Continental IO-360-AF - a joke? - MOGAS discussion

One critical point in mogas or any no-avgas fuel is the different chemicals in it, alcohol is NOT the problem. I did a test several weeks ago , storing typical NBR o-rings and rotational shaft seals in super plus fuel for two weeks. Result: All NBR material had a lot of swelling to the point that the sealing lip was too wide to contact the shaft with nominal diameter. All Viton items were OK, and all items dumped in white spirit (ethanol) were completely unaffected. So when using auto fuel you will have to watch all “rubber” hoses and maybe change seals for Viton types. For avoiding vapor locks by cavitation in the fuel pump I fitted an electric feeder pump low down in the fuselage, low wing aircraft. And don´t argue any more with car engines running at 20 percent power all the time: Just take a small car with say 50 hp, even in the fifties and sixties there were lots of these with 40 to 50 hp, they were thrashed 100 percent ALL the time to see some velocity at all. Now taking in account the relatively poor oil specs then , even so these engines did a few hundred thousand kms no problems – now convert this to hours. Of course small engines with small bores have an easier life for pistons. Typical American aero engines are in fact far from ideal , I´d say a sick design as a gasoline engine with bores of much more than 100 mm . This is only acceptable with a Diesel engine and truck engines do millions of kms at what percentage of power ??? The common aero engine is definitely no longer a sound design in engineering, in more than one place, when maxed out to hp figures we see today. Vic

Peter I thought the issue wasn’t power loss (that happens with Avgas too, no?) but fears of Mogas vapor locking in the pipes at altitude – the ECU ain’t going to fix that. Re – differences in the fuel system: tank lower than engine, electrical fuel pump, injectors… at least piping wise I don’t see much of a difference. The only difference is metering.

I have a 3.5kW Briggs & Stratton generator whose entire fuel gauge dissolved and fell out into the tank, due to alcohol in the petrol which wasn’t there a few years before.

So checking out “fuel system compatibility” is an understatement

We are heading for 10% alcohol here and the TB20 fuel system is specified to max of 2%. One uses ~1% of IPA for anti fuel icing purposes so that’s OK.

at least piping wise I don’t see much of a difference. The only difference is metering.

Maybe car petrol is good for 14000ft. It probably is. I recall a similar figure in some CAA document on mogas approvals. I am sure others have been up this road, and asked the same Q about Bolivia.

But 14k is not a useful ceiling for Eurocontrol IFR in Europe, particularly as the margin at 14k might be rather thin – but nobody cares because a car can’t plummet with a stopped engine, and there probably aren’t many motorways in Bolivia where you could get an engine stoppage at 70mph (or 100mph ) in the middle of a 3 lane packed road.

The other thing about ethanol in petrol (gasahol) is that it’s less energy dense – even if your fuel system is compatible, you’ll need to burn more litres per hour to make the same power.

It’s also not green: it’s debatable whether the EROEI for ethanol from corn is greater than 1.

Peter,

as I said, ethanol is NOT the problem, it is the other thinners in the fuel. Just do a test with white spirit with any rubber or plastic. If ethanol was so bad I would not recommend whisky at all.

Vic

What is the verdict on 91UL, after all this time?

It does seem like a failed market-push experiment by TOTAL, who tried all they could to get airfields to drop 100LL.

91UL is reasonably big in Sweden. Perhaps not surprising as a Swedish company pioneered it and has been pushing it for about 30 years.

You cannot make UL91 cheaper than 100LL,

In Sweden, 91UL is sold 5-10% cheaper than 100LL.

In Sweden, 91UL is sold 5-10% cheaper than 100LL.

That does not necessarily mean the production is cheaper. It can have all kinds of reasons, like marketing, lower tax …

And yet car fuel is totally fine for aero engines so you’re making a point to make a point, LeSving.

My point was simply that UL91 IS mogas, but with aviation spec. Except MON/RON that spec has nothing to do with the engine itself. Avgas has specs concerning oxidation, vapor pressure, water solubility, hydrocarbon content and so on that is lacking in mogas.

Re – lacking mogas specs, you’ll find they’re actually not that lacking.

http://www.chevron.com/documents/pdf/MotorGasTechReview.pdf

Yes and I am also very concerned to use a watch that is not a pilot watch. Obviously my sunglasses have to meet aviation specs, too. Obviously I would never breathe medical oxygen, only aviation oxygen and fly 300NM to buy it for 150 € a shot.

Your argument is that of a UL91 salesman, FUD about car fuel which has been working fine in aero engines for decades.