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Subaru running on LPG

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Brünner

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As the title says.
Has anyone ever done it? I think there were several Subaru cars running with after-market kits, would it be feasible to do it on an airplane?

Thanks,
Brünner
 

plncraze

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There was a Starduster in Sport Aviation in the 70's that had a Continental radial that ran on propane. Also there were manuals printed for people to convert car engines to propane. Start your search propane vaporizer regulator kit. Impco might have made one.
 

berridos

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Its super easy to convert the honda generators to propane. A 5 min job and they work much better and cheaper afterwards
 

Vigilant1

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Useful if you are someplace where you can get propane but not good mogas, or some other niche cases (very high taxes on mogas that make it much more expensive than propane?). Other than that, it is not very popular due to the higher weight of the containment vessel and the lower btu/gal of propane (so, a larger container needed).
 

plncraze

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Oh yes, the tank! On the above mentioned Starduster the front pit was replaced by a fuel tank making the airplane a single seater. The owner, who wanted low operating costs, had no problem with this since he was never going to fly anywhere and the fuel was delivered to him cheaply and his spark plugs would last longer!
 

BBerson

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Propane has more energy per pound. Measure range by fuel weight, not gallons. I bet homemade integral tanks could be lighter using EA-B standards instead of consumer.
 

berridos

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Winding lpg containers out of carbon roving makes very strong lightweight tanks. There are companys doing this. Guess the danger is they havent got any plastic deformation at crash
 
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Vigilant1

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I bet homemade integral tanks could be lighter using EA-B standards instead of consumer.
The details of use would be important. I wonder what type of hoops one would need to jump through to get approval to store LPG in an enclosed municipal airport hangar if it isn't in a DOT approved bottle. And if the tank is integral to the plane, we'll need some way to flow LPG into it (rather than bringing a full 30 lb bottle to the plane and swap it out). Certainly not impossible, but another thing.
 

BBerson

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Propane will flow by gravity if the bottle is upside down. Or call the propane truck if you want 50 gallons.
Most hangars are not very air tight. No different than the propane bottle EAA hangar uses for the radiant heater at meetings. Propane doesn't go bad. My 1975 propane truck gets started about every two years and fires up no problem. That's a plus for infrequent use of sport planes.
 

rv7charlie

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200 psi (plus safety margin) pretty much defines the tank shape, unless you have access to some NASA postulated nano-materials.
 

rv7charlie

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The tanks you linked are far stronger than needed, but if that's the example you want to use, you're looking at less than 4 gallons of capacity in a 12 lb tank. I think that is roughly the weight of one of my 21 gallon RV7 tanks.

Taxiing up to the automotive gas station pump seems to be relatively easy out west in the areas with nothing but dirt & concrete, but a little tougher closer to towns. If you're talking about a removable tank, then you have the issue of manhandling 20-30 gallons (+tank weight) into the plane, and securing them, each time you refuel. Even if physically possible, it adds another layer of risk, needing to re-secure the tank with every fillup. Now for those of us who do a lot of local flying from our private strips, an on-site bulk tank could work pretty well.

You might want to rethink your secondary use comment, or figure you'll never visit the USA in the future.
 

Dana

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Propane has more energy per pound. Measure range by fuel weight, not gallons. I bet homemade integral tanks could be lighter using EA-B standards instead of consumer.
Hmmm, you're right... I wonder why my dual fuel generator has a lower output on propane vs. gasoline? Might be due to the air / fuel ratio and carb size?

Either way, unless you have a convenient source of propane considerably cheaper than gasoline, it seems like a solution in search of a problem. Cross country flights could be a hassle...
 

Vigilant1

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Hmmm, you're right... I wonder why my dual fuel generator has a lower output on propane vs. gasoline? Might be due to the air / fuel ratio and carb size?
Propane has an equivalent octane rating of 104 (pump octane ) to 110 (research octane), so it has a higher resistance to detonation than pump gasoline does. But, to get the stated energy value from propane you'd need to vary the ignition timing and the CR from the gasoline settings. The same engine can be made to make more power with propane than with gasoline, but only if it is properly modified/set up.
 
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BBerson

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Hmmm, you're right... I wonder why my dual fuel generator has a lower output on propane vs. gasoline? Might be due to the air / fuel ratio and carb size?
If the engine is designed for propane it should be same power (as Roush claims). As Vigilant1 said, need high compression, advanced timing and a few other details. With a turbo boost get plenty of power.
Propane motor fuel is third after gasoline and diesel. Filling stations are out there. Or can be delivered, as I mentioned. In return, engine life is tripled, oil and spark plugs almost never need to be changed. What is that worth?
 

Hephaestus

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With all the construction (rental) equipment that runs on propane - we actually have a great network of mobile filling stations... I don't think it'd be a major challenge to get a LPG truck out to an airport with a 100' hose. Just need to make sure you're able to accept the common fittings they use.
 
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