0-360 autogas STC

[w cary]

Has anyone info on the feasability of the mogas stc? Are there mods required to eliminate thermal or vapor lock issues? Cost of an STC? This eng. is in my RV6 w/ 350 hrs smoh.
Bill
KC

[Mel]

Supplemental Type Certificate (STC) does not apply to experimental aircraft.
Experimental aircraft do not have a Type Certificate, so there's nothing to supplement. It is up to the owner/operator of an experimental aircraft to determine what is appropriate. It is generally good practice to follow STC guidlines and operating procedures.

[osxuser]

You can pretty much just use mogas in your low-compression O-360 if you want. Just make sure the mogas doens't have ethenol in it first. (Most does now.)

[gmcjetpilot]

Originally Posted by w cary

Has anyone info on the feasibility of the mogas stc? Are there mods required to eliminate thermal or vapor lock issues? Cost of an STC? This eng. is in my RV6 w/ 350 hrs smoh.
Bill KC

I'll give you the CON of auto fuel. I am sure some will tell you about there positive experience. I'm no expert on the subject but I looked into it for my Plane. KC for the O360 you have to use premium, the O360 is not a low compression engine. The O360 is considered a moderately high compression engine at 8.5 to 1. It needs 91 octane, that would be premium gas. Mogas at airports I believe is not high enough. It is OK for 80/87 octane engines. So you are out of luck with your 91 octane engine. However if you can get suitable premium auto fuel into your plane, yea it might work with a lot of caveats, but how do you get premium auto gas in your plane?

The biggest problem is variation in quality of auto fuels and additives and enhanced fuels that can damage our engine or even make it loose power (ie vapor lock). Also RV's have tight cowls, which is not good for running auto gas that is prone to vapor lock with lower vapor pressure than Avgas. You can take precautions. The question you will have to ask yourself at the end is the cost savings, may be $4/hr, worth the risk and hassle.

By auto fuel I mean fuel you buy at the local car gas-station. You have to haul it to your plane in your vehicle. So there you are with a trunk of 5 gal jugs that you are toting over the wing a poring into the tank (and on the wing).

Finding un-altered auto fuels without additives, like ethanol is getting impossible. The idea of handling fuel, transporting and storing it, is also not my idea of fun or even safety. You will have to test you fuel to assure it does not have too much alcohol in it. Also its not possible to really buy auto gas on a cross country. I would avoid do-it-your-self auto-fuel like the plague myself.

Mogas is no good for the O360. The O360 is designed for 91 octane. Mogas is typ 80/87 I believe. The O235 is also a higher compression engine needing 91 octane.

Mogas, short for motor gasoline, is auto gas you can buy directly from a pump right at the airport. You can find it at some airports but not all or even many. When you can find it the price difference is small verses 100LL. It is a volume thing. They just sell more 100LL. It is about 40-60 cents more for 100LL, but it's available at 100% of the airports with fuel. Mogas is limited, even if you could use it. There may be a new UL91 (unleaded) fuel we can pump at the airport coming down the road some day (may be never?). Right now all we have is Avgas 100LL and low oct mogas at few airports and not really that cheap either.


Remember RV's are tightly cowled (hot). A vapor return line from the carb fuel line back to the tank is recommended. A "T" right at the carb and incoming fuel line has a small return line with a restrictor. This allows air bubbles to return to the gas tank or a place where it can mix back with cool fuel. You can (should) also extensively insulate and shield all fuel lines, gascolator, fuel pump and carb. Air-blast tubes and shields may be a good idea.

Remember the STC for factory planes is not only for the engine but the installation. There are some factory planes that can not get STC's, even after much effort. The reason is vapor lock from tight hot cowls. I took the hint myself. I think the Mooney is one that does poorly on Autogas and is not approved.

Personally no thanks to auto fuel. Go out and really shop price on premium auto gas or Mogas (assuming you could use it). Now shop price on 100 LL. Look local and cross country. You'll find the price difference is not that great.
You will also find Mogas availability can be poor even if you could use it. The savings is not worth the risk and hassle to me.

As far as getting car gas from the corner station, it has problems. There are laws, both highway and airport, about doing your own fueling. I just hate fueling from Jugs or Cans. Getting a big tank or 55 gal barrel drum and pump in the back of a pickup does not appeal to me. There's no way the airport will allow you to have a gas barrel in your hanger if they know about it. Also the gas station may have something to say about you backing your truck up with a big barrel drum to fill. I don't know, I never did it.

Also You have a high risk vapor lock and damaging seals if you get gas with alcohol or ethanol. If you had and engine that could run on 80/87 octane, which you don't, Mogas would make more sense, but even than I would not mess with it. If you do a lot of cross country forget it, since you will be fueling with 100LL Avgas mostly anyway. You have to decide if the fuel savings is worth it for local flying and carrying around Jerry cans around in your truck or car is doable. Don't forget all the aircraft modification you will need to make under the cowl to the fuel system, including a vapor return line and insulation.

I know one guy who uses autogas in one tank and Avgas in the other. He starts, takes off and lands with the Avgas and cruises with the mogas. The idea is to reduce vapor lock which he was having problems with. Hey if it's ain't good enough to takeoff , climb and land with I don't want it in my plane.

[mahlon_r]

If you install low compression pistons(7:1) in the O-360 you will de-rate the engine from 180 HP to around 168HP but you can then use the lower octane auto fuel from an octane stand point. The 7:1 compression ration engine is rated for 80 octane av gas not 91/96 like the 8.5:1 180 HP version.
Good Luck,
Mahlon
?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at you own risk.?

[RVbySDI]

Originally Posted by gmcjetpilot

You have to decide if the fuel savings is worth it for local flying and carrying around Jerry cans around in your truck or car is doable. Don't forget all the aircraft modification you will need to make under the cowl to the fuel system, including a vapor return line and insulation.

But, if I have the ability to have my own fuel tank at the airfield (because it is on my property) I can control what fuel I use and the ease and safety of fueling my plane becomes a non-issue. If I build my airplane with the fuel system designed to accept non-100LL fuel (because it is going away) I do not have problems with vapor lock or other issues that have been engineered out of my airplane. Yes all of those things George mentioned are things to consider, but if a builder can address all of those "things" then where is the problem?

Originally Posted by Mahlon

If you install low compression pistons(7:1) in the O-360 you will de-rate the engine from 180 HP to around 168HP but you can then use the lower octane auto fuel from an octane stand point. The 7:1 compression ration engine is rated for 80 octane av gas not 91/96 like the 8.5:1 180 HP version.

I appreciate Mahlon's answer here as well as in other posts. There are ways and means for doing pretty much anything that we as builders think about doing. Why not do it if you feel that doing something is going to work out best for you? We don't all live in LA, DC, NYC or any other large metropolis with a restrictive airport environment that would limit our abilities. Others have done it so why not you? Besides, even if others have not done it, that doesn't mean that it isn't a feasible idea that you could make work for you.

[Jconard]

But, if I have the ability to have my own fuel tank at the airfield (because it is on my property)

Don't bet on it. Owning property does not guarantee that you can store what you want on that property. Municipalities, and regulatory agencies (The Metropolitan Airports Commission in my case), can regulate a number of issues, and of course fuel storage is one of them.

Remember also that fuel with alcohol in it will result in higher fuel consumption because it has a lower specific heat content per volume.

When I was racing, periodically a sanctioning body would specify some pump gas as a required fuel. You had to buy it at a specified gas station next to the track, and they used an electronic measuring device to compare your sample to the known sample. This was to save the racer money. What it actually did was result in blown engines, or needless disqualifications, because of the vast inconsistency. If the track bought their sample on Wednesday, and the gas station got re-supplied before the weekend, the racers who bought fuel on Saturday often had gas that did not match.

In addition, pump gas was just unsuited for race engines and tuning, it was a garbage disposal combination of different additives.

Most racers would bring their own race fuel, in sealed drums, and their own fuel measure. By adding Nitro methane, we could often make race gas match the sample. We had to cheat to be legal.

All this is said just to point out that car fuel is not consistent, or predictable.

[RVbySDI]

Originally Posted by Jconard

Don't bet on it. Owning property does not guarantee that you can store what you want on that property. Municipalities, and regulatory agencies (The Metropolitan Airports Commission in my case), can regulate a number of issues, and of course fuel storage is one of them.

Well, I live in farm country where every farmer has multiple fuel tanks for diesel, gasoline, even propane. I have a propane contractor drive their truck right up to my backyard to fill up my propane tank. Fuel trucks from the local COOP deliver farm fuel all day long.

I agree with you that one can never be sure of the quality of the fuel at any gas station. However, I would also have to say that the same goes for any airport in America dispensing 100LL. Why should I trust fuel from an airport tank I have never used before any more than the gas station on any interstate in America? Yet, how much thought do any of us give to whether that fuel at the local gas station is going to blow up our car engine or not? Anyone who is honest with themselves would have to say they give no thought at all to the notion that some tankfull of gas they got at the local 7-11 will destroy their engine.

[tomcostanza]

Mahlon,

Is it possible/practical to build an alcohol (gasahol) friendly engine?

Tom

[Jconard]

Why should I trust fuel from an airport tank I have never used before any more than the gas station on any interstate in America?

1. Because 100LL is a standardized national blend which cannot be altered by localities the way that auto fuel can and is.

2. Because 100LL is standard in the winter and in the summer, so there is no mixing of additives between two blends of fuel every season.

3. Because the ability to trace fuel contamination back to one pump and create huge liability is much easier.

4. Because the 100LL fuel itself is much less subject to break down over time, it is more stable.

5. Because the fuel itself is not hygroscopic, and offers some margin against all the various water issues.

6. Because the dye used in 100LL will go pale if mixed with other fuel, instantly telling you if there is contamination.

7. Because your average FBO is owned and staffed by professional with a level of knowledge and concern that goes far beyond the nose-ring manager at the local 7-Eleven.

As to the farm, I am not sure if you can put farm fuel in an airplane. I know you cannot put it in a car, in fact in many states there is a red dye, in the fuel to prevent this because that fuel is sold without highway taxes. I imagine it is also sold without aviation taxes, state-federal-or local.

Using this fuel in a car can, and has subjected people to liability under the tax code. Buying untaxed fuel to use in a vehicle subject to fuel tax seems like a good way to draw negative attention to oneself.

Oh, and most of the farmers today must get a permit for the fuel tank.