What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Vapor Lock

ronschreck

ronschreck

Well Known Member
I recently started useing Mogas in my IO-360 and have experienced vapor lock during extended climbs. Turning on the boost pump always eliminates the problem, but I am hoping for a solution that would not require the boost pump. I have run a 1.5 inch blast tube down to the mechanical fuel pump but this has not helped much. It seems to me that the problem is in the lines supplying the mechanical pump. I have them wrapped in fire sleve. I have gone back to runnning 100LL in one tank, but would like to solve the vapor lock problem so I can run Mogas exclusively. Is there something else I can do? Suggestions welcome.
 
Most of the mogas STC's include fuel system modifications which eliminate sharp bends in fuel lines. 90 degree fittings are replaced by 45's, etc. That helps prevent turbulence in the fuel lines and reduces bubbles...
 
Pump Shroud

Ron -

Did you put a shroud on the pump, or just point the blast tube at it?
 
during construction

I was very careful to make gentle radius bends (2") in all of my hard tubing for fuel, and changed out all of the 90 degree fittings for 45 degree on my system in front of the fuel servo. I've been running my XP-360 (IO) for over two years on mogas with no vapor lock issues.

Have you tried the climbs with the electric boost pump on? I've never had to do that, but it would help keep the system pressure up and might prevent vapor from forming behind the mechanical pump.
 
Bubbles can come out of solution (fuel) even if the heat is well controlled as (1) the atmospheric pressure is reduced and (2) the pressure is further reduced as the engine pump "sucks" the gas from the tank. Even the car manufactures have addressed this by putting the pump back in the tank providing increased pressure to keep those little buggers (air bubbles) in solution and they don't typically have to be concerned about significantly reduced atmospheric pressure.

You are expecting an awful lot from car gas to expect a bubble free system without using the boost pump considering all the stresses that tend to cause bubbles; reduced atmospheric pressure, drag through the lines, drag through the non-operating boost pump, drag through the filter, fuel valve, fuel flow sensor, uphill, elbows, bends, heat, and ethanol that is often added.
 
To answer some of your questions: Yes, I use the boost pump during climbs if the fuel pressure drops. The blast tube just blows on the mechanical pump. I didn't buy one of those super expensive pump shrouds. If it comes to that I will make one for $1.98 worth of welding rod and some scrap aluminum. I do have some 90-degree bends prior to the mechanical pump and I'll look into making some changes there.
Has anyone considered directing some of that blast air into a sleeve surrounding the fuel line? I might try that!

Thanks for the replies. Gotta love this forum. Thanks dr.
 
ronschreck said:
To answer some of your questions: Yes, I use the boost pump during climbs if the fuel pressure drops. The blast tube just blows on the mechanical pump. I didn't buy one of those super expensive pump shrouds. If it comes to that I will make one for $1.98 worth of welding rod and some scrap aluminum. I do have some 90-degree bends prior to the mechanical pump and I'll look into making some changes there.
Has anyone considered directing some of that blast air into a sleeve surrounding the fuel line? I might try that!

Thanks for the replies. Gotta love this forum. Thanks dr.
Click to expand...

I wouldn't worry about trying to actively COOL the incoming fuel lines, as much as I would try to INSULATE them. Use the cooling air on the heat source - this is the fuel pump that is mechanically bolted to the hot engine block. Build a shroud and use your cooling air to keep that as cool as realistically possible, and insulate the incoming fuel lines FWF. The other major hitter for you will be to eliminate sharp bends and filter restriction points, anything that can produce a pressure drop on flow rates between the tank and the pump is going to hurt you in this scenario.

Of course, ultimately the best way to solve this is to eliminate the engine-driven pump entirely, and go with electric pumps in the wing root such a Frankh did, and I'm building towards. The vapor lock occurs on the SUCTION side of the pump, and is a factor of pressure and temperature of the fuel. Putting the pump at the tank eliminates most of your fuel-line induced pressure drops, and eliminates all external heat sources. This will give you pressurized fuel right up to the manifold with no opportunity for bubbles. The car guys figured this out many years ago...
 
airguy said:
Of course, ultimately the best way to solve this is to eliminate the engine-driven pump entirely, and go with electric pumps in the wing root such a Frankh did, and I'm building towards. The vapor lock occurs on the SUCTION side of the pump, and is a factor of pressure and temperature of the fuel. Putting the pump at the tank eliminates most of your fuel-line induced pressure drops, and eliminates all external heat sources. This will give you pressurized fuel right up to the manifold with no opportunity for bubbles. The car guys figured this out many years ago...
Click to expand...

I'm betting you are not running fuel injection. With the price of high-pressure FI pumps, putting one at each wing root is a mightly expensive solution. :cool: Not so with a carbureted engine.
 
ronschreck said:
I'm betting you are not running fuel injection. With the price of high-pressure FI pumps, putting one at each wing root is a mightly expensive solution. :cool: Not so with a carbureted engine.
Click to expand...

Not running anything yet - my fuse kit will arrive next week - but yes, I'll be running fuel injection. With the total cost of the entire airplane, by the time I put a CS prop and glass IFR panel in it, I would feel pretty foolish trying to skimp out on a minor issue like the fuel pumps to save a few dollars. All it takes is ONE episode of vapor lock at the wrong time to make you rethink where you put your dollars during the build process. Build the fuel system in a hydraulically correct manner, and be done with it.

It's cheap insurance - the cost of the pumps is a fraction of the annual insurance premium, and it's a one-time purchase. It just makes sense.

If you're that worried about the dollars and cents of it, put one electric FI pump in the cabin and eliminate the engine driven pump - you'll get the same vapor lock protection, but without the benefit of a second pump in case the first fails. The wing root location allows the removal of a fuel valve to control which tank is pumping, to switch tanks you simply turn one pump on and the other off. If one pump dies, flip on the other one and land before your fuel imbalance gets ugly.
 
Last edited:
Hi Ron......

....we've been running mogas for quite some time in the -6A with our 0-360 but we usually try and keep around 50% Avgas so it's diluted but we still have enough lead. So far, so good, with no vapor locks (yet??)

Regards,
 
ronschreck said:
I'm betting you are not running fuel injection. With the price of high-pressure FI pumps, putting one at each wing root is a mightly expensive solution. :cool: Not so with a carbureted engine.
Click to expand...

Not so... just get two Facet 40185 cube pumps @11.5 psi for each side, and run them in series; the 40185's don't have a pressure relief built-in, so you can boost pressure by running them in series AND you have the benefit of some redunancy there at partial pressure. On the bench I tested mine with a digital calibration gauge, and they put out 23psi @35GPH. This is the setup I'm using in the rocket, cost is $50 ea, $200 total. They only draw 1.6A apiece.

Eliminate that POS unreliable mechanical pump! :) And get rid of the fuel selector while you're at it.

I got mine from another fine aviation parts establishment:
http://www.yachtsupplydepot.com/mec...tate-electric-fuel-pump-40185/prod_23424.html

The specs are wrong on this page, its a 9-11.5psi pump. Mine put out 11.5psi each.
 
rocketbob said:
Not so... just get two Facet 40185 cube pumps @11.5 psi for each side, and run them in series; the 40185's don't have a pressure relief built-in, so you can boost pressure by running them in series AND you have the benefit of some redunancy there at partial pressure. On the bench I tested mine with a digital calibration gauge, and they put out 23psi @35GPH. This is the setup I'm using in the rocket, cost is $50 ea, $200 total. They only draw 1.6A apiece.

Eliminate that POS unreliable mechanical pump! :) And get rid of the fuel selector while you're at it.

I got mine from another fine aviation parts establishment:
http://www.yachtsupplydepot.com/mec...tate-electric-fuel-pump-40185/prod_23424.html

The specs are wrong on this page, its a 9-11.5psi pump. Mine put out 11.5psi each.
Click to expand...

That's an interesting setup and I hope it works out for you. Not sure if 11.5 psi is enough to keep FI running. Mine starts to stumble at 9 to 10 psi, so you haven't got a lot of margin there if one of your electric pumps go south, but then again you have the other tank and pumps as a backup. At $635 each, I'm not about to put a second Airflow Performance pump in, even if I had the room to do it. The mechanical "POS" pump works just fine 99% of the time and when it decides to vapor lock I have plenty of warning to switch on the boost pump. Not an ideal setup, but it's not so easy to retrofit as one pleases and I don't want to rebuild the airplane. Thanks for the input and good luck with the Rocket.
 
airguy said:
Not running anything yet - my fuse kit will arrive next week - but yes, I'll be running fuel injection. With the total cost of the entire airplane, by the time I put a CS prop and glass IFR panel in it, I would feel pretty foolish trying to skimp out on a minor issue like the fuel pumps to save a few dollars. All it takes is ONE episode of vapor lock at the wrong time to make you rethink where you put your dollars during the build process. Build the fuel system in a hydraulically correct manner, and be done with it.

It's cheap insurance - the cost of the pumps is a fraction of the annual insurance premium, and it's a one-time purchase. It just makes sense.

If you're that worried about the dollars and cents of it, put one electric FI pump in the cabin and eliminate the engine driven pump - you'll get the same vapor lock protection, but without the benefit of a second pump in case the first fails. The wing root location allows the removal of a fuel valve to control which tank is pumping, to switch tanks you simply turn one pump on and the other off. If one pump dies, flip on the other one and land before your fuel imbalance gets ugly.
Click to expand...

Just curious. What pumps do you plan on useing? Mine cost $635 each, which is almost half of my annual insurance premium. No, I would not even think of running without the benefit of a second pump. The mechanical pump works fine with mogas 99% of the time and the boost pump handles the remaining 1% when needed. If I were building another airplane I might consider a dual electric setup as you describe, but retrofitting that into a finished aircraft is another story. Trust me, once you get yours flying you will want to minimize the down time and just enjoy the flying. :D
 
Thought I had better chime in

As I am responsible for all this putting pumps in the wingroot milarky..

I have a FI'd IO360 and have a FI pump in each wingroot.

If you do a search under my name you will find the model of the pumps I am using and they cost $130 each. Then you need a pressure relief valve, non return valve and a filter..Total cost should be around $200 per side..At least it was when I built.

Thats close to the cost of a mechanical pump..and it actually works all of the time..:)

At least folks are not trying to burn me at the stake for not using a mechanical pump anymore..It was touch and go for a while..:)

Frank
 
ronschreck said:
That's an interesting setup and I hope it works out for you. Not sure if 11.5 psi is enough to keep FI running. Mine starts to stumble at 9 to 10 psi, so you haven't got a lot of margin there if one of your electric pumps go south, but then again you have the other tank and pumps as a backup. At $635 each, I'm not about to put a second Airflow Performance pump in, even if I had the room to do it. The mechanical "POS" pump works just fine 99% of the time and when it decides to vapor lock I have plenty of warning to switch on the boost pump. Not an ideal setup, but it's not so easy to retrofit as one pleases and I don't want to rebuild the airplane. Thanks for the input and good luck with the Rocket.
Click to expand...

The cube pumps have a MTBF of 2000 hours, and I personally I've never seen one fail, and in my RV the same type of pump has been perfect. I've had one mechanical pump failure, and know of many failures of the mechanical pumps so that's why I have a certain opinion of them. :)

But if you really want to run mogas, the best path for compatibility involves getting rid of the mechanical pump and pushing fuel thru the system. And ethanol-blended fuel becomes a non-issue. Actually I've been running ethanol-blended 87 for several months, and don't have any trouble with vapor lock except for in the summer, and I solved that by running the boost pump all of the time. Been running 87 octane for over 900 hours now.
 
Last edited:
ronschreck said:
...I do have some 90-degree bends prior to the mechanical pump and I'll look into making some changes there...
Click to expand...
Ron,

I'm not sure you can eliminate them all. There is a 90 degree bend in the tank for the fuel pickup. Granted, that one is cooled by the fuel in the tank.

airguy said:
I wouldn't worry about trying to actively COOL the incoming fuel lines, as much as I would try to INSULATE them...
Click to expand...
Good advice as I had a few (OK, four) engine stoppages before I insulated the 180 degree elbow leading to my fuel flow meter. Since adding the fire sleeve, I have had no problems.
 
True

rocketbob said:
The cube pumps have a MTBF of 2000 hours, and I personally I've never seen one fail, and in my RV the same type of pump has been perfect. I've had one mechanical pump failure, and know of many failures of the mechanical pumps so that's why I have a certain opinion of them. :)

.
Click to expand...

I also ran the cube pumps in my old Zenair Zodiac (thats where I developed the wingroot fuel pump system)..These were the 40106 units (4 to 6psi) and they were perfect for 500 hours and they are still going strong two owners later.

I did have an infant mortality on one of my FI pumps at 60 hours or so..Replaced it and no further problems..Even then it did not quit pumping..output pressure dropped to 12psi but the engine still ran fine.

Its just the audible warning from the Dynon kinda freaked out my CFII...:)

In 350 hours have had no further problems however.

Frank
 
Out of interest Pierre

pierre smith said:
....we've been running mogas for quite some time in the -6A with our 0-360 but we usually try and keep around 50% Avgas so it's diluted but we still have enough lead. So far, so good, with no vapor locks (yet??)

Regards,
Click to expand...

Why do you think you need the lead?..Are you just talking about VL protection? Or do you think you need it for the engine?

The engine really doesn't need the lead unless your engine is more than about 20 years old with the soft valves and seats.

Cheers

Frank
 
rocketbob said:
The cube pumps have a MTBF of 2000 hours, and I personally I've never seen one fail, and in my RV the same type of pump has been perfect. I've had one mechanical pump failure, and know of many failures of the mechanical pumps so that's why I have a certain opinion of them. :)

But if you really want to run mogas, the best path for compatibility involves getting rid of the mechanical pump and pushing fuel thru the system. And ethanol-blended fuel becomes a non-issue. Actually I've been running ethanol-blended 87 for several months, and don't have any trouble with vapor lock except for in the summer, and I solved that by running the boost pump all of the time. Been running 87 octane for over 900 hours now.
Click to expand...


You are starting to make a believer out of me! If that "POS" mechanical fuel pump of mine ever quits, I'll be looking for an all-electric solution. (Hey, I'm the guy that doesn't have any magnetos, vacuum pump, gascolator, carburetor or mechanical gyros.) Maybe the era of the mechanical pump is about over as well. Right now I'm just looking for a simple solution to occasional vapor lock. BTW, are there not some corrosion issues with running ethanol-blend fuel?
 
ronschreck said:
Just curious. What pumps do you plan on useing?
Click to expand...

I was planning on running the same setup Frankh has - though the series pump arrangement that rocketbob is talking about definitely caught my attention. It's not hydraulically as clean as a single pump, but it's cheap and effective, replacement pumps are easily acquired, and it quite evidently works well. Either way, I do fully intend to run an IO360 with wing root pumps, and feed it mogas. We know it can be done with proper fuel system design, the engine really does not care as long as you're running stock compression. I'm not sweating the decision just yet on which pump to run, I haven't even received my fuse kit yet so I'm a good ways from that point.

ronschreck said:
BTW, are there not some corrosion issues with running ethanol-blend fuel?
Click to expand...

Some, but mostly it's overblown. I alodined all the fuel-wetted aluminum surfaces (including pickup and vent tubes) to give extra protection. The ethanol-laced fuel can carry more moisture, which CAN increase the corrosion potential. You know it can't be too terribly bad, or we'd be seeing automobile damage left and right from the same material compatibility problems. There are lots of aluminum components between the fuel cap and the engine block in our road cars that are exposed to the same ethanol blended fuel, and they are working fine for the last several years. The biggest issue that causes heartburn with ethanol is rubber components in the fuel system - and we can design those out.
 
Last edited:
Don't do it

ronschreck said:
You are starting to make a believer out of me! If that "POS" mechanical fuel pump of mine ever quits, I'll be looking for an all-electric solution. (Hey, I'm the guy that doesn't have any magnetos, vacuum pump, gascolator, carburetor or mechanical gyros.) Maybe the era of the mechanical pump is about over as well. Right now I'm just looking for a simple solution to occasional vapor lock. BTW, are there not some corrosion issues with running ethanol-blend fuel?
Click to expand...

You'll be branded a herotic and burned!..Ask me how I know?..:)

It is interesting to me how a lot of builders choose two Lightspeed ignition systems (thus making their engine electrically dependant) but won't consider two electric fuel pumps..I mean..It requires a redundant electrical system in either case.

Frank..Proud starter of all kinds of trouble..:)
 
Oh and

I agree the ethanol problem debate is way overblown..I had an unpainted alumimium airplane for 8 years and there were a few white specs of corrosion on it..but just not enough to notice.
 
OK now you go me thinking

airguy said:
I was planning on running the same setup Frankh has - though the series pump arrangement that rocketbob is talking about definitely caught my attention. It's not hydraulically as clean as a single pump, but it's cheap and effective, replacement pumps are easily acquired, and it quite evidently works well. Either way, I do fully intend to run an IO360 with wing root pumps, and feed it mogas..
Click to expand...

So what if you put a single Facet pump in each wingroot and then two pumps in series on the cabin floor in series?

Each of the pumps is internally relieved (at least the 40106's are) and the total pressure will be 3*11.5 =35 psi.

If one pump quits it will still be 23 psi minus the forward pumping loss of the dead pump.

The Airflow performance FI servo is happy between 14 and 90psi..so this system is failure tolerant and maybe quite a bit cheaper..Ok its more pumps but those little things are pretty light weight.

If a wingroot pump goes down..well suck through it to get to your destination..if it vapour locks then run off the good pump till you land..but I bet for en-route flying it will give you access to the full quantity of fuel which my system currently will not.

Hmm..this has some merit, and no pressure relief vales to buy and plumb in.

Normal opperation will prevent VL because of the pump in the wingroot.

Darn..i thought MY system was perfect..Now look what you've done...hehe

Frank
 
ronschreck said:
You are starting to make a believer out of me! If that "POS" mechanical fuel pump of mine ever quits, I'll be looking for an all-electric solution. (Hey, I'm the guy that doesn't have any magnetos, vacuum pump, gascolator, carburetor or mechanical gyros.) Maybe the era of the mechanical pump is about over as well. Right now I'm just looking for a simple solution to occasional vapor lock. BTW, are there not some corrosion issues with running ethanol-blend fuel?
Click to expand...

Guys, there is another side of the equation that I don't think has been mentioned, if it has I apologize. The much maligned mechanical fuel pump needs no electricity. Loose all power, and your a glider, unless you have a backup redundant battery set up.

I'm not trying to rain on anyone's parade, but like the old saying goes, most things in aviation are compromises.

I run 100% mogas and have for years. I've had vapor lock on climb out as mentioned. Just hit the boost pump and presto!, no more VL.
 
Last edited:
Geico266 said:
Guys, there is another side of the equation that I don't think has been mentioned, if it has I apologize. The much maligned mechanical fuel pump needs no electricity. Loose all power, and your a glider, unless you have a backup redundant battery set up.

I'm not trying to rain on anyone's parade, but like the old saying goes, most things in aviation are compromises.

I run 100 mogas, and have for years. I've had vapor lock on climb out as mentioned. Just hit the boost pump and presto!, no more VL.
Click to expand...

You are absolutely correct. A well designed electrical system is essential for my dual Lightspeed configuration and it will serve me well with dual electric fuel pumps as well should I decide to go that route. :D
 
Exactly my point

Builders opt for dual ligthspeeds without a second thought...Two electric fuel pumps and its "grab yer pitchforks!"

Its the same level of risk..Or more to the point two electric pumps is no additional risk to two Electronic ignitions.

either/or/both require a redundant electrical system..But that really is no big deal these days.

Frank
 
2-3 Facet pumps in series

in the cabin would be a little noisy wouldn't it? I would think the non-synchronized rhythm would be very annoying when audible.

Bevan
RV7A wiring
 
Audible

Well that would only be taxiing on the ground, you'd never hear them in flight.

Frank
 
Five airplanes running on auto gas, here is our experience

We use auto gas in my 9A O-360, a C152, a C150, a Piper, and a 182. We buy 1,000 gallons at a time and the local distiller removes all ethanol for us. Check in your city.

Whenever a load arrives, my job is to test the volatility and the water content using the Petersen gauges. Most times the volatility is 6.0 which is the low end of the Petersen scale. By mixing 3 parts auto gas to 1 part av, volatility rises to 7.5. 50 / 50 is probably overkill but better safe than sorry.

My 9A has the most trouble with auto gas out of the fleet but the 3-1 ratio seems to eliminate all issues which include surging during deceleration into the pattern, stalling on the runway after landing, & low fuel pressure as measured by the Dynon (thanks to the elec pump it never becomes an issue).

I removed the screens in front of the tank vents and that seemed to reduce VL. One theory is that the increased pressure on the fuel in the tank (due to the elimination of the restriction caused by the screens) facilitates remedy. I'm planning another cross country on Sun and will report if anyone is interested. Yes, I protect against bugs when parked.

My procedure is to keep the right tank with 3-1 (or 2-1) for takeoffs and landings, and use the left tank once I achieve cruise altitude.
 
Altitude?

Interesting thread, but I've seen no mention of the affect of altitude on the vapor lock issue.

Some posts have mentioned "air" or "vapor" coming out of solution causing the problem. That is not quite true - the vapors are boiling fuel components. Keep in mind that boiling does not mean hot by human touch standards. At high altitude, the overall pressure on the fuel is less, so the worst case for vapor lock might be at high altitude. Seems like I recall the boiling temperature for 100LL fuel at sea level (14.7 psi actual) is around 140F. 100F and it is around 4 to 7 psi actual.

This is all very important stuff, as I would not be surprised to see the current powers-that-be summarily outlaw 100LL.
 
Altitude is not an issue

Well with a hydrailically correct fuel system it isn't at least.

I'd need to look up some numbers but bsically the temp drops fast with altitude...In other words if its not boiling on the ground it won't boil at altitude due to the standard drop in temp..At least thats the numbers I came up with I last looked at htis.

now of course this holds true for a wingroot pump system..I don't know what happens when you add some suck from a conventional system.

Frank
 
The Secret Formula!

MrNomad said:
Whenever a load arrives, my job is to test the volatility and the water content using the Petersen gauges. Most times the volatility is 6.0 which is the low end of the Petersen scale. By mixing 3 parts auto gas to 1 part av, volatility rises to 7.5. 50 / 50 is probably overkill but better safe than sorry.

My 9A has the most trouble with auto gas out of the fleet but the 3-1 ratio seems to eliminate all issues which include surging during deceleration into the pattern, stalling on the runway after landing, & low fuel pressure as measured by the Dynon (thanks to the elec pump it never becomes an issue).
Click to expand...

That is valuable information. Thanks for sharing.
 
rocketbob said:
And get rid of the fuel selector while you're at it.
Click to expand...

You got my attention Bob, can you elabotate? I've often thought this fuel tank control valve was not needed, but I've never said it out loud before. Are you doing away with it?
 
frankh said:
Well with a hydrailically correct fuel system it isn't at least.

I'd need to look up some numbers but bsically the temp drops fast with altitude...In other words if its not boiling on the ground it won't boil at altitude due to the standard drop in temp..At least thats the numbers I came up with I last looked at htis.

now of course this holds true for a wingroot pump system..I don't know what happens when you add some suck from a conventional system.

Frank
Click to expand...

Frank, you are correct that the vapor pressure of the fuel doesn't really matter with your setup - at least as far as getting the fuel to the engine - but, most don't have the pumps by the tank outlets as you have. Also, the fuel in the tank will not cool as fast as these planes can climb to thinner air...
 
Suction pressure drop

Hey Ron,

A simple solution may be to relocate your flow meter to the metered fuel line if its not there already. This will eliminate some pressure drop on the suction side of the mechanical pump. And if your using a Weldon boost pump some times the bypass valve opens at a little higher pressure than necessary, thus putting more pressure drop on the suction side of the mechanical pump.

Just a thought, rather than to redesign the fuel system with different pumps.

Don
 
right

AlexPeterson said:
Frank, you are correct that the vapor pressure of the fuel doesn't really matter with your setup - at least as far as getting the fuel to the engine - but, most don't have the pumps by the tank outlets as you have. Also, the fuel in the tank will not cool as fast as these planes can climb to thinner air...
Click to expand...

This thread did drift into alternative fuel system designs, hence the comment.

Good point on the rate of climb question... Personally I have never noticed an issue, but then unless I can see into my tanks I would not know if the fuel was boiling or not..Personally i have never noticed an issue however..But once again with a standard system I could not gurantee that result.

Frank
 
Wing root installation

Does anyone have any pictures of the facet pump wing root installation ? This has been a very interesting and informative thread, I think the abolishion of Avgas is likely to happen here in the UK before it happens in the US and any information we can get on fuel system designs etc for RV's will help to put the modification case to our LAA engineers. Even if we are not allowed a modification at this time, it has got to happen eventually so planning the fuel system for MOGAS now will save a great deal of time and work later.
 
Yes I do

shiney said:
Does anyone have any pictures of the facet pump wing root installation ? This has been a very interesting and informative thread, I think the abolishion of Avgas is likely to happen here in the UK before it happens in the US and any information we can get on fuel system designs etc for RV's will help to put the modification case to our LAA engineers. Even if we are not allowed a modification at this time, it has got to happen eventually so planning the fuel system for MOGAS now will save a great deal of time and work later.
Click to expand...



Yes here you go


http://www.vansairforce.com/community/showthread.php?t=30402&highlight=wingroot+fuel
Frank
 
Carb Vs FI

The system I showed is for a FI'd system (although running 4 Facet pumps one in each wingroot plus two in series is an intrigueing idea)..For a carbed system simply replace everything that I have in the wingroot with a 40106 facte fuel pump..i would probably syill put the filter ahead of each pump however.

Everything else stays the same.

Frank
 
frankh said:
That is exactly what it is..The standard fuel system design is poor from a VL perspective.

Frank
Click to expand...

I think you have proven quite well that mogas works in an airplane and is safe. The key is getting fuel under pressure as close to the tank as possible.

My experience with mogas has been good. The Subby system had 2 electric pumps just forward of the spar on the cabin floor. I flew with Walmart gas when the OAT was over 100F and it worked without incident and the fuel was laced with ethanol.

But I am not doing it today with the Lycoming. The problem is the ethanol. I am not sure the mechanical pump seals will hold up and I am not sure about aviation grade fuel hoses and ethanol. The previous system was 100% auto technology and it is impervious to ethanol. Ethanol itself is not a problem except when introduced to incompatible components.

If I could buy mogas without ethanol, I would be using it. The issue of heat at the mechanical pump is real and can be a problem with 100LL, but is defeated if fuel coming through the firewall is under pressure. I do not have a problem running an electric pump 100% but am hung up on the ethanol situation.
 
Can't help

you on the compatibility of the Mechanical fuel pump internals with ethanol...Same as with the carb.

I do know the AFP FI system is ethanol compatible and I would suspect the Bendix is also but I don't know for sure.

I can tell you that the teflon lined aviation grade hoses are ethanol tolerant.

We use Teflon tubing just about everywhere for almost every type of chemistry at work. Its wonderfully impervious stuff to just about anything.

The only other material compatibility issue is the fuel drain O rings..These are available from McMaster Carr in Flourosilicone which is ethanol compatible.

Frank
 
Backing up what Frankh has already stated. That, and the rubber O-rings that Vans includes in the kit for the fuel sender seals and for the drain ports - toss 'em, and go with a thick ring of proseal on the senders, and flourosilicone O-rings on the drain ports. The rubber will soften and swell over time with ethanol exposure, and eventually leak, some people claim you'll experience the same problem with the mechanical fuel pumps - but I don't know with any certainly what material the diaphragm is made of, so can't say.

To replace the rubber seals on the fuel senders, I laid a good bead of proseal unmolested in a circle where the plates will screw into in place of the rubber ring, and let it set up about 12 hours in 75-80 degrees. It was just to the point where you could still move it around with difficulty, would barely hold a fingerprint, and I screwed the senders into position over that bead, spreading it out and compressing it. I did use fresh proseal on the threads of the screws, and it came out leak free - life is good.

Teflon fuel hoses will take full gasoline and ethanol exposure, they are (chemically speaking) bulletproof.
 
in tank fuel pumps

I've read that the best place for the fuel pumps is in the fuel tank, like we have in our cars. This eliminates vapor lock issues, but is of course kind of a hassle to install or retrofit. Just food for thought.
 
It is

yes the very best place for the pump is in the tank, but as you say a nightmare to live with!

Frank
 
You must log in or register to reply here.
Back
Top