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Vapor Lock and E-10 mogas

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Arty Trost

Joined: 25 May 2006
Posts: 206
Location: Sandy, Oregon

Posted: Thu Mar 19, 2009 9:18 pm Post subject: Vapor Lock and E-10 mogas

In this month's issue of Ultraflight magazine, in Rotax Talk by Ronnie Smith, he says (for those of us using two-strokes and E-10 mogas):



"Remember also that there will be an altitude limit on the use of this 10% [ethanol gas]. I think it's around 7500 ft. MSL. Why? Well, car gas will start to vapor lock at higher altitudes so you have to watch this." 



He goes on to say that if we're flying about 7500 ft MSL we should use 100LL which has a lower vapor pressure than auto gas.



Anyone heard of this? Had this happen?  I know I'll be flying above 7500 MSL on my flight to Florida and am curious if any of you other two-strokers have ever experienced this or heard of it.  



Arty Trost

Sandy, Oregon

www.LessonsFromTheEdge.com/uladventure2009.htm

experimentalab(at)yahoo.c
Guest

Posted: Fri Mar 20, 2009 4:51 am Post subject: Vapor Lock and E-10 mogas

I've flown my 582 upwards of 10K MSL many times without a problem...FWIW!

  

 Andrew

 KF3 582/C-Box

          [quote][b]

Roger Lee

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

Posted: Fri Mar 20, 2009 12:48 pm Post subject: Re: Vapor Lock and E-10 mogas

Hi Arty,



Two trains of thought with two types of people. The people who know it's a very unlikely scenario (but possible) or the worriers. Rotax has in writing that 5% is OK and I hear through the grapevine that they might be bumping that number up shortly.

The very, very slight possibility of a vapor lock is possible and that's why Rotax wanted people to install a return fuel line. This helps in keeping any chance to a minimum.  Plus you fly with an exposed engine which remains cooler than one in a tight hot cowling. The cooler fuel is less likely to lock than really hot fuel in a metal line. I fly and I know maybe hundreds of guys who fly with 10% ethanol and up to 12.5K and have never had any issues. I even know a few that have been to 16K-17K and no issue, but not recommended. The circumstances would have to be just right, not impossible, but not likely. If it were a real big problem then all the autos, motorcycles, atv's and any other engine would be vapor locking just driving up above this elevation in the mountains. Most gas station's ethanol content seems to be running around 5-7%. Really haven't found many at the full 10%. 



So you fall into the one type who will use it and not worry or you will be afraid of falling out of the sky and only use 100LL. 100LL shouldn't be used in a 2 stroke if you can avoid it. In all my hours and using 91 oct. at 10% I have never ever had any issues in a Rotax that was set up properly and I have flown all over the country.



Of course you didn't even mention phase separation yet?    



Bottom line I have followed your trips and met you at a fly-in or two. Use your 91 Octane and have a good time.

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

lucien

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

Posted: Fri Mar 20, 2009 2:25 pm Post subject: Re: Vapor Lock and E-10 mogas

 	  Roger Lee wrote: 	
		  Hi Arty,



Two trains of thought with two types of people. The people who know it's a very unlikely scenario (but possible) or the worriers. Rotax has in writing that 5% is OK and I hear through the grapevine that they might be bumping that number up shortly.

The very, very slight possibility of a vapor lock is possible and that's why Rotax wanted people to install a return fuel line. This helps in keeping any chance to a minimum.  Plus you fly with an exposed engine which remains cooler than one in a tight hot cowling. The cooler fuel is less likely to lock than really hot fuel in a metal line. I fly and I know maybe hundreds of guys who fly with 10% ethanol and up to 12.5K and have never had any issues. I even know a few that have been to 16K-17K and no issue, but not recommended. The circumstances would have to be just right, not impossible, but not likely. If it were a real big problem then all the autos, motorcycles, atv's and any other engine would be vapor locking just driving up above this elevation in the mountains. Most gas station's ethanol content seems to be running around 5-7%. Really haven't found many at the full 10%. 



So you fall into the one type who will use it and not worry or you will be afraid of falling out of the sky and only use 100LL. 100LL shouldn't be used in a 2 stroke if you can avoid it. In all my hours and using 91 oct. at 10% I have never ever had any issues in a Rotax that was set up properly and I have flown all over the country.



Of course you didn't even mention phase separation yet?    



Bottom line I have followed your trips and met you at a fly-in or two. Use your 91 Octane and have a good time. 	




Actually I'm surprised no one's mentioned this on this list yet but... 



Rotax is already telling our distributors that E10 has been approved for the 912 series (I don't know about the 2-strokes tho). If everything else in the fuel system is compatible with it, the engine is ok with it. They tested it with something like 20% ethanol even....



Rotax is also raising the TBO for the 912 series to 2000 hours (that according to Ronnie Smith at SMLA).



Again, I don't know about the 2-strokes. Hopefully when they release the bulletin, they'll say something about them too.



LS

_________________
LS
Titan II SS

Roger Lee

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

Posted: Fri Mar 20, 2009 7:19 pm Post subject: Re: Vapor Lock and E-10 mogas

Rotax approved 10% ethanol is coming. It's just when will it come in writing. They are already talking about it in Rotax classes.

Increased TBO hours for the 912 is coming, too. I try not to speak out too far in advance of something put in writing as I hate it when I get the rug pulled out from under me at the last minute.

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

Float Flyr

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

Posted: Wed Apr 01, 2009 5:36 am Post subject: Vapor Lock and E-10 mogas

I agree with most of what you have read with the exception that an open engine will run cooler.  If that was true aircraft manufacturers and engine manufacturers have wasted many millions of dollars developing efficient pressure cowlings.



A well designed pressure cowl will help keep the barrels on your 9XX rotax nice and cool.



Noel



--- On Fri, 3/20/09, Roger Lee <ssadiver1(at)yahoo.com> wrote:

[quote]

From: Roger Lee <ssadiver1(at)yahoo.com>

Subject: Re: Vapor Lock and E-10 mogas

To: rotaxengines-list(at)matronics.com

Received: Friday, March 20, 2009, 6:18 PM



--> RotaxEngines-List message posted by: "Roger Lee" <[url=/mc/compose?to=ssadiver1(at)yahoo.com]ssadiver1(at)yahoo.com[/url]>



Hi Arty,



Two trains of thought with two types of people. The people who know it's a very unlikely scenario (but possible) or the worriers.

The very, very slight possibility of a vapor lock is possible and that's why Rotax wanted people to install a return fuel line. This helps in keeping any chance to a minimum.  Plus you fly with an exposed engine which remains cooler than one in a tight hot cowling. The cooler fuel is less likely to lock than really hot fuel in a metal line. I fly and I know maybe hundreds of guys who fly with 10% ethanol and up to 12.5K and have never had any issues. I even know a few that have been to 16K-17K and no issue, but not recommended. The circumstances would have to be just right, not impossible, but not likely. If it were a real big problem then all the autos, motorcycles, atv's and any other engine would be vapor locking just  driving up above this elevation in the mountains. Most gas station's ethanol content seems to be running around 5-7%. Really haven't found many at the full 10%. 



So you fall into the one type who will use it and not worry or you will be afraid of falling out of the sky and only use 100LL. 100LL shouldn't be used in a 2 stroke if you can avoid it. In all my hours and using 91 oct. at 10% I have never ever had any issues in a Rotax that was set up properly and I have flown all over the country.



Of course you didn't even mention phase separation yet?    



Bottom line I have followed your trips and met you at a fly-in or two. Use your 91 Octane and have a good time.



--------

Roger Lee

Tucson, Az.

Light Sport Repairman - Maintenance Rated

Rotax Service Center

520-574-1080





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=235405#235========================http://www.matrop://forums.matronics.com" bsp;               -Matt Dralle, List Adontribution" target="_blank">http://www.matronics.com/contribution

       Ask a question on any topic and get anhoo! Answers.[/b] [quote][b]

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

rampil

Joined: 04 May 2007
Posts: 870

Posted: Wed Apr 01, 2009 6:38 am Post subject: Re: Vapor Lock and E-10 mogas

Ah, if only like were as simple as some think!



Vapor lock occurs when the working fluid transitions to gas and the

rotary fuel pumps no longer propel the fluid.



Vaporization depends on the fuel composition and importantly, the

temperature and pressure surrounding the fluid.



It is flat impossible to say that there is a flat altitude limit due to

ambient atmospheric pressure for several reasons.

1) it is the density altitude that really matters for ambient.

2) No mention is made of the fuel temperature which will vary widely 

depending on where the hose is and how it is shielded if firewall forward

3) fuel in a hose in an aircraft is usually under pressure! Maybe 5psi gauge

if carbed, or 50 psi gauge if injected.  Fuel will not vaporize until the

temperature pushes the vapor pressure of the fluid to above the 

atmospheric pressure plus the gauge pressure inside the hose.



and 4 if you like) All rotax 4 strokes have a fuel return line to keep the

liquid fuel temp down to fuel tank temperature and as far from 

vaporization as practical without refrigeration.  Try it, you'l like it!

_________________
Ira N224XS

Roger Lee

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

Posted: Wed Apr 01, 2009 8:27 am Post subject: Re: Vapor Lock and E-10 mogas

Several people here have very valid and accurate points and vapor lock certainly has more than a single facet. Keeping things simple in a public forum helps everyone no matter what their background understand the topic discussion. I agree with what most have said about the vapor lock as several things do affect its formation or lack of.



Hi Noel,



I don't necessarily agree with the cowling verse fully exposed engine. A fully exposed engine like on a Kolb Mark III which I did own and had one of the very first 912ULS's on it. (It was called a Super Kolb at the time and took Sun and Fun Grand Champion one year.) I came from the Ultralight day's of 1980. The open air setup does such a good job of heat exchange off the engine that it can be hard to keep temps up sometimes and of course it causes more drag. The cowling on planes help reduce and clean up drag for the overall performance and even it's aesthetic value. Once the engine was enclosed the cowling had to be designed to allow cooling of the engine. Some cowling's do a good job of cooling the enclosed engine and some do a terrible job and that of course is why a number of people have tried to re-design their air flow under the cowling for certain aircraft. An enclosed engine depending on its cooling characteristics and capacity can help induce or help reduce a chance of vapor lock. Another issue is a lot of Rotax 912's on different types of aircraft and depending on their age don't have return lines.

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

rampil

Joined: 04 May 2007
Posts: 870

Posted: Wed Apr 01, 2009 1:59 pm Post subject: Re: Vapor Lock and E-10 mogas

Hi Roger,



Re return lines:  If the Rotax installations were all certified, then the

presence of a return line would be mandatory by AD. If older installs,

dont have it, it should be easy to add and should be to fix an identified 

airworthiness issue. Up til now most Rotaxs have been in homebuilts

so the owners could do the job. Thats why I said: Try it you'll like it! I believe most of the LSA installs have been since the SBs about return 

lines.



As for simplicity, I am a huge fan of Einstein (yes, that one) who said

"Keep things as simple as possible, but not more so"  Sometime the

chat on these forums simplifies so much that the truth falls out of the 

discussion. It's nice to know where "rules" come from and understand

why and where they break down.



I do always appreciate your comments o0n this forum

_________________
Ira N224XS

craig(at)craigandjean.com
Guest

Posted: Wed Apr 01, 2009 2:20 pm Post subject: Vapor Lock and E-10 mogas

Which SBs talk about return lines? I see information in the installation

manual but a quick search through the SBs on rotaxowner.com didn't show any.



-- Craig



--

trigo(at)mail.telepac.pt
Guest

Posted: Wed Apr 01, 2009 2:38 pm Post subject: Vapor Lock and E-10 mogas

And where are the return lines connected from?  

   

Carlos  

   

   

[quote] --

craig(at)craigandjean.com
Guest

Posted: Wed Apr 01, 2009 3:03 pm Post subject: Vapor Lock and E-10 mogas

In the stock engine the fuel return line connects to a banjo bolt with a restrictor on the fuel manifold that clamps to the balance tube between the carbs. I’ve attached two figures from the 912 installation manual (Edition 1 /Rev. 0, May 01/2007). If Matronics doesn’t pass them through let me know and I’ll mail them directly to you.  

   

-- Craig  

       

From: owner-rotaxengines-list-server(at)matronics.com [mailto:owner-rotaxengines-list-server(at)matronics.com] On Behalf Of Carlos Trigo

 Sent: Wednesday, April 01, 2009 4:37 PM

 To: rotaxengines-list(at)matronics.com

 Subject: RE: Re: Vapor Lock and E-10 mogas  

  

  

   

And where are the return lines connected from?  

   

Carlos  

   

   

[quote] --

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Roger Lee

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

Posted: Wed Apr 01, 2009 5:29 pm Post subject: Re: Vapor Lock and E-10 mogas

Hi Craig and Ira,



Looks like you guys are on top of it. The return lines are very easy to install. Many just return to a gasolator like many of the SLSA's and ELSA's or back to a header tank if you don't have a gasolator. 



p.s.

Don't forget to put your fuel line in fire sleeve and dip the ends of the fire sleeve, plus you should be using band clamps (Otiker is one type and easy to use) and not worm drive clamps.



There is no return line specific SB. It is in the installation manual. Even though there is not an SB you should be keeping up on manual changes for your engine health and your personal safety. Your right that many of the older engines were put in homebuilt's and many didn't have them under cowl, but of course some did. It didn't seem to be a big issue many years ago (but we learned), but todays planes, the way we fly and where we fly has changed, fuels are changing and finally our knowledge is catching up. You brought up owners doing the work and that's perfectly ok, but some do it wrong for a number of reasons, but all should take a Rotax class and do it right.

Rotax has been manufacturing the 912 since late 1989 and it has had 4K changes since then. Some very small or minor and some very significant changes.

*Note*

If I ever sound like I'm being disrespectful in some way to anyone I never ever mean it that way, but in emails it is easy to get the tone of the message wrong. I enjoy helping others with problems and working with people and sometimes throw a little philosophy in along the way. I usually get at least 2 calls a day from out of state with 912 issues and people bring me their 912 engined plane's to work on from 5 or 6 different states.



*** Bottom line in all this dicusion thread is a return line is a good idea and can be found in the Installation manual.

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

craig(at)craigandjean.com
Guest

Posted: Wed Apr 01, 2009 5:54 pm Post subject: Vapor Lock and E-10 mogas

One problem with the factory design of the fuel manifold with return line is

the difficulty of measuring fuel flow. You either:



1. Modify the factory design to place the flow transducer after the return

line and before the "T" to the two carbs (increasing the risk of vapor lock)

2. Use two (expensive) flow transducers (either on the feed and the return

or one for each carb) which places extra requirements on the instrumentation

3. Try to compensate or estimate the volume flowing through the return line

(which makes my EFIS's fuel range calculation worthless)



I just don't see a good solution. Option 2 is the safest and most expensive

(what a surprise).



-- Craig

rampil

Joined: 04 May 2007
Posts: 870

Posted: Wed Apr 01, 2009 6:28 pm Post subject: Re: Vapor Lock and E-10 mogas

Craig,

The usual 912 or 912s return flow is a very small fraction of the

forward flow, in essence a slow drip. For these engines a single

Floscan works fine (if a < 5% error is OK). I use this approach.



For 914 engines the return line has always been mandatory so far as

I recall.  The return flow is a much higher fraction of the forward flow

as well. Here, two floscan sensors are required with an A-B computation.

If price is more important than accuracy, several manufacturers

make much less expensive sensors. Aveo and MGL come to mind.

_________________
Ira N224XS

craig(at)craigandjean.com
Guest

Posted: Wed Apr 01, 2009 6:44 pm Post subject: Vapor Lock and E-10 mogas

Thanks for the concrete numbers. I knew the restrictor was small. I wonder

how such a small flow reduces the chance of vapor lock.



Actually I have an MGL EFIS (I moderate the user group on Yahoo). Part of

the expense with MGL is that the current engine pod ("RDAC") only has a

single flow input. So in addition to the second flow sender you need a

second RDAC. There is a guy in New Zealand who has put together a small

circuit that adds the pulses from two senders and puts out a proportional

pulse stream. So two of MGL's nylon senders and the board might do the job

if I give each carb its own flow transducer.



-- Craig



--

rampil

Joined: 04 May 2007
Posts: 870

Posted: Thu Apr 02, 2009 4:55 am Post subject: Re: Vapor Lock and E-10 mogas

Hi Craig,



re the small resitrictor on return flow.

I suspect that it really is there to give any formed vapor a place to go

and get it out of a dangerous area!



Ira

_________________
Ira N224XS

gfmjr_20(at)hotmail.com
Guest

Posted: Thu Apr 02, 2009 7:38 am Post subject: Vapor Lock and E-10 mogas

 	  Quote: 	
		  Don't forget to put your "fuel line in fire sleeve and dip"OK Roger  Cyou got me on this one. What do you mean by dip the ends and into what.?George May601XL 912 	




[quote] Subject: RotaxEngines-List: Re: Vapor Lock and E-10 mogas

 From: ssadiver1(at)yahoo.com

 Date: Wed C 1 Apr 2009 18:29:53 -0700

 To: rotaxengines-list(at)matronics.com

 

 --> RotaxEngines-List message posted by: "Roger Lee" <ssadiver1(at)yahoo.com>

 

 Hi Craig and Ira C

 

 Looks like you guys are on top of it. The return lines are very easy to install. Many just return to a gasolator like many of the SLSA's and ELSA's or back to a header tank if you don't have a gasolator. 

 

 p.s.

 Don't forget to put your fuel line in fire sleeve and dip the ends of the fire sleeve C plus you should be using band clamps (Otiker is one type and easy to use) and not worm drive clamps.

 

 There is no return line specific SB. It is in the installation manual. Even though there is not an SB you should be keeping up on manual changes for your engine health and your personal safety. Your right that many of the older engines were put in homebuilt's and many didn't have them under cowl C but of course some did. It didn't seem to be a big issue many years ago (but we learned) C but todays planes C the way we fly and where we fly has changed C fuels are changing and finally our knowledge is catching up. You brought up owners doing the work and that's perfectly ok C but some do it wrong for a number of reasons C but all should take a Rotax class and do it right.

 Rotax has been manufacturing the 912 since late 1989 and it has had 4K changes since then. Some very small or minor and some very significant changes.

 

 

 *Note*

 If I ever sound like I'm being disrespectful in some way to anyone I never ever mean it that way C but in emails it is easy to get the tone of the message wrong. I enjoy helping others with problems and working with people and sometimes throw a little philosophy in along the way. I usually get at least 2 calls a day from out of state with 912 issues and people bring me their 912 engined plane's to work on from 5 or 6 different states.

 

 *** Bottom line in all this dicusion thread is a return line is a good idea and can be found in the Installation manual.

 

 --------

 Roger Lee

 Tucson C Az.

 Light Sport Repairman - Maintenance Rated

 Rotax Service Center

 520-574-1080

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=237323#237323

 

 

 

 

 

 

 Quick access to your favorite MSN content and Windows Live with Internet Explorer 8.  Download FREE now!  [quote][b]

ptag.dev(at)tiscali.co.uk
Guest

Posted: Fri Apr 03, 2009 2:57 am Post subject: Vapor Lock and E-10 mogas

Hi!Ira

Re:- the small restrictor....it is to control back to tank volume.(as

well as any vapour possibly) Without the restrictor on some systems the

flow back to tank will take priority so starving the carbs hence the

restrictor keeps the pressure up to the carbs.

Regards

Bob Harrison G-PTAG



--

rampil

Joined: 04 May 2007
Posts: 870

Posted: Fri Apr 03, 2009 4:38 am Post subject: Re: Vapor Lock and E-10 mogas

Hi George,



If I interpret your note correctly, you want to know about dipping

fire sleeve.



It is recommended to clamp and dip fire sleeve to prevent possible

wicking of fuel into the loose fiberglass insulation inside and along its

length.  There are several anti wicking compound (see AircraftSpruce).

I use hitemp (red) silastic.

_________________
Ira N224XS

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