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Washed gas technical considerations

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KeysFox

Joined: 05 Jan 2009
Posts: 137

Posted: Sat Oct 23, 2010 6:48 pm Post subject: Washed gas technical considerations

We may be missing important differences between Rotax 912 4-stroke engines

and Rotax 2-strokes. The 4-strokes risk lead plating out of the crancase

oil. Rotax 2 - strokes do not have crancase oil and therefor are different

beasts. In Rotax 4 - strokes, lead plating occurs because our Rotax

approved 4-stroke crankcase oils do not suspend lead that blows by the

piston to cylinder interface nearly as well as conventional ashless

dispersent aviation oils, which are not recommened for Rotax 4 - strokes.



With this difference in mind, for the 4-stroke 912s, Consider washed gas

with about 30 percent 100 LL added plus 25 hour oil changes. These two

protocols should do 2 things. One is prevent significant lead plating.

Second is, insure adequate octane for the 100 hp Rotax. Read more details

below.



AMOCO engineers working with the EAA on thier auto gas STCs for General

Aviation engines years ago, reported that even 30 percent 100 LL, when

mixed with 70 percent high octane unleaded auto gas would boost the octane

of the auto gas enough to provide an octane rating much higher than the

base auto gas and make octane no problem in high compression ratio

mid-1960s Corvettes and other muscle car engines as well as the Lycoming

in my normally aspirated Mooney.



At 30 percent 100 LL,  The large amount of lead in the 100 LL should

return the 2 - 3 octane points lost washing premium auto gas so that 100

hp Rotax engines are happy. If anyone knows better, please chime in. This

may be important to the 15 percent ethanol discussion.



As an aside, the premium auto gas was bad for the wet wing gas tank

sealant in the Mooney, accelerating weapage and requiring resealing which

Mooney wet wing tanks were notorious for under the best of circumstances.



The 25 hour oil changes in the 912s may also be valuable so that the small

amount of lead that blows by the 4-stroke Rotax rings is carried out by

our Rotax approved oils. Longer oil change intervals may overcome the oils

capacity to suspend lead. Keep in mind that 912s have very little blow by

compared to big bore aircooled general aviation aircraft engines which use

100 LL exclusively.



It may be wise to Avoid fully synthetic oils in 912s when using a fuel mix

with 100 LL, unless they have ashless dispersant qualities. Fully

synthetic oils typically hold very little lead in suspension. Unlike our

Rotax 912s, big aircooled aviation engines require Aviation grade ashless

dispercent oils which hold lots of lead in suspension. This is necessary

because Continentals and Lycomings have very wide piston to cylinder

tolerances allowing lots of lead blow by compared to 912s. Many will

remember that Fully synthetic Mobil 1 caused engine failures because it

did not keep lead in suspension, ruining engines. Fully synthetic Mobil 1

was pulled from aviation use because of this.



By the way, in addition to the different considerations between 4-stroke

and 2-stroke engines in terms of 100 LL use, my Kitfox has FIBERGLASS

TANKS THAT ARE NOT ETHANOL RESISTANT, so washing premium auto gas and

adding 30 percent 100 LL seems like a logical alternative. I get plenty of

octance and my fuel filters are not clogged by deteriorating fiberglass

from the effect of ethanol on the gas tanks.



I hope others weigh in on these comments, maybe with more current

technical knowledge.



BJ

N154K Kitfox IV  80 hp Rotax

N626NR PA 39 Turbocharged Twin Comanche

 

[quote] <n29cx(at)ridgeviewtel.us>



 Ok, then what should we do? Use 15% ethanol, use 100ll 50% of the time,

 and

 15% ethanol 50% of time .... my personal hope is that 100ll goes away as

 soon as possible and whatever substitute is made available will be better

 for the 912...high enough octane, no lead...a dream proabably...it won't

 happen until long after I am dead.....I really don't know what to

 do...'washing' ethanol-laced fuel doesn't appeal to me and ethanol-free

 auto

 gas is no longer available in my area.



 Your suggestion?

 ---

_________________
B Jones
N154K
443-480-1023

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Sat Oct 23, 2010 7:55 pm Post subject: Re: Washed gas technical considerations

Hi B Jones,



If you wash your fuel and drop the octane to 88 then you will need to use at least a 50/50 mix of auto fuel and 100LL to get you safely back to the 91-92 octane. This is what Rotax calls for when using 87 Octane Mogas. No less than a 50/50 blend.

You are correct about not using a full synthetic oil because it will not suspend lead. If you are going to use 100LL all the time at any percent use a semi synthetic oil  i.e. Aero Shell Sport Plus 4 or Golden Spectro 4 and they absolutely do need to be motorcycle oils. Car oils do not have the additives for our engine / gearbox system. Our engines are like our motorcycles and the engine and gearbox oil is the same. The car oils can not handle the "shear" issues with our gearbox.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Sat Oct 23, 2010 8:08 pm Post subject: Rotax engine issues, but it wasn't their fault

This statement is not aimed at anyone particular, but just a general statement.



The worst thing that happens to a Rotax engine is it's owner. If you follow Rotax's maint program and recommendations you rarely ever have issues. It's only when an owner wants to deviate and experiment because they think they no more than Rotax that has been making these engines since late 1989 and spent millions of dollars in research. The owner usually has never spent a dime in research and it's the first 912 they have ever owned. Seems a little lopsided to me. What we do with most things that are successful is use what we call our "Best Practices". That means we test and run things down until we find what works best and throw out the mistakes. Letting bad history repeat itself is not productive and very expensive with a $19K engine if it's a 912ULS. The SLSA aircraft have vary few engine issues compared to experimental's and that's because the SLSA group has to follow the Rotax protocols. 



I hear all sorts of myths or inaccuracies about the Rotax engine or it's maint. I recommend to all to seek out a knowledgeable authorized Rotax repair person for your info and not always just believe your neighbor, even if he is a nice guy.



Please follow the Rotax maint. and recommendations. You will be a happier flier with less maint overall and a lot more money left in your wallet in the long run not to mention peace of mind knowing that the engine will more than likely be there for you.

It's taken me years of classes and in field trials to see this and practice this, but I'm definitely there now.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Sun Oct 24, 2010 2:20 am Post subject: Re: Washed gas technical considerations

WEll Said Roger.  Same in neck of the woods. Everyone has a better idea.



Used to be long before the 912 came out that some could not run a 2 stroke without fiddling and screwing it up. Some say you must use marvel mystery oil bla bla bla.  etc etc etc 



Stick to the book and things work well. Rotax 2 strokes and 912 UL run fine on mogas. Avgas is asking for trouble with extended use. 



I run Rotax 582 and use NGK from Rotax only and get 150 hours + out of them.  



Roger I just passed 1100 hours in Rotax 2strokes with Ethanol gas.



is there a proble with ethanol gas ?



The ones that whine about it -heck might not fly much ?



Armchair captains



Check my videos -- Real time proof it works .



I am not a supporter of ethanol gas but it here and I ain't got no choice. SO I MAKE IT WORK

_________________
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http://www.youtube.com/user/kitfoxflyer
Hundreds of Kitfox Movies
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KeysFox

Joined: 05 Jan 2009
Posts: 137

Posted: Sun Oct 24, 2010 2:45 am Post subject: Washed gas technical considerations

Roger,



Thanks for chiming in on the 50 : 50 100 LL to premium auto gas mix to

boost octane back to acceptable levels for 100 hp 912s when using washed

gas. This seems like it should work well.



I  wil mention that the Amoco engineers working with EAA were adamant that

a smaller percentage of 100 LL would give a greater octane boost to

umleaded fuel than represented by the percentage of 100 LL added because

the first increases in octane required relativlely small quantities of

lead. Splitting hairs here.



When I took the Rotax courses and attended the seminars by Lockwood I

forgot  to ask and don't recall anyone else asking about using a small

percentage of ashless dispersant aviation oil along with 25 hour oil

changes.



Given that our 912 Rotax engines have very little blow-by compared to

conventional old air cooled aviation engines it would seem that we would

need very little ashless dispersant behavior from our oil if we use 25

hour oil changes.



I actually suspect that Shell would include ashless dispersant

characteristics in thier new 4 - stroke LSA oil knowing that 100 LL will

be used by many pilots but don't recall reading or hearing that they do.



Do you recall anything on this.



B Jones

 	  Quote: 	
		  

 Hi B Jones,



 If you wash your fuel and drop the octane to 88 then you will need to use

 at least a 50/50 mix of auto fuel and 100LL to get you safely back to the

 91-92 octane. This is what Rotax calls for when using 87 Octane Mogas. No

 less than a 50/50 blend.

 You are correct about not using a full synthetic oil because it will not

 suspend lead. If you are going to use 100LL all the time at any percent

 use a semi synthetic oil  i.e. Aero Shell Sport Plus 4 or Golden Spectro 4

 and they absolutely do need to be motorcycle oils. Car oils do not have

 the additives for our engine / gearbox system. Our engines are like our

 motorcycles and the engine and gearbox oil is the same. The car oils can

 not handle the "shear" issues with our gearbox.



 --------

 Roger Lee

 Tucson, Az.

 Light Sport Repairman - Maintenance Rated

 Rotax Repair Center

 520-574-1080





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=316830#316830

_________________
B Jones
N154K
443-480-1023

Dick Maddux

Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl

Posted: Sun Oct 24, 2010 4:48 am Post subject: Washed gas technical considerations

Roger, You are 100% right. I too have seen wrong paper fuel filters,oil  filters,sloppy work etc. Bottom line...go to school.The engine you save,  might be yours.

  Now on to fuel.

  In my state of Florida we have to go 100% to ethanol at the end  of the year. 99% are there now however 2 stations in my town still have no  ethanol premium. After the end of the year they could dispense no ethanol fuel  to boats,classic cars,airplanes,off road equipment,etc at a designated  pump. We are trying to sweet talk the owners of the two stations to retain a  pump for that purpose.He would do quite nicely at that pump if he does...so  maybe.

  Another source for no alcohol fuel   would be marinas,and farm  supply bulk plants. One in our area will deliver 100 gal of no alcohol fuel even  after the first of the year as they are not compelled to use alcohol in off road  gas( airplanes are certainly off road) 

  Something to consider

                                        Dick Maddux

                                       Kitfox  4

                                        912UL .

   

 PS: I too am worried about my Kreem (old blend) coated fuel tanks flaking.                      

  [quote][b]

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Sun Oct 24, 2010 5:29 am Post subject: Re: Washed gas technical considerations

I'm with Roger on this too - the Rotax manuals pretty much tell you what you need to do as far as gas/oil goes. They grant no other rights 



I mean, I do deviate a little, but the only ways I do that are with filters. I run a PureOne oil filter instead of the Rotax (the Rotax oil filter is actually the only one that has ever given me problems, it's not as well made as the PureOne). I also use large area paper fuel filters which is against Rotax' recommendations (I've used paper filters for decades with no problems, the large area gives me a fighting chance of avoiding clogs in case of gunk or something in the tank)



Otherwise, whenever Roger/Thom and Rotax say jump, I ask how high 



When it comes to ethanol, yes we'll be forced to deviate from the ethanol requirements once EPA pushes E15 onto everyone. But again I think it'll be far better than the lead in 100LL at least on a continuous basis. 



As Roger said, the problems with lead are long-term and don't show up right away. At least that was the case with my old cars back in the leaded mogas days. You didn't really know you had a problem until about 80K miles when the engine started to smoke and lose a little power. Then you were looking at a complete overhaul at 100K....



LS

_________________
LS
Titan II SS

pchristensen10(at)austin.
Guest

Posted: Sun Oct 24, 2010 3:57 pm Post subject: Washed gas technical considerations

Another consideration for washing gas is that beside ruining fiberglass 

tanks ethanol tends to rust out steel header tanks. I get rust flakes in 

my gascolator from the small amount of water that condenses in my 

tanks.  I believe it is coming from my header tank.  I'll soon have to 

deal with this issue.

Pete

On 10/23/2010 9:46 PM, bjones(at)dmv.com wrote:

[quote] 

 We may be missing important differences between Rotax 912 4-stroke engines

 and Rotax 2-strokes. The 4-strokes risk lead plating out of the crancase

 oil. Rotax 2 - strokes do not have crancase oil and therefor are different

 beasts. In Rotax 4 - strokes, lead plating occurs because our Rotax

 approved 4-stroke crankcase oils do not suspend lead that blows by the

 piston to cylinder interface nearly as well as conventional ashless

 dispersent aviation oils, which are not recommened for Rotax 4 - strokes.

 With this difference in mind, for the 4-stroke 912s, Consider washed gas

 with about 30 percent 100 LL added plus 25 hour oil changes. These two

 protocols should do 2 things. One is prevent significant lead plating.

 Second is, insure adequate octane for the 100 hp Rotax. Read more details

 below.

 AMOCO engineers working with the EAA on thier auto gas STCs for General

 Aviation engines years ago, reported that even 30 percent 100 LL, when

 mixed with 70 percent high octane unleaded auto gas would boost the octane

 of the auto gas enough to provide an octane rating much higher than the

 base auto gas and make octane no problem in high compression ratio

 mid-1960s Corvettes and other muscle car engines as well as the Lycoming

 in my normally aspirated Mooney.

 At 30 percent 100 LL,  The large amount of lead in the 100 LL should

 return the 2 - 3 octane points lost washing premium auto gas so that 100

 hp Rotax engines are happy. If anyone knows better, please chime in. This

 may be important to the 15 percent ethanol discussion.

 As an aside, the premium auto gas was bad for the wet wing gas tank

 sealant in the Mooney, accelerating weapage and requiring resealing which

 Mooney wet wing tanks were notorious for under the best of circumstances.

 The 25 hour oil changes in the 912s may also be valuable so that the small

 amount of lead that blows by the 4-stroke Rotax rings is carried out by

 our Rotax approved oils. Longer oil change intervals may overcome the oils

 capacity to suspend lead. Keep in mind that 912s have very little blow by

 compared to big bore aircooled general aviation aircraft engines which use

 100 LL exclusively.

 It may be wise to Avoid fully synthetic oils in 912s when using a fuel mix

 with 100 LL, unless they have ashless dispersant qualities. Fully

 synthetic oils typically hold very little lead in suspension. Unlike our

 Rotax 912s, big aircooled aviation engines require Aviation grade ashless

 dispercent oils which hold lots of lead in suspension. This is necessary

 because Continentals and Lycomings have very wide piston to cylinder

 tolerances allowing lots of lead blow by compared to 912s. Many will

 remember that Fully synthetic Mobil 1 caused engine failures because it

 did not keep lead in suspension, ruining engines. Fully synthetic Mobil 1

 was pulled from aviation use because of this.

 By the way, in addition to the different considerations between 4-stroke

 and 2-stroke engines in terms of 100 LL use, my Kitfox has FIBERGLASS

 TANKS THAT ARE NOT ETHANOL RESISTANT, so washing premium auto gas and

 adding 30 percent 100 LL seems like a logical alternative. I get plenty of

 octance and my fuel filters are not clogged by deteriorating fiberglass

 from the effect of ethanol on the gas tanks.

 I hope others weigh in on these comments, maybe with more current

 technical knowledge.

 BJ

 N154K Kitfox IV  80 hp Rotax

 N626NR PA 39 Turbocharged Twin Comanche

> <n29cx(at)ridgeviewtel.us>

>

> Ok, then what should we do? Use 15% ethanol, use 100ll 50% of the time,

> and

> 15% ethanol 50% of time .... my personal hope is that 100ll goes away as

> soon as possible and whatever substitute is made available will be better

> for the 912...high enough octane, no lead...a dream proabably...it won't

> happen until long after I am dead.....I really don't know what to

> do...'washing' ethanol-laced fuel doesn't appeal to me and ethanol-free

> auto

> gas is no longer available in my area.

>

> Your suggestion?

> ---

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Oct 25, 2010 5:38 am Post subject: Washed gas technical considerations

And now a word about using leaded fuel in two stroke engines...  Rotax or

otherwise.



The process that a two stroke engine uses is to draw the fuel mixture into

the base of the engine then to push it into the open ported piston when the

piston is close to bottom.  This push of air fuel pushes exhaust gasses out.

The problem with this is if we are using leaded fuel the fuel/oil mixture

coats the bearings of the engine which unlike four stroke engines are roller

type bearings.  The mixture is subjected to some pressure in the bearings

and this can cause some of the lead in the fuel to plate out on either the

bearing surfaces or the race.  Get enough lead on the bearings and it will

fail.  Will this happen by using leaded fuel for an hour or two?  No but it

certainly can happen with extended use.



Lowering the concentration of lead in the fuel by mixing a bit of 100LL with

unleaded gas, washed or otherwise will obviously lessen the plating process.

If I were to use it in a two stroke engine I'd shorten the TBO to perhaps

300 hr..  This is because the crank has to come out to inspect the condition

of the bearings.



As much as I hate the idea of flying on ethanol contaminated fuels I think I

would still prefer to do that rather than use leaded fuel.  If I were to use

gasohol I would take certain precautions.  Like never leaving fuel in the

plane, always using fresh fuel, and draining the tanks if I thought the

plane may not be flown for several days, especially if they were rainy days.



As for washing the gas by all means for use in an engine that only requires

low octane fuel.  Higher compression engines which require higher octane

fuel will have to find a good, emphasis on the word, "good", octane booster.

So far I haven't found one that actually works.  None of the boosters I've

seen will actually give the octane rating of the booster itself so a person

can decide how much to use to increase their fuel to the required octane.



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Oct 25, 2010 5:56 am Post subject: Washed gas technical considerations

A 50:50 blend of 88 RON mixed with 100LL will produce 94 octane fuel.  To

raise 88 RON to 91 RON will require a mix of around 70:30. 



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

sdemeyer

Joined: 31 Jul 2009
Posts: 45

Posted: Mon Oct 25, 2010 1:13 pm Post subject: Re: Washed gas technical considerations

The focus seems to be whether or not Rotax engines will run fine on ethanol laced fuel. I agree that the engine itself is happy with this fuel. The problem is the rest of the fuel system is not happy. I had a Kitfox tank disintegrate from Ethanol laced fuel. The seams literally melted apart. This happened to me while I was flying. Having fuel running all over you at 1,000 feet is not fun in the least bit. 



Fortunately I can get uncontaminated fuel from a local Indian Reservation. If no uncontaminated auto fuel was available I would use 100LL with Decalin.



Scott

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