Engine Breathing

Discussion in 'Track Prep & Tech' started by jamesa, Jan 18, 2017.

  1. jamesa Forum Junkie

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    A subject that`s always interested me and refreshed after reading Dave R`s recent posts; also recalling what `Nige` and `vw-singh` have done with theirs. Thanks to all for sharing.

    Personally, I have concerns where I see non-return / check / flap valves fitted, driven by experience outside automotive hence looking to understand a bit more on the subject / applications.

    Info. for interest / discussion ...

    http://www.burtonpower.com/tuning-guides/tuning-guide-pages/engine-breather-system.html

    ... for HIGH PERFORMANCE ENGINES

    [​IMG]
     
  2. MUSHY 16V

    MUSHY 16V Moderator Moderator

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    Why do you have concerns with check valves ? in some cases they are needed to stop the crankcase vapors from being ignited by a backfire of course it depends on the system you are using and whether it is evacuated by the inlet/exhaust or not
    If it's not you are right you have little or no need for a non return valve in the case it is venting the the atmosphere it needs non
     
    Last edited: Jan 18, 2017
  3. jamesa Forum Junkie

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    Appreciate the `flame trap`philosophy, learned on Ford`s Kent engine :)

    Many non-automotive check valves require a significant, positive pressure differential in order to `work`, interested in how these automotive types compare when used as part of modifications e.g. Dave R`s check valve in the catch tank oil return to the sump ... I need to consider a similar mod. on my Mk1 16v.
     
  4. vw_singh Events Team Paid Member

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    When I first setup the catch can setup on my turbo build, I had cam and crank case breathers into a baffled catch can from which a suction feed was connected to the inlet air pipe in order to draw out the fumes more effectively and stop the fumes getting dragged into the cabin. Fine for high load and full throttle driving.
    I later found out that a mayonnaise type build was occurring in the breathers and the catch can. So a small one way valve or check valve as it's know was added to the feed from the crank case and fed back into the plenum. Reasons for this is at part and no load conditions, the engine actually runs under vac and the breather system doesn't do anything. In this scenario the small vac line to the plenum sucks the crank case fumes which includes moisture from a cold engine and part load driving. As soon as you come onto boost, the positive pressure shuts the check valve eliminating a boost leak and the larger breather system kicks in. Since doing this mod, no more mayo ever.

    Gurds
     
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  5. notenoughtime

    notenoughtime Moderator Moderator

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    Thanks Gurds
    Do you have any pics of the setup please?
     
  6. vw_singh Events Team Paid Member

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    Yes there are pics in my build thread. I can supplement any that are missing as the check valve stuff might not be there.

    Gurds
     
  7. Nige

    Nige Paid Member Paid Member

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    Similar to what Gurds said really.

    On ITB`s I didn`t have a major issue with engine breathing and the catch tank vent was fed back to the inlet. Because they never see pressure it wasn`t a problem and the vent worked fine.

    Once I fitted the Turbo I started getting a lot of engine breathing. Catch tank would regularly fill. The drain back to the sump obviously helped but it wasn`t ideal.

    baffled and vented rocker also helped but didn`t cure the Mayo that would accumulate in the catch tank.

    I now have a PCV on the line from the block breather to the catch tank and that fixed it. Under boost the PCV stops crank pressure getting to the catch tank, under deceleration (vac) it sucks the vapour from the catch tank AND the block back into the plenum and then the engine.

    If you have an engine that`s worn and breathing badly this wouldn`t really help, you`d just burn a lot of oil but on a healthy boosted engine the PCV made a big difference :thumbup:

    [​IMG]
    RED hoses are 2 from the rocker and one from the block breather to the catch tank
    GREEN WAS separated oil drain to Sump (not needed so removed)
    BLUE is vapour into inlet before Turbo

    Dotted Yellow Vent from block to plenum via PCV valve
     
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