Testing for ethanol

[planesmaker]

Just to pass on how to quickly and easily test for ethanol in fuel, a few drops of water based food colour added to clear testing container add fuel sample, if it contains ethanol the whole sample will change colour, if no ethanol food colouring remains as globules on the bottom( can even be used again)

cheers

[F10]

Fuels are interesting, my aircraft has a Rotax 912A, the manual lists fuel types in order of preference, top of the list is 95 octane Mogas, below that is 98, considered is not ideal too many additives as such, 91, Too much ethanol. Surprisingly Avgas not recommended unless you have to, lead leaves lots of lead deposits in the oil, deposited a grey sludge at the bottom of your oil tank... Interesting, as apart from lead deposits occasionally closing up spark plug gaps, I’ve never heard of Avgas lead content being problematic in GA engines? Lead of course is an anti detonation additive. The monster piston engines of WW2 aircraft, ran some high compression ratios, using 100 octane or even higher was available. The Merlin 60/70 series engines were 27 litre V12’s, producing 1750 Hp, the German fuels were low octane, so interestingly, they made up for that by engine capacity, the BMW radial powering the Fw190, putting out similar power, was around 42 litres as I recall.

[spacesailor]

And the larger the capacity, the lager the fuel used.

Surely if you Have to use low octane fuel, a drop of Oil will help. Like in the old days  !,Lovely smell of Caster oil at most race-car tracks.

spacesailor

[facthunter]

Castor oil was usually used with Methanol fuelled engines. It gets gummy when left in engines. (Oxidation) Doesn't prevent corrosion either. Pure Castor was used in Model engines except PETROL (Spark engines  like Olsen and Forster  (bit rusty on the names).  Castor doesn't mix with Petrol unless some mixant used.  and you can expect problems if you add it.  Modern CASTOR has a lot of "other " stuff in it, including synthetics. Nev

[onetrack]

The other main reason for the use of Tetra Ethyl Lead additive, besides eliminating combustion knock, was lubrication of the valve seat. But lead is one of the most insidious poisons known to mankind.

No level of exposure lead is safe, and it never leaves the environment. The article below is one of the most informative articles I have found as regards lead in our fuels and environment.

 

http://www.todayifoundout.com/index.php/2011/11/why-lead-used-to-be-added-to-gasoline/#:~:text=Today I found out why,valve seats within the motor.

[F10]

Correct, valves rotate as they operate, hardened valve seats sort this out in low or no lead engines. Otherwise valve seat recession occurs and you end up with no valve push rod, rocker or tappet clearance, which means, the valve will not close properly, leading to no compression and a burned valve, valve failure and an involuntary visit for coffee with a local farmer. Amazing where life can lead us!

[facthunter]

Most valves don't rotate as they operate. You have to use special  fittings on the spring ends to make it happen. It helps stop warping of the valve(s) by more even heating and eases carbon /lead build up that causes  poor seating.. In any case when seated there's no movement as there would be insufficient force to make it happen.. Seat recession is usually when there's no hardened seats and the seats erode with the flame, high  pressure and scouring  a bit like the top of the bores do..  Only the exhaust valve SEAT gets lubricated by the lead additive IF the local temps are high enough, which they are NOT on a 912 Rotax hence the "don't use avgas frequently" recommendation.. Nev

[F10]

Ok, I thought they rotate only on opening and closing, not continuously. This was exactly as you said, to avoid hot spots allow even heat distribution or avoid carbon build up and to keep the seating of the valve clean as such? Interesting. 

[facthunter]

It's considered a good thing if you can arrange it. it may take quite a number of openings to do one turn. Generally the valve is not an even temperature so like a spit roast things work better if it rotates.  If it did rotate a lot wear of the collet grooves could be expected. I don't know of any aero engine which does it but it has been desired and used on sidevalve engines as they are most uneven of all engines regarding port temperatures.  Nev

[skippydiesel]

Ah! Caster Oil/Castrol R - takes me back to the sixties, when my mates & I would pool are pocket money to purchase a gallon. It was then  dolled out , tea spoon at a time, into each of our BSA 2/ - not as an effective mix but to get the right smell from the exhaust.

[walrus]

The Rotax Avgas rule is that oil has to be changed at 50 hrs instead of 100 hours if 100LL is used for more than 30% of volume. The lead builds up on gears, sludges in the oil tank and fouls the spark plugs. Decalin Runup is an acceptable (by Rotax) fuel additive to 100 LL that minimizes problems by scavenging much of the lead by converting it to lead phosphate which mostly departs in the exhaust.

 

Mogas 95 has about 3% more energy content than Avgas anyway, but the Avgas has better vapour pressure and long term shelf life.

[facthunter]

Compression can suffer also on the 912 due build up on the valve  seat which gets uneven, I've seen that a couple of times. Reverting back to Mogas can rectify it but some permanent seat damage is possible.  A n earlier ingredient  used in Avgas to get rid of lead build -up was a Bromine additive which is probably very  toxic. It caused a tell tale white to show inside the exhaust stubs which doesn't happen now.  . Nev

[kgwilson]

Why anyone with a Rotax or Jab engine still uses Avgas is a mystery to me. It costs more, isn't as widely available, is poisonous and is bad for your engine. Jabiru recommend avgas but that is just to cover their arse from possible litigation. Mogas keeps the engine clean including the oil and doesn't foul plugs. Arguments regarding quality control, vaporisation and shelf life are easily countered by buying from a busy servo, not exceeding 10,000 feet or gravity electric pump feed and adding some fresh if fuel in the tank is more that a few weeks old. I've used Mogas in my Jab 3300A since new & plugs stay clean, leakdowns are within 75/80, no oil topups between changes & the oil stays clean.

 

The only downsides are Mogas stinks being aromatic based and I have to lay the dipstick on a tissue to check the level as I can't see clean oil on the dipstick.

[planesmaker]

Using Mogas in Jabiru’s it’s very important to test for ethanol as it will eat your fuel tank sealer. I don’t trust fuel distributors to not have ethanol, best to test. 

[spacesailor]

IF you buy 95 mogas then test, to find it Has ,ethanol , ! What can you do, tip it inside  the servo to peeoff the innocent checkout operator.

spacesailor

[kgwilson]

41 minutes ago, planesmaker said:

Using Mogas in Jabiru’s it’s very important to test for ethanol as it will eat your fuel tank sealer. I don’t trust fuel distributors to not have ethanol, best to test. 

This only affects Jabirus built prior to 11 March 2005. After that the sealant was changed so that ethanol has no effect. The only reason that ethanol would be present in 95 and 98 octane Mogas is from contamination from a tank previously used for an ethanol blend fuel or possibly mixing in the delivery tanker. Both situations would be very rare as most tankers and service stations have specific tanks for their fuel types.

 

Some retailers no longer stock 95. I used to use BP 95 but they changed to 94 which is an ethanol blend so now I run exclusively 98.

[F10]

I remember there was a big furore over ethabol as it was corroding some carburettor components in cars, but this seems to have gone quiet? If dealers sell 94, is it labelled 94? Most servos in Gippsland area have 95. I would tend to use 98, but my Gazelle manual actually states it can have too many additives, so although allowable, not top of the list.

[walrus]

KGW, I always use mogas from a busy brand name station. However if you are touring, you are stuck with using Avgas from the bowser as very few airports have mogas dispensers. The alternative is the tedious business of jerry cans and taxis - and I fully expect airports will eventually ban that practise - for (ahem)safety reasons of course.

[skippydiesel]

3 hours ago, walrus said:

KGW, I always use mogas from a busy brand name station. However if you are touring, you are stuck with using Avgas from the bowser as very few airports have mogas dispensers. The alternative is the tedious business of jerry cans and taxis - and I fully expect airports will eventually ban that practise - for (ahem)safety reasons of course.

Collapsible 20L  x 2  bladders make life a great deal easier and I have yet to see any airport persons take interest in my fueling activities - why would they ban something hey dont even see?

Edited May 11, 2021 by skippydiesel

[kgwilson]

 There is less & less Avgas being sold & unless they produce a lead free option it will likely be banned sooner or later. The main issue is Avgas is Paraffin based & needs TEL to bring its octane rating to 100 whereas Mogas is based on aromatics so additives like toluene, xylene, benzene etc raise the octane rating without lead.

 

We have been approached by 3 companies wanting to supply a self contained Avgas tank/pump etc but there are not enough users locally to make it viable & Council want a 20k bond so that stopped it dead. I use Avgas when I can't get Mogas but keep 2 x 20 litre jerrycans on board when going long distance. Apart from that when I built my plane I installed wing tanks to boost my capacity from 100 to 170 litres so I have about 8 hours endurance.

[walrus]

I still require the step ladder in addition to the jerry cans. Ikea seems to be best, but takes up space.

[Bruce Tuncks]

Is it possible to change the sealant in an old Jabiru tank? I imagine removing and drying the tank, then sloshing it with the new sealant. Is this enough? What if some rubber bits in the old Jab fuel system and carby are attacked by ethanol?

[skippydiesel]

10 hours ago, walrus said:

I still require the step ladder in addition to the jerry cans. Ikea seems to be best, but takes up space.

Walrus me old mate! I & many others have already posted suggestions on this: I have been using this home made vain pump for some years now. Completely removes the need to lift "jerry" cans. I plug into "ship" power (Anderson plug). You will still need a light folding step to reach up to the over wing filling point, there are lots of options out there. I plug the open end of hose & spear(polly riser) when not in use. The spear can be easily removed to take up less room in the aircraft. The pump (a Chinese Holly copy) is self priming. Whole thing cost about $90. I would also sugest the use of a filter funnel - I made my own but you can purchase a "Mr Funnel."

 

 

[F10]

That looks cool! What type of pump is that? Superchreap Aeronautics or Range & Endurance Performance Co seem to only sell the solenoid type? Is that a fuel pump or some other fluid pump? Where do you get them? I mounted my Mr Funnel, onto a piece of foam backed plywood, so at least it sits upright on the wing, unaided. No more training my pet octopus to fuel out of a can, hold the funnel, hold the can, hang onto the wing, wipe spilled fuel before it runs over the rear deck Lexan windows, re-attach the bonding clamp........

[skippydiesel]

14 minutes ago, F10 said:

That looks cool! What type of pump is that? Superchreap Aeronautics or Range & Endurance Performance Co seem to only sell the solenoid type? Is that a fuel pump or some other fluid pump? Where do you get them? I mounted my Mr Funnel, onto a piece of foam backed plywood, so at least it sits upright on the wing, unaided. No more training my pet octopus to fuel out of a can, hold the funnel, hold the can, hang onto the wing, wipe spilled fuel before it runs over the rear deck Lexan windows, re-attach the bonding clamp........

Hi F10,

 

The pump is a Chinese copy of a Holly (USA) high performance fuel/petrol transfer pump - used in muscle car type applications. So it's a genuine petrol (as apposed to diesel) fuel pump. Cant remember the performance statistics but I find it empties a 20 L container in a very few minutes. For the best price,  find them on line in the $60-80 bracket (a genuine Holly is in the many $100's).

 

Yeah! Mr Funnel has 3 drawbacks - 1. high price, 2. hard to find a stable position, 3. they retain a few mm of petrol/water i the "sump" that inevitably spills onto something you dont want it to.

 

One of the good points of my pump is that you can hold the fuel delivery end in one hand, the other hand can hold the on/off switch & steady the funnel. 

 

I did try having an "in line" filter on the pump suction side but it cut down the delivery volume a bit too much and the filter was to big to fit into some of my fuel containers.