Help me understand: UL94 fuel approval vs. compression ratio vs other aspects?

[A64Pilot]

This is an interesting read, the last three paragraphs or so are interesting

https://generalaviationnews.com/2019/01/28/all-100-octane-fuels-are-not-equal/

[RobertGary1]

6 hours ago, N201MKTurbo said:

Because as the OP said, He can buy 94UL at his airport, but you can't buy G100UL anywhere.

The question is why the industry is wasting time with the 94ul deadend. 

[1980Mooney]

On 2/11/2022 at 1:37 PM, N201MKTurbo said:

They will run an instrumented engine on different octane fuels and find out when it detonates……The CR, mixture and timing all effect the detonation octane number.

Also affecting it is the flow through the cylinder head, how the burn front propagates, hot spots in the cylinder head, spots of higher pressure in the head due to air/fuel mass flow momentum, how and where detonation (knock) starts, how the detonation shock wave propagates etc.  It is a dynamic process in which not everything happens uniformly - like watching a creek or river, the water does not flow evenly - eddy currents appear. And although it is a vapor, there is still a momentum influence as the air/fuel mixture flow is started and stopped violently with each valve closing and opening - this creates additional dynamics of pressure and temperature that may not be instantaneously uniform. 
 

Safe operating ranges/conditions and the point of detonation knock are not all predicable without testing. 
 

 

 

 

Edited February 13, 2022 by 1980Mooney

[N201MKTurbo]

1 hour ago, RobertGary1 said:

The question is why the industry is wasting time with the 94ul deadend. 

Because UL94 is basically unleaded auto fuel with no ethanol. As the OP stated, it is relatively cheap. There are quite a few airplanes that can use it. If it was available at my airport, I would buy it for my Cessna.
 

Heck, every time I fill my truck there are three grades available, why not at the airport? G100UL will be more expensive then UL94. Are you going to force the Cessnas to buy premium when they don’t need it? 

[N201MKTurbo]

On 2/11/2022 at 12:49 PM, jaylw314 said:

There are a ton of IO-360's out there, hopefully they'll come up with something reasonable and easy, like "200 HP limited to 5 minutes continuous" or something like that.  

You can’t do that. The detonation would happen in the 5 minutes. The power limitations you are talking about are thermal limits.

[A64Pilot]

14 hours ago, RobertGary1 said:

The question is why the industry is wasting time with the 94ul deadend. 

Read the article I linked to, or at least the last couple of paragraphs.

It explains that apparently there is more to detonation resistance than just octane, apparently leaded fuel with the same octane is more resistant to detonation, so even if there is a 100UL, it won’t replace 100LL.

To me it makes sense why back in the day some lead was kept when fuel was reformulated, because it was necessary.

Majority of the GA fleet can run 94UL, so it makes sense to me to provide a fuel for the majority of the fleet, just like the majority of Auto’s can burn regular, Sure the high HP cars need Premium, but it’s not logical to force a little economy car to buy it.

Edited February 13, 2022 by A64Pilot

[RobertGary1]

1 minute ago, A64Pilot said:

Read the article I linked to, or at least the last couple of paragraphs.

It explains that apparently there is more to detonation resistance than just octane, apparently leaded fuel with the same octane is more resistant to detonation, so even if there is a 100UL, it won’t replace 100LL.

To me it makes sense why back in the day some lead was kept when fuel was reformulated, because it was necessary

But Gami is claiming g100ul is a full drop in replacement. 

[RobertGary1]

12 hours ago, N201MKTurbo said:

Because UL94 is basically unleaded auto fuel with no ethanol. As the OP stated, it is relatively cheap. There are quite a few airplanes that can use it. If it was available at my airport, I would buy it for my Cessna.
 

Heck, every time I fill my truck there are three grades available, why not at the airport? G100UL will be more expensive then UL94. Are you going to force the Cessnas to buy premium when they don’t need it? 

There may be a lot of little Cessnas out there but we’re told they make up a small part of the amount of fuel purchased. The big motors burn the most gallonage purchased. 
If fbos sold the volume of fuel that Costco did 2 may make sense (gas stations only have 2 octanes the third is blended at the pump). 

[A64Pilot]

16 minutes ago, RobertGary1 said:

But Gami is claiming g100ul is a full drop in replacement. 

Think about that statement.

100LL was a drop in replacement for 100, which meant no requirement for an STC.

Do you need an STC for Gami’s fuel?

Edited February 13, 2022 by A64Pilot

[A64Pilot]

10 minutes ago, RobertGary1 said:

There may be a lot of little Cessnas out there but we’re told they make up a small part of the amount of fuel purchased. The big motors burn the most gallonage purchased. 
If fbos sold the volume of fuel that Costco did 2 may make sense (gas stations only have 2 octanes the third is blended at the pump). 

I’ve heard that for decades, and I’m sure it used to be true, back in the 80’s Fedex had a fleet of Beech 18’s and every bank check flew home almost always in big twins.

 But go to the Airport, it seems those big twins of old are now BizJets, PC12’s etc. and it’s rare to see a B58 etc like you used to.

So I’m not sure it’s as true as it used to be.

If you think about it IF 94UL is just 100LL without the lead, couldn’t lead be blended in in a similar manner as Prist is to jet fuel to make 100LL from 94UL?

This is solvable, only question is there enough profit to be made doing so?

Edited February 13, 2022 by A64Pilot

[PT20J]

What’s unknown about G100UL is it’s actual octane rating. I believe it was tested in a number of engines to show detonation resistance at least equal to 100LL. G100UL might just be a name similar to the way LED bulbs are labelled with the equivalent wattage ratings of incandescent bulbs. In the end, it doesn’t really matter what you call it.

Skip

[A64Pilot]

One thing that could be done and was done by at least the Germans back in WWII to prevent detonation is water injection.

It wouldn't be hard at all to build a system that injects water above a set manifold pressure.

Read the section labeled “Use in Aircraft”

https://en.wikipedia.org/wiki/Water_injection_(engine)

[ArtVandelay]

One thing that could be done and was done by at least the Germans back in WWII to prevent detonation is water injection.
It wouldn't be hard at all to build a system that injects water above a set manifold pressure.
Read the section labeled “Use in Aircraft”
https://en.wikipedia.org/wiki/Water_injection_(engine)

Having to carry water in addition to fuel would lessen our payload, not to mention corrosion concerns having to store water.

[RobertGary1]

7 hours ago, A64Pilot said:

I’ve heard that for decades, and I’m sure it used to be true, back in the 80’s Fedex had a fleet of Beech 18’s and every bank check flew home almost always in big twins.

 But go to the Airport, it seems those big twins of old are now BizJets, PC12’s etc. and it’s rare to see a B58 etc like you used to.

So I’m not sure it’s as true as it used to be.

If you think about it IF 94UL is just 100LL without the lead, couldn’t lead be blended in in a similar manner as Prist is to jet fuel to make 100LL from 94UL?

This is solvable, only question is there enough profit to be made doing so?

I’ve wondered about that with lead. When we order Prist it’s mixed at the truck why not the same for lead? A quick temporary solution for California’s coming ban on lead.  

[A64Pilot]

1 hour ago, ArtVandelay said:

Having to carry water in addition to fuel would lessen our payload, not to mention corrosion concerns having to store water.

I doubt it would be more than a gallon and water in a tank causes corrosion? Probably be a mix of alcohol and water too.

 It would however allow the same 200 HP on lower octane fuel though, wouldn’t I assume help those with turbos used to increase HP over seal level HP though.

 

Not saying it will be done, but it’s been shown to work a long time ago, on much higher “tuned” engines than ours.

[N201MKTurbo]

Our engines were not certified with water injection. It would take an STC for every airframe to make it work. Along with the water injection hardware. 
 

Good luck, who is going to do this work? Where is the monetary incentive to do it?

[RobertGary1]

1 hour ago, N201MKTurbo said:

Our engines were not certified with water injection. It would take an STC for every airframe to make it work. Along with the water injection hardware. 
 

Good luck, who is going to do this work? Where is the monetary incentive to do it?

Once lead is banned next year a workable stc will be worth a lot of money. 

[N201MKTurbo]

1 minute ago, philip_g said:

I've run methanol injection on forced induction cars. It's quite simple but it's never going to be worth it on our planes.

I’m not saying it won’t work, I’m saying it isn’t the simplest solution to this problem. 

[Andy95W]

Water/methanol has already been done and approved, and the current company is still in business.

Petersen got its system approved back in the 80s/90s.  At some point the system was sold to Airplains, which is still in business.  It is currently approved for the Cessna 180/185 and maybe a few others.  I’m not sure about adapting it to a Lycoming.

 

[ArtVandelay]

Water/methanol has already been done and approved, and the current company is still in business.
Petersen got its system approved back in the 80s/90s.  At some point the system was sold to Airplains, which is still in business.  It is currently approved for the Cessna 180/185 and maybe a few others.  I’m not sure about adapting it to a Lycoming.
 

That system is only used when MAP >25”…which translates to full power below 4500’, which is 80-90% horsepower.
So if you don’t used full throttle, then I assume 94 octane is safe to use…seems placard stating that would be cheap fix. A cumbersome $12,000 (plus labor) not necessary.

[N201MKTurbo]

All the info on the Airplains ADI system seems pretty stale. The system with a full tank weighs 63 pounds. That is kind of heavy. It was $12000 in 2011. I have to think it is a bit more today. I don’t know if that price includes installation either. If you go to Airplains website, there is no mention of the ADI system.  It seems that it has been installed on 3 aircraft so far. That won’t recover the development costs.

[N201MKTurbo]

3 hours ago, ArtVandelay said:

That system is only used when MAP >25”…which translates to full power below 4500’, which is 80-90% horsepower.
So if you don’t used full throttle, then I assume 94 octane is safe to use…seems placard stating that would be cheap fix. A cumbersome $12,000 (plus labor) not necessary.

I completely agree a MP reduction Would be the easiest solution. It would be a lot more involved than just a placard. All the performance charts would need to be updated.

[A64Pilot]

3 hours ago, ArtVandelay said:

That system is only used when MAP >25”…which translates to full power below 4500’, which is 80-90% horsepower.
So if you don’t used full throttle, then I assume 94 octane is safe to use…seems placard stating that would be cheap fix. A cumbersome $12,000 (plus labor) not necessary.

Yes, the higher octane is only required at high power and high temps. Detonation could be handled by reduced power, but then of course you lose useful load, climb rate etc. etc.
So if lead is outlawed we need a fuel that won’t detonate, and I’d prefer it to not be stupid expensive, and until it actually exists in a reasonable quantity, I don’t think any guess on price now is anything but a guess.

Or we need a system that will allow whatever fuel there is to be used without detonation, water injection has worked in the past, why not now?

Remember how cheap the Eclipse jet was supposed to be? Well those numbers were actually based on mostly facts, if they had ever achieved the production rate they may have been achievable. So what’s Gami’s 100UL only a dollar a gl more based on?

Even Ethanol containing car gas caused all sorts of additional unplanned problems, the Chevron Jobber I used to buy fuel from in my home town would not deliver it to farms and private tanks, only shipped straight gas to them, the reason was to change to ETH fuel the tanks had the be cleaned and at least the hoses replaced and often the pumps too. For that reason ETH is not shipped in the pipelines, it’s trucked in and blended at the Jobber as fuel is loaded into the trucks.

So is 100 UL going to be able to go into the same trucks with no modifications? 
Remember ETH auto fuel was supposed to be seamless, it wasn’t supposed to eat up boat fiberglass tanks or it’s solvent action cause gunk to be cleaned out of existing fuel storage, deteriorate hoses etc.

[A64Pilot]

39 minutes ago, N201MKTurbo said:

All the info on the Airplains ADI system seems pretty stale. The system with a full tank weighs 63 pounds. That is kind of heavy. It was $12000 in 2011. I have to think it is a bit more today. I don’t know if that price includes installation either. If you go to Airplains website, there is no mention of the ADI system.  It seems that it has been installed on 3 aircraft so far. That won’t recover the development costs.

A few observations, first they have a 5 gl metal tank, in the video the guy said he didn’t remember last time it was filled, at least 40 hours ago. So maybe 5 gls is a bit excessive. So a lot of weight could be lost if it were say a 1 or 2 gl plastic tank and why not plastic? Many, many car guys that do this run windshield washer fluid as it’s apparently just the right mix or close enough anyway and every windshield washer tank I’ve seen is plastic.

Then 12G seems excessive for what it is too, but then 2G seems excessive for an alternator for my C-140, the Plane Power STC one is 1G.

One hopes that number is based on very limited production rate, but if the demand supports it, there will be copy cat STC’s very quickly, Joe Brown of Hartzell would be among the first I’m sure, and competition will drive the price down, but even if it’s 10G, if it allows Premium Auto fuel to be used, right now in my area that’s about $2 a gl less, could be worth doing on that alone?

If you burn 10 GPH and it’s 10G, then it pays for itself in 500 hours?  Less for the big motor guys?

How long would an engine last with no lead, and if cyl head temps were always capped at 400F?

I woudn’t be surprised if plug cleanings were almost gone and oil changes go to 100 hours.

Savings in Maintenance may also not be insignificant.

Still without lead some engines may suffer from valve wear.

Edited February 14, 2022 by A64Pilot

[ArtVandelay]

Can’t a electronic ignition system solve the same problem simply by changing the timing, based on cylinder temperatures and MP just like the water injection system?