Audizine - An Automotive Enthusiast Community

Results 1 to 15 of 15
  1. #1
    Active Member One Ring emocupcakes's Avatar
    Join Date
    Jun 17 2018
    AZ Member #
    420809
    Location
    Vancouver, BC (CANADA)

    Question Crankcase Ventilation System (aka Spider hose assembly) - working details

    Guest-only advertisement. Register or Log In now!
    Hello everyone,

    I've been trying to get a better sense for how things work with about the APB's particular positive crankcase ventilation (PCV) system.

    The central distributor piece on my spider hose assembly is completely broken and exposed to atmosphere. So, I am embarking on the making my own spider hose with some plumbing parts and an oil catch can, but before I get a head of myself, I did a lot of reading of many related posts on audizine, and other forums to get a better sense of how all the moving pieces work together. However, some questions still remain.

    Figure 1 - Stock Late Spider Hose Assembly



    This blue hose (in Figure 1) that goes from the central distributor piece on the spider hose assembly through the PCV valve and then to the Intake Manifold; I'm a little confused about what this does exactly.

    From what I've read on the forums, and youtube videos on crankcase ventilation systems, I understand that this blue hose's purpose is to be a conduit for the excess gas pressure created in the crankcase to escape through.
    This only sort of makes sense to me, as it makes me wonder that if the primary goal of the crankcase ventilation system is relieve the pressure generated in the crankcase (so that crankseal gaskets don't blow and other bad things to happen), why not just have some simple system that let's the excess pressure from the crankcase just vent into the atmosphere - as opposed to plumbing it back into the intake manifold.

    Does the plumbing of it back into the intake manifold take place because this excess pressure has something useful in it, that the intake manifold can re-use?

    Now for this green hose. I understand this hose to serve an important purpose in the crankcase ventilation system, whereby when the turbos are engaged and pushing a lot boost, this process of sucking up a lot of air from the air intake will force the PRV (pancake) to get sucked/closed shut on the Y-Pipe (effectively sealing it, so that no air from atmosphere will enter the Y-Pipe), and that this negative pressure (vacuum) in the Y-Pipe will be force-drawing pressure away from the excessive pressure generated in the crankcase. When the motor is driven hard, the turbos spin faster, which in turn lead to a stronger vacuum environment to exist in the Y-Pipe, which means that through the PRV (pancake) the excess pressure generated in the crankcase will get plumbed into the Y-Pipe.

    Again, this only sort of makes sense to me - as if the primary goal of the crankcase ventilation system is to relieve pressure, why not just let this excess pressure go out into the atmosphere, rather than plumb it into the air intake (Y-Pipe)?

    Is it plumbed back into the Y-Pipe, because doing so makes it easier for the turbos to suck in more air (with the excessive pressure of the crankcase ventilation system actively pushing air to the Y-Pipe), than would be possible by trying to have the turbos suck all of the air it needs from the atmosphere?

    Why do these motors have two separate conduits (one to the Intake Manifold, and one to the Y-Pipe via the pancake) to relieve the positive crankcase pressure? Isn't it typically just one conduit on other motors?

    Sorry for all the questions - I am intensely interested, and this patchwork of understanding is what I managed to cobble together through online sources.

    Thank you all in advance.

    David

  2. #2
    Established Member Two Rings
    Join Date
    Dec 15 2015
    AZ Member #
    365860
    Location
    Perth Western Australia


  3. #3
    Senior Member Two Rings Protection's Avatar
    Join Date
    Feb 24 2011
    AZ Member #
    71438
    Location
    Long Island NY

    I canít answer all your questions, but I think you are on the wrong track because of your erroneous assumption that the crankcase ventilations primary purpose is to relieve pressureóit is not. The primary purpose is to reduce emissions. Primarily by diverting oily crankcase gasses back into the intake to be burned by the engine.

    A byproduct of these oily gasses circulating through hoses and PCV valves, is they leave residue over time, resulting in plugged hoses and PCV valve.


    Sent from my iPhone using Tapatalk

  4. #4
    Veteran Member Four Rings bobkatkat's Avatar
    Join Date
    Jun 07 2012
    AZ Member #
    94826
    Location
    North of the 49th parallel

    Glad that little spread sheet is still getting some use.

    There is a great diagram that shows the two main flows of the PVC system on 1.8 and 2.7s but I can't seem to find it now. I will try to summarize it a bit.

    First the reason why the stock setup vents back into the ypipe and even the N75 valve do not vent to atmosphere are purely for pollution control. Unfortunately all these systems on all Audi's really only work well when the cars are new and not modified. They quickly get clogged with time or overwhelmed when extra boost is added.

    There are two conditions that the PCV system must function under, Boost and Vacuum. Under normal driving conditions like cruising or deceleration we are in vacuum so the pancake valve (PRV), which is a relief valve, has a diaphragm and a small opening that bleeds pressure back into the y-pipe. In this condition there is not enough crank case pressure to open the PCV valve that is connected to the intake manifold. Under boost the PRV closes and the PCV valve opens and CC pressure is directed directly into the intake manifold. This system works great when new, at 70 degrees on sunny days, when the roads are smooth, your favorite song is radio, you just left your favorite drive through.... Perfect conditions.

    When we modify the boost levels we we create more pressure, more blowby etc. that creates more oil vapor in the system. That is why we sometimes need a catch can or air/oil separator to catch the oil before it goes back into the ypipe. You can vent to atmosphere, but on really modified cars that can get smelly. Good solution is a good separator that vents multiple times to atmosphere. Another way is a exhaust scavenger valve and burn it off there.

    hope this helps.

  5. #5
    Veteran Member Three Rings RocksForsSale's Avatar
    Join Date
    Oct 11 2014
    AZ Member #
    288266
    Location
    Allentown, Pa

    Crankcase Ventilation System (aka Spider hose assembly) - working details

    Itís simply not vented to atmosphere because of emissions and itís messy (if you just plum it open) IMG_4588.JPG

    The catch can is the happy compromise. You get the octane benefits of an open vent but affectively cleans, ďcatchesĒ, the oil vapor and moisture in the can you periodically empty.

    I ordered the 034 one because I had broken a plastic snap ends typically required to go on the crankcase/valve covers. Itís no thought to take it off now and came with a billet pcv. I got it from somewhere with a coupon code a few years ago. Itís held up pretty good. I donít run a catch can myself but itís petty simple to add with the 034 setup. I believe you plum it between the main hose form and the pancake.


    Sent from my iPhone using Audizine

  6. #6
    Active Member One Ring emocupcakes's Avatar
    Join Date
    Jun 17 2018
    AZ Member #
    420809
    Location
    Vancouver, BC (CANADA)

    Thanks Bob!

    Considering two different designs for hooking up the catch can.

    SETUP-01




    SETUP-02




    Judging by anecdotal evidence (photos of the majority of the setup for a catch can on the B5 S4 motor) - I get the sense that cleaning up the crankcase gases, and removing the oil content in it, before feeding the gases back into the Intake Manifold (NOT Y-Pipe) seems to be unnecessary in the eyes of many, or that is not very important. Is my intuition correct on this???

    Based on my research, it appears that cleaning up the oil content before feeding the gases into the Y-Pipe (with or without the PRV pancake) is the primary goal of adding an oil catch can to these motors.

    Can anyone attest to the efficacy of these two different setups? Did you catch significant amounts of oil after 2000+ miles?

    Are my setup designs any good? Which design would you recommend? Do you foresee any problems with using an aftermarket PCV valve (UPR 5/8" check valve), as I have specified in the designs?

    My application:

    2002 S4 (6 speed manual transmission)
    Stage 3 (frankenturbos)

    Thank you all in advance!

  7. #7
    Active Member One Ring
    Join Date
    Jan 10 2017
    AZ Member #
    390358
    Location
    French Creek

    Looks good to me, but Id use a smaller check valve.
    Id fear that using a big one is going to make it tougher for the tbody to control idle.

    The oem one is kinda weird.
    Its like at small flow/vac it is open all the way, but if you really blow/suck on it, its like it closes back up a lil.
    Grab an oem one if you can and youll see. I think it does that so the pancake doesnt have to do so much work at high vac.

    I used one of the valves that comes with the 034 rail kit for the check valve on the last one I did. I think the smaller dia gives kinda the same affect at high flows.

  8. #8
    Active Member One Ring emocupcakes's Avatar
    Join Date
    Jun 17 2018
    AZ Member #
    420809
    Location
    Vancouver, BC (CANADA)

    Thanks for the reply.

    Is your configuration akin to SETUP-01 or SETUP-02 ?

    Or is it completely different?

  9. #9
    Veteran Member Four Rings zillarob's Avatar
    Join Date
    Nov 16 2010
    AZ Member #
    67118
    My Garage
    2kS4, 84gli, 84caddy dsl
    Location
    WetSide, WA

    Neils is oem iirc.

    We usually run pretty close to the oem config on street cars, and just replace that hard plastic hose crap with silicone.
    The early fhose stuff I will often get rid of just for ease of maint. Kind of a goofy setup and doesnt really do much anyway.
    Late is easy enough to deal with so I usually leave it.
    The only catch cans I remember messing with were vta on track cars. None like your setups above.

    Of your 2, 01 is prob the most common so you can put the can over by the abs module. Not much room for one behind the motor.
    You dont need to pipe the n75 back into it, many just let it vta. The smaller size can make it kinda tough to tap into the pcv also. I think mine is T'd into the evap line to inlet on that side.
    There are only 2 things needed to make an Audi work properly - Duct tape and WD40. If it moves and it shouldn't - Duct tape. If it doesnít move and it should - WD40.

  10. #10
    Veteran Member Four Rings vavJETTAw36's Avatar
    Join Date
    Jul 04 2012
    AZ Member #
    96276
    Location
    Woodbridge, VA

    Quote Originally Posted by emocupcakes View Post
    Thanks Bob!

    Considering two different designs for hooking up the catch can.

    SETUP-01




    SETUP-02




    Judging by anecdotal evidence (photos of the majority of the setup for a catch can on the B5 S4 motor) - I get the sense that cleaning up the crankcase gases, and removing the oil content in it, before feeding the gases back into the Intake Manifold (NOT Y-Pipe) seems to be unnecessary in the eyes of many, or that is not very important. Is my intuition correct on this???

    Based on my research, it appears that cleaning up the oil content before feeding the gases into the Y-Pipe (with or without the PRV pancake) is the primary goal of adding an oil catch can to these motors.

    Can anyone attest to the efficacy of these two different setups? Did you catch significant amounts of oil after 2000+ miles?

    Are my setup designs any good? Which design would you recommend? Do you foresee any problems with using an aftermarket PCV valve (UPR 5/8" check valve), as I have specified in the designs?

    My application:

    2002 S4 (6 speed manual transmission)
    Stage 3 (frankenturbos)

    Thank you all in advance!
    I would avoid the use of the UPR check valve on its own. I used this and it allowed the manifold to draw a lot of vacuum. So much that i had difficulty removing the oil cap. I added the old check valve in line with the UPR and that worked perfectly. You just need a flow limiter... what better device to use than the old check valve? I used the old 034 billet i had, so now I have a backup when the billet 034 check valve gets stuck open again.

  11. #11
    Veteran Member Four Rings christianb5s4's Avatar
    Join Date
    Aug 24 2014
    AZ Member #
    277489
    Location
    Newport Beach, CA

    Is there any definitive answer on the drawbacks of deleting the F hose and check valve?
    Imola 2001 Stage 3 S4: 313K - 2.4sec FATs - Completely Refreshed/Built Motor - SRM K24s w/ Custom Turbosmart wastegates - Ringer Racing 4+ - Etspec - Cinesnow WG/Oil Lines - SRM V3 Intercoolers - AA built trans - 4:1 Diff - JHM Trio - 034 - H&R Coilovers - FCP - Bosch Motorsports - OZ Racing - SRM/SSAC exhaust - Tons of New OEM parts

    2009 C6.5 A6 3.0T Prestige - stock, daily driver

  12. #12
    Veteran Member Four Rings bobkatkat's Avatar
    Join Date
    Jun 07 2012
    AZ Member #
    94826
    Location
    North of the 49th parallel

    Quote Originally Posted by christianb5s4 View Post
    Is there any definitive answer on the drawbacks of deleting the F hose and check valve?
    No issues at all if you have a proper separator. On the stock setup under boost excess vapor goes into the manifold and is burnt. If you do the Fhose/pcv removal, and your catch can or separator can't keep up and you have it plumbed back into the Ypipe then oil will start to build up and collect in your intercoolers.

  13. #13
    Active Member One Ring
    Join Date
    Jan 10 2017
    AZ Member #
    390358
    Location
    French Creek

    Any time the mani is above ~0psi, the check valve is closed, and the fhose part of the system is not used.
    Nothing really changes oem vs fhose delete in that area.

    Removing the pancake restriction and allowing the ypipe to pull harder on the crankcase could go both ways.
    Maybe it pulls more oil, maybe it helps the rings seal for less blowby? Hard to say.
    I always wondered how much the different angles on the early/late ypipe port affected it.
    The early ypipe looks to me to have a better angle for allowing the incoming air to draw harder on the pcv port.

  14. #14
    Veteran Member Four Rings christianb5s4's Avatar
    Join Date
    Aug 24 2014
    AZ Member #
    277489
    Location
    Newport Beach, CA

    Quote Originally Posted by bobkatkat View Post
    No issues at all if you have a proper separator. On the stock setup under boost excess vapor goes into the manifold and is burnt. If you do the Fhose/pcv removal, and your catch can or separator can't keep up and you have it plumbed back into the Ypipe then oil will start to build up and collect in your intercoolers.
    What about having a setup to let the car just vent to atmosphere during racing events? Capping the y-pipe and letting all the vents go to a catch can that's vented?
    Imola 2001 Stage 3 S4: 313K - 2.4sec FATs - Completely Refreshed/Built Motor - SRM K24s w/ Custom Turbosmart wastegates - Ringer Racing 4+ - Etspec - Cinesnow WG/Oil Lines - SRM V3 Intercoolers - AA built trans - 4:1 Diff - JHM Trio - 034 - H&R Coilovers - FCP - Bosch Motorsports - OZ Racing - SRM/SSAC exhaust - Tons of New OEM parts

    2009 C6.5 A6 3.0T Prestige - stock, daily driver

  15. #15
    Veteran Member Four Rings zillarob's Avatar
    Join Date
    Nov 16 2010
    AZ Member #
    67118
    My Garage
    2kS4, 84gli, 84caddy dsl
    Location
    WetSide, WA

    If you gonna do what Bob does (bob is a gnarly mofo), you shouldnt be asking these Q's.
    just look at whats going on there, its not that difficult.
    There are only 2 things needed to make an Audi work properly - Duct tape and WD40. If it moves and it shouldn't - Duct tape. If it doesnít move and it should - WD40.



Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


    © 2001-2018 Audizine, Audizine.com, and Driverzines.com
    Audizine is an independently owned and operated automotive enthusiast community and news website.
    Audi and the Audi logo(s) are copyright/trademark Audi AG. Audizine is not endorsed by or affiliated with Audi AG.