Kitfox Aircraft Stick and Rudder Stein Air Grove Aircraft TCW Technologies Dynon Avionics AeroLED MGL Avionics Leading Edge Airfoils Desser CPS Parts EarthX Batteries
Results 1 to 9 of 9

Thread: Fuel manifold on newer 912 ULS engines

  1. #1

    Join Date
    Oct 2008
    Location
    Bend, Or.
    Posts
    6

    Default Fuel manifold on newer 912 ULS engines

    what is everyone doing with the nipple fitting on the fuel manifold that says “fuel tank”. I assume they are talking about a fuel return line. I am changing out a 2005 912ULS with a 2019 912ULS and I do not have a return line. Most the people I’ve talked to said they have never heard of a fuel return line on a carburetor engine. Are you blocking this connection off?

    Bruce

  2. #2
    Senior Member efwd's Avatar
    Join Date
    Jun 2015
    Location
    Yorba Linda, CA
    Posts
    1,991

    Default Re: Fuel manifold on newer 912 ULS engines

    Look at the Rotax website. They explain why the fuel return line is necessary. I believe its a vapor lock thing.
    Eddie Forward
    Building
    SS7, 912iS, Garmin G3X

  3. #3

    Join Date
    Oct 2008
    Location
    Bend, Or.
    Posts
    6

    Default Re: Fuel manifold on newer 912 ULS engines

    I did read it was essential to the operation of the fuel system, but not sure why. There was no fuel return line on the 912ULS I am taking out.. Don’t know why it would be essential on this new engine.

  4. #4
    Senior Member jiott's Avatar
    Join Date
    Jun 2010
    Location
    Portland, OR
    Posts
    2,246

    Default Re: Fuel manifold on newer 912 ULS engines

    Just do it. I don't think you want to find out why the hard way. It is very good insurance (not 100%) against vapor lock.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  5. #5

    Join Date
    Oct 2008
    Location
    Bend, Or.
    Posts
    6

    Default Re: Fuel manifold on newer 912 ULS engines

    Can it just be T’d back into the fuel line before it goes to the fuel pump?

  6. #6
    Senior Member Dave S's Avatar
    Join Date
    Oct 2008
    Location
    St Paul, MN
    Posts
    1,482

    Default Re: Fuel manifold on newer 912 ULS engines

    Bruce,

    There is quite a bit of historic information on this list regarding issues with the "old system" without a return line.

    Do an Advanced search using the terms "Vapor Lock"

    As Jim O said, this is not a 100% deal; however, the current design Rotax system with the return line solves many of the flooding, hot soak and vapor lock issues that are somewhat uncool to experience with the old system.

    Certainly a person with an experimental can make deviations from plan; however, it's hard to beat doing the installation completely to specification for best reliability.

    How well the return system works depends on how closely the installation matches the design. The check valve is critical to prevent unfiltered backflow to the carburetors, where the return line goes back to relates to the potential for recycling volatilized fuel back to the engine; and, the orifice regulates the correct amount of return flow.
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

  7. #7

    Join Date
    Jul 2010
    Location
    Westfield, IN
    Posts
    27

    Default Re: Fuel manifold on newer 912 ULS engines

    Others in this thread sent their return line to the top port of their gascolator. I was planning to do the same.

  8. #8
    Senior Member jiott's Avatar
    Join Date
    Jun 2010
    Location
    Portland, OR
    Posts
    2,246

    Default Re: Fuel manifold on newer 912 ULS engines

    I know several have returned into the gascolator, but in my opinion this is not the best way to do it. It sort of defeats the whole idea of the return, which is to bring a small amount of the coolest fuel (from the header tank) to replace the hot soaked fuel from the engine compartment. If you tee in the return anywhere after the header tank you are not getting full advantage of the return system. As my daddy used to say "if a job is worth doing, it is worth doing well".
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  9. #9

    Join Date
    Oct 2008
    Location
    Bend, Or.
    Posts
    6

    Default Re: Fuel manifold on newer 912 ULS engines

    Quote Originally Posted by Dave S View Post
    Bruce,

    There is quite a bit of historic information on this list regarding issues with the "old system" without a return line.

    Do an Advanced search using the terms "Vapor Lock"

    As Jim O said, this is not a 100% deal; however, the current design Rotax system with the return line solves many of the flooding, hot soak and vapor lock issues that are somewhat uncool to experience with the old system.

    Certainly a person with an experimental can make deviations from plan; however, it's hard to beat doing the installation completely to specification for best reliability.

    How well the return system works depends on how closely the installation matches the design. The check valve is critical to prevent unfiltered backflow to the carburetors, where the return line goes back to relates to the potential for recycling volatilized fuel back to the engine; and, the orifice regulates the correct amount of return flow.
    Thanks Dave and thanks to everyone who replied. I talked to one of the techs at Lockwood today. He said yes you need to run the line. He did say it was alright to tee it into the header tank. I put a 3 way tee in the line between the fuel tank and the header tank. So, I think I am good to go now.. Appreciate the feeb back

    Bruce

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •