I thought this video had some good overlap with the chemistry themes of BITOG. Apparently the forced early adopters of the new unleaded 100 octane G100UL fuel for piston powered airplanes in California are having issues with paint, o-rings, and potentially seals inside of fuel tanks. This is disappointing as I was hoping it would be a painless drop-in for legacy piston powered airplanes. I guess if it was easy, we would've long ago had an unleaded 100 octane fuel.
G100UL fuel: O-ring, seal, paint problems?
- Thread starter 2.7ecoboostFordBronco
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Thx for posting that video. I've been following this with great interest and a bit saddened to see the continuing problems. The prev gen Swift fuels guys came here to FL to meet me years ago and I very much liked the TriNitroToluene blend they were promoting, (a little joke) er, ah, Trimethylbenzene and isopentane mix. It had issues with cold start, but was otherwise inert and performed remarkably well with regard to detonation resistance.
I love my turbocharged race engines, and in the distant past, finding unleaded fuels that work under high boost conditions has been an incredible struggle. Yes E-85 is boost-magic today, but that was not an option then for range reasons, and not likely to be a great choice for aircraft either. I liked clean non ethanol 93 or VP C9 96oct, mixed with 20% added Toluene. Which gave enough detonation resisitance to run any sane boost level. That had it's own set of issues, but worked when the fuel was heated prior to the injectors.
The GAMI 100 octane non-oxygenated unleaded fuel sure did seem to have promise. The epoxy dissolving Amine in GAMI's G100UL is m-toluidine (meta-toluidine), a nitrogen-containing aromatic amine used as an octane booster and helps G100UL achieve the high octane rating needed to match or exceed 100LL Avgas performance without tetraethyl lead.
Just thinking aloud here, maybe the GAMI fuel will be viable with component changes, tank reseals and so on.
But I still believe a version of the Swift 100 (UL or R) is the better choice. Thinking the cold start issue simply needs a a "Turbine Engine" ignition system to light it off when cold. Which is about 300x more spark energy. Lower voltage than a magneto generally, but a substantially higher intensity spark. I said 300X more, but it can be even more than that.
Anyone that's experimented with turbine engine ignition systems know they produce a small electrical explosion, and not a 'spark'. The thought was an "add on" digital ultra high intensity ignition that simply attached to the plugs. Triggered by the magneto, powered by the aircraft, used only for start and initial warm up.
I love my turbocharged race engines, and in the distant past, finding unleaded fuels that work under high boost conditions has been an incredible struggle. Yes E-85 is boost-magic today, but that was not an option then for range reasons, and not likely to be a great choice for aircraft either. I liked clean non ethanol 93 or VP C9 96oct, mixed with 20% added Toluene. Which gave enough detonation resisitance to run any sane boost level. That had it's own set of issues, but worked when the fuel was heated prior to the injectors.
The GAMI 100 octane non-oxygenated unleaded fuel sure did seem to have promise. The epoxy dissolving Amine in GAMI's G100UL is m-toluidine (meta-toluidine), a nitrogen-containing aromatic amine used as an octane booster and helps G100UL achieve the high octane rating needed to match or exceed 100LL Avgas performance without tetraethyl lead.
Just thinking aloud here, maybe the GAMI fuel will be viable with component changes, tank reseals and so on.
But I still believe a version of the Swift 100 (UL or R) is the better choice. Thinking the cold start issue simply needs a a "Turbine Engine" ignition system to light it off when cold. Which is about 300x more spark energy. Lower voltage than a magneto generally, but a substantially higher intensity spark. I said 300X more, but it can be even more than that.
Anyone that's experimented with turbine engine ignition systems know they produce a small electrical explosion, and not a 'spark'. The thought was an "add on" digital ultra high intensity ignition that simply attached to the plugs. Triggered by the magneto, powered by the aircraft, used only for start and initial warm up.
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This video does a great job boiling it down to the facts. I was able to play it fast, so it was about 5 mins.
Note the Swift 94 fuel did result in microwelds on exhaust valves as all of us expected. The users discontinued it's use.
I tend to love VP Racing fuels, but it seems even they can't create enough unleaded Avgas octane for aircraft engine use when 'full rich' high load conditions exist.
Note the Swift 94 fuel did result in microwelds on exhaust valves as all of us expected. The users discontinued it's use.
I tend to love VP Racing fuels, but it seems even they can't create enough unleaded Avgas octane for aircraft engine use when 'full rich' high load conditions exist.
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Doubletap, please disregard
Wow, thanks for the detailed tech info. I'm using dual electronic ignition (lightspeed) on my Lyc. IO-360 which is touted to be a stronger spark, I wonder if it would suffice for the Swift.
I'm guessing the electronic ign would not have been be nearly enough to deal with the original fuel Swift 100SF: Which was a binary fuel, 85% mesitylene (1,3,5-trimethylbenzene) and 15% isopentane by weight. The issue with the first gen Swift 100 fuel not starting is very poor vaporization at temps below 40ºF. If you've ever tried to quickly light off Kerosene, it's a similar thing. Generally not possible without a kaboom of a spark or a bunch of heat held in place for a time.
Speculation: Swift Fuels new 100R has lower Trimethylbenzene content, has toluene/xylene and now contains MTBE, ETBE and maybe even a small quantity of ethanol (a blend of this might work) and maybe much more sophisticated than this, containing isobutanol or more. As the patent references oxygenates. Swift says it does not contain Amines.
Swift's 100R would seem to be less troublesome on the surface.
My thoughts are yeah certification is expensive but why did Lycoming and Continental not see this coming a decade ago and at least start the process for development of an engine not needing lead? Second I'll have to dig for the article but recently Cessna has updated a couple of the 172s with type certificates to allow 100 octane no lead fuel. A supplier at one of the FBOs is selling it.
Yeah, GAMI got an STC for approval in almost all spark-ignition engines with the G100UL. One of the exceptions that doesn't apparently have STC approval is talked about in the video; the PPponk aka Northpoint XP470 conversion engine, which is a popular upgrade to TCM O-470/520 powered cessnas.
I am suspicious that perhaps Textron/Lycoming doesn't care and would just presume exit the piston aviation market rather than come up with anything new, but maybe I am wrong. The profit margins and liability exposure are probably a lot better on their businees jets and I get the feeling they would rather just do that.
Theres a company in Colorado springs that has an engine conversion using a GM LS engine. It's apparently a start and go just like driving. No mag checks etc.
There are plenty of aircraft engines that are certified to, and can safely operate on lower octane, unleaded fuel. Nearly all of the parallel valve lycoming engines, for example. O-235/320/360/540 and some of the injected versions of those same engines.
The higher output angle valve engines are unable to tolerate lower octane fuels. That is a clear "don't do it" situation. Heck, the angle valve Lycoming engines even detonate on 100LL sometimes!
An example of a 315HP, AEIO 580 angle valve Lycoming engine in an Extra NG stunt plane. The non square shape of the valve covers is the hint that it is an Angle Valve, high compression engine. Lycoming did try to lower the compression on these beasts and was not able to achieve enough detonation resistance to run on Swift 94UL.
The better choice is the O/IO-540 Lycoming parallel valve. Which can make 260HP. It is lighter, so the power to weight is about the same.
This engine in the pic does not come with an oil filter. Just a screen.
I thought I'd add that the Extra 300/300L and NG's wing fuel tanks are carbon fiber and epoxy (as is the entire wing). The fuel is captured forward of the carbon fiber spar and in the leading edge area. Sealed in with epoxy and baffles. Knowing how the spar is immersed in fuel, and the GAMI 100 fuel dissolves epoxy, I'd never consider the GAMI 100 fuel for these planes. I'm sure someone will do it, and end up needing a new wing.
In the pic, the fuel is where the blue wing leading edge paint is.
In the pic, the fuel is where the blue wing leading edge paint is.
The main problem with the automotive conversions is the gear reduction system. The simplicity and reliability of a direct drive engine is tough to beat. With that said, Rotax has what seems like a good geared offering with their 916is turbo which is rated at 160 HP for takeoff and 137 HP continuous, and takes auto gas.
I lost a friend due to a gearbox failure on a Chevy V8 conversion. Not really a great airplane engine. Tons of cooling drag, poor BSFC.
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