G100UL paint testing by YouTuber mluvara

[gabez]

2 hours ago, EricJ said:

We don't know that.   We don't know how G100UL affects the integrity or longevity of tank sealant, but we have reason to believe it may affect it adversely.   According to the Textron letters there are multiple OEMs who have indicated tank sealing issues sufficient for Textron to be concerned enough to write the letters.

how does it work if an STC is used but Textron says no? where does the liability fall to? 

 

[jetdriven]

That certainly looks like detonation, but it may also be things like improperly, sized piston, and cylinder fit or incorrect ring gap. I could have a fairly massive intake gasket leak, or perhaps the intake gasket was not even installed.

[EricJ]

53 minutes ago, Pinecone said:

No idea.  Engine was fairly low time since OH.  It had an issue with glazed cylinders, most likely from improper breakin.  Rehoned the cylinders and did a new break in.

All was good.  Then took off, climbing through about 2500 feet, maybe 5 miles from airport, rough running and reduced power.  They returned and landed.

Engine was overhauled again.  No idea what happened. And only the one cylinder.

 

If it was only one cylinder it was probably preignition from a broken spark plug or something like that.   +1 that it could have been an intake issue on that cylinder as well.

[PT20J]

3 hours ago, gabez said:

how does it work if an STC is used but Textron says no? where does the liability fall to? 

 

Only FAA determines airworthiness requirements, so if you have an STC, it’s approved by the FAA. Liability is determined by the courts. Lycoming’s statement may or may not help it in a court case. 

[A64Pilot]

On 1/4/2025 at 10:58 AM, McMooney said:

i wish i had more information, my understanding of the detonation issues, is that at the absolute worst conditions 500deg cht, worse mixture possible the engine detonates when producing max hp. why couldn't I just avoid operating in detonation possible conditions?  so ex  with my io-360-a1a, couldn't i just avoid running the thing above say 28in mp when its 110degs outside ?

The numbers are 25” MP and 400 F cyl head temp.

The ADI STC’s I’m familiar with the ADI is off below those numbers.

Could you takeoff at 25” MP? I guess you could, anyone operating out of an airport at 5,000 ft or higher does, but I don’t want to.

Could you operate with 94UL at full throttle without detonating? Probably if you kept Cyl head temp down, but your safety margin is of course less and it’s not legal.

But sometimes engines detonate operating on 100LL, engines with monitors. Why? I honestly don’t have an answer.

People don’t understand ADI, it’s a very simple system, pretty much nothing to break, 2 pumps on different electrical busses, and the pump is the only moving part

[redbaron1982]

2 hours ago, A64Pilot said:

But sometimes engines detonate operating on 100LL, engines with monitors. Why? I honestly don’t have an answer.

Can't hot spots within the cyl cause detonation? Like a carbon deposit that gets too hot?

I don't know if this has been posted here before: 

 

[A64Pilot]

Hot spots, like carbon or maybe a plug helicoil hanging down etc I believe technically cause pre-ignition, but as I believe that can quickly lead to detonation I think it doesn’t matter to the guy who pays the bill. Likely pre-ignition is more damaging but either way it’s destructive.

I think it’s like arguing he didn’t die from a gunshot, he died from loss of blood

Personal opinion

Edited January 13 by A64Pilot

[EricJ]

Just now, redbaron1982 said:

Can't hot spots within the cyl cause detonation? Like a carbon deposit that gets too hot?

Hot spots can lead to pre-ignition, which may or may not cause detonation.    Pre-ignition certainly can cause detonation, but doesn't always.

Just now, redbaron1982 said:

I don't know if this has been posted here before: 

 

Another interesting data point is that during WWII the German avgas fueling all of the 1500+ hp gasoline fighter engines was 91/100 octane.   I see 100LL described as 100/130 using dual-octane ratings.  So the Germans figured out how to get a lot of power at high boost using relatively low octane.  They were using direct-injection, which probably helped a lot.   If they'd won the war we'd probably have plenty of aircraft engines running UL as well as diesels running Jet-A, since they had a number of successful high-output diesel aircraft engines.   I'm not sure how all that technology got left behind other than there was a lot of "not invented here" bias in engineeing that lasted many decades after the war.

[McMooney]

2 hours ago, A64Pilot said:

The numbers are 25” MP and 400 F cyl head temp.

The ADI STC’s I’m familiar with the ADI is off below those numbers.

Could you takeoff at 25” MP? I guess you could, anyone operating out of an airport at 5,000 ft or higher does, but I don’t want to.

Could you operate with 94UL at full throttle without detonating? Probably if you kept Cyl head temp down, but your safety margin is of course less and it’s not legal.

But sometimes engines detonate operating on 100LL, engines with monitors. Why? I honestly don’t have an answer.

People don’t understand ADI, it’s a very simple system, pretty much nothing to break, 2 pumps on different electrical busses, and the pump is the only moving part

on the hottest days 110 degs my engine doesn't go above 380, so if i could limit myself to say 2700rpm 25/26 inches approx 170-180hp which is about what a m20c makes, yeah i'd be fine.  i take off in 1500ft instead of 1000, i can make that trade if i don't have other options.  once i get above a few thousand feet it becomes a non issue anyway.

I have no problem with adi, as long as it doesn't cost me a fortune to install and i'm not using gallons of fluid every flight.   If it's as miserly as the def usage in my diesel, heck yeah.

 

[A64Pilot]

I believe in WWII pretty much ALL Avgas was 80ish octane.

The US I believe manufactured 100 Octane using a French process to a British Standard and it was supplied to the Brits just prior to the Battle of Britain, this gave the Merlin lots more HP being able to run at higher boost, that and the fact that the Brits were allowed to build a constant speed prop under license from a US manufacturer also made a HUGE difference, without those two things the 109 was a superior fighter, the prop and fuel really woke up the Spit. I think the Brits had a two pitch prop previously.

I believe the Benz motor on the 109 couldn’t make enough boost for the 100 Octane to be as beneficial as it was on the Merlin.

The Germans used ADI for higher power down low and I think maybe we adopted ADI from the German’s.

At high altitudes the Germans used Nitrous Oxide for higher power.

‘Now all this is from memory from YEARS ago,so maybe I got it wrong.

[McMooney]

hmm, looking at the video think they could make it simpler, no need for a computer just calibrated temp / pressure switch should work.  be nice if i could just cheap vodka for the fluid, instead of messing with methanol

[McMooney]

1 minute ago, McMooney said:

hmm, looking at the video think they could make it simpler, no need for a computer just calibrated temp / pressure switch should work.  be nice if i could just cheap vodka for the fluid, instead of messing with methanol

nitrous injector would be nice also,  little bit of help when i take my flatland plane out to mountain territory

[Fly Boomer]

28 minutes ago, EricJ said:

Hot spots can lead to pre-ignition, which may or may not cause detonation.    Pre-ignition certainly can cause detonation, but doesn't always.

This article lays it out pretty well:

https://www.savvyaviation.com/detonation-and-pre-ignition/

In particular, the section entitled Detonation-Induced Pre-Ignition.

[A64Pilot]

2 minutes ago, McMooney said:

on the hottest days 110 degs my engine doesn't go above 380, so if i could limit myself to say 2700rpm 25/26 inches approx 170-180hp which is about what a m20c makes, yeah i'd be fine.  i take off in 1500ft instead of 1000, i can make that trade if i don't have other options.  once i get above a few thousand feet it becomes a non issue anyway.

I have no problem with adi, as long as it doesn't cost me a fortune to install and i'm not using gallons of fluid every flight.   If it's as miserly as the def usage in my diesel, heck yeah.

 

Watch the above link.

Most worst cases are taking off heavy at sea level and climbing to altitude for cruise. Above 5,000 ft approx you can’t get above 25MP without forced induction.

So let’s say you take off at seal level and climb at 500 FPM to above 5,000 for cruise, your using the ADI for 10 min.

I don’t know what the flow rate is, but again from memory a WWII fighter making 2500 HP used a little over 9 lbs per min.

IF and it’s a big if, but we should I think use about 1/10 the amount as we are about 1/10 the HP, if so then we would use a little over 1 gl in 10 min.

This is speculation, but the STC has a 5 gl tank.

The cost of the fluid is or should be insignificant, about half the price of fuel if you mixed your own, and you might be mixing your own as it’s unlikely I think to be sold at most FBO’s.

 

[A64Pilot]

4 minutes ago, McMooney said:

hmm, looking at the video think they could make it simpler, no need for a computer just calibrated temp / pressure switch should work.  be nice if i could just cheap vodka for the fluid, instead of messing with methanol

I don’t think it’s much of a computer, just turns the pump on and off is all and maybe automatically turn the backup on if the primary isn’t pumping as indicated by pressure?

Remember these are Certified aircraft, so we have to go STC, your not getting a field approval if an STC is available, for an Experimental I’m sure I could knock out an ADI for very little money, that pump in the Video is just a cheap Facet Automobile fuel pump.

‘But there is more to it, if running Mogas you have to ensure you don’t vapor loc, that’s one reason why I think 94UL and ADI is another answer to get us to lead free

[Pinecone]

On 1/13/2025 at 1:14 PM, McMooney said:

nitrous injector would be nice also,  little bit of help when i take my flatland plane out to mountain territory

Look on You Tube for some videos of Reno air racers running nitrous.  Some pretty impressive engine failures.

[GeeBee]

On 1/13/2025 at 12:45 PM, EricJ said:

 I'm not sure how all that technology got left behind other than there was a lot of "not invented here" bias in engineeing that lasted many decades after the war.

Here is a possible answer. 5 gallons methanol, figure about 35 pounds. Tank and installation figure another 12 pounds so 47 pounds off of payload. $12,000 installation cost is a little off the wallet payload. Then you have the corrosive nature of methanol, more maintenance costs.  Simpler, cheaper and greater payload/range to burn high octane. 47 pounds is a 45 minute reserve in most SE airplanes.

[EricJ]

3 minutes ago, GeeBee said:

Here is a possible answer. 5 gallons methanol, figure about 35 pounds. Tank and installation figure another 12 pounds so 47 pounds off of payload. $12,000 installation cost is a little of the wallet payload. Simpler, cheaper and greater payload/range to burn high octane. 47 pounds is a 45 minute reserve in most SE airplanes.

Yes, some German fighter aircraft carried MW-50 (50-50 water-methanol) and also nitrous injection at high power demand.   Some allied aircraft, e.g., P-51, also used methanol injection at emergency power settings.   German avgas was 90/100, US was 100/130 (generally for both for much of the war).  There were still a large number of German high-output engines that ran on 90/100 and made a lot of power.   I'm not sure what all the tricks were, but they seem to have been effective.

[A64Pilot]

On 1/16/2025 at 4:00 PM, GeeBee said:

Here is a possible answer. 5 gallons methanol, figure about 35 pounds. Tank and installation figure another 12 pounds so 47 pounds off of payload. $12,000 installation cost is a little off the wallet payload. Then you have the corrosive nature of methanol, more maintenance costs.  Simpler, cheaper and greater payload/range to burn high octane. 47 pounds is a 45 minute reserve in most SE airplanes.

Couple of things, first the corrosive nature of methanol is mitigated / eliminated by the 1% of oil in the mix, and as it’s not present in the engine the corrosion if any is in the tank and fuel pump.

You do know that the windshield washer fluid in your car is Methanol / water mix at about the same mixture ratio right? Is it corroding your car?

What is this increased maintenance you speak of? If anything I believe it would decrease maintenance as water injection cleans the combustion chambers / plug.

But yes it will cost 12K most likely, and will weigh about 50 lbs. but that’s a full tank, if you’re really weight conscious yiu could go with less mixture. But what is this 100 Octane replacement fuel going to cost? Will it come with problems?

94UL if anything should cost less than 100LL, but I’m not kidding myself we will be lucky if the price remains the same as 100LL. but IF 94 UL is the same fuel as 100 LL, just without the lead, we’ll we can I believe be pretty sure it’s not going to cause any problems with the rubber and paint etc.

 

Edited Saturday at 10:46 PM by A64Pilot

[Justin Schmidt]

On 1/16/2025 at 12:54 PM, Pinecone said:

Look on You Tube for some videos of Reno air racers running nitrous.  Some pretty impressive engine failures.

Fun watching at the race track too

[A64Pilot]

On 1/16/2025 at 4:11 PM, EricJ said:

Yes, some German fighter aircraft carried MW-50 (50-50 water-methanol) and also nitrous injection at high power demand.   Some allied aircraft, e.g., P-51, also used methanol injection at emergency power settings.   German avgas was 90/100, US was 100/130 (generally for both for much of the war).  There were still a large number of German high-output engines that ran on 90/100 and made a lot of power.   I'm not sure what all the tricks were, but they seem to have been effective.

It was ADI. The German Benz motor in the 109 anyway couldn’t make enough boost to need the US manufactured British spec 100 Octane fuel.

https://runway.airforce.gov.au/jimmy-doolittle-hap-arnold-and-battle-britain-100-octane-story

https://www.nytimes.com/1978/12/03/archives/new-jersey-weekly-4-who-helped-win-battle-of-britain.html

The first link is a quick synopsis the second a little better, but there is all kinds of data available on the internet.

It was two things that gave the Brits an advantage, fuel was one, but probably just as important was the US allowing them to build constant speed props from I believe Hamilton Standards drawings that made at least as much difference, the 109 had variable pitch, but not constant speed and managing prop pitch was increased workload.

The Germans had all kinds of fuel at times in the war, but the Luftwaffe in 1940 fought the Battle of Britain with 87 Octane fuel, there are numerous sources for that and I’m pretty sure 87 Octane was the standard throughout the war.

[GeeBee]

15 minutes ago, A64Pilot said:

Couple of things, first the corrosive nature of methanol is mitigated / eliminated by the 1% of oil in the mix, and as it’s not present in the engine the corrosion if any is in the tank and fuel pump.

You do know that the windshield washer fluid in your car is Methanol / water mix at about the same mixture ratio right? Is it corroding your car?

What is this increased maintenance you speak of? If anything I believe it would decrease maintenance as water injection cleans the combustion chambers / plug.

But yes it will cost 12K most likely, and will weigh about 50 lbs. but that’s a full tank, if you’re really weight conscious yiu could go with less mixture. But what is this 100 Octane replacement fuel going to cost? Will it come with problems?

94UL if anything should cost less than 100LL, but I’m not kidding myself we will be lucky if the price remains the same as 100LL. but IF 94 UL is the same fuel as 100 LL, just without the lead, we’ll we can I believe be pretty sure it’s not going to cause any problems with the rubber and paint etc.

 

My car is not aluminum. Any of us who have TKS systems know what a PIA it is to maintain a system like this. Pumps, tubing leaks not to mention the fluid is highly toxic. If the methanol in an injection system does not kill your dog, the glycol in TKS will.

[A64Pilot]

The prop story

https://airandspace.si.edu/stories/editorial/better-propellers-few-desmond-cookes-legacy-battle-britain

In the above article it indicates that the ME-109 had constant speed props, I believe that came later.

The linked video which I haven’t watched I believe explains the manual prop control the Luftwaffe had in 1940 in the field on the BF-109

I believe most of the 109’s in the Battle of Britain were of the BF variety, not ME. below explains the difference. I believe there were some ME’s IE the Emil or E model.

https://www.historynet.com/what-is-the-difference-between-the-designation-bf-109-german-fighter-and-me-109/

[A64Pilot]

9 minutes ago, GeeBee said:

My car is not aluminum. Any of us who have TKS systems know what a PIA it is to maintain a system like this. Pumps, tubing leaks not to mention the fluid is highly toxic. If the methanol in an injection system does not kill your dog, the glycol in TKS will.

Well the hood on my 20 yr old Miata is aluminum, and has no corrosion from wiper fluid, ALL Miata’s hoods are aluminum, not sure about the newer ones though, but there are still 97 models running around and don’t have any corrosion.

My Tesla also has an aluminum “hood” Aluminum is pretty common in Autos.

I have no experience with TKS, but I’m pretty sure it way more complex than one line running from a tank to the injector plate that would go under the fuel servo.

A far as toxicity I bet this Gami fuel is more toxic, and seemingly less kind to the aircraft than Methanol.

[GeeBee]

I am not opposed to methanol injection IF it is the only way to get to where we need to be. I would strongly prefer as a cross country flyer, not to give up 50 pounds of payload and range if I don't have to do so.