"The BIG BOV thread" (Where all bov question threads get merged) - Page 401
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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; Originally Posted by killthelights14 here ill post a video of me driving without silencer. you can hear the turbo spool ...

  1. #6001
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    Quote Originally Posted by killthelights14
    here ill post a video of me driving without silencer. you can hear the turbo spool up loudly, and when i get off the gas fast you can hear it go...."pshh" lol. youll like it. hopefully nothing is wrong with my car.... lol.

    but ill post the video later on today
    cool..

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  3. #6002
    Registered User killthelights14's Avatar
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    it will be up in about 3 hours still shooting
    02 wrb wrx stock turbo fmic 26 psi (it can be done)

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    Registered User Fox05's Avatar
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    I wish i had the abality to do that but i dont and i dont know how
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    BOV or WASTEGATE

    I did a search, but im still alittle confused. I have a vf34 and dont know wweather I should get a bov, or a wastegate. any input wooule be great.I ordered the HKS SSBOV, and I hope I made the right choice.
    My Mods: Cobb Access Port, VF34 turbo, STI fuel injectors, Walbro fuel pump, Perrin Turbo back exhaust, Perrin fuel rails, Tein S-tech springs, AGX Adjustable Struts, 17" RS-GT rims.

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    Registered User amukaoen's Avatar
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    from what i understand..

    from what I understand they are two differnt things. of course my understanding isnt complete but im hoping that the general idea holds true. (PLEASE correct whatever I get wrong)

    your turbocharger spools and compresses air as exhaust gases flow through it.. and since your car is always making exhaust, its always going to spin which is great and all... but the problem is that it'd keep spinning faster and faster and faster, and keep compressing more and more air untill you'd break a massive amount of engine parts.

    thats where the wastegate comes in. the wastegate allows your turbocharger to spin without it compressing any additional air because it will vent it off. lets say your wastegate's spring allows it to stay closed until you hit 10 psi. so the second you hit say... 10.1 psi.. the waste gate will open, then close when it drops back down to 10 again... and repeat... over and over and over and over (from what I understand its a really quick process)

    the blow off valve / by pass valve simply vents off the compressed air when you shift so you dont break anything. There is some weird phenomon that occurs when the throttle is closed (to shift) and where air is still being compressed the boost pressure can shoot up to extremely high pressures (30-50 psi) and blow off hoses and break a lot of things

    BPVs vent off the gases (So you lose all your boost) but it'll keep the turbocharger spinning freely (because its under no load), so when you're done shifting and get back on the throttle you'll be able to build boost again quite quickly

    on the other hand...

    BOVs, vent off the gases into the atomosphere to make that really cool sound (you lose all your boost once again).. but its not nessisarly the same thing because without the BPV the compressor wheel will tends to stall... and if you've ever looked at your boost gauge on your car before while trying to make boost, you'll see that getting it spinning in the first place and making the first like 5 psi is what takes the longest to do. so swapping off your bpv for a bov puts you at a horrible disadvantage.
    Last edited by amukaoen; 10-30-2005 at 11:22 AM.
    they call STi's STDs because everyone is getting them.

  7. #6006
    Registered User ScoobVee's Avatar
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    Quote Originally Posted by amukaoen
    the blow off valve / by pass valve simply vents off the compressed air when you shift so you dont break anything. There is some weird phenomon that occurs when the throttle is closed (to shift) and where air is still being compressed the boost pressure can shoot up to extremely high pressures (30-50 psi) and blow off hoses and break a lot of things
    The main reason for the BOV is to prevent throttle surge. Throttle surge can kill your turbo by putting stress on the center cartridge, however ball bearing turbos will be able to withstand higher levels of throttle surge
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  8. #6007
    Registered User amukaoen's Avatar
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    Quote Originally Posted by ScoobVee
    The main reason for the BOV is to prevent throttle surge. Throttle surge can kill your turbo by putting stress on the center cartridge, however ball bearing turbos will be able to withstand higher levels of throttle surge
    I guess throttle surge is that weird phenomon im thinkin about then... makes sense
    they call STi's STDs because everyone is getting them.

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    Registered User E-Wrex's Avatar
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    I believe amukaoen is right in saying that the wastegate is to control boost pressures, and the BOV just dumps excess pressure when you are not using it, and if that pressure wasn't dumped, you get compressor surge, which is good for turbo lag, and bad for everything else.
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    Registered User wrxracer87's Avatar
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    Ok I have a question. What if your car is skrewing up because of your exhaust and you have to have a mbc to contol the turbo correctly.<-- my problem. My car started acting funny at full to almost full boost about a week after I put my down pipe on it. It wont hold full boost any more it just peaks and then lets off. I took it to the dealership and they told me that they couldn't fix it and that it was because of my downpipe. I'm thinking of buying a dual stage txs boost controller but only have the stock boost gauge I was wondering if what mark on the stock boost gauge is equal to 15 psi. So that I can adjust it.

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    Registered User Cuztom15's Avatar
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    ok wow, im sorry, i couldnt let this go on. Your right but your not completly right. Compressor surge is bad period. Thats compressed air bouncing off the throttle plate or not escaping the BOV and going back into the outlet of the compressor housing, i.e. spinning the wheel backwards. That can produce dramatic wear and possible damage if let go for a period of time.

    A bov/bpv/w/e you want to call it/ is used to let excess gas ,created by teh compressor wheel still spinning after the throttle plate has been closed, escape either into the atmosphere, or back into a recirculation hose which is routed before the compressor inlet on the intake pipe/turbo inlet hose to shove the air back into the compressor (spinning the wheel the same way) and thus reducing a rich condition and turbo lag.

    Your pretty much correct on the wastegate. It is used to allow exhaust gasses to bypass the turbine wheel and go out the wastegate to prevent overboosting. When the car reaches its preset boost, the wg will be opened and allow the gases to bypass the turbine wheel and prevent damaging components.

    So you would only need an external wastegate if your internal wastegate fails to bypass enough exhaust gas around the turbine wheel. mmmmmmm tial 40mm wg dump pipe
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  13. #6012
    Administrator Trainrex's Avatar
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    You already have a wastegate built right into your VF34. Your stock BOV is better than just about any on the market. Stick with the stocker.

  14. #6013
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    Quote Originally Posted by Trainrex
    You already have a wastegate built right into your VF34. Your stock BOV is better than just about any on the market. Stick with the stocker.
    ^ I agree....

    get a refund on the HKS BOV, & get a catless uppipe(its not in your mod list)....

    BOV = + 0 whp

    catless uppipe = + 5 - 10 whp...
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    nuff said
    Last edited by IronMedic; 03-11-2006 at 07:27 PM.
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