Crank case Breathers | The Z Club of Great Britain
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Crank case Breathers

Discussion in 'S30 (240Z,260Z,280Z) Engine' started by Turn & Burn, Jun 13, 2019.

  1. Turn & Burn

    Turn & Burn
    Z Club Member

    Hi, I’m wondering what people with triples or ITBs are doing with regards to crank case vents.
    I’m considering running a line off both the block and cam cover to a common catch pot with a filtered inlet. There doesn’t seem to be any easy way to extract fume with sufficient flow as per the original design with extract on the manifold and inlet breather on the air filter.
  2. johnymd

    Z Club Member

    I think most people just don't consider how the crankcase ventilation system is designed to work and its purpose. So they just put a filter on the rocker cover and point the bottom hose down. This wont provide sufficient airflow through the crankcase as intended but if you if you orientate the bottom pipe to act as a venturi with air passing across it then maybe it will draw a bit of airflow through the crankcase.
  3. Turn & Burn

    Turn & Burn
    Z Club Member

    Is this what u do with urs?
  4. johnymd

    Z Club Member

    I hadn't actually got around to doing anything on the new silver project. Left both the top breather and the block breather open. Nothing ever comes out of the top but I had a fair bit of oil droplets all over the engine bay after the track session at Spa. My plan is to have a small filter on the rocker cover so clean air can enter the engine. Run the bottom crankcase vent to a catch can then and outlet from the top of the can to under the car, in airflow to try and create a negative pressure in the can.
    Turn & Burn likes this.
  5. jonbills

    ZClub Administrator
    Staff Member Moderator

    I just have it vent into a catch tank (old 1L oil bottle!) with a little filter on top.
    No road draught stuff. Nothing seems to go wrong. Very little goes in the catch tank.
    Turn & Burn and moggy240 like this.
  6. SacCyclone

    Z Club Member

    Catch tank.

    Woody928, AliK, MaximG and 3 others like this.
  7. Turn & Burn

    Turn & Burn
    Z Club Member

    Thanks all!
  8. AliK

    Z Club Member
    Staff Member Moderator

    My limited understanding (and Johnny et al feel free to correct me) is that the main purpose is to allow blow-by gasses and pressure to escape; given that they have nasties from the combustion process (such as sulphur vapour) they are not considered environmentally friendly to just vent hence are put back into the intake to burn off oil droplets, nasties and general blowby fumes.

    Also I understand that a bit of vacuum in the crank case helps the rings seal better for mo powaaaaa.

    My 0.3L catch tank, which isn’t baffled, takes the crankcase pipe and the rocker cover pipe and has a filter on top. It fits just under the second intake on the airbox (originally designed to take air from over the top of the manifold for cold starting / warm up).

    After 1200 miles or so of engine running in, thrashing about. I found it was a third full with what seemed to be “yellow water”. So unable to resist like any typical man, I dipped my finger in and gave it a taste. It was a full bodied and nutty flavour with a hint of Halvoline’s finest produce!

    I hear that ideally you should aim for a baffled tank to better filter out the nasties and levitated micro oil drops, especially if you plan to feed through the intake again.

    The filter is often steaming after a good thrash and eggy f@rty smells were common when previously I had it in a different position.

    So have I missed anything fundamental about the operation of this circuit for non EFi cars?
  9. moggy240

    moggy240 INSURANCE VALUATIONS OFFICER Staff Member Moderator

    "So unable to resist like any typical man, I dipped my finger in and gave it a taste. It was a full bodied and nutty flavour with a hint of Halvoline’s finest produce!"

    That made me laugh!!!!!
    AliK likes this.
  10. Rob Gaskin

    Rob Gaskin Treasurer Staff Member Moderator

    I just joined mine (like Jon) into a water bottle. Ran it like that for 10 years of trackdays. All I ever got in the bottle was a little oily-water that I never needed to empty out. No oil consumption.

    So you can go into the theory as much as you like (like a lot of things) but my car seemed to run ok like that.
    AliK and Turn & Burn like this.

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