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Thread: Aftermarket BOV (plumb back) make any performance differences?

  1. #1

    Default Aftermarket BOV (plumb back) make any performance differences?

    Just compiling a list of mods that I'd like to have done and it seems that a lot of people change their BOV.

    If I were to get one, it will be recirculated, so I wouldn't be changing it for the noise. However, is the stock BOV weak (leaks boost) or slow at closing at all? Its a few hundred dollars to change one...

    Also why are people getting the Forge bov? Besides the fact that it replaces the OEM without any mods so ease of installation is a plus, the fact that you need to service it just sounds stupid. I dont know of any other bov you need to service.

    Has anyone changed to an aftermarket recirculated bov noticed any difference in boost (spool up times, peak figure) and/or throttle response?

  2. #2

    Default

    LUP15, There are a million posts on BOVs on forums around the world. At least 50% of what is written is tripe. Many people don't understand the purpose of a BOV or how it functions. Look at all the idiots that want to put a BOV on a non-turbo car for example.

    Most stock BOVs are 100% bypass, that is, all the air vented upon throttle closure goes back to the turbo inlet. The reason for changing to an after-market one is either: 1 - to get one that holds more boost; 2 - to allows partial or full vent to atmosphere (VTA) and/or 3 - to make a venting noise; 4 - to enable adjustment . Most stock BOVs lack any adjustment.

    Changing from a stock BOV will not improve performance per se, all other things being equal. What it can do is solve the problems of a leaky BOV (rare); solve the problem of a BOV that is fine at stock boost but which leaks under boost above stock specs such as when boost control is tweaked up; or as a protective measure intended by the manufacturer against inadvertent boost spikes or deliberate tinkering.

    But most importantly, it can enable a BOV to be adjusted. By doing so, the performance benefit that comes is not power, but arises by tweaking the BOV so just enough air is vented to Bypass to keep the turbo from stalling, while the remainder of the air under pressure remains in the plumbing and is thus still under some pressure so that there is less lag to full pressure build-up when you get back on the throttle - hence improved throttle response and apparent "quicker turbo spool up".

    This should be YOUR reason to replace your stock BOV if it is not already adjustable, which I assume is the case seeing your handle tells me you have an MPS3. Set it up by screwing it in so you don't get backfires (if VTA or partial VTA), but not so far as to cause compressor stall - you'll feel it when you get there, so back off from that point. Make 1/4 turn changes and drive each time. It can take days. Best to take your time and not try to do it all in a day. I still believe the Turbosmart is the most user friendly around - it is a 3:1 BOV and the base is adjustable to you can get it sitting right to suit your plumbing. It can be fitted to the MPS3 in minutes. Don't drop anything down the intake pipe - block up the exposed flange with clean rag!

    But beware of anecdotal tales from folks, who don't know much, about how it "adds heaps of power". If they say this then the odds are that they may not even know how to adjust one. If they get it right first off and report better throttle response and "more power" it is possibly just dumb luck - remembering also that better response often feels like "more power" too.

    Cheers
    Last edited by Doug_MPS6; 04-08-2010 at 04:24 PM.
    CP_e Standback & PNP; CP_e 3" SS Downpipe; Corksport FMIC with Top-mount K&N filter & OEM Ram CAI; Turbosmart BOV; Dashhawk; Prosport Boost Guage; JBR solid shift bushes; DBA 4000 Wiper-Slot front rotors; Hawk Ferro-Carbon HPS Street front brake pads (@ 69,000km); Sumitomo HTRZIII's in 225/45 x 18

  3. #3

    Default

    Good job Doug

    Upgrading the BOV to a larger item may be necessary for larger flowing turbos to allow the more air flowing to vent.

    I know for a fact that the stock BOV can handle upto 22psi.

  4. #4

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    2XS, thanks. I agree. I left that one off my description as I didn't think it was going to happen from LUP15's post.

    In fact my BOV can't dump enough air due to build up of pressure in the 2m of plumbing on the turbo outlet side of the FMIC, and I still get compressor stall, hence my proposals for a second one. I've explored every other possibility and that is all that is left. My existing BOV dumps all it can off the throttle intake side of the FMIC just fine.

    As explained before, my son has a blown V6 Holden (19psi for around 350Kw if I recall) and unbeknown to me had the same problem. He was stripping the teeth of the drive belts when the vanes stalled, and getting a noticeable "stumble" on lift off. A 2nd BOV (100% VTA) fixed it. Supercharged engines are strange cattle, whether with turbo or driven vanes.

    PS: I love it................"I wasn’t born with enough middle fingers to let you know how I feel."
    Last edited by Doug_MPS6; 04-08-2010 at 07:33 PM.
    CP_e Standback & PNP; CP_e 3" SS Downpipe; Corksport FMIC with Top-mount K&N filter & OEM Ram CAI; Turbosmart BOV; Dashhawk; Prosport Boost Guage; JBR solid shift bushes; DBA 4000 Wiper-Slot front rotors; Hawk Ferro-Carbon HPS Street front brake pads (@ 69,000km); Sumitomo HTRZIII's in 225/45 x 18

  5. #5
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    Default

    I had an aftremarket one on my 3 and besides the sound i beleive it was the biggest waste of cash ever. went back to std and everything is better, mostly the way the car feels between shifts.. i'd consider going back to aftermarket if it was free but i'm not planning on it. I beleive there are no gains to be had from an aftermarket setup on a fairly std engine

  6. #6
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  7. #7
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    Time to dust off the pushy lol

  8. #8

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    nice 1 jmac.

    they should sell that kit and make millions

  9. #9

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    Update for a 20psi dyno run with stock BOV

    Electronic boost controller set @ 20psi

    As you can see, the boost is held, but, it has some irregularites.

    Last edited by 2XS; 08-08-2010 at 07:40 PM.

  10. #10
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    That vid was hilarious... lol

  11. #11
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    BOV/BPV Threads should be banned... its the same over and over again.. i bet people get sick of having to repost the same again and again..

    i remember on my old VW forum i had a Post that i had Saved in microsoft word to copy and paste the same time any one asked this particular question..

  12. #12

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    I agree - almost - there needs to be some avenue for discussion left open, but I've written heaps on it and have kept a few old posts as a C&P source too. I just wish people would search for prior threads and research the net before asking questions. It's stamping out all the misinformation that irritates me most - "I luuurve the noise - can I put a BOV on my pushbike....duh!"

    Come to think of it - there have been a few duplicated threads here lately - it'd be nice if they could all get combined into a single thread but I know that gets fiddly.
    CP_e Standback & PNP; CP_e 3" SS Downpipe; Corksport FMIC with Top-mount K&N filter & OEM Ram CAI; Turbosmart BOV; Dashhawk; Prosport Boost Guage; JBR solid shift bushes; DBA 4000 Wiper-Slot front rotors; Hawk Ferro-Carbon HPS Street front brake pads (@ 69,000km); Sumitomo HTRZIII's in 225/45 x 18

  13. #13
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    At times i just feel like telling people go ahead.. go buy a VTA... enjoy the CEL.. peace yo!

  14. #14
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    Ummm, Maybe I'm missing something here.... Admittedly I have not slept for 30 hours....

    Make the good BOV/BPV thread a sticky? Surely that would solve the problem?

  15. #15
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    Quote Originally Posted by Scaredycrow View Post
    Ummm, Maybe I'm missing something here.... Admittedly I have not slept for 30 hours....

    Make the good BOV/BPV thread a sticky? Surely that would solve the problem?
    Nope... People still get trigger happy and post the same freaking thread a million times over..

    Especially with Blowoff Valves... Probably one of the least important parts of your engines function...

    If you are loosing boost thru it Replace it... if you want to change it change it.... the rest is personal preference depending how legal you want to stay or how noisy and stupid you wish to play...

  16. #16

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    sure its easy to say just search, but short search strings don't work such as BOV. also you cant say VW is the same as Mazda. ALthough the principle of the BOV will be the same between different manufacturers, there may be other things which is car specific.

    also this is a discussion forum, my post was not what a bov does, not what bov should I get, but a specific question about throttle response (amongst other questions) of an aftermarket bov compared to stock. If your sick of the 'same' bov thread, then just dont read it. no one is forcing you to.

    sorry for ranting, but although I am well aware of some aspects of turbo cars, I have not owned a MPS 3 before. Even when noobs come and ask the 'same' question, they shouldn't be ridiculed into thinking they aren't allowed to ask questions. thats how we learn. if you don't want to aide that, then just dont read. no need for negative input

    end rant/

  17. #17
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    Stickied.

  18. Default

    Its for the noise! Just get one you can change between plumb back or vent, when you get sick of the noise.

  19. #19
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    I got a GFB BOV recently, simply because I wanted the option of venting to Atmosphere for track and drag meets (not that I have done any yet) it's plum back daily though, but to my surprise even recirculated sounds better, and I know it's not hugely breaking the law. Haven't researched the legalities of having a BOV with the option to vent to air, but know its illegal to vent to atmosphere due to noise emotions or something crazy like that.

  20. #20

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    I don't have a huge amount of input other than to echo what has been said - if it ain't broke don't fix it. The stock valve works fine, and is probably the most driveable option.

    But if you DO replace with an adjustable valve, make sure you understand how it works before you go ahead and install it - otherwise you will almost certainly make your car perform worse and use more fuel.

    Like Doug said, it took me a long time to tune my Turbosmart to find that fine balance between open and shut scenarios. It was frustrating me so much that i took it off to service it and was amazed by how much smoother the car drove with the stock valve on. Trying to set it up for 50/50 VTA and i found that too tight and you get a jerky and grumpy car that only performs well on full throttle. Too loose and you get backfiring and a massive drop in fuel economy. I had to really get my head around the way it worked to be able to get that factory driveability feel.

    In the end I found it best to run it full recurcilating - which means - I was pretty much back at the function of the stock valve!

    So in summary, if you want the wank factor of a VTA BOV, go nuts - you're probably less concerned about things like economy and driveability anyway. But otherwise, just stick to the stock setup.

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