC if you will be using Mogas. I thought a lot about the 160 HP 8.5 to 1 engine that I have going into my RV9 project. I decided not to derate it to 150, based on the hope that there will be 93 octane auto fuel sans the ethanol. So far, that has been available here on the NC coast at most of the marinas.
I am sure others will chime in on the subject with vastly differing opinion, as there seems to be much current discussion on the subject.

Hope this helps,
Chris

Did you purchase the Superior engine and if so how did it work out for you?

[Hum]

http://www.youtube.com/watch?v=1O5sBrq4MJM

[Neal@F14]

Originally Posted by carguy614

The 150 HP with the 7 to 1 is also OK, and you can run a lower octane fuel in that engine, but I am not sure of the Minimum octane.

Minimum octane is 87 and the 150hp O-320 will run just fine on 87 octane regular unleaded without a trace of any evidence of detonation. I have the Petersen STC for my Cherokee and have used autofuel in the past with great success before they started added ethanol here in Texas and also outlawed the sale of those nice 6 gallon easy-pour plastic "Blitz" jerry cans, which together made hauling gasoline to the airport too much of a hassle for the small cost savings.

However, after flying around in a Cherokee 140 on a really hot Texas summer afternoon (e.g. > 110+ deg F), with 87 octane unleaded regular, after you shut the engine down and let the engine's built-up heat boil the contents of the fuel system forward of the firewall for a few minutes, it will vapor lock pretty badly on the ramp, making a hot start near impossible until the cowl is opened up to let the heat out and cool down for a while, whereas I've never had any vapor lock problems with 91 octane super unleaded or with 100LL avgas.