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Thread: Oil separator

  1. #1

    Join Date
    Nov 2013
    Posts
    31

    Oil separator

    I've acquired a Laser that has the oil separator on the left side of the fire wall. My Pitts has the separator on the right side per Lycoming and Christen installation instruction. Any Laser operators out there can shed some light on this alternate location of the slobber pot? Are there any obvious disadvantages?

    Cheers, Hans


  2. #2

    Join Date
    Oct 2011
    Location
    New Hampshire
    Posts
    1,225
    Since no one has spoken up, I will make some observations about the installation of the Christen system on Lycoming engines.

    1 - The firewall oil valve is supposed to be installed at the same level as the lower oil screen. That screen is on the right side of the rear accessory case. That screen is at the intake to the oil pump and the oil valve is on the suction side of the system. Putting the oil valve below the correct level in relation to the engine makes the pump work harder and delays recovery of oil pressure when executing a maneuver that gets the balls in the valve bouncing between the upright and inverted positions. and you want the hoses short, which means putting the oil valve on the right side near the screen.

    2 - If the system is set up as originally designed, with a "T" fitting connecting the oil circuit and the vent circuit, you want the hoses as short as practical because the oil circuit and the vent circuit share some, which generally means putting the overflow tank, or slobber pot, on the right side. The "T" fitting is intended to be mounted on the firewall above the oil valve. Again on the right side of the engine. With this configuration, as with the original design configuration, we typically live with a long vent hose from the upper left side of the accessory case, looping across the firewall, to the overflow tank. We generally have to install a spring in the vent hose to avoid it collapsing at its acute bend.

    3 - If you separate the oil and vent circuits, discarding the "T" and plumbing the oil circuit into a fitting at the accessory case's vacuum pump location, then you can put the overflow tank on either side as there are no longer any critical hose lengths. In fact, since the engine's breather fitting is on the upper left rear of the accessory case, with a leftside tank installation, you can use a much shorter hose to connect. But you should fly your knife-edge passes to put the tank on the high side.

    #3 above may be what you are looking at.

    Best of luck,

    Wes

  3. #3
    Hi Hans,

    I have seen two performance mods to the original Christen inverted oil system: the B&C pick-off that eliminates the T fitting; the mounting of the valve unit on a flange that is about 30 degrees to the firewall so the valve position does not float during verticals. The other differences I have seen have been installation specific to get everything stuffed inside of the cowling.

    Tom.

  4. #4

    Join Date
    Nov 2013
    Posts
    31
    Hi Tom,

    Since originally posting my question I have learned that it's common for the slobber pot to be on the opposite side of what I normally see on Pitts. On the Laser I acquired, the oil return line was too long and ending in an " S " trap similar to what you have under a sink. By eliminating about 8" of that line and nominal rerouting, I think the issue I had will be mitigated.

    Thanks for your reply.

    Cheers, Hans

  5. #5

    Join Date
    Nov 2013
    Posts
    31
    Wes,

    Thank you for your detailed description also and I have #3 that you explain.

    Cheers, Hans

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