The place for technical discussions about GA and flying.
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#1777314
Inspired by the thread on TEL, I had a look to see whether I could fly my PtoF aeroplane with Mogas or other fuels than Avgas 100LL.

My specific engine is stamped as an O-360 A1D but has had a Bendix AMS 4290 injection system and a Christen inverted oil system fitted.

Looking at the Lycoming specified fuels chart as shown on their website https://www.lycoming.com/sites/default/ ... 0Fuels.pdf it indicates that the O-360 A series of engines can use Automotive fuels with an octane number above 93 and complying with standards ASTM D4814 or EN228.
I note that this would require an additive as specified. I also note that there is some discussion about methane content in MoGas (more important for the fuel system than the engine itself, I think) which would need to be checked.

But whereas the O-360A series can use Mogas, the IO-360A and AIO-360A cannot.

Does either the Bendix injection system and/or the Christen inverted oil system change the ability of the O-360 to run on Mogas? The engine should still have 1:8.5 compression ratio of the A1D, not the 1:8.7 of the IO-A1D?

Can I use Mogas as long as I don't fly inverted :clown: ?

(I've asked LAA engineering the same question - I'll add their reply to the thread when available)

@Mods: maybe move to technical discussion - apologies!
#1777344
I would expect the higher compression engine, 8.7:1 to be 200hp where the 8.5:1 would be 180hp? My A1B6 is 8.7:1 and 200hp. It can't use mogas.

I would think the 8.5:1 could use a lower octane fuel than 100LL but you need to be careful as it's on the ragged edge. Have you converted 93 AKI into RON to see what mogas could be used here? The 97 RON high octane unleaded here is around 92-93 AKI, so could be slightly too low. According to Wiki, "Shell V-Power Nitro+ 99" and "Tesco Momentum 99" are equivalent to the US AKI 93, though I don't know where those fuels are available.

I saw a discussion recently about the availability of 93 in the US, apparently there's an east/west divide with perhaps half the states not having 93 available.

I'd have thought UL91 avgas, being 91 MON, maybe 103ish RON, 97ish AKI, would be ok for the 8.5:1 engine but don't quote me on that.
#1777409
Morten wrote: I also note that there is some discussion about methane content in MoGas (more important for the fuel system than the engine itself, I think) which would need to be checked.


I think you may mean ethanol rather than methane. Close, but different (chemically).

If so, depending where you are in the country some retailers of super unleaded are still ethanol free (BP ultimate where I am, apparently).

Also, test kits are available to test for the presence of ethanol, although from the USA.
www.fuel-testers.com

Andy
#1777412
@Morten EN228 has potentially 5% ethanol and whilst your engine might be happy with it, you need to check every other single piece of your fuel system for compatibility. tanks, pipes, values, O-rings, the whole jolly lot. You only need one rotted O-ring to spoil your day.
#1777413
Morten wrote:
Does either the Bendix injection system and/or the Christen inverted oil system change the ability of the O-360 to run on Mogas? The engine should still have 1:8.5 compression ratio of the A1D, not the 1:8.7 of the IO-A1D?



I believe, (but cannot recall where I saw this) that the limiting factor that prevents mogas use is the function of the Bendix injection system.

If I recall, there is a fuel/vapour separator swirl pot device that is designed to elimanate vapour entering the injector lines. Straight run avgas is essentially a single refined component with a homogeneous evaporation point so has no trouble with this vapour/liquid device.
Mogas is a complex blend of all sorts of hydrocarbons all of which evaporate at different pressures and something about the swirl pot venting off the lighter fractions of mogas and/or vapour lock is the reason Mogas can't go through a Bendic mechanical injection system.

It was a while ago I read this and I have no idea of the publication it was in. Sorry.

If any, or all, of the above is bollox I'm sure someone will be along with the right explanation soon!

Cheers

Andy
#1777422
Thanks for thoughts and info by PM.

(Yes, apologies for my sloppy chemistry memory re ethanol/methanol/ethane/methane. I do remember vividly the class fool being fooled into drinking some methanol in the chemistry lab which we had scratched the M on the label off ...)

Via PM, my attention was drawn to the lower vapour point of Mogas compared to Avgas. This could give vapour lock issues more often and be more critical than the lower octane number. I will need to read up on this. There was also a comment that doing aerobatics would be more likely to lead to be vapour forming - so the restrictions on the AE-models may well be due to their intended use and not the engine itself - my :clown: may have been misplaced and carried some truth :shock:

Andy's point on the Bendix swirling function may also be relevant for injection systems in general.

I thought that the main differences between Avgas and Mogas would be the lead, the octane number and the 'certifiable purity'. I guess it is the latter which causes issues with the vapourisation and potential swirlability.

Googling a bit more, I also found this on the LAA website quite informative and helpful: http://www.lightaircraftassociation.co. ... MATION.pdf (Thanks LAA :thumleft:)

(BTW - I'm not really looking to save money but looking at the convenience of carrying some jerrycans versus needing to fly into an Avgas enabled airfield en route.)
#1777511
(Yes, apologies for my sloppy chemistry memory re ethanol/methanol/ethane/methane. I do remember vividly the class fool being fooled into drinking some methanol in the chemistry lab which we had scratched the M on the label off ...)


Wow, 10 ml ( 2 teaspoonsful) can cause permanent blindness and lethal dose is about 100ml in humans. What were the consequences for the victim and the perpetrators? https://en.wikipedia.org/wiki/Methanol_toxicity
#1777517
Dodo wrote:What were the consequences for the victim and the perpetrators?

Gosh, I can think of far worse things kids did to eachother at the time. Just as well we didn't have wikipedia back then ;) But as a guess:
The victim - Gag, spit, outrage
The perps - Bouts of laughter

HSE has probably closed down most chemistry lessons nowadays?
#1777713
Paul_Sengupta wrote: "Shell V-Power Nitro+ 99" and "Tesco Momentum 99" are equivalent to the US AKI 93, though I don't know where those fuels are available.


Tesco is quite a well known shop around these parts. If you come to Norfolk I will show you a couple.

Rob P
#1778034
andytk58 wrote:
Paul_Sengupta wrote:Please check that they do the 99+ before I come over. :D

They don't have it in Aberdare.


I know you're kidding, but its worth pointing out that Tesco 99+ is riddled with the dreaded ethanol, no way would I put that in an aeroplane.

Andy


I bought some Tesco Momentum 99 about 3 weeks ago in Lewes (East Sussex). To my great surprise when I tested it, it was alcohol free.
Of course that mey not be consistently so, I'm sure they buy all over the place.
Esso still publicly declare their Super to be ethanol free in most parts of the country.