$10 gallon Avgas

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Daleandee

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Corvairs were designed for 87 octane weren't they? Clark's corvair says they'll do fine on ethanol blends too.
Perhaps the original engines were but the conversion changes the cam, compression ratio, and timing curve. My engine calls for 93 octane as a minimum but slight reduction in timing would allow a lower octane. With that I'd have to give up some power (probably in the 2% range).

I believe everything in my system is ethanol resistant but not sure about the carb as it's a Marvel Schebler from an O-200. Besides, I just think it's wise not to put ethanol in my airplane. There may come a day but it ain't here yet.
 

TXFlyGuy

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Besides, I just think it's wise not to put ethanol in my airplane. There may come a day but it ain't here yet.
Check the Van's forum. Many there reporting hundreds and hundreds of trouble free flight hours burning E10. Some even going up into the lower flight levels without issues.
 

Bigshu

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Check the Van's forum. Many there reporting hundreds and hundreds of trouble free flight hours burning E10. Some even going up into the lower flight levels without issues.
And Premium E10 is rated at 93 octane.
 

Bigshu

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Perhaps the original engines were but the conversion changes the cam, compression ratio, and timing curve. My engine calls for 93 octane as a minimum but slight reduction in timing would allow a lower octane. With that I'd have to give up some power (probably in the 2% range).

I believe everything in my system is ethanol resistant but not sure about the carb as it's a Marvel Schebler from an O-200. Besides, I just think it's wise not to put ethanol in my airplane. There may come a day but it ain't here yet.
Well, the cam change is to increase the duration of the valves opening, right? And the compression ratio typically is lower in flight engines, yes? I don't know about the timing curve's effect, but 87 octane E10 gets burned in a tremendous variety of engines, from turbo 4's with relatively high compression, to some pretty big V8's. I see people buying it all the time at the station, in a staggering number of different engine setups with apparently no issues. I get that Corvairs are an old design, but just adding forged pistons and rods and a hotter cam shouldn't preclude running E10. Check with your local Corvair club and see what they run...
 

Daleandee

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I get that Corvairs are an old design, but just adding forged pistons and rods and a hotter cam shouldn't preclude running E10. Check with your local Corvair club and see what they run...
I appreciate what you are saying but I have no intention of ever running ethanol fuel in my airplane unless there is no alternative.
 

Daleandee

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Your airplane. Your money. Your choice. At least for now.
Yes sir you are quite correct. I've heard for a number of years that 100LL is going away ...

A friend used to always say, "Fly! While you can still get gas!"
 
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Bigshu

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I appreciate what you are saying but I have no intention of ever running ethanol fuel in my airplane unless there is no alternative.
100% with you, for what you do with your aircraft. I'm just thinking we'll see an alternative to leaded fuel sooner rather than later. It might even be electricity!
 

Daleandee

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100% with you, for what you do with your aircraft. I'm just thinking we'll see an alternative to leaded fuel sooner rather than later. It might even be electricity!
You may be on to something as we might be flying batteries before they can make a lead free 100 octane fuel available. LOL!
 

TXFlyGuy

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My Mustang will burn unleaded, either 93UL, or 92UL E-Free gas.
It’s my prediction that the foot dragging by the FAA on non-leaded avgas will continue.
There is an option now, 94UL. But in the infinite wisdom of the FAA, because it’s not 100% applicable to the GA fleet, it will not be certified and distributed. In other words, we will all continue to suffer.
 

pwood66889

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Gasoline has been a political football for some time, and likely will remain so. As TXFly noted, many of us can burn a non-leaded fuel. But for those who Must Have 100LL (LL = Lots of Lead) for their high-pro planes, it could become very tough. Yes, I have the Auto Fuel STC. And plenty of unleaded boat gas here in NW FL, USA.
 

Bigshu

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Gasoline has been a political football for some time, and likely will remain so. As TXFly noted, many of us can burn a non-leaded fuel. But for those who Must Have 100LL (LL = Lots of Lead) for their high-pro planes, it could become very tough. Yes, I have the Auto Fuel STC. And plenty of unleaded boat gas here in NW FL, USA.
I still think the auto fuels available now can cover high performance engine needs. Electronic ignition and fuel injection help a lot getting HP without knocking. There are street engines rated at hundreds of horsepower that run just fine on 93 octane fuel. Even race engines are running fuel blends that are lead free, and pretty much every street engine is capable of running high ethanol blends (everyone calls it E85, but in the midwest, the highest blends we were asked to offer were 75% E, and 65 to 70% were the most commonly delivered blends) without damage to their fuel systems or engines, even if their fuel economy suffers a little.
 

Vigilant1

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It's not just octane, it is valves.
Given the scope of the perceived lead problem, I wonder if a simple and relatively cheap approach would be for the government to pay for suitable replacement valves and seats for acft engines that truly require TEL. If the EPA eliminates TEL without a replacement that allows the engines to survive, it would be (IMO) a "taking" that justifies compensation. So, for a period of 10 years, buy new suitable valves and seats (guides too?) for engines that need them. That is better than losing airfields to public pressure, and fixes the problem using fuels available now.
 

rv7charlie

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I'd suggest finding some aviation-focused sources to read on the 'whys' of 100LL replacement difficulties. I doubt that you'll see valves mentioned anywhere, except that they won't stick anymore with any of the UL fuels. The problems all seem to stem from the extreme ends of the operating spectrum; not just detonation but extreme temperatures, at the altitudes where many turbocharged a/c operate. On the detonation front: just because an LS motor, with a combustion chamber shape designed this century, can run 93 octane, that doesn't mean that a Lyc or Cont with combustion chamber shape created in the middle of the previous century can do it.

We're all flying experimentals here, very few of us fly in the nosebleed altitudes, and very few of us are flying compressions north of about 9-1 in a/c engines. So all we need to do is verify that the 'soft parts' in our fuel systems are E-proof (fairly simple to do), and then run 93 octane pump gas from the corner gas station. For most of us, 100LL would be a relatively rare purchase, while on extended cross-countries.
 

N804RV

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One word: “Greta”.

I’m pretty sure piston powered aircraft will soon be relegated to the scrap heap, except for a few historically significant examples.

I hope I’ll be dead and gone by then. My heirs can squabble about what to do with my airplane and all my parts and tools.
 

Vigilant1

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I'd suggest finding some aviation-focused sources to read on the 'whys' of 100LL replacement difficulties. I doubt that you'll see valves mentioned anywhere, except that they won't stick anymore with any of the UL fuels.
I'm sure there are many opinions. FWIW, Shell Oil says this:
Lead compounds from TEL form a protective layer on the valve seat and prevents the soft valve seats from eroding. Without TEL small areas of a soft metal valve seat will fuse to the valve and be 'plucked' from the face of the seat.

Once attached to the valve they form an abrasive surface which further damages the valve seat. This combination of actions is known as Valve Seat Recession (VSR) as the seat of the valve is worn away ...
Petersen Aviation also believes TEL does protect valve seats (and they make money via mogas STCs):
Valve Seat Recession
Throughout the debate on eliminating leaded fuel, the focus has always been on what lead does for octane which is clear cut and well established. However, lead has also been found to protect valves and seats against valve seat recession. Some people deny that there is any benefit to using lead other than its ability to enhance octane, but this is not the case. Particularly in older designs, the small Continentals, Franklins, and in all radial engines, lead is necessary to prevent valve seat recession. Without it they may last as little as 30 hours.
 

Bigshu

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I'm sure there are many opinions. FWIW, Shell Oil says this:

Petersen Aviation also believes TEL does protect valve seats (and they make money via mogas STCs):
Well, we didn't expect the government to pay for our ADS-B equipment, which is mandatory for some airspace, and a really handy thing to have even if not in those airspaces. So, I don't see why we would expect the government to pay for our valve work either. When ULSD came along, nobody subsidized the railroads for the work it took to get locomotive diesels to run without substantial amounts of Sulphur in the fuel. And I doubt the R&D costs for the automobile manufacturers to redesign all their diesel engines were subsidized either. The brutal truth is if 110 LL production was outlawed tomorrow, there'd be a mad scramble to get the new parts in our engines before the supply (of parts or fuel) ran out. We just need to do it. The fact that automobile engines can do it with no problem is an indictment of the the FAA and the aircraft manufacturers. Maybe Part 23 reforms will allow some engine design improvements to finally show up in certified engines.
 
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