Recirculating Blow off valve...

Discussion in 'Tuning ~ Supercharger ~ Turbo ~ Nitrous Upgrades' started by SHOspazz92, Oct 1, 2007.

  1. SHOspazz92

    SHOspazz92 Banned

    Joined:
    Jul 31, 2002
    Messages:
    6,938
    Likes Received:
    3,646
    Occupation:
    2T2X1 : Air Transportation Specialist.
    Location:
    Angier NC / Pope AFB
    Home Page:
    Don't care for Atmospheric units, So... Anyone know where I can find a nice aftermarket recirculating Unit? Thanks!

    -Sam

    *This post you are reading does not exsist as SHOspazz92 Died off when he was thanked to death*
     
    SHOKING91 likes this.
  2. SHOKING91

    SHOKING91 Asshole OUt

    Joined:
    Jul 8, 2007
    Messages:
    112
    Likes Received:
    5
    Location:
    OKLAHOMAAAAAAAAAAAAAAA
    ^^^^

    ebay
     
  3. JSIL1

    JSIL1 Mainlining

    Joined:
    Jul 8, 2003
    Messages:
    711
    Likes Received:
    4
    Occupation:
    Teir 2 Tech
    Location:
    Mile High and Gaspin
    Home Page:
    I wonder if you could use the ones off of the 2000-2002 S4's. The forged diverter valves are supposed to be top notch.
     
  4. Toolman

    Toolman Boost it! Staff Member Club Mod

    Joined:
    Jan 28, 2001
    Messages:
    6,148
    Likes Received:
    2,632
    Occupation:
    Firefighter
    Location:
    Grand Lake, Oklahoma, USA
    Technically speaking, there is no such thing as a 'recirculating bov', as a bov by definition vents to atmosphere.

    To answer your question, most places that sell BOV's also sell bypass/recirc valves.
     
    Last edited: Oct 1, 2007
  5. Sho Amo

    Sho Amo SmkTyresntDrugs

    Joined:
    Feb 23, 2006
    Messages:
    3,298
    Likes Received:
    854
    Location:
    Olney, Md
    werd?
     
  6. Racer X

    Racer X SHO Pilot

    Joined:
    Oct 27, 2002
    Messages:
    3,447
    Likes Received:
    1,569
    Occupation:
    IT/ Telecommunications
    Location:
    Queens, NYC
    Home Page:
    Wouldn't the only time you need to recirc your BOV be when it's plumbed after the MAF? If it's before the MAF, then no worries, as the air hasn't been metered yet.

    At least, thats my understanding of it...
     
  7. Mrpeepers

    Mrpeepers New Member

    Joined:
    Sep 30, 2007
    Messages:
    30
    Likes Received:
    7
    Occupation:
    Buy/fix/sell cars
    Location:
    WI
    The theory is that the air re-entering the intake keeps the turbo spooled between shifts. It is also much quieter. With a draw through maf setup it is especially important to recirculate(called a CPV, compressor bypass valve) to keep the engine from running rich between shifts and causing a plethora of problems.

    The BOV/CPV whatever you want to call it from a 90-94 turbo Talon, Eclipse, Laser(1st gen DSM) is capable of holding 20 psi or so before leaking, and are dirt cheap. There are also many modifications the can be done to hold MUCH more psi with a little DIY. You would need a flange to mate up to it though.
     
  8. Toolman

    Toolman Boost it! Staff Member Club Mod

    Joined:
    Jan 28, 2001
    Messages:
    6,148
    Likes Received:
    2,632
    Occupation:
    Firefighter
    Location:
    Grand Lake, Oklahoma, USA
    I have heard that the longest running most powerful turbo SHO in existence has ran an after MAF vent to atmosphere BOV for many years and many thousands of miles.
     
  9. Mrpeepers

    Mrpeepers New Member

    Joined:
    Sep 30, 2007
    Messages:
    30
    Likes Received:
    7
    Occupation:
    Buy/fix/sell cars
    Location:
    WI
    And venting metered air to the atmosphere greatly impacts gas mileage, washes the cylinder walls with gas when it runs rich as you let off the throttle(along with gas mixing with the oil), and depending on the BOV(especially a CBV) it can suck in air at idle causing a lean condition. Just stating some facts.
     
  10. Toolman

    Toolman Boost it! Staff Member Club Mod

    Joined:
    Jan 28, 2001
    Messages:
    6,148
    Likes Received:
    2,632
    Occupation:
    Firefighter
    Location:
    Grand Lake, Oklahoma, USA

    Hmmm, wonder why that car gets 26mpg (@80mph), still has cross-hatch on the cylinder walls, never throws a CE light, and idles like a champ? Must be because venting metered air is just not that big of deal. Serisouly guys, been venting to atmosphere for 60k+ miles. The effects are seriously overstated on the internet.
     
  11. Mrpeepers

    Mrpeepers New Member

    Joined:
    Sep 30, 2007
    Messages:
    30
    Likes Received:
    7
    Occupation:
    Buy/fix/sell cars
    Location:
    WI
    Like I said, when you let off the throttle, cruising won't affect it. Also, it depends on the type(and adjustment) of BOV, as stated before about the idle. The effects of the fuel on the cylinder wall isn't the main concern, it's when the fuel gets mixed with the oil. Truth is, you may not experience any usual symptoms, but it is still affecting your engine negatively. Arguing about this is a lost cause. By all means, do what you want to do with your car and setup.
     
    Last edited: Oct 2, 2007
  12. adidas_kn

    adidas_kn LOWSHO

    Joined:
    Mar 24, 2002
    Messages:
    1,182
    Likes Received:
    28
    Occupation:
    IT supportfor Wilson Fire Equip.
    Location:
    Houston Texas
    Home Page:
    Remember the measure of Boost or PSI is a measure of restriction in the intake manifold. Not indicative of actuall CFM or air flow. Soo higher boost on a freeflowing built SHO motor will require all sorts of airflow. When the throttle blade is closed durting throttle lift or shifting it will need a bigger BOV/Recirc Valve then a 4cyl runng the same amount of boost will. I actually bought a dual purpose valve from Turbonetics called the Godzilla(it's huge). It is reconfigurable from an atmospheric dump to a recirc with its replaceable outlet and an optional tube to route the 2" outlet back into the area between the MAF and Turbo inlet. That route back is for the Turbos with the MAF on the inlet(sucking) side. My GT-K650 has a 4" inlet and will be using a 4" metal tube with a 2" welded inlet for the Godzilla to blow back through after my 90mm MAF.

    Those Forge and other CPV's will support up to a certain flow rate and hp rating. Get one too small for your application and you will start hearing a fluttering sound under throttle lift. That sound is the rest of the air that couldn't fit out that small BOV opening pushing back on the compressor blades essentially getting chopped up by going the wrong way. This will cause premature wear on the turbo and piping.

    Thats my .25 cents

    BTW, I heard that that "Guy" with the original turbo SHO is affraid to turn the boost up higher. Thats just what I heard. Cough, cough Toolman.
     
    Last edited: Oct 2, 2007
  13. Mrpeepers

    Mrpeepers New Member

    Joined:
    Sep 30, 2007
    Messages:
    30
    Likes Received:
    7
    Occupation:
    Buy/fix/sell cars
    Location:
    WI
    Nevermind my idea of using a DSM CBV. No way it will flow enough CFM for a turbo SHO through a 1" hole :p

    BTW, compressor surge can be caused by a BOV that is adjusted to tight as well. In particular, one that doesn't have an extra bottom port to be connected to the compressor outlet. Being adjusted too tight won't allow it to be pulled open all the way from the manifold vacuum alone, causing surge or stall.
     
    Last edited: Oct 2, 2007
  14. somedude_001

    somedude_001 SHO Member

    Joined:
    Jun 2, 2004
    Messages:
    2,657
    Likes Received:
    312
    Location:
    Western NY
    your wrong I read on the internet somewhere...
     
  15. TT SHO PROJECT

    TT SHO PROJECT New Member

    Joined:
    Aug 29, 2005
    Messages:
    582
    Likes Received:
    1
    Occupation:
    im a bum...
    Location:
    OHIO
    Home Page:
    <----another venter lol.. maf pre turbo... venting.. no problems unless if i vent near idle speeds but i rarely do that :p and even then... its just a cel for a couple secs and a small stumble and it recovers :p not a big deal at all.
     
  16. 2L8V8_4sho

    2L8V8_4sho SHO Connoisseur

    Joined:
    Sep 20, 2003
    Messages:
    382
    Likes Received:
    3
    Occupation:
    Ask your momma
    Location:
    Washington DC
    Home Page:
    To answer the original post, you're looking for a Bypass valve like Toolman stated.

    Also, to add to the discussion, in THEORY venting metered air is bad as it causes a momentary rich condition but in PRACTICE it has gone to show no noticeable problems as far as I've seen on the SHO's or any of the other cars I've seen running the same setup. Alot of the guys with the 2.3t's run a atmospheric BOV and blow off metered air and they have no problems.
     
  17. somedude_001

    somedude_001 SHO Member

    Joined:
    Jun 2, 2004
    Messages:
    2,657
    Likes Received:
    312
    Location:
    Western NY
    the man speaks the truth
     
  18. SHOspazz92

    SHOspazz92 Banned

    Joined:
    Jul 31, 2002
    Messages:
    6,938
    Likes Received:
    3,646
    Occupation:
    2T2X1 : Air Transportation Specialist.
    Location:
    Angier NC / Pope AFB
    Home Page:
    Well, This is not for my SHO, This is for my legacy. :)

    Running a Atmospheric unit on this car will make it stall at every stoplight (There's a lot of them out here! ;) ) and make this car run a lot more rich then they already do. I went ahead and tried a HKS Suquential BOV I had laying in my closet know that it would probably make my car run like shit and man was I right. These Boxer 4's are tempermental little shits, Ecspecially in the Twin Turbo form.

    -Sam
     
    Last edited: Oct 3, 2007
    SHOKING91 likes this.
  19. yamahaSHO

    yamahaSHO E85 whore

    Joined:
    Jul 25, 2002
    Messages:
    10,594
    Likes Received:
    2,370
    Occupation:
    FEMA... You like camping?
    Location:
    Colorado
    Turbo's don't have MAJOR ill effects when it come to venting to the atmoshpere when you have a pre-MAF blower. Once the throttle is closed, the air stops coming. In my case, with the throttle closed and engine braking from 8,000 - 5,000 RPM, I'm still boosting my pipe....

    Placement and size are key as well.
     
    somedude_001 likes this.
  20. Power Surge

    Power Surge SHO Member

    Joined:
    Apr 14, 2007
    Messages:
    608
    Likes Received:
    27
    Location:
    Palm Coast, FL
    SHO people get away with running the blow off/bypass improperly because the SHO's old EEC4 is pretty simple (primitive). You can't get away with running the blow off/bypass the wrong way on a newer Ford with much more sensitive calibration strategies. You WILL have many drivability issues, if the vehicle will even run at all at idle if you vent the air to atmosphere after it goes through the MAF.

    The RIGHT way to do it is to recirculate the air if it's been metered. Can you get away with it the wrong way on a SHO? Apparently. You can also open door with a grenade, but I prefer to use the doorknob.

    Just my 2 cents :).
     

Share This Page

If you wish to help keep SHOforum running, please click the donation button below