vent gases and vapour thingy... | FerrariChat

vent gases and vapour thingy...

Discussion in '206/246' started by yakxx21, Nov 2, 2015.

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  1. yakxx21

    yakxx21 Karting

    Jun 29, 2013
    230
    #1 yakxx21, Nov 2, 2015
    As we all know its not good to have air /leaks into the inlet (carb) system....or anywhere come to that....so can somebody please explain how the gas vent connection works. Here we have two carbs open via a couple of plastic lines to the atmosphere both via a funny little connector that opens up into the inlet air box and also via the vent and blow by unit....
    does'nt make sense to me really....just how does all this work ...and could it be part of my problem of backfiring on the over run....obviously not I suppose as it was designed that way...just dont understand how it works and why....
    pls enlighten me....

    thanks
     
  2. BigTex

    BigTex Seven Time F1 World Champ
    Owner Rossa Subscribed

    Dec 6, 2002
    79,218
    Houston, Texas
    Full Name:
    Bubba
    #2 BigTex, Nov 2, 2015
    You need to review the fuel and vent system diagram.

    On my 308, the fuel pressure line returns to the RH tank, after feeding all the carbs..

    That is totally different from the fuel tank venting, which goes thru a check valve and a charcoal canister to vent eventually to atmosphere. There are also cross connect tubes for the two tanks.

    Any line going back to the airbox, I would wager is actually crankcase venting, returning air with oil vapors for burning, back thru the engine.

    That's just a brief summary, of the tubes lots of people feel are "real complicated and not necessary" and start to rip off and throw away.
    Guess what, they are necessary!!
     
  3. yakxx21

    yakxx21 Karting

    Jun 29, 2013
    230
    #3 yakxx21, Nov 3, 2015
    Thanks and yes its the crankcase venting I dont understand...there is a tube from the CC going to a grey cannister and then into two of the three carbs ....but it also goes up to a Junction contraption that is open at the top and goes into the big Carb box....so in effect air will just pass into this contraption and then into the carbs..UNLESS...somthing is missing like a check valve.....in which case it might be the problem I have with backfiring all the time ....more thoughts ???
     
  4. yakxx21

    yakxx21 Karting

    Jun 29, 2013
    230
    #4 yakxx21, Nov 3, 2015
    Studying the thing more it seems there should be some sort of valve in the spaghetti junction thingy....which is missing I think...maybe I will try blocking off the two little pipes going to the inlet manifold...might help with my backfiring problem....
     
  5. Ken Ivey

    Ken Ivey Karting
    Silver Subscribed

    Jan 6, 2013
    228
    Portland, OR, USA
    Full Name:
    Ken Ivey
    #5 Ken Ivey, Nov 3, 2015
    I'll confirm what you have figured out...
    Originally, the tube coming from the oil collector went to an aluminum casting that threated into the intake box. The casting had two arms for small tubes that went directly to nipples on the intake manifold runners. If those tubes are missing and the nipples at the intake manifold have not been capped - you have a vacuum leak. Life will be a lot better if you simply put a rubber cap over those nipples.
     
  6. Pantdino4

    Pantdino4 Karting

    Sep 17, 2015
    160
    Los Angeles
    Full Name:
    Jim Oddie
    #6 Pantdino4, Nov 3, 2015
    You should not have any tubes or openings open to atmosphere. If you do that could be the cause of your backfiring, so put rubber caps or plugs of some kind on or in them to seal them off.
     

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