sr20det breather setup ??

Thread in 'Technical Questions' started by g6mmc, Aug 26, 2010.

  1. g6mmc

    g6mmc Member

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    can someone that knows show me the correct way to have the breather setup on a redtop s20det running a top mount ? i have searched everywhere but too many people disagree.i just want the correct way of doing it !!
     
  2. chrisb

    chrisb Member

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    pcv valve needs to be connected to produce vacume at idle

    on 14 rocker, block straight up into head at back 90

    90 half way up rocker to catch tank then plumbed into the intake before turbo, pref before afm to produce vacume when on boost

    yes you are effectivly putting hot air into the intake but the only other alternative is to run a vacume pump and thats not cheap. or vent to atmosphere but then you will get a pressurised crank case etc, they need vacume for rings to seal correctly,
     
    #2 chrisb, Aug 26, 2010
    Last edited: Aug 26, 2010
  3. g6mmc

    g6mmc Member

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  4. JohnJ

    JohnJ Active Member

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    My rear one is as stock, heatwrapped.

    Front one goes to a catch tank vented to atmosphere.

    That seems to be how most people do it.

    What is happening in that photo I don't know!
     
  5. chrisb

    chrisb Member

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    only thing that would make that work is if the pipe from the catch tank on the right hand side, (you can just see the 90 fitting going to wards the bulk head) is if it goes to the exhaust or a vacume pump


    thats wrong, the engine needs vacume to work correctly, not that big of an issue in low boost situations but high boost you will notice the affect alot more.

    its been proven that the difference in vacume to no vacume can be as much as 2-25hp depending on boost, turbo, engine etc
     
  6. JohnJ

    JohnJ Active Member

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    Where have you got that information from?
     
  7. damian 666

    damian 666 Member

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    good question....validate please...
     
  8. g6mmc

    g6mmc Member

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    anyone else wanna give their 50pence worth on this ?

    before i destroy a fresh engine !
     
  9. JohnJ

    JohnJ Active Member

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    Mine has been running with the setup I described above all year with no problems. And it is on track a lot.
     
  10. SteveC200

    SteveC200 Used to drift, now I don't.

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    But when youre on boost the PCV valve is closed so makes no difference. It only opens when in a vacuum situation like idle or cruising which will make no difference to power.
     
  11. Ted

    Ted DRIFT*DIVISION

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    I'd say at least 75% of SR20 setups i've seen run there breather to atmosphere. Make you assumptions from that.
     
  12. g6mmc

    g6mmc Member

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    i really dont like to assume anything to be honest, i like questions answered with a reason where possible.

    most people are running daily drivers around 1bar boost , im talking about a dedicated sr20det drift car running about 1.6bar .

    do any of the professionally built sr20det cars vent to atmosphere or upgrade PCV side with a catch can and upgrade rocker cover/air intake side with a catch can keeping the vacuum system in place ?
     
  13. Captain Muppet

    Captain Muppet Pro-tard

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    When on boost you'll be using the WOT breather that vents to the slight vacuum behind the air filter. Venting the WOT breather to atmosphere works nearly as well.

    Running with no breather is bad, very bad, but running with it vented to atmosphere makes cock all difference unless you are getting massive blow-by or running drag-race levels of boost.
     
  14. SteveC200

    SteveC200 Used to drift, now I don't.

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    I know.;)

    My breather set up is basically vent everything to atmo apart from the block to rocker cover which is left as is. I went for this after finding sustained high revs with a stock breather set up (bar a catch can vented to atmos) resulted in the crank case pressurising as keeping all the oil in the head, which eventually would blow out the breather pipes. Now it doesnt.:)
     
  15. martinb

    martinb Member

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    someone above is speaking rubbish..

    there is no vacuum present in the manifold whilst on boost.! so the valve in the PCV shuts...

    the pcv is for emissions purpose.. remove it. and blank the vac port from the inlet.

    run your breathers open.. dont breathe back into motor.. youll be suprised how much longer your oil lasts.
     
  16. g6mmc

    g6mmc Member

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  17. martinb

    martinb Member

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    where are you thinking your getting significant vacuum to scavenge the crankcase? the breathers in oem return to the intake side of the turbo for emissions control.. not because nissan thought it pulls the sump into vacuum..
     
  18. Captain Muppet

    Captain Muppet Pro-tard

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    You do get a depression (slight vacuum) behind the air filter, which aids crank case breathing. And obviously it's handy for emisions to burn blowby gasses instead of venting them via a filter. It's also cheaper and lighter to recycle the blowby gasses rather than have a seperate breather filter, or have a catch tank. The OEM system is also designed to seperate out the oil before it gets to the intake, which is why on most engines the breathers go up the inside of the block, through the head, through a labyrinth seperator in the cam covers and only then in to the intake system - rather than just sticking a pipe between the crank case and the intake.

    The OEM system is set up for a bunch of valid engineering reasons, not just "emissions". Venting to atmosphere does mean you get to add some shiny things under the bonnet, and also can make the intake plumbing easier.
     
    #18 Captain Muppet, Sep 1, 2010
    Last edited: Sep 1, 2010
  19. damian 666

    damian 666 Member

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    good thread,learnt stuff,,not too much bitching either,,cool;-)
     
  20. martinb

    martinb Member

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    this is good...

    just to add... the stock breathing system is designed for use at the stock HP level.. hence the reason we must upgrade breathing systems..

    for me.. the gain in inlet vac is far outweighed by the dilution of charge by oilgases.. so ill always VTA breathers.
     

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