"The BIG BOV thread" (Where all bov question threads get merged) - Page 297

This is a discussion on "The BIG BOV thread" (Where all bov question threads get merged) within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; Going from fully atmo to fully recirc you can feel a difference in lag after shift. I wish I could ...

  1. #4441
    Registered User StarquestAndyR's Avatar
    Join Date
    Oct 2004
    Location
    Georgia
    Posts
    204
    Going from fully atmo to fully recirc you can feel a difference in lag after shift. I wish I could quantify it for you but I can't. My buddy couldn't tell the difference from one to the other, but I could. I felt the difference, however miniscule it was.
    I'm new to WRX's but definitely not new to turbo charging. the reason that there is slightly more lag with ATMO is because the turbo has to work to get the air through the intake all over again.

    Now, if you take the air that the turbo just compressed, shoot it out of the BOV right into the intake plumbing BETWEEN the air filter and the turbo, then you just forced the air to go two directions - one is out through the intake, and the other is right back into the turbo - causing positive pressure in the intake piping. The air going back into the turbo allows it to spool much easier due to the intake pressure caused by the BOV. If it is vented to ATMO then there is no pressure in the intake piping, but there is in fact a vacuum - and the turbo must work harder in a vacuum to get boost.

    hope thats clear.
    Last edited by StarquestAndyR; 11-09-2004 at 07:12 AM. Reason: to make my point clearer
    2002 Black WRX wagon
    1997 GMC Suburban. TURBO Diesel, 4x4 Runs on WVO

    Your post count does not equal your intelligence. I don't care how many times you replied with "tacos rule"

  2. Remove Advertisements
    ClubWRX.net
    Advertisements
     

  3. #4442
    Registered User
    Join Date
    Jan 2004
    Location
    MI
    Posts
    414
    Quote Originally Posted by dark_rex
    wrapping/ coating (like jethot2000) might help that.

    either way, that's not a good thing!
    no kidding. so these headers dont fit around the oil pan and need the subframe modified. sounds like alot more work than i had hoped for...

  4. #4443
    Registered User
    Join Date
    Jan 2004
    Location
    MI
    Posts
    414
    Quote Originally Posted by StarquestAndyR
    I'm new to WRX's but definitely not new to turbo charging. the reason that there is slightly more lag with ATMO is because the turbo has to work to get the air through the intake all over again.

    Now, if you take the air that the turbo just compressed, shoot it out of the BOV right into the intake plumbing BETWEEN the air filter and the turbo, then you just forced the air to go two directions - one is out through the intake, and the other is right back into the turbo - causing positive pressure in the intake piping. The air going back into the turbo allows it to spool much easier due to the intake pressure caused by the BOV. If it is vented to ATMO then there is no pressure in the intake piping, but there is in fact a vacuum - and the turbo must work harder in a vacuum to get boost.

    hope thats clear.
    as crystal.

    so, it does seem that atmospheric valves will undoubtably cause lag. it might be very small but that definatly adds validity to, "reasons not to use 100% atmospheric valves."

  5. #4444
    Registered User jibco's Avatar
    Join Date
    Aug 2003
    Location
    In a cube, CO
    Posts
    1,925
    Quote Originally Posted by BigClunke
    Truthfully, i am very new to the turbo charging process.
    I wondering where this post came from......

  6. #4445
    Registered User Timdog1650's Avatar
    Join Date
    Aug 2002
    Location
    Virginia Beach, VA
    Posts
    6,170
    THIS IS NOT A JOKE:

    If you want to increase your stock BPV's ability to hold boost, take it off, put it on a level surface, and dent the top of it in with a sledge hammer about 1/4". This will compress the spring and make it PERMANENTLY more boost holding (note that if you do it too much, you may cause some surge, but if you're running a big turbo, this is a great and CHEAP way to make your BOV stop leaking).

    Seen it on cars with T3/T4 kits, works great if you dont wanna blow 300 on a useless chunk of shiny metal.

  7. #4446
    Moderator MidKnight's Avatar
    Join Date
    Oct 2002
    Location
    Bergen, NJ
    Posts
    4,711
    I Support ClubWRX
    Quote Originally Posted by Timdog1650
    THIS IS NOT A JOKE:

    If you want to increase your stock BPV's ability to hold boost, take it off, put it on a level surface, and dent the top of it in with a sledge hammer about 1/4". This will compress the spring and make it PERMANENTLY more boost holding (note that if you do it too much, you may cause some surge, but if you're running a big turbo, this is a great and CHEAP way to make your BOV stop leaking).

    Seen it on cars with T3/T4 kits, works great if you dont wanna blow 300 on a useless chunk of shiny metal.
    I've seen this done on the DSM stock BPV and have no doubt that this would work on the wrx bpv. As you said, if you do it too much you can cause surge, so do it carefully.

    StarquestAndyR, your point about positive pressure in the intake is an interesting one, but I question your saying that air goes out the air filter. This would mean that there is air going the wrong way past the maf. Wouldn't this cause disturbances that will alter your MAF readings?
    '03 WRX
    '01 2.5RS
    MODS | PICS | Dyno
    "Stuff sold by the gram is always going to be more exciting than stuff sold by the pound." - Jeremy Clarkson

  8. #4447
    Registered User StarquestAndyR's Avatar
    Join Date
    Oct 2004
    Location
    Georgia
    Posts
    204
    StarquestAndyR, your point about positive pressure in the intake is an interesting one, but I question your saying that air goes out the air filter. This would mean that there is air going the wrong way past the maf. Wouldn't this cause disturbances that will alter your MAF readings?
    possibly.
    I come from a DSM background, and I can say for a fact, that if you vent your BOV to ATMO, it will cause the car to buck and surge between shifts because the MAS on a DSM is actually relying on air pressure in the intake tubing between shifts. On a DSM this also causes stumbling when driving in high RPM's at half throttle. I have no idea what is causes on the WRX (if anything) because my BOV is still stock. If I ever change my BOV I'll comment then with my first hand experience.

    But, I dont see how the BOV releasing into the intake piping would not have air escaping through the filter unless it had a one way valve in it or something similar, which no car does (that I know of). Positive pressure will always go to the path of least resistance. But I'm sure that the ECU calibrates for this if the car came with a stock BOV. Other turbo cars that come without a BOV (older mitsubishi cars did - the conquest/starion did not have a BOV) will experience similar problems for the same reasons above if you add a BOV to them. Unless, of course, the car is heavily modified.
    2002 Black WRX wagon
    1997 GMC Suburban. TURBO Diesel, 4x4 Runs on WVO

    Your post count does not equal your intelligence. I don't care how many times you replied with "tacos rule"

  9. #4448
    Registered User EtherealWRX's Avatar
    Join Date
    Oct 2004
    Location
    Downey
    Posts
    675
    Like always. Threads about BOV veer off the original topic idea into an escapade of mixed viewpoints. There are plenty of other threads to look at for these topics, for everyone who's still interested, do a search.
    Have a Greddy Evo 2 cat-back Exhaust system, willing to trade for: Greddy Ti, Apex'I N1, or Apex;I GT cat-backs. California only! PM if interested!

  10. #4449
    Registered User
    Join Date
    Jun 2004
    Posts
    269
    Quote Originally Posted by StarquestAndyR
    possibly.
    But, I dont see how the BOV releasing into the intake piping would not have air escaping through the filter unless it had a one way valve in it or something similar, which no car does (that I know of). Positive pressure will always go to the path of least resistance. But I'm sure that the ECU calibrates for this if the car came with a stock BOV. Other turbo cars that come without a BOV (older mitsubishi cars did - the conquest/starion did not have a BOV) will experience similar problems for the same reasons above if you add a BOV to them. Unless, of course, the car is heavily modified.
    Actually, I'm pretty sure the turbine doesn't just *stop* between shifts. Even if it just spinning a little, this with the vacuum from the engine will likely create a negative pressure in the intake. That shoud draw the re-vented air back towards the turbo, keeping the MAF readings correct. ALso, remember that the biggest reason for the re-circ is to preserve the MAF readings. So having the vented air burp back out through it would cause the same problem as having an atmo. BOV.

  11. #4450
    Registered User ma1ade's Avatar
    Join Date
    Dec 2003
    Location
    Eastern CT and Quantico VA
    Posts
    332
    I'm reading all this and despite the hundreds of words there doesn't seem to be any actual conclusions based on anything besides opinion. The biggest point the 100% atmo bov "haters" seem to be making is that the car runs rich momentarily (true) as it shows up on a wbo2. However, put it into context where you are actually driving. You are ending 2nd gear, shift (woosh) you run rich. Common knowledge dictates that running rich = less power. This loss of power though comes in between shifts. As soon as you are on the gas again after the shift the small amount of time that you were rich is over. It wouldn't matter if a car is making 1000 hp in between shifts because it isn't power that will ever see the pavement. Any problems that I've ever heard of coming from BOVs seem to be guilt by association or OE. I have never once had the engine stutter after a shift or bog due to the BOV. When installed correctly and adjusted properly you get a very nice noise maker with no effects anymore adverse than a silencer delete.


    +1 opinion reply

  12. #4451
    Registered User
    Join Date
    Oct 2004
    Location
    Kent, WA
    Posts
    365

    I have some questions about BOV.

    I have my own plans and i was wondering if there's any
    adjustments needed...so fix me plz.
    here are the lists from order.

    From Stock
    1. Catback Exh.
    2. Blow Off Valve (ordered HKS yesterday)
    3. Rims.
    4. Shocks and Coilovers (should i lower or no?)
    5. Take off wing.
    6. Work on details for engines

    OOps, the question i wanted also ask was..
    my friend has told me that if i'm gonna be running lower than 20 psi,
    i shouldn't get BOV, because it will rather take powers away..
    or am i just having different definition of BOV...
    well anyways, so lower than 20 psi = no BOV? or is it okay?

    correct me =) suggestions would be appreciated also
    Last edited by sadkorean34; 11-09-2004 at 11:27 AM.
    03' C i

  13. #4452
    The Default One SeattleJeremy's Avatar
    Join Date
    Jul 2004
    Location
    Seattle, WA
    Posts
    4,488
    On Subaru's a BOV will make the car run very rich durring shifts. They are not suggested with near stock cars.

    Not sure what the cut off is for PSI ratings for having a BOV, but if your running a stock turbo. Its just not nessassary. (BTW: Stock psi is 13, stock turbo is most efficent at ~16.5)

    Your money is better spent on an uppipe and/or Downpipe, then cat back later.

    Also there is no need to make more than one thread on one subject.

  14. #4453
    Registered User WRX-games's Avatar
    Join Date
    Oct 2003
    Location
    Arvada, CO
    Posts
    4,719
    Check here! You can find more information in that forum.
    James

    "Never criticize a man until you've walked a mile in his shoes. That way, if he doesn't like what you have to say, it'll be OK because you'll be a mile away and you'll have his shoes."

  15. #4454
    Administrator Trainrex's Avatar
    Join Date
    May 2003
    Posts
    26,590
    I Support ClubWRX
    It's not necessary until about 19 psi. If you can't live without the sound try to get a 50% recirc. valve. Definately do a search, and read the sticky at the top of the forum to come up with your own conclusion on it, it's been covered eleventy billion times

  16. #4455
    Registered User
    Join Date
    Oct 2004
    Location
    Kent, WA
    Posts
    365
    thx for point out guys.
    sorry for double posting. =(
    03' C i

Posting Permissions

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