Seriously? Another unleaded avgas thread . . . ?

[A64Pilot]

The whole Diesel thing just doesn’t make sense to me, it’s actually pretty easy to build a gasoline engine burning auto fuel that makes WAY more power than 200 HP. The secret is in a Modern four valve head and combustion chamber, sure that takes liquid cooled heads, but even Rotax can do that, it’s not hard.

Dodge has an engine that makes over 1,000 HP on E-85, and it even passes emissions.

I bet lunch you could easily make our 200 HP Lycomings run just fine on E-85, Lycoming has an IO-540 Certified and running in Brazil on pure Ethanol, has for years.

Fuel burn would go up with E-85, how much? Maybe not a whole lot who knows?

My guess is the way to go might be build an Experimental engine that once well proven etc then you Certify it.

[Pinecone]

23 hours ago, Echo said:

UL94.  I am in.  Ditch the lead.  Same infrastructure.  No STC.  Lower fuel costs.  DO THIS!

Can you burn UL94?  I can't.  Edit, nope, M20E is not listed on the Swift site.  So great, the world does to UL94 and your airplane is now worthless and not flyable.

Most 200 HP IO-360s can't.  My 180 hp AEIO-360 on my other airplane was originally certified for 91/96, so can.

 

[Chris K]

GAMI received an STC by the FAA a while back and already being sold at a handful of airports.  Swift for only certain engines, and VP racing in the process of testing.  So far the only complaints on the GAMI I've heard about were via Cirrus owners (fuel leakage through seals/gas tanks).  To the OP, it's easier to test and switch the fuel being used than an entire GA fleet of engines.  Are some of the technologies outdated?  Without a doubt considering how far ahead the auto industry has come vs aviation in terms of efficiency and power output from new technologies.  Part of the problem is government certification requirements.  With computer modeling and other streamlined testing methods available today, the entire process is in dire need to be revamped. Surely if costs of testing and certifying engines for existing aircraft were reduced, there likely would be newer/modern engines available to consider as replacement when TBO rolls around.

Separately, wondering if anyone in the Mooney community has tried any of the new fuels yet?

[IvanP]

1 hour ago, Chris K said:

 

Separately, wondering if anyone in the Mooney community has tried any of the new fuels yet?

Check the General Mooney Talk forum. Very long thread on G100UL

[EricJ]

2 hours ago, Chris K said:

So far the only complaints on the GAMI I've heard about were via Cirrus owners (fuel leakage through seals/gas tanks). 

...

Separately, wondering if anyone in the Mooney community has tried any of the new fuels yet?

Yeah, you really need to get caught up via the thread on G100UL.

[A64Pilot]

On 2/5/2025 at 9:33 AM, Pinecone said:

Can you burn UL94?  I can't.  Edit, nope, M20E is not listed on the Swift site.  So great, the world does to UL94 and your airplane is now worthless and not flyable.

Most 200 HP IO-360s can't.  My 180 hp AEIO-360 on my other airplane was originally certified for 91/96, so can.

 

While I don’t have data on UL-94, we all should be able to with ADI.

We could run Mogas too engine wise, but I suspect there would be some kind of airframe mod because of the different vapor pressure causing vapor lock.

Having said that it’s likely that Mogas may not be today’s Auto fuel, I say that as auto fuel changes significantly by area, Urban Auto fuel is blended to pollute less, and Summer Auto fuel differs significantly from Winter, and of course California has their own Auto fuel, the huge price difference isn’t apparently all taxes.

‘Apparently even E85, isn’t. Seems it can be anything from 51% to 83% ETH https://en.wikipedia.org/wiki/E85 

As there are so many different fuels plus the fact it may change again in the future it might be difficult to Certify to. Company I worked for wasted a lot of time and money trying to Certify a Turbine to burn Bio-Diesel but couldn’t because Bio-Diesel isn’t really defined, it can be and is many different things both plant and animal fat based for example.

But I assume 94UL is made to an ASTM standard? If it really is just 100 LL without the lead it should have the same vapor pressure and there shouldn’t be any compatibility issue. Again I have never even seen 94 UL, so what little I think I know could be wrong.

As it sits now from what little data I have I don’t see anything with less risk and could be implemented with less cost and faster than 94UL, and ADI if you need it, a great many won’t. Most of GA carbureted fleet won’t. I think it safe to say that any aircraft that are eligible to burn Mogas could burn 94UL.

Might be worth reading https://www.lycoming.com/content/unleaded-fuels-part-1

 

Edited Saturday at 09:47 PM by A64Pilot

[T. Peterson]

On 2/3/2025 at 12:13 PM, 76Srat said:

. . . well, not quite.  Here's my thought:  Just like you guys, I've been reading just about everything I can find on the boiling EAGLE/100LL/unleaded debate/debacle/call-it-what-you-will issue.  And I apologize if this specific idea has been thrown around in here and I just can't find it, but I've been wondering a lot if we're simply missing the point altogether here.  Instead of wringing our hands over unleaded fuel options du jour and all of the worries with supply chain, distribution, pricing, loyalties between suppliers, does-it-play-well-with-others, etc?, should we get to pondering a larger opportunity?  

With credit to the latest article on the topic in this month's "EAA Sport Aviation" magazine, I think the solution might be in not trying to proffer the best "fuel" alternative and instead proffer the best reciprocating engine alternatives.  What do I mean by this?  Well, for starters, we have to wonder if on the fuel/engine side we're sitting on an upcoming sea-change in technology, not on the fuel side, but on the engine side.  And in support of this (possibly) exciting change, should we look no further than what has happened with avionics since the day the GNS430 was born?

Cue the logical coffee spewing over computer screens at this point, and I'm not trying to stir a long-tormented hornet's nest, but since the certification process is what it is (anything but cheap), should we as the marketplace look for a cheaper/viable engine replacement program instead of just pushing the rope further uphill on fuel alternatives?  The real answer lies in the cert process and the example shown us from those who dared to tread the shark-filled void of avionics upgrades, circa late 1990s.  It was said then, as it is being said now for engines in legacy types such as our beloved Mooneys, that "uprooting the legacy steam-gauges will never catch on" in the legacy piston fleet.  We see now how short-sighted that viewpoint was then and just how great it has been since.

I agree that there are legion reasons a recip engine replacement wouldn't be viable or feasible for most, if not all legacy piston fleets.  But, long term, a viable SAF-burning alternative recip engine for IO-320/360/IO-470/520/550 fleets out there seems to me to be money far better spent toward certification than a yet-to-be-determined acceptance rate of unleaded fuel replacements.  It is less than ironic to me that in the time you have to wait for a FOH we'll likely have the debate over the very unleaded fuel we'll be forced to use in that FOH solved--this is not a sustainable logic.  Let's put that effort in to gaining the best engine replacement for a longer term, instead of wasting this decade-plus over a fuel to be burned in engines that aren't sustainable themselves.   

We now have streaming and digital music.  Is this entire debate about unleaded avgas replacement going to end up being the VHS/Betamax debate?  Fast forward 5 or 10 years from now and will this fuel debate end up on the academic editing room floor, when we really should be debating not if, but which recip alternatives should be out there? 

Just read through the whole thread. Lots of gainsayers, but I like how you think. I don’t discount some of the other solutions, but I would love to see an answer from the engine side also!

[1980Mooney]

1 hour ago, T. Peterson said:

Just read through the whole thread. Lots of gainsayers, but I like how you think. I don’t discount some of the other solutions, but I would love to see an answer from the engine side also!

Our current engines and fuels are optimized for power, weight, functionality, simplicity and reliability.  "viable SAF-burning alternative" sounds fine but there will be unintended consequences.  E85 weighs 10% more than a gal. of Avgas and a gallon of E85 only has 79% of the energy (BTU's) of Avgas.  Less energy density - who cares?  Well maybe not if you are flying a 182 or a Dakota.  But if you are in a Mooney, with limited Useful Load as it is, it can really limit the usefulness of our planes. A pound of Avgas has about 18.75K BTU.  A pound of E85 only has 13.5 K BTU (some less).  That means you need to haul an extra 39% more pounds of fuel to make the same trip.  

For those with the efficient 4 cylinders that might mean a 4 hour trip with half hour reserve, the fuel required will weigh an extra 105 lbs. (57 gal E85 vs 45 gal Avgas)

But for those with the big 6's - many times we make a 4.5 hour trip with half hour reserve - I plan on 15 gph.  That is 75 gallons Avgas.  But with E85 the fuel required will weigh and extra 176 lbs.  (104 gal E85 vs 75 gal Avgas).  We will not be making that trip - extra fuel stops.

If you are thinking about automotive efficiency and power then you need a solid block, water cooling and a lot, lot more complexity.  And diesel? Look at the current Cont and Austro diesel solutions - tremendous complexity and not light.  And DeltaHawk?....they are less complex but they are in their umpteenth redesign trying to shed weight to become competitive - it remains to be seen if their 2 stroke will be efficient.  

[McMooney]

1 hour ago, 1980Mooney said:

Our current engines and fuels are optimized for power, weight, functionality, simplicity and reliability.  "viable SAF-burning alternative" sounds fine but there will be unintended consequences.  E85 weighs 10% more than a gal. of Avgas and a gallon of E85 only has 79% of the energy (BTU's) of Avgas.  Less energy density - who cares?  Well maybe not if you are flying a 182 or a Dakota.  But if you are in a Mooney, with limited Useful Load as it is, it can really limit the usefulness of our planes. A pound of Avgas has about 18.75K BTU.  A pound of E85 only has 13.5 K BTU (some less).  That means you need to haul an extra 39% more pounds of fuel to make the same trip.  

For those with the efficient 4 cylinders that might mean a 4 hour trip with half hour reserve, the fuel required will weigh an extra 105 lbs. (57 gal E85 vs 45 gal Avgas)

But for those with the big 6's - many times we make a 4.5 hour trip with half hour reserve - I plan on 15 gph.  That is 75 gallons Avgas.  But with E85 the fuel required will weigh and extra 176 lbs.  (104 gal E85 vs 75 gal Avgas).  We will not be making that trip - extra fuel stops.

If you are thinking about automotive efficiency and power then you need a solid block, water cooling and a lot, lot more complexity.  And diesel? Look at the current Cont and Austro diesel solutions - tremendous complexity and not light.  And DeltaHawk?....they are less complex but they are in their umpteenth redesign trying to shed weight to become competitive - it remains to be seen if their 2 stroke will be efficient.  

I don't know about the continental diesel but the austro isn't overly complex.  yes you have a turbo but you also have no ignition system, no plugs, wires, distributor etc...

there will be tradeoffs no matter what we do but i'd accept a higher hp engine burning  75% of the fuel for a 150ish lb diff.  also given more hp, thinking they could increase ul a bit to offset some.

 

Edited 12 hours ago by McMooney

[Ibra]

On 2/5/2025 at 1:46 AM, A64Pilot said:

Dodge has an engine that makes over 1,000 HP on E-85, and it even passes emissions

Even 1600hp on Jeskos with E85 on Octane < MON91

https://www.roadandtrack.com/new-cars/car-technology/a27029039/koenigsegg-jesko-engine-explained/

Clever and innovative stuff (these words unheard of in aviation context) 

Then you have the problem of alcohol in fuel system, airframe…but again sports cars don’t have much of these issues (ahem, regulatory limitation or lack of imagination). On limitations, I think all non-turbos Mooneys should be able to run UL94 (assuming they can have variable timing) as long as one sacrifies some power and plan for extra more runway length on takeoff. 

We flew uncertified with IO360 using UL91 (MON91) and SP98(MON88), these have less octane than UL94 and 100LL, the temperatures were slightly hot on takeoff but other than that “it works”, yet they are not approved by Lycoming !

Edited 9 hours ago by Ibra

[EricJ]

1 hour ago, Ibra said:

Even 1600hp on Jeskos with E85 on Octane < MON91

https://www.roadandtrack.com/new-cars/car-technology/a27029039/koenigsegg-jesko-engine-explained/

Clever and innovative stuff (these words unheard of in aviation context) 

Continuing my interest in how the Germans managed this in WWII, the Daimler DB 605 V12 engines that powered things like the Me109 made around 1800 hp with a design spec fuel of 87 Octane.    On that fuel they could run 43.4 inhg MAP, and with the later 90/100 fuel they could make nearly 60 inhg MAP.   If the 90/100 fuel wasn't available and they had to run the old spec fuel (which happened a lot), they were restricted to 43.4 in MAP.

I don't know how they did that, but clearly it's possible.

 

[A64Pilot]

45 minutes ago, EricJ said:

Continuing my interest in how the Germans managed this in WWII, the Daimler DB 605 V12 engines that powered things like the Me109 made around 1800 hp with a design spec fuel of 87 Octane.    On that fuel they could run 43.4 inhg MAP, and with the later 90/100 fuel they could make nearly 60 inhg MAP.   If the 90/100 fuel wasn't available and they had to run the old spec fuel (which happened a lot), they were restricted to 43.4 in MAP.

I don't know how they did that, but clearly it's possible.

 

In MP isn’t much boost for starters. For instance the 30 PSI in my Motorhome is when added to the 14.7 PSI atmospheric is around 90 inhg in MP.

You get roughly 30 in per 15 PSI of course.

But secondly assuming it’s like the old Pratt’s like the R-1340 with its Supercharger that had a T/O rating from memory of around 40 something inches it had roughly again from memory a compression ratio of about 6 to 1. That’s why you can prop a 1340 cuin engine. It will run just fine on standard 87 car pump gas and I’m sure lower.

Now the 1340 evolved over the years of course as it first flew I think in 1925? So HP and boost I’m sure varied greatly and I’ve not seen a 1340 with ADI which would allow much more boost. The twin row Wasp R-1830 did of course run ADI.

The older DB-601 Benz motors in the BF-109 apparently couldn’t make much boost, they didn’t get a HP boost from 100 Octane like the Merlin did. I think the later DB-605 engine could though

Germans ran ADI for high boost and Nitrous Oxide for very high altitude

I’m pretty sure they carried enough ETH/water for at least 20 min of use.

All this is from memory, and my memory may be a little wrong, but I believe ADI was exceedingly common in WWII and it of course significantly increased HP.

The US 4360 on T/O burned 3,000 lb per hour without ADI, but 2500 an hour with ADI and made significantly more power in a “wet” takeoff.

Again from memory.

 

Edited 7 hours ago by A64Pilot