Dangerous mogas

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Dangerous mogas

Unread post by Flooi » Sat Oct 13, 2018 7:48 am

Just had float in Bing carb replaced by Leon at Legair. Damaged by mogas. [-X
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Re: Dangerous mogas

Unread post by pietmeyer » Sat Oct 13, 2018 12:10 pm

I only use avgas in my Jabi
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Re: Dangerous mogas

Unread post by vildwillie » Sat Oct 13, 2018 12:59 pm

Rotax sent out a service advise about 2 years back on some engines in the market with float problems IIRC? I think they use bing carbs on certain engines like the 912/914.
Could it not just have been a pouris or faulty float? Mogas should not eat into the float material
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Re: Dangerous mogas

Unread post by Flooi » Sat Oct 13, 2018 2:49 pm

Float seems to be made up of two halves glued together. Alcohol in mogas
may disolve - or soften? whatever is used as adhesive..... in any case, the float
was half filled with fuel resulting in an over filled chamber. The new float
sorted out the problem........ and sticking to avgas. Would like to get comments
from you. Horace Blok... what you think?
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Re: Dangerous mogas

Unread post by Biltong » Sat Oct 13, 2018 5:15 pm

What exactly was the damage / problem with the float?
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Re: Dangerous mogas

Unread post by Mrb13676 » Sun Oct 14, 2018 12:39 pm

Where did you get the Mogas? Ie do you usually use a specific brand or from a specific filling station? I’ve heard that Sasol not great for Rotax as they do have more alcohol...not sure if true or not
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Re: Dangerous mogas

Unread post by IWG » Mon Oct 15, 2018 3:42 pm

Hi Flooi

How old was the float, as Bing carbs on some older BMW bikes use the same floats and they last at least ten years.
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Re: Dangerous mogas

Unread post by jvdl » Mon Oct 15, 2018 4:11 pm

Flooi wrote:
Sat Oct 13, 2018 2:49 pm
Alcohol in mogas may disolve - or soften? whatever is used as adhesive.....
I asked my fiancee whether this would be possible... Apparently it depends on whether the adhesive is "polar" or "non-polar". Chemistry was never my strong suit.

She sent me the following journal article which may contain some information on component wear due to using mogas. I think Section 5 will be of interest to you.
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Re: Dangerous mogas

Unread post by IWG » Tue Oct 16, 2018 11:21 am

It's all about operating inside the box.

Our Jabi fuel systems are automotive based and have the added carb heat to make them safer for aircraft use.
Automotive electric backup fuel pumps are mounted below tank level away from engine heat.
We generally don't fly in way below freezing conditions and once airborne the airflow is sufficient to prevent
vapour lock, even at high summer temps.
The mixture under hot and high conditions is the one I found to be a limiting factor and by using the mixture control
the "box" could be sufficiently expanded to eliminate this problem.
The difference in Avgas/Mogas fuel flow has been about 4% for similar conditions over a number of flights.
No fouled plugs and fuel availability at many microlight fields are two major advantages of running on Mogas.

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Re: Dangerous mogas

Unread post by ZuluBen » Thu Nov 01, 2018 10:29 am

The Manual is the final authority on your plane, and it says that Mogas is OK.

Common sense says stay away from fuels with high alcohol and other chemicals. such as Sasol.

And I was told that Shell uses an octane booster that is not good as well? :shock:
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Re: Dangerous mogas

Unread post by BigglesSA » Tue Nov 20, 2018 9:09 pm

Ben it is hourses for courses on this one.

You will find good and bad points for or against all mogas brands.

Best to avoid mogas where you have a choise.
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Re: Dangerous mogas

Unread post by markus_m2 » Wed Nov 21, 2018 9:16 am

Personally, I like to run on Mogas - not all the time, but maybe 50% - 75% of the time and add a good filling of Avgas in between...
This is on our C182's.

While I cannot give any scientific evidence, I find Mogas runs slightly cooler, it's obviously cheaper, there's talk of your oil keeping better on it (no lead-contamination in the oil - see Lycoming's service bulletin increasing oil change interval to 100hrs if running on unleaded fuel, remains 50hrs on leaded Avgas), and I have not had any engine issues that the AMO / engine shop could point directly to Mogas use.

For me, I'll keep testing for ethanol and if clear, gooi and go...
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Re: Dangerous mogas

Unread post by BigglesSA » Wed Nov 21, 2018 10:51 am

markus_m2 wrote:
Wed Nov 21, 2018 9:16 am
Personally, I like to run on Mogas - not all the time, but maybe 50% - 75% of the time and add a good filling of Avgas in between...
This is on our C182's.

While I cannot give any scientific evidence, I find Mogas runs slightly cooler, it's obviously cheaper, there's talk of your oil keeping better on it (no lead-contamination in the oil - see Lycoming's service bulletin increasing oil change interval to 100hrs if running on unleaded fuel, remains 50hrs on leaded Avgas), and I have not had any engine issues that the AMO / engine shop could point directly to Mogas use.

For me, I'll keep testing for ethanol and if clear, gooi and go...
Right you are Markus. For me though a Jab motor prefer Avgas :wink:
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Re: Dangerous mogas

Unread post by Flooi » Wed Nov 21, 2018 6:24 pm

Some feedback here.... Initially running very very rich and missing at low revs as well as during full power climb.

I think mogas loses octane over time AND if left standing for long enough,
it will leave a sediment. Therefor using fresh mogas and flying often is fine- maybe even better
and a cleaner engine. I believe my problem was because of tanks half filled with mogas and standing
for looong time- maybe months and months; not sure. Bought it like that. Idling jet clogged and what not????
Leon cleaned out carb and fuel pump. Then there is the theory (or fact) that mogas dissolves some adhesives
used in tanks and floats- Who knows? Otherwise Jabi is a great plane!!!

Testing tomorrow and will see. ONLY AVGAS!!!
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Re: Dangerous mogas

Unread post by Flooi » Thu Nov 22, 2018 4:46 pm

Sorted. Legair at FASI. Great service!
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