Captain_John

Captain_John

Well Known Member
Hi All,

I am looking for pics of anyones tanks who have installed a vapor return line. I want to do so and would appreciate seeing how others have done it.

I am thinking that the line could penetrate the tanks somewhere adjacent to the vent line and parallel it all the way to the last outboard bay of each tank.

Am I on the right track?

:confused: CJ
 
I'm not sure of what you are referring to. I ran a purge line that allows me to purge my FI system back into the fuel tanks. Is that what you're looking for?
 
I suppose that would be it. ECI calls it a vapor return line. It returns any vapors and fluids from the mechanical fuel pump/atomizer and delivers it back to the tank.

I understand that some people dump it overboard, but I don't want to do it that way.

Do you have any pics?

:) CJ
 
fuel return

John,

Thanks for raising the issue. I have been thinking about that as well. I intend to install a bendix fuel injection system. Of course, I will need a high pressure boost pump. I am told that a "purge" or "fuel return" line should be installed to return hot fuel back to the tank, in order to avoid vaper lock.

I have seen pics of a line which runs to the fuel selector valve and is connected with a Tee fitting to the fuel line before the fuel line enters the valve. I would prefer to run the return line all the way back to the tank in order to give the fuel more time to cool and to mix with the other fuel in the tank before it is re-introduced into the fuel system.

I would run the line all the way to the back of the tank if possible. Since my tanks are already finished, I will have to settle for dumping the fuel back into the tank at the wing root.

Now, my question. Where do you connect the other end of the line to pick up the "purged" fuel? What high pressure fuel pumps are available, where do you get them and how much do they cost? I have heard that most people use the Air Flow Performance pump, which requires a purge line that attaches to the pump.

I am attaching a link to the site of Mickey Coggins, which shows his installation. Micky has a great site that I use a lot because it is so well documented with photos and descriptions. Thanks Mickey.

http://www.rv8.ch/article.php?story=20040704204434728
 
Hmmmm,

Tony, thanks for the link! Great stuff! My thoughts:

Use proseal instead of snap in bushings. Proseal is likely to last longer, the fuel won't be deliterioius to it and I have plenty of the stuff!

Also, I have slow build tanks, so I am thinking of running the line al the way to the outboard bay.

Does everyone agree that the 90 degree fitting in the bottom of the bay is the way to go?

As I pass through the bays, should I offset up towards the top of the tank?

Should I go on the top of the bay the whole way across?

What do you think?

:confused: CJ
 
Hi Team,

I have an Airflow Performance FI system and for the purge line, I have returned this back through the firewall near the brake reservoir (RV-6) with a flexible line and then used an aluminium line from the firewall down the RH side of the fuselage to exit next to the vent line in the wing root. From there the line simply enters the fuel tank at the top - once again next to the vent.

The amount of fuel that purges back into the tank is minimal (about half a cup) so I have not worried about over filling the tank etc.

This is much nicer than throwing the fuel onto the ground under the machine.

Just be aware that a "vapour return line" or "unmetered return line" is not the same as a purge line in some installations (usually larger engines like 0-540's etc). This system takes unrequired (or unmetered) fuel from the system and returns it to the tank being used. This is because the fuel being supplied by the pump is in excess of the fuel required to run the engine. Do not confuse the two systems, they have different plumbing requirements.


Regards,

Mike
 
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Thank you for the advice, Platenutz!

I will run alongside the vent line and use the same fittings as the vent to make things "standard".

Does anyone have anymore pictures?

:rolleyes: CJ
 
More plumbing questions...

Would someone please confirm my recollection that using ordinary plumbers teflon "pipe dope" for proper assembly of AN fittings.

I seem to recall hearing this is a good alternative to fuel lube. Is that true?

...AND,

I am wondering if I need two vapor return lines. If I install only one vapor return line in say, the left tank... and then plumb a "T" around the output ports of the fuel selector leading back to the tank with a single line going to only the left tank... would that pose any issues?

Is there anything "improper" with that setup? Are there any considerations I haven't thought of?

Input, please!

:rolleyes: CJ
 
Hi John,
The ECI fuel injection system operates much like the TCM fuel injection system. This will bring plumbing changes to any one who uses it. The system will be returning fuel at certain times of operation all the time. This is very much different then the purge valve setup that AFP used for hot starts. In another words the vapor return system in the ECI system will be active during engine operation while the AFP purge valve is not. Thus My guess is you would want to return fuel to the tank you are using rather then return to a single tank, as ding so with that tank full would cause fuel to be wasted and vented overboard at an alarming rate. You could always make a habit of selecting the return tank first and then running that down and then switching to the return tank but I don't know how you aircraft will fly that way with only one and then possibly two passengers. I think andair makes a stacked fuel selector that would do this job quite well. I would also think seriously about installing a one-way check valve in the vapor return line allowing flow toward the tank only.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts
are hopefully helpful to you. Please use the information provided responsibly and at you own risk."
 
I called Van's when I plumbed my fuel system & questioned them on "Teflon Pipe Dope". The never used the term "Pipe Dope", but did confirm it is alright to use. I think you don't want to use teflon tape because a piece of it might get into the fuel system-Not good.

Derrell
RV7A
Canopy
 
Thanks for the repies, guys!

Mahlon, it looks like I will be plumbing in 2 return lines... one in each tank. Last night I purchased a pair of AN ells and associated nuts and sleeves to do the job. I guess in the back of my mind, I planned on installing 2 return lines and needed to give it due diligence.

Derrell, thanks for the confirmation on the pipe dope. I just needed to do a doublecheck on it!

I will post pics when I am done for all to comment on.

Thanks again!

;) CJ
 
Just a warning that running two return lines will add considerable complexity and cost. On a tri-gear it's already pretty crowded on the front side of the carry-through spar with fuel lines, brake lines, and wiring. And check out the cost of the Andair duplex valves versus the regular valves versus Van's standard valve. Ouch. What's the advantage of having a continuously running fuel return line versus a purge valve like AFP uses? The only vapor lock issues I've heard about are during start-up soon after shut-down on a hot day. Purge the vaporized fuel and you're set to go. With the purge valve you can simply return the fuel upstream of the fuel selector on one side (see Dan C's site for an example).

All of this is based on my limited understanding from reading other's experiences. Feel free to correct me if I'm wrong.

Dave
 
Hi Dave,
The purge valve in the AFP system does and acts exactly as you say. The return line that John wants to possibly use with ECI's new FI system will be returning fuel to the tanks during engine operation. Sometimes at a considerable rate. It is not a purge system for starting, like the AFP system, but rather a actual fuel return for fuel that isn't being used by the system when leaning. So the reasoning behind returning to the tank you are drawing from becomes attractive, as you won't have the worry of returning fuel to a tank that doesn't have room for it, thus venting the return fuel overboard through the vent in the full tank. If you always burn off the retune tank first say 1/2 way down and the switch to the non return tank, you can overcome this problem as you are effectively transferring fuel from the full non return tank to the return tank. But if aircraft loading makes you want to burn the non return tank first, you can't, without wasting fuel, as any fuel being retuned during operation will be going to a full tank and get vented overboard.
I suppose there are may ways of solving the issue rather the using an expensive selector but who knows. What do the car engine guys do? I think, but am not totally sure, most of them return fuel all the time when in flight. They might be a good resource for plumbing and practical advice.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at you own risk."
 
Does the bendix fuel injection system need a return line

Does the bendix fuel injection system need a fuel return line? I plan on installing a purge line if the pump that I will be using requires it.

It seems that a purge line will help with hot starts if it removes the vaporized fuel.

If the bendix FI system utilize requires, or can benefit by a fuel return line, I need to rethink.
 
Does the bendix fuel injection system need a fuel return line?
Click to expand...

I asked that same question directly to Mahlon on Friday. This is what he said:

"The Bendix/Precision Airmotive SilverHawk fuel injection system does not have provision for a purge/return line and doesn't require one."

According to Mahlon, the whole vaporized fuel problem has been blown out of proportion. There are many certified fuel injection systems running out there without purge and/or return lines. I have heard that auto gas vaporizes more easily, so that may be a different story.

I just read about ECI's new fuel injection system in KitPlanes over the weekend. Now I understand. Their new system requires a fuel return line. And it makes the most sense to route it back to the same fuel tank that you're feeding from.

The third fuel injection option is AFP's system which has an optional (at least I think it's optional) purge line, which doesn't return fuel all of the time.

Dave
 
Dave,

In that Kitplanes article, did they mention that the ECI system got an extra inch of manifold pressure?

The sales propaganda I saw at OSH said it did this by omitting a venturi or port or something like that.

I am just curious what they said regarding the how's and why's of the system.

Combine the inch of MP with a slick marketing campaign and it kinda hooked me.

What is your take?

Mahlon? Others?

:cool: CJ
 
The article in Kitplanes was a "preview" of new engine technology. Because of the long lead time, they wrote the article before all of the details were available. The article mentioned Lycoming's new roller tappets, ECI's new sump/manifold, and of course ECI's new fuel injection system. There was no mention of increased MP that I remember. The main advantage stated in the article was lower cost and simplified operation.
 
Dominik,
I saw the system at Oshkosh. it is pretty much a clone of TCM's system operationally. They boasted lighter then the other alternatives. One thing that wasn't so good was it uses a rotary pump instead of the diaphragm pump found on most Lycoming?s. So to use it, will require an accessory housing change and some drive gear changes for a good majority of the engine s out there.
I would imagine, as they get closer to production they will have some stuff on their web site.

John, I don't know about the 1" of MP but it is a straight shot air throttle body with out any venturi, so it could get a little less pressure drop through the body when the throttle was wide open.
They said they would send me some stuff to play with so we will see.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts
are hopefully helpful to you. Please use the information provided responsibly and at you own risk."
 
Thanks for the information Mahlon, so we have to wait untill we know more about this system from field-reports.

It is very very difficult to build the fueltanks, without made the decision which FI to buy already! Return line, purge line, dual return line and fuelselector .... also difficult to change or build it in later :confused: especially with an A version, there is not so much room for additional fuel lines. :confused:

I do not know what to do now, I'm short before closing the 2nd fueltank.

Dominik
 
Fuel return line

Dominik said:
I do not know what to do now, I'm short before closing the 2nd fueltank.
Click to expand...
Easy - just don't close it yet. The tanks don't need to be finished before you continue on with the fuselage! :)
 
Hello Mickey

Yes, I can wait, but not as long as neccesary ... I dont like to go ahead like this, I want to finish the wings put them aside and start the fuselage. Will see how does I go on ...

Sorry, i missunderstod you, I was meaning the rear baffle is still open and I want to close it to go ahead in fueltank construction. The accesscover can wait, but only until I do the leak test, and that must be done bevore I mount the tank to the wing.

Dominik
 
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AFP and an IO-360A1B?

Excuse me if I come to this late, but I have an AFP and an IO-360A1B/Bendix FI. The Vans instructions did not show a return line to the tank. Do I need one?

Thanks
 
pipe thread compound

The latest and greatest according to our AI is EZ turn a product of United. I got the part no. on aircraft spruce web last night. The 5oz. tube part no. is
09-00306 for $11.70.
I rubbed some between my fingers and it is a slicker material than I have ever felt. Very hard to get off of the fingers also.
Ted
 
Hard Knox said:
Excuse me if I come to this late, but I have an AFP and an IO-360A1B/Bendix FI. The Vans instructions did not show a return line to the tank. Do I need one?
Click to expand...

The cool part about this forum is that even if you arrive at the party late, you can read the previous posts (like about 9 up) and it will still answer your question.
 
Hey All,

Here is what I came up with. Sorry for the fuzzy pic.

P8260056.jpg


The extra AN fitting on the bottom facing aft is the Vapor Return line. It looks like it will parallel the the fuel feed line all the way to the fuel selector switch.

Is there adequate room to pass both lines through the fuse at the same location?

Anyone?

:) CJ
 
ECi Fuel Injection System

I will be installing the ECi FI system on my RV6 as soon as I am finished testing the New ECi sump and cold air induction system with the Bendix FI system. I am testing both systems for ECi to do a comparison of the two system. I will have pictures of the ECi FI installation on my web site with all the details as soon as I get it installed, in about 6 weeks.
Robbie
 
ECI is Airmotive is Bendix

I think Bendix FI was bought by Airmotive and is what ECI uses on their engines. G
 
ECi is Not The Bendix / Precision

The ECi FI system is an improved design and looks somewhat like the TCM FI system. The TCM FI system has been around 50 years and has a pretty good reputaion. The air intake is not a venturi like the Bendix / Precision so it should produce more manifold pressure. That remains to be seen. I should have some numbers on that in a couple months.

Robbie
 
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Talking past each other?

I think you're all talking past each other - I'll try to summarise the situation as I understand it. The new ECI injection system is similar to that fitted to Continental engines. There is a good explaination of the system on the ECI website.

To date I believe fuel injected ECI engines have been supplied with either Precision (was Bendix) or Air Flow Performance system - they are both very similar - at the customer's choice.

Airflow also make a high pressure electric fuel pump that a lot of experimental builders install when using fuel injection. They also make a bypass valve that is meant to ease hot starting problems.

The bypass valve is typically used before starting to circulate cool fuel from a tank around the injection system to remove any fuel vapour - especially from the mechanical fuel pump. A relatively small amount of fuel is circulated, which should be returned to a tank. If this valve is used once the engine is running it will stop (and can be used to shut down the engine). The valve is not required to make an FI system work, there are other ways to get rid of the vapour lock (perhaps a little more technique is required). I believe the valve can be fitted to either an Airflow or Precision system, if you really want.

As has been pointed out already, the Continental (new ECI) system works on a rather different principle. Fuel is returned from the injection system much of the time. A "duplex" fuel valve is a good idea to send the fuel back to the tank that it came from.

I would have thought that the return line could be connected to the fuel tank outlet using a T fitting between the fuel valve & the tank?

Yours, Pete (body armour on awaiting incoming flak ...!)
 
penguin said:
I would have thought that the return line could be connected to the fuel tank outlet using a T fitting between the fuel valve & the tank?

Yours, Pete (body armour on awaiting incoming flak ...!)
Click to expand...

Pete, I suppose it could. I suppose it has been done that way a time or two. I also don't see how my method wouldn't be a little "better". Don't you?


:confused: CJ
 
full return system

Captain_John said:
I also don't see how my method wouldn't be a little "better". Don't you?
Click to expand...
The advantage I can see of your method is that the fuel will stay cooler. BTW, I used a similar method for my fuel return, so I'm somewhat easy to convince!
 
John,

Completely agree that your method is better. I was wondering if anyone knew any reasons for not using the T-fitting method?

Pete
 
Clarification

Vapor return line is a Continental thing. The purge line is a AFP thing, and a regular bendix FI shouldn't have either.
 
Hello, I'm new here this is my first post. haven't started to build, do have a training kit.
My thinking on the tee method is if any air gets into the fuel line it will be reintroduced into the line. Returning to the tank will eliminate the air from the fuel system. That's my 2cents worth.
 
air in the line

dirtmanf800 said:
...My thinking on the tee method is if any air gets into the fuel line it will be reintroduced into the line. Returning to the tank will eliminate the air from the fuel system. That's my 2cents worth.
Click to expand...
I think you are right. Same with water.
 
FI vapor return line

Captain_John said:
I illustrated/documented my tank internals in this thread if anyone is interested.

Let me know if I missed anything or if you think of ways to improve it!
Click to expand...
Almost exactly how I did it. I put my return line very low, in a probably unnecessary attempt to reduce foaming. I'm really not even sure if gasoline foams, to be quite honest.
 
Mick, your install was one of my resources!

I chose higher because I am imagining it easier too tie in to the fuse later. I can work above the fittings instead of having it's contents (fuel) spilling into my eyes from a maintenance standpoint, later.

My install also (like yours) has a straight shot and no bends are required.

Thanks, Mick!

:D CJ
 
Return Lines... Best Practices?

I am reviving this thread because I'm on the tanks... and I have questions! :D

I *AM* going to run vapor/purge/return lines back to the tanks... no doubt about it. While CJ has shown us his great installation, I have found a variety of implementations, and I am trying to figure out which is best, preferred, or has advantages.

I have found it done the following ways...
1) Hight and out to the far outboard bay (parrallel to the vent line)
2) Low and to the center of the tank (Subie installs, Mickey's)
3) Top/middle to the center of the tank (CJ's)

First I was leaning towards #1, but now I am thinking either #2 & #3 might be ideal... A line entering the tank top or bottom to the center of the tank. BTW, I am using flops and caps.

Any thoughts, recommendation, comments, or experiences? Thanks!
 
Brad, my unsubstantiated, unprofessional, totally and entirely experimental rationale is as follows:

Center Bay/High dump because...

1) Fitting sits up top on the root side so maintaining it will mean working on it from the top. No fuel in my eyes.

2) Straight shot through tank (no bending) and doesn't interfere with caps.

3) Likely not to affect total capacitance because it is spaced the farthest from a plate. (probably just a "feel good" reason").

4) Not as long a run to the outside bay, but far enough from the root/pick up for good mixing with the remaining fuel for cooling and settling.

These are probably all "feel good" reasons, but isn't that what is most important?

:D CJ
 
Hi RV7factory,

I asked CJ's about his setup. I also emailed and asked Van's, they said they have not done it before, but did say if they would try it they would most probably keep it high to limit back pressure.

I made my own small adjustments. I used flops and normal senders.I kept it high in close proximity to the normal position of the vent line. I positioned the vent and vapour lines on close and on both sides of the normal vent position, with just enough clearence for the round spacers on the back of the fittings. If the normal vent line fits that proximity there would be no problem to access the vapour line either. I kept it high due to flop tube clearence. I made sure my fittings have at least 90 degree angle difference between them to get easy access to both. I terminated mine in the second bay, bend down to limit fuel foaming. I don't have Cap senders so I did not worry about interference.

Anycase your need to evaluate your own requirements and then just drill it where you feel comfortable. We are on our own with these experiments!

tank_vapor_return_01.jpg


tank_vapor_return_02.jpg


Good luck, Kind Regards
Rudi
 
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Hey Rudi,

Van suggested keeping it high to reduce back pressure. All well and goo, so I am glad that I did that. I didn't know of that at the time, but all well and good.

Q: You kept the fitting high but immersed the outlet in the deepest part of the fuel. This will maintain back pressure for most flight conditions. Isn't that contradictory?

tank_vapor_return_02.jpg


:confused: CJ
 
Hi CJ,

Isn't that contradictory? Yes I know? :D "I made my own small adjustments." After thinking on what Vans said for a while the back pressure will be small and nothing a Fuel Injected Fuel pump would be abe to overcome. So my main reason for still staying high is clearence and access. Bend down for fuel foaming if it occurs. I could not cater for all the initial design requirements so something had to give.:p

If you follow Vans "suggestion", I guess you could just add a nipple high on the inboard rib and "spray" the fuel back into the first bay. I did not want to do it that way. At least I can say I did it my way, and I am happy with my decision.

Kind Regards, Rudi.
 
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Thanks guys! The info helps a lot.

For the most part I will be replicating your implementations, they only difference being is that I have decided to go with -6 fittings and tubing, only because it will provide the largest amount of flexibility in the long term. It is such a short run and it will only add a minute amount of weight compared to the -4.
 
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gmcjetpilot said:
I think Bendix FI was bought by Airmotive and is what ECI uses on their engines. G
Click to expand...

George,
The Bendix fuel system division was purchased by Precision Airmotive. ECI does offer this system with their engines. However, at Sun N' Fun this year, they introduced a new system of their own design. This system uses a throttle body with a throttle position sensor. It is not a servo in the sense of Bendix or Airflow Performance. It is closer to the Continental fuel injection system. I got a good look at the system while I visited ECI's tent at Sun N' Fun.
The new ECI and Continental systems use a vapor return line. As discussed earlier, this differs from the Airflow Performance "purge" line, in the fact that fuel/vapor are returning all the time. This is set up like modern automotive fuel systems, which purge excess fuel pressure via a return line. These systems will require the use of Andair's $400+ dollar duplex fuel selector valve (or similar) You will also need a third fuel line (in addition to the feed and vent lines) routed to each fuel tank.
Charlie Kuss
 
Vertically???

All right boys...

Did we ever reach a consesus on the VERTICLE placement of this line? I see all three possibilities represented on various websites. I'm not completely clear on the quantity/pressure issues, but can see the pros/cons of all three placements. BTW, I'm leaning towards an ECI Kit engine with the mechanical FI system.

Don't make me post a "poll" over this line placement!! :D


Bushings, fittings, aluminum line, and proseal in hand, now where do I stick the bit???

Joe
 
Hey jFerraro,

It is experimental, not in the plans, so think which one you agree with most, then attempt at your own risk. I'm not flying yet. So only time will tell.

If you do it at bottom you might get back pressure, if you do at top you might get fuel foaming. The easiast way is just to put a nipple in the inboard rib and let the fuel spray into the first bay, top or bottom you decide.

Or you can go the extra mile (6") and let fuel flow back into second bay.

Regards
Rudi
 
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