GAMI presentation from OSH '24

[201Steve]

  On 7/31/2024 at 12:08 AM, Shadrach said:

 

Not sure if you have an axe to grind, but it kind of comes off that way.

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Eric plays devils advocate on a lot of subjects. I’ve never had the impression it’s anything other than a different perspective to consider. Option to further investigate or leave alone at the readers discretion. 
 

the logic is right. Anyone who’s ever read or produced a pro forma, projected P&L, or business plan outlook knows that the numbers can be skewed. You can try as hard as you want to make it as accurate as possible but when your bias is for the business to work, it’s really hard to dig in to the details that may reveal land mines. Your bias, however so slight, is naturally drawn to the more favorable logic. Neither is dead right or dead wrong, it’s just one path of several. 
 

but, the problem for Braly’s competition, they have not seemed willing to equip themselves with the same vigor, passion, and shear will to disprove him. So you could say it’s their fault if something is wrong with his data. But it’s hard to match enthusiasm with a highly qualified mom and pop, if you’re a big corporation backed entity. Especially when you consider the audience here. 

[Brandt]

  On 7/31/2024 at 7:47 PM, EricJ said:

Nope, just some counterpoint to those that seem to think the GAMI stuff is a slam dunk or hang on whatever George says.    He's got some stuff going on, but it's not a slam dunk and it most certainly is not the entire story.

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I prefer fact based criticism over innuendo.  The old adage is ‘if you can’t win on the facts, attack the prosecutor.”  Telling me he’s a salesman or a lawyer is simply attacking the prosecutor.  I have no idea whether he is right, wrong, of incomplete in his fact presentation.  But if you have a fact based criticism, I’d welcome it.  Otherwise, it’s not helpful.  

[tony]

So I have been reading this thread and I am so suspect.  This guy is so proud of his data and continually refers to his data which cases me to ask myself, what is he not telling me?  a lot of his focus is on predetonation but there are other things to consider.

Questions I cant find the answers too maybe someone could answer:

• Has continental and lycoming endorsed this as an approved fuel?  Has any engine manufacturer endorsed this as an approved fuel?
• Why does he need an STC?  that means something is different?  If I lived in California, and put this stuff in my airplane, its not airworthy until I purchase an STC from him?  Really?  
• He claims to have more energy density, so I assume that all the performance charts should be better than what's published, If he is so big on data, I'd like to see that testing published.
• Has there been any independent testing?
• What happens to an engine over time, with a fuel that has no lead and more energy density?
• Is the latent heat of vaporization the same as 100LL?

[Pinecone]

  On 8/1/2024 at 12:29 PM, tony said:

So I have been reading this thread and I am so suspect.  This guy is so proud of his data and continually refers to his data which cases me to ask myself, what is he not telling me?  a lot of his focus is on predetonation but there are other things to consider.

Questions I cant find the answers too maybe someone could answer:

• Has continental and lycoming endorsed this as an approved fuel?  Has any engine manufacturer endorsed this as an approved fuel? That is covered by the STC.  They were invited to test the fuel, even provided the fuel and no cost and they declined.  FYI, they are the same companies that preached the LOP would burn up your engine and put out performance charts having engines running in the heart of the danger area.  Also the same companies that did not approve the use of MOGAS in the early 80s.
• Why does he need an STC?  that means something is different?  If I lived in California, and put this stuff in my airplane, its not airworthy until I purchase an STC from him?  Really?  There is no way in the law or regulations for a fleet wide blanket approval.  It either has to meet ASTM D910 (witch requires lead) or be approved by STC.  And yes, if you want to run this fuel, you need to buy the STC.  Just like for the MOGAS guys.  Yes, I would have loved for the STC to be cheaper, but GAMI has spent 20 years on this without ANY revenue.
• He claims to have more energy density, so I assume that all the performance charts should be better than what's published, If he is so big on data, I'd like to see that testing published.  It is published.  The fuel weighs 3% more per gallon, but contains more energy per gallon. So you can fly further on the same number of gallons, or carry less fuel.   I think the statement that has higher energy DENSITY is a bit off, as it has more energy per gallon, but weighs about the same amount more. 
• Has there been any independent testing? The fuel was tested to the FAA protocols with the FAA watching over their shoulders.  
• What happens to an engine over time, with a fuel that has no lead and more energy density? It runs cleaner, allows longer oil change intervals (Lycoming already has an SB that allows 100 hours between oil changes with UL fuel), allows the introduction of full synthetic oils which will reduce friction (less wear, more power and even longer change intervals).  And preliminary data is showing lower wear particles in the oil with normal oils..    Also, long spark plug life.  The higher energy density just means your fuel flows (in GPH) will be slightly less.  My 10.1 GPH will be 9.8 GPH.  And that also means I get more flying per gallon to offset the slightly higher price.  Engines burn fuel in pounds, not gallons.  We just use gallons as it is easier and traditional.  Also, density on AVGAS can vary and has over time.  Mooney uses 5.83 pounds per gallon while the ASTAM spec saw 6.02,
• Is the latent heat of vaporization the same as 100LL?  Why? Our engines are not cooled by the latent heat of vaporization, but the rich mixture reducing combustion pressure.

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In the early 70s, UL car fuels came out.  Before then, we changed oil every 3,000 miles and an engine was worn out by 100,000 miles.  Now days, oil change intervals are over 15,000 miles and cars are considered just broken in at 100,000 miles.

[GeeBee]

As to his data, it was ran through two FAA offices independently. Wichita and Atlanta. Both witnessed, both signed off as complete and rigorous. It is tough to attack his methodology when the FAA admits his lab and methods are better than theirs. GAMI's lab is considered the finest in the world. I don't know what else has to be done but the data set looks to be stellar. 

[Pinecone]

  On 7/31/2024 at 11:25 PM, McMooney said:

you guys should all be really scared right now, if no competitors come along we're most likely very screwed.

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There are 4 refineries making 100LL in the US.  There is ONE plant making TEL, locating in England.  GAMI does not make G100UL and has no plans to do so.

Due to the handling of the TEL, no new 100LL refineries will ever come on line.  And we have already lost a couple.  Also, shipping and distributing 100LL requires dedicated equipment due to lead contamination.

G100UL is licensable to anyone who wants to start making it.  It is simply blending things that are already present at most refineries.  Or you could buy a license, buy a big tank, and buy the components and blend it.

So, ANY refinery can get into the market.  And while the AVGAS market is small, the profit per gallon is a lot higher than MOGAS.

So potentially there are a lot MORE competitors.  In fact, Vitol, who blended a batch of around 1,000,000 gallons of G100UL is NOT a maker of 100LL.  So a new source right there.

[EricJ]

  On 8/1/2024 at 11:20 AM, 201Steve said:

but, the problem for Braly’s competition, they have not seemed willing to equip themselves with the same vigor, passion, and shear will to disprove him. So you could say it’s their fault if something is wrong with his data. But it’s hard to match enthusiasm with a highly qualified mom and pop, if you’re a big corporation backed entity. Especially when you consider the audience here. 

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We're not the audience for most of the players, so we generally don't see their data or their arguments.    They save those for the actual decision-making audiences, which are the FAA, the standards body, and the distributors.   We don't really matter at this stage of the process, so we're in the dark for the majority of the inputs.

  On 8/1/2024 at 11:37 AM, Brandt said:

I prefer fact based criticism over innuendo.  The old adage is ‘if you can’t win on the facts, attack the prosecutor.”  Telling me he’s a salesman or a lawyer is simply attacking the prosecutor.  I have no idea whether he is right, wrong, of incomplete in his fact presentation.  But if you have a fact based criticism, I’d welcome it.  Otherwise, it’s not helpful.  

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As I mentioned previously, my comments are based on a lot of experience with very similar technical processes.   Take all that fwiw, I just offer it as a perspective.   In this case we are only seeing one side of a multi-faceted process, and, as I mentioned above, the other players generally aren't sharing information to the public.    It can be counterproductive for them to do so, so we're very limited in what we know.    Only being able to see one side (or part of one side) of a multi-faceted issue can be expected to cause some skepticism, and certainly gives one pause on being able to make an informed decision.

 

[201Steve]

  On 8/1/2024 at 2:17 PM, EricJ said:

We're not the audience for most of the players, so we generally don't see their data or their arguments.    They save those for the actual decision-making audiences, which are the FAA, the standards body, and the distributors.   We don't really matter at this stage of the process, so we're in the dark for the majority of the inputs.

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That’s true. Except, Swift for example, is taking a massive hit in consumer confidence. To the extent that, it very well could end up trickling into the conscious of the above. 
 

Braly, not as politically connected into the oil and gas business, is coming at it by way of consumer confidence. And he very well may win the nod that way. It’s Yet to be seen how that strategy works out but it certainly appears that the only reason (there is no data to discredit him yet) he’s not gotten backing by any federal body is the lack of connectedness in that business. The grass roots method may prevail. We shall see. 

[Marc_B]

  On 8/1/2024 at 12:29 PM, tony said:

• Has continental and lycoming endorsed this as an approved fuel?  Has any engine manufacturer endorsed this as an approved fuel?
• Why does he need an STC?  that means something is different?  If I lived in California, and put this stuff in my airplane, its not airworthy until I purchase an STC from him?  Really?  
• Has there been any independent testing?

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I don't gather that Continental or Lycoming will be leading the direction of how to run engines with any UL fuel.  I stopped by TCM booth at Osh and one rep said G100UL would be fine; the other said run 100LL or expect problems.  https://www.advancedpilot.com/   GAMI has been leading the way in how to run engines safely and more efficiently for a long time.  According to Continental I should be running my engine at 75% HP at peak TIT, or just far enough on rich side of peak to keep TIT at or below 1650.  I don't see any of my fellow Mooney pilots who follow that instruction from my POH from Continental.  I think engine manufacturers will lead from a position of liability and apprehension; but ideally they are the ones poised to be running independent tests, figuring out performance numbers, and changing magneto timing / power restrictions for certain fuels.

I think the STC is purely from the need for FAA approval.  GAMI patented a recipe and isn't a refinery, aviation fuel dealer, or producer.  Essentially the FAA granted ability to use G100UL to an extensive list of piston engine aircraft that previously were not type certified to use this fuel by way of Supplemental Type Certificate.  You can put anything you want, but if you don't follow the FAA "rules" it's not defined as airworthy by the government.

What I find most interesting, and seems telling, is that other companies could easily test G100UL and their own fuels and compare them...but I haven't seen any of this.  I gather that some will be fans of G100UL (or another UL) regardless, and some will be apprehensive regardless.  Most companies surrounding this have been more fearful of litigation than transparent sharing of data.  But if G100UL is "hiding data" and "not telling you things" then why isn't there other labs showing this data? 

GAMI's reputation as a test facility and at the forefront of aviation engine management lead me to believe that probably their testing is years/decades away from any of competition.  I'm not sure of EAGLEs agenda as far as G100UL is concerned; but I gather petrol companies are dragging feet intentionally towards 2030 and I suspect a lot has to do with 100LL still has a great profit margin, doesn't require testing, doesn't open door to suggestion of liability, and overall is easier for them and more profitable...until it isn't.

 

Edited August 1, 2024 by Marc_B

[KSMooniac]

  On 8/1/2024 at 2:40 PM, Marc_B said:

GAMI's reputation as a test facility and at the forefront of aviation engine management lead me to believe that probably their testing is years/decades away from any of competition.  I'm not sure of EAGLEs agenda as far as G100UL is concerned; but I gather petrol companies are dragging feet intentionally towards 2030 and I suspect a lot has to do with 100LL still has a great profit margin, doesn't require testing, doesn't open door to suggestion of liability, and overall is easier for them and more profitable...until it isn't.

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This is likely the root of the problem.  100LL production is highly profitable, albeit in a small market, is firmly established/understood, and has a high barrier to entry due to the lead content.  Those refiners and distributors have a lot of motivation to maintain the status quo.  Creating a 100UL product potentially opens up the market to essentially any gasoline refinery and distributor network, so presumably that should lower prices for us at the pump eventually.  Businesses will naturally try to protect their profitable markets and I think we're seeing that with the endless programs that haven't solved the problem after a few decades of talk and study.

[Marc_B]

As an aside, the thing from Braly's presentation that is most disturbing to me is that he could take the Swift 94UL fuel and change how it was run and decrease detonation.  I'm sure the information Swift would present would be how their fuel runs "right."  But I think the collective apprehension from the GA community is from the uncertainty of how an UL fuel runs "wrong."  i.e. does this change how we manage or maintain our engines.  Will we need to change mag timing?  Will we need to change max cruise HP recommendations?  i.e. if UND used Swift 94UL but advanced mag timing to 20 deg, would the study have been a "success"???

I think that we all assume that a lot of this real world data won't come out until years down the line with lessons learned.

[Brandt]

  On 8/1/2024 at 2:17 PM, EricJ said:

We're not the audience for most of the players, so we generally don't see their data or their arguments.    They save those for the actual decision-making audiences, which are the FAA, the standards body, and the distributors.   We don't really matter at this stage of the process, so we're in the dark for the majority of the inputs.

As I mentioned previously, my comments are based on a lot of experience with very similar technical processes.   Take all that fwiw, I just offer it as a perspective.   In this case we are only seeing one side of a multi-faceted process, and, as I mentioned above, the other players generally aren't sharing information to the public.    It can be counterproductive for them to do so, so we're very limited in what we know.    Only being able to see one side (or part of one side) of a multi-faceted issue can be expected to cause some skepticism, and certainly gives one pause on being able to make an informed decision.

 

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Sincere question. Has Braly ever overpromised and underdelivered?  I like his injectors but that is the extent of my knowledge about his work.

[Marc_B]

“There is no such thing as a drop-in unleaded fuel to replace 100 [LL],” Dan Pourreau, business development manager with LyondellBasel Industries, told the publication “We thought initially we were going to be able to do that, but we discovered we can’t do that either.” Pourreau said paper and technical modifications will be required on some engines to allow them to run safely on unleaded fuel.

https://aviationweek.com/business-aviation/aircraft-propulsion/avgas-developer-drop-fuel-100ll-not-possible

But Pourreau didn't comment on G100UL and he didn't say that it was impossible to make a replacement fuel, but rather that you'd likely need to adjust engine specs... 

Does anyone have video of Pourreau's presentation from Osh?

[KSMooniac]

  On 8/1/2024 at 3:16 PM, Marc_B said:

“There is no such thing as a drop-in unleaded fuel to replace 100 [LL],” Dan Pourreau, business development manager with LyondellBasel Industries, told the publication “We thought initially we were going to be able to do that, but we discovered we can’t do that either.” Pourreau said paper and technical modifications will be required on some engines to allow them to run safely on unleaded fuel.

https://aviationweek.com/business-aviation/aircraft-propulsion/avgas-developer-drop-fuel-100ll-not-possible

But Pourreau didn't comment on G100UL and he didn't say that it was impossible to make a replacement fuel, but rather that you'd likely need to adjust engine specs... 

Does anyone have video of Pourreau's presentation from Osh?

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"The physical and chemical properties of UL100E “are nearly identical” to those of 100LL, Pourreau said. It is fully miscible, or mixable, with 100LL and meets most requirements of ASTM D910, the industry standard specification for avgas."

I think what has to be read between-the-lines is that there is no drop-in that meets ASTM D910 (100LL industry spec).  Braly and his team recognized this back in 2010 and started down their path that led to G100UL.  They chose the difficult STC path because (believe it or not) it was easier than creating a new ASTM spec, which would require approval from the members that are entrenched in 100LL production and would be loathe to approve a competitor product that could undercut their profitable 100LL business.  ASTM is a consensus/industry-based organization, moves even slower than the FAA.

[GeeBee]

Just a guess, but I suspect the PAFI candidates are finding out they can't "get there from here" without infringing on GAMI's patents. First they started by using FBO trade groups to diss GAMI, now it is, "it can't be done." Next I am sure we will hear the dog ate the data.  Yes it can be done, you just got to pay the man.

[Fly Boomer]

  On 8/1/2024 at 12:29 PM, tony said:

So I have been reading this thread and I am so suspect. 

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You need to go beyond this thread.  There are mountains of videos, tests, papers, articles, testimonials, discussions on on other forums, etc. to consume.

[Hank]

  On 8/1/2024 at 3:16 PM, Marc_B said:

“There is no such thing as a drop-in unleaded fuel to replace 100 [LL],” Dan Pourreau, business development manager with LyondellBasel Industries, told the publication “We thought initially we were going to be able to do that, but we discovered we can’t do that either.” Pourreau said paper and technical modifications will be required on some engines to allow them to run safely on unleaded fuel.

https://aviationweek.com/business-aviation/aircraft-propulsion/avgas-developer-drop-fuel-100ll-not-possible

But Pourreau didn't comment on G100UL and he didn't say that it was impossible to make a replacement fuel, but rather that you'd likely need to adjust engine specs... 

Does anyone have video of Pourreau's presentation from Osh?

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I have yet to see a "paper modification" effect anything . . . and I've spent much of my career in process development and improvement, complete with statistical justification of the end results.

[Shadrach]

  On 8/1/2024 at 11:20 AM, 201Steve said:

Eric plays devils advocate on a lot of subjects. I’ve never had the impression it’s anything other than a different perspective to consider. Option to further investigate or leave alone at the readers discretion. 
 

the logic is right. Anyone who’s ever read or produced a pro forma, projected P&L, or business plan outlook knows that the numbers can be skewed. You can try as hard as you want to make it as accurate as possible but when your bias is for the business to work, it’s really hard to dig in to the details that may reveal land mines. Your bias, however so slight, is naturally drawn to the more favorable logic. Neither is dead right or dead wrong, it’s just one path of several. 
 

but, the problem for Braly’s competition, they have not seemed willing to equip themselves with the same vigor, passion, and shear will to disprove him. So you could say it’s their fault if something is wrong with his data. But it’s hard to match enthusiasm with a highly qualified mom and pop, if you’re a big corporation backed entity. Especially when you consider the audience here. 

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I’ve read a lot of P&Ls. I’ve also read lots of engine data graphs.  I think the analogy sub optimal. There are lots of line items on a P&L that can be massaged depending on whether your goal is minimizing or maximizing profit.  
 

George showed a granular presentation of a short term engine run, complete with graphic depictions of multiple fuels (G100UL, 100LL, and 94UL) running back to back without shutting down and with no other changes to the operating parameters. If you believe he has a sophisticated engine test stand and knows how to use it (which I do), it is difficult to imagine the results are biased even though George might be. The UND test was halted because it damaged cylinders. GAMI wouldn’t be testing this fuel if it weren’t for the failure of the trial. I suspect George knew what happened and was all too happy to showcase it. That doesn’t mean his data is wrong or has been cooked. He is merely taking an opportunity to showcase his competitor’s failures.

[McMooney]

  On 8/1/2024 at 1:02 PM, Pinecone said:

There are 4 refineries making 100LL in the US.  There is ONE plant making TEL, locating in England.  GAMI does not make G100UL and has no plans to do so.

Due to the handling of the TEL, no new 100LL refineries will ever come on line.  And we have already lost a couple.  Also, shipping and distributing 100LL requires dedicated equipment due to lead contamination.

G100UL is licensable to anyone who wants to start making it.  It is simply blending things that are already present at most refineries.  Or you could buy a license, buy a big tank, and buy the components and blend it.

So, ANY refinery can get into the market.  And while the AVGAS market is small, the profit per gallon is a lot higher than MOGAS.

So potentially there are a lot MORE competitors.  In fact, Vitol, who blended a batch of around 1,000,000 gallons of G100UL is NOT a maker of 100LL.  So a new source right there.

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so here's what i would do if i was an investor.  I'd give george 1 billion dollars for his formulae and stc.

after 100LL goes away, i turn around and charge 10$ per gallon, tell me what can be done?  you have no alternative, pay me or don't fly.

wasn't there some private equity firm that just purchased a number of airplane part suppliers then JACKED the prices up?  why would they NOT do this?

and as far as i can tell, due to regulations, litigation, fear, capitalism, etc... NO other alternatives will come about.   isn't that new diesel engine like a minimum of100k?

 

Edited August 2, 2024 by McMooney

[PeteMc]

  On 8/1/2024 at 11:37 AM, Brandt said:

I prefer fact based criticism over innuendo.

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Totally agree.  That's why I was asking if I had missed something that I (we) should all take note of.  So far, there has been no "fact based" counter.

 

[Pinecone]

  On 8/1/2024 at 6:45 PM, McMooney said:

so here's what i would do if i was an investor.  I'd give george 1 billion dollars for his formlae and stc, now i own  it.

after 100LL goes away, i turn around and charge 10$ per gallon, tell me what can be done?  you have no alternative, pay me or don't fly.

wasn't there some private equity firm that just purchased a number of airplate part supplies then JACKED the prices up?  why would they NOT do this?

and as far as i can tell, due to regulations, litigation, fear, etc... NO other alternatives will come about.   isn't that new diesel engine like a minimum of100k?

 

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The only thing we can hope is George is a long time GA pilot.  And that he will not throw GA to the wolves.  If no other reason, it will affect HIS flying

[PeteMc]

  On 8/1/2024 at 12:29 PM, tony said:

Has continental and lycoming endorsed this as an approved fuel? 

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As @Marc_B mentioned, at this time I don't think Continental or Lycoming have come out and Approved or Disapproved G100UL.  And that's part of the problem. 

As a result, Cirrus has said you can't run it in their planes because it is not an "Approved" fuel, so if someone destroys their engine using G100, the engine warranty is invalid.  Even if they prove the reason for the failure was totally an manufacturing issue, Continental may claim unapproved fuel and stick Cirrus with the bill.

[Ibra]

I still don’t buy low octane argument from UL94 in Archer?

Down here we run same aircraft (Archer) and same engines (O360-A) using Total Avgas UL91 with 91 MON and with Peterson STC for Mogas AKI93, SPUL+ or SP98 (SuperPlus) with octane ratings as low as 88 MON 

If there is something wrong it’s likely with UND fleet and the way how they operate, maintain, measure or lean? 

If’s hard to understand how this engine (1:8.5) runs ok on SuperPlus from car pumps yet can’t handle Swift UL94, I am more inclined to believe Lycoming assessment, “it’s aromatics” 

If GAMI has real hard data that O360-A in Archers do need octane min MON100 octane (100LL or G100UL), then Lycoming & FAA will have to review many similar engines in the same bracket: about 40 other engines with 1:8.5CR in 360 series (O360 , IO360, HO360, LVIO360, AEIO360) are approved for UL94, UL91 as well as Mogas: SP, AKI93, EN228…

Only Lyco O320 series (1:7CR) are left to use UL94, UL91 and Mogas

https://www.lycoming.com/sites/default/files/attachments/SI1070AB%20Specified%20Fuels.pdfOn a side note does anyone know where to find this paper? it seems removed from FAA website 

Schlickenmaier, H. W., Wilkinson, R., & Atwood, D. (2014). General Aviation Engine Fleet Assessment for Octane Requirement

It was far the most balanced paper on octane requirement versus (CR, BMEP) plus sensitivity analysis to bore, strike, temperature, altitude and timing

 

Edited August 1, 2024 by Ibra

[tony]

  On 8/1/2024 at 7:12 PM, PeteMc said:

As @Marc_B mentioned, at this time I don't think Continental or Lycoming have come out and Approved or Disapproved G100UL.  And that's part of the problem. 

As a result, Cirrus has said you can't run it in their planes because it is not an "Approved" fuel, so if someone destroys their engine using G100, the engine warranty is invalid.  Even if they prove the reason for the failure was totally an manufacturing issue, Continental may claim unapproved fuel and stick Cirrus with the bill.

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I found this today....

https://www.avweb.com/aviation-news/lycoming-clarifies-g100ul-warranty-impact/

 

[Marc_B]

  On 8/1/2024 at 7:42 PM, Ibra said:

If there is something wrong it’s likely with UND fleet and the way how they operate, maintain, measure or lean? 

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From the video Braly stated UND used WOT, leaned to peak EGT which depending on the altitude could be 65-70% HP.  I'm sure you could get any engine to detonate depending on how you ran it.  But my suspicion is that UND fleet are run way harder than a typically privately owned aircraft would be.  The idea of the red fin/box I'm sure comes to play with this.  A training aircraft has to spend a MUCH higher percentage at full throttle than your typical aircraft...and depending on how it was leaned that could mean recipe for detonation.

From what I understand (limited), most have said that valve recession was either a detonation event or a microwelding event from lack of lead.  The data presented at Osh was clearly built to detect detonation events.  The initial graphic Braly showed was at 73%HP with CHTs 400-430F in a Continental Engine with 8.5:1 compression and 22 deg timing.  (UND 25 deg timing Lycoming engine).  Next graphic was reported at 69%HP with CHTs still in the 400-430F range with mixture enrichened "somewhat rich of best power mixture".  But clearly looks like UL94 gets into the "red fin" when 100UL and 100LL do not.

The idea of higher octane acting to help prevent detonation is pretty self explanatory and the graphics showing 94UL has detonation events when G100UL/100LL do not, seems to makes sense.   I didn't quite understand why not try to replicate UND use case as closely as possible (i.e. same engines, similar power settings)?  I gather (my impression/interpretation) that Braly was showing that UL94 has a lower detonation safety margin than 100LL/G100UL and offering that his interpretation of valve seat recession was due to detonation events.

If you listen to Mike Busch, for a Continental he recommends keeping CHTs below 380F.  Even Continental recommends an engine in the 375-385 is the happy range.  HOWEVER, CHTs were still below redline; so I'd expect that below redline within normal POH operation these detonation events shouldn't be happening, and with 100LL/G100UL they weren't.

Edited August 1, 2024 by Marc_B