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raymondj(at)frontiernet.n
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 Posted: Sun Mar 31, 2013 1:25 pm Post subject: fuel return line? |
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I'm plumbing the wings on my 750 and was wondering if the 912 uls needs a fuel return line to the tank. I'm guessing it doesn't, but I thought I'd better check.
Thanks in advance.
[quote]--
Raymond Julian
Kettle River, MN.
"And you know that I could have me a million more friends,
and all I'd have to lose is my point of view." - John Prine [b]
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pautenried
Joined: 01 Nov 2009
Posts: 2
Location: Vermillion, SD
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| Posted: Sun Mar 31, 2013 1:37 pm Post subject: fuel return line? |
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Not for the Rotax 912 ULS, but yes for the Rotax 912 iS.
On Sun, Mar 31, 2013 at 4:24 PM, rayj <raymondj(at)frontiernet.net (raymondj(at)frontiernet.net)> wrote:
| Quote: | I'm plumbing the wings on my 750 and was wondering if the 912 uls needs a fuel return line to the tank. I'm guessing it doesn't, but I thought I'd better check.
Thanks in advance.
| Quote: | --
Raymond Julian
Kettle River, MN.
"And you know that I could have me a million more friends,
and all I'd have to lose is my point of view." - John Prine
ist" target="_blank">http://www.matronics.com/Navigator?RotaxEngines-List
tp://forums.matronics.com
_blank">http://www.matronics.com/contribution
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Peter Autenried
114 N Yale St.
Vermillion, SD 57069
Home: (605) 658-0211
Work: (605) 677-5174
Cell: (860) 692-2781
[quote][b]
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Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
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| Posted: Sun Mar 31, 2013 2:11 pm Post subject: Re: fuel return line? |
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Hi Raymond,
The 912UL and ULS needs a return line. It is in the Installation manual. The orifice size is .35mm or .014". The line comes off up by the carb feed where it bifurcates to the carbs on the cross over balance tube and can go back to either a wing, a header tank or the gascolator. It is absolutely necessary if you have the new style fuel pump or you may easily flood the carbs and puke fuel out the vent tube. This helps for carb flooding and vapor lock.
I looked through the 912Si Installation manual and found no return line. Here are the pages from each Installation manual.
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| Description: |
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Download |
| Filename: |
912 Fuel Injection Installation manual.pdf |
| Filesize: |
78.98 KB |
| Downloaded: |
508 Time(s) |
| Description: |
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Download |
| Filename: |
New 912 Rotax Installation manual.pdf |
| Filesize: |
21.69 KB |
| Downloaded: |
444 Time(s) |
| Description: |
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Download |
| Filename: |
912ULS Rotax Installation manual.pdf |
| Filesize: |
20 KB |
| Downloaded: |
453 Time(s) |
_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056 |
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raymondj(at)frontiernet.n
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| Posted: Sun Mar 31, 2013 3:51 pm Post subject: fuel return line? |
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Thanks, that's what I needed. I haven't purchased the engine yet, so no installation manual.
| Quote: | Raymond Julian
Kettle River, MN.
"And you know that I could have me a million more friends,
and all I'd have to lose is my point of view." - John Prine |
On 03/31/2013 05:11 PM, Roger Lee wrote:
[quote] [b]
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bob(at)fly-ul.com
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| Posted: Sun Mar 31, 2013 3:53 pm Post subject: fuel return line? |
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On 02:36 PM 3/31/2013, Peter Autenried wrote:
| Quote: | Not for the Rotax 912 ULS, but yes for the Rotax 912 iS.
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Huh? That's wrong.
--
Bob Comperini
e-mail: bob(at)fly-ul.com
WWW: http://www.fly-ul.com
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Guy Buchanan
Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA
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| Posted: Sun Mar 31, 2013 4:17 pm Post subject: fuel return line? |
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So if I can route the return to the gascolator, how is that different
than simply routing it back to the fuel line on the pump inlet side? I
understand the difference if I route to the top of the tank.
(Theoretically no back pressure there, but certainly significant head
pressure for a high wing installation.)
Guy Buchanan
Ramona, CA
Kitfox IV-1200 / 912-S / Warp 3cs / 500 hrs. and grounded
Now a glider pilot, too.
On 3/31/2013 3:11 PM, Roger Lee wrote:
| Quote: | The 912UL and ULS needs a return line. It is in the Installation manual. The orifice size is .035. The line comes off up by the carb feed where it bifurcates to the carbs on the cross over balance tube and can go back to either a wing, a header tank or the gascolator. It is absolutely necessary if you have the new style fuel pump or you may easily flood the carbs and puke fuel out the vent tube. This helps for carb flooding and vapor lock.
|
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_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too. |
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Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
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| Posted: Sun Mar 31, 2013 8:09 pm Post subject: Re: fuel return line? |
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Hi Guy,
All the Flight Design's have the return line back to the gascolator. I think it needs to go back far enough to make sure it gets cool fuel and not warm or hot fuel. They put the warm fuel from the top back down to cooler fuel. This is what help reduce the chance of vapor lock. If it went back into a line up on the engine then it would all be warm or hot fuel and serve no purpose as far as the vapor lock part. I haven't personally seen any go back into a line up on the engine.
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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056 |
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Guy Buchanan
Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA
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| Posted: Sun Mar 31, 2013 9:19 pm Post subject: fuel return line? |
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Thanks Roger. So if I plumbed back into the inlet line, say at the firewall, eventually the looping fuel would be really hot, though I suppose it depends on the percentage of looping fuel versus that coming from the tanks. Do you have any idea what the ratio might be? (I guess if the FD's do it to the firewall it must work, though.)
Guy Buchanan Normal Guy Buchanan 2 21 2011-09-20T05:05:00Z 2011-09-20T05:05:00Z 1 31 183 1 1 213 14.00 <![endif]--> 59 false false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 <![endif]--> <![endif]--> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} <![endif]--> <![endif]--> <![endif]-->Guy Buchanan
Ramona, CA
Kitfox IV-1200 / 912-S / Warp 3cs / 500 hrs. and grounded
Now a glider pilot, too.
On 3/31/2013 9:09 PM, Roger Lee wrote: [quote] | Quote: | All the Flight Design's have the return line back to the gascolator. I think it needs to go back far enough to make sure it gets cool fuel and not warm or hot fuel. They put the warm fuel from the top back down to cooler fuel. This is what help reduce the chance of vapor lock. If it went back into a line up on the engine then it would all be warm or hot fuel and serve no purpose as far as the vapor lock part. I haven't personally seen any go back into a line up on the engine.
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[b]
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_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too. |
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jan_de_jong(at)casema.nl
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| Posted: Sun Mar 31, 2013 11:52 pm Post subject: fuel return line? |
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"I looked through the 912Si Installation manual and found no return line."
The fuel requirements behind the firewall of the 912Si are pretty much
the same as those of the 914, except at higher pressure. Pressure
regulation depends on the presence of a low pressure drop, high flow
return line to the tank.
Jan de Jong
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raymondj(at)frontiernet.n
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| Posted: Wed Apr 03, 2013 12:36 pm Post subject: fuel return line? |
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Greetings Roger,
Thanks for the items you posted below. I looked at them and then went back later to save them and the one for the ULS gives me a 404 error. Please post them again so I can down load a copy.
Thanks again for your help.
| Quote: | Raymond Julian
Kettle River, MN.
"And you know that I could have me a million more friends,
and all I'd have to lose is my point of view." - John Prine |
On 03/31/2013 05:11 PM, Roger Lee wrote:
[quote] [b]
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Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
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| Posted: Wed Apr 03, 2013 3:23 pm Post subject: Re: fuel return line? |
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They are in the installation manual.
These files above should all be PDF files. There should not be a 404 error. That usually is for opening a web page. I tried them on a different computer and they all displayed.
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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056
Last edited by Roger Lee on Thu Apr 04, 2013 5:51 am; edited 2 times in total |
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Thom Riddle
Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)
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| Posted: Thu Apr 04, 2013 4:56 am Post subject: Re: fuel return line? |
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The certificated engine installations, like in my Katana, have the return line for the carbureted engines. The primary purpose is to preclude vapor lock.
Plumbing back into the supply line is not the same as running the return line back to the gascolator, particularly if you have an electric backup fuel pump between the tank and the "tee". In this case, you will be pressurizing both sides of the fuel system when the electric pump is running. I suppose you could put a check valve in the return line to fix that. Running back to the gascolator returns the excess fuel back to unpressurized ambient pressure location.
In experimental or other non-certificated installations, if your operating environment (not high altitude, not intense heat) does not encourage vapor lock, then adding a return line is not absolutely necessary. If you do operate in these potential vapor lock conditions, running your electric fuel pump will help reduce the risk by pressurizing the supply line up to the mechanical pump.
Back in the dark ages when I was a drag racer, an electric fuel pump at the tank outlet generally resolved vapor lock issues on hot sunday mornings at the drag strip.
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_________________
Thom Riddle
Buffalo, NY (9G0)
Don't worry about old age... it doesn't last very long.
- Anonymous |
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Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
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| Posted: Thu Apr 04, 2013 5:48 am Post subject: Re: fuel return line? |
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Hi Guys,
Do not return the fuel re-circulation line back into the fuel feed line. If you are using a new Rotax fuel pump then you will absolutely need the re-circulation line and even if you don't have that pump now your old pump can go at anytime and then you'll be using the new pump. It is easy enough to install the re-circulation line. It helps control vapor lock and over pressure. By the way the new Rotax max fuel pressure is no longer 5.8, but 6.2 psi. If you have a Dynon EMS or some other EMS with fuel pressure limits then it is a good idea to reset the red line fuel pressure to a higher value.
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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056 |
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