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Thread: Catch can

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    Catch can

    Since my engine has twice been so badly gunked up it wouldn't start, I installed an inexpensive catch can. Installation was easy and only took a few minutes. The can is actually a filter, and was installed in the tube after the PCV valve and before the intake manifold. The can fastened to the airfilter box.

    I had a hunch that possibly blow-by was contributing to the reoccuring gunk formation, that being reason for trying a catch can. During the timespan between both gunked-up occurences, the valves were impecably clean, that verified by endoscope. The car has about 100 000km (60 000miles) on it, and the compression is a bit lower than normal ever since the first gunk "repair" at the Mitsubishi dealer. It needs no extra oil between oil changes. The gunk covering the intake valves forces them to remain open, causing massive compression loss and thus no starting possible.


    For that story see thread: https://mirageforum.com/forum/showth...ar-won-t-start




    During repair when the intake manifold was out of the car for gunk clean-up, I notice that behind the throttle, the manifold was perfectly clean inside. However on the cylinder head side, the inside of the intake manual was coated with a black, oily, gritty, carbon-like substance, some sort of combustion residue. Near the middle of the intake manifold is where the tube from the PCV valve merges into it. From there on, the inside of the manifold is coated with residue. Before that tube, the manifold is clean. That was the reason for trying a catch can. It might not stop gunk coating the valves, but can't do any harm.

    Test results:

    The catch can has a very fine brass filter inside for catching droplets from the blowby mist, and it does collect more than I thought.

    UPDATE after one week:

    The catch can pictured below catches oil at the rate of about 3ccm every 1000km.
    This model will collect about 12ccm until I call it full. That is the point when the caught oil begins to touch the fine brass filter.
    In other words, only about 4000km and the catch can needs emptying out. Therefore I ordered a similar but inexpensive bigger one for a few bucks.

    This is the catch can originally bought:

    https://www.ebay.de/itm/Car-Universa...8AAOSwwFlfBvnh
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    Here some pix how it was installed. The original tube that was on the PCV valve was not shortened, it connects can output with manifold. A new piece of tube a few cm length (in medieval: "inches") was put between PCV valve and the intake of the can. Important: although the can and tubes have no real pressure to withstand, they absolutely must be airtight! If not, the engine will not idle properly or may not start.
    Btw, there is a TSB about non-starting engines where the rubber tube slipped off the PCV valve.

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    Last edited by foama; 09-06-2020 at 05:55 PM.

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    CROSSBOLT (03-28-2022),Daox (09-02-2020),FreeYourSOUL (03-28-2022),inuvik (09-01-2020),Marklovski (09-03-2020),mohammad (10-11-2021),Top_Fuel (09-01-2020),x111951753 (03-28-2022)

  3. #2
    Moderator Eggman's Avatar
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    Thanks for the info, foama. Looking forward to how this goes for you. Hope you can post lots of pictures of your work.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


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    UPDATE:

    The catch can in post 1 catches oil at the rate of 3ccm every 1000km.
    The specific model in that post will collect about 12ccm until I call it full, the point when the level of caught oil begins to touch the brass filter.
    In other words, only about 4000km and the catch can needs emptying out. Therefore I ordered a similar but inexpensive bigger one for a few bucks as an upgrade.
    Last edited by foama; 09-06-2020 at 06:00 PM.

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    mitsumi (09-06-2020)

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    Senior Member Mitz's Avatar
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    Hey folks, can I share mine too?

    I had a Greddy installed on 10/2015 (with baffle added)


    Oil Collected after 6481 KMs of use


    Replaced it 08/2019 w/ one that has a bronze filter + baffle


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    mitsumi (09-07-2020)

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    Senior Member mitsumi's Avatar
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    @Mitz
    whats the size of the hose you use for the OCC?

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage GLS 1.2 manual: 3,108.4 mpg (US) ... 1,321.5 km/L ... 0.1 L/100 km ... 3,733.0 mpg (Imp)


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    Senior Member Mitz's Avatar
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    Quote Originally Posted by mitsumi View Post
    @Mitz
    whats the size of the hose you use for the OCC?
    3/8 in. pal..

    if a 9mm hose is available, it would fit more snug.

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    mohammad (10-11-2021)

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    With the catch can mounted to the airbox, does that mean you have to remove the PCV hose just to change the air filter? Also how does the drain valve work on the catch can? Do you have any updates about the current oil capture rate? And finally do you have any idea why the PCV hose is foam covered/insulated?

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    Quote Originally Posted by mohammad View Post
    With the catch can mounted to the airbox, does that mean you have to remove the PCV hose just to change the air filter? Also how does the drain valve work on the catch can? Do you have any updates about the current oil capture rate? And finally do you have any idea why the PCV hose is foam covered/insulated?

    A lot of questions!
    My can does collect, but not anywhere near as much as in Mitz pix. Probably because I drive very economically, and Mitz presumably likes driving fast?
    With the can mounted as in post one, I don't have to remove the pcv hose to change the air filter. I now have a much larger catch-can, with about 0.4L (in mediveal about a pint) capacity. It is mounted on the same horizontal piece the hood lock is mounted on. At the rate it collects, it is big enough to be emptied only once every 15000km oil change.
    The OEM PCV hose is actually covered with a foamy hose for two reasons. It prevents it from mechanical harm from stuff rubbing on it, and it also prevents the hose from getting bent too much and also from collapsing and deforming from the vacuum. The PCV function must be correct, otherwise the car will not run properly and may not start. The catch can will not interfere with that if done properly, not a difficult task.

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    Quote Originally Posted by foama View Post
    A lot of questions!
    With the can mounted as in post one, I don't have to remove the pcv hose to change the air filter.
    im highly confused how do you remove the engine air filter with the catch can mounted on the housing like that?


    please consider checking out my Mirage related youtube channel: https://www.youtube.com/channel/UC6c...IEViRFw/videos

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