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Oil Catch Tank

Discussion in 'S130(280ZX) Engine' started by Huw, May 4, 2019.

  1. Huw

    Z Club Member
    Staff Member

    I want to put an oil catch tank between the crank breather and the PCV valve in the inlet manifold (injection). Any suggestions or recommendations on makes or brands?

    I’m guessing one with a breathable cap won’t do, due to the need to maintain the vacuum at partial throttle?


  2. AliK

    Z Club Member
    Staff Member Moderator

    From what I've read, mocal, Mishmoto and OBP brands are people's faves.

    My advice is get a baffled catch tank and one with an external level indicator. I've been surprised by how much I had in mine after just 1000 miles. Half a 0.3L catch tank.

    The baffled bit is important as a cheap one without the baffles (like mine) will not capture enough of the oil / etc if you are sucking it back into the engine. Mine vents via a filter so lack of baffles is not an issue.

    Look here ....


    And here ...

    https://www.demon-tweeks.com/uk/search/shop-by/q/Oil catch tank/
  3. Huw

    Z Club Member
    Staff Member

    Thought I would update this thread after doing some investigation.

    I ended up with a Mishmoto unit, it was on a special. Nicely made with an internal baffle and vapour filter.

    My initial assumption was to fit the filter between the crank case breather on the block and PVC valve on the inlet manifold. With the peculiarities of the EFI system, it made sense to place it here as the line is open to vacuum from the inlet manifold under partial throttle drawing blowback gases back into the inlet to be burnt. Any oil and residue from blowback gasses should be collected in the can before heading back into the inlet.

    Having run the car for several long trips with the catch can in this position, I got nothing but a little condensation. So back to the drawing board.

    Next was to reposition the unit to pick up the blowback gases between the valve cover breather and the inlet pick up point prior to the throttle body on the inlet.

    Under partial throttle the engine will draw fresh air through the valve case breather due to the vacuum present at the inlet manifold and expel the blowback gases that way. At full throttle however there is no vacuum in the inlet manifold and blowback gases will vent through the top of the engine through the valve cover breather and exit back into the inlet, so the engine eats its own gunk.

    Again, ran the car with the catch can in this position for several long trips. This time there was about a teaspoon full of brown oily liquid. So a result I believe.


    So the catch can has now become a permanent feature. Because the can is quite small it has been secured to the inlet manifold to keep the pipe runs as short as possible to stop the pipe bends filling with gunk instead of the can. Plus the can is easily reached in this position to unscrew and empty. Result is a cleaner air supply to the engine and cleaner inlet ports.


  4. Farmer42

    Z Club Member

    Sounds like a result mate. Nice looking little unit that.

    Let's hope it stops the little puffs of blue smoke you were getting:smoke:
    Huw likes this.
  5. johnymd

    Z Club Member

    Very interesting.
    I would have assumed the flow would be:
    Clean air enters the engine (via a filter) at the rocker cover.
    Bypass gasses are sucked down the engine and out the block breather.
    The air is then filtered by the catch tank and cleanish air then goes through the pcv and into the intake.
    Huw likes this.
  6. Huw

    Z Club Member
    Staff Member

    That’s correct Johny, but only at partial throttle due to the vacuum present in the inlet manifold that pulls the gas that way. As the revs go up and the throttle opens fully the vacuum falls off allowing the gases to flow the other way around and vent out of the rocker breather as there is low pressure present there due to air flow coming through the throttle body. Explains it quite well in the service manual. :)
    moggy240 likes this.

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