Mysteries of the UrS6 Moisture Trap (aka Fuel Condensor)

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  • UrS4boy
    S2Forum Obsessed
    • Feb 2006
    • 11859
    • Country: Canada

    #1

    Mysteries of the UrS6 Moisture Trap (aka Fuel Condensor)

    Our AAN engines have fuel injectors that inject atomized fuel into the intake manifold runners, just outside of the intake valve ports. As such there is always going to be a certain amount of fuel vapour in the intake manifold. To protect the G71 manifold absolute pressure (MAP) sender in the ECU, the factory installed a fuel condensor (aka "moisture trap") in the vacuum boost line between the intake manifold and the J220 ECU (as shown schematically in this vacuum line post HERE).

    Okay there really isn't a big mystery regardling the UrS6 moisture trap other than where it lives and why the clamps don't come loose as much (if any) like the UrS4 moisture trap clamps do. The other mystery is why Kate says the UrS4 and UrS6 moisture traps (or to use her terminology "fuel condensor") are the same PN ( 034131527A). This can't be correct because the UrS4 fuel condensor/moisture trap is black and has an inlet at one end and an outlet at the other end, as shown below, and, as you will see, the UrS6 moisture trap is white plastic and has the inlet and outlet at the same end.



    The UrS6 moisture trap/fuel condensor lives down by the ECU which, in the case of the LHD cars, is in the passenger side footwell, right hand side of the car. Access to the ECU area is documented HERE.

    Once you get the carpet pulled back you might see this:


    Or this:


    If you pull the white plastic condensor/trap out you will see this:



    As you can see above, for the UrS6 owner, the vacuum/boost hose going the ECU, downstream of the moisture trap/fuel condensor provides an potential location for "T"ing in for an aftermarket boost gauge without having to worry about fuel vapours getting into the gauge (like could happen if the "T" was placed in the UrS6 engine bay. (For the UrS4, the "T" can be placed in the vacuum/boost hose, in the engine bay, just AFTER the black moisture trap.

    IF any UrS6 owners can confirm the part number that would be appreciated. (TIA).

    Obviously all of the above was geared to LHD UrS6s. If anybody with a RHD UrS6 has access to their car's moisture trap/fuel condensor and can take and PM me photos, I will add the RHD version to this post.

    Thanks to those who posted the images and photos used in this post.
    Last edited by UrS4boy; 24 September 2011, 00:02.
    RS2'd 93 UrS4 5 spd sedan
    94 UrS4 V8 6 spd manual avant
  • macspring
    S2Forum Zealot
    • Mar 2005
    • 6371
    • Home: Ireland Current: Wallis & Futuna

    #2
    Dave,

    Do these moisture traps ever need replacing ?

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    • UrS4boy
      S2Forum Obsessed
      • Feb 2006
      • 11859
      • Country: Canada

      #3
      Originally posted by David in Dublin
      Do these moisture traps ever need replacing ?
      I don't think so. I order one once to see what was inside and there were none in stock in North America and they were going have to bring one in from Germany. I am still waiting for my order to be filled. (This is about 3 years ago).

      On that basis I have to assume that they don't need replacing.

      Word of caution. Replacing on with a low pressure plastic fuel filter that looks similar would likely result in the fuel filter blowing up under WOT boost, e.g. 22 psi to 28 psi.
      RS2'd 93 UrS4 5 spd sedan
      94 UrS4 V8 6 spd manual avant

      Comment

      • mcandmar
        S2Forum Zealot
        • Apr 2004
        • 5118
        • Country: Ireland

        #4
        Interesting stuff as always. You are right about the S4 ones popping hoses off, BTDT. The S6 looks to be the same part as an ABY S2, not sure about a 3B.
        91CQ20v - Gone to a new home
        93UR-S4 - The Magic Carpet
        94S2Bus - The Emerald Express

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