"The BIG BOV thread" (Where all bov question threads get merged) - Page 295

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; Donít accept the appeal to authority fallacy... They don't recommend them because they donít make them... (IMO, they dont make ...

  1. #4411
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    Donít accept the appeal to authority fallacy...
    They don't recommend them because they donít make them... (IMO, they dont make them because they probably dont offer consistent power increase that justifys the cost, but that by no means implys power loss)
    Also, a whole lot of tuners do in fact, recommend and make them.
    I have provided you with the understanding of how these pieces work, so you can draw your own conclusions rather than just accepting mine.
    How many of those tuners brandish their ase certifications rolleyes:
    Though I am not certified I have taken college level classes and passed (certification is a PITA! Iím not going to be a mechanic for a living, so I didnít bother). That has to count for something right...

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  3. #4412
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    if you tune for all these little things then theres no problem..

    i think the major problem lies w/n the fact alot of kids go buy these cars and carry over the BOV/CAI thought process from other car manfs.

    subarus arent hondas arent dsm's...

    anything done right wont hurt a thing...most people just dont do it right.
    Vanitas vanitatum...et omnia vanitas

  4. #4413
    Banned dark_rex's Avatar
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    couple comments.

    Quote Originally Posted by scoobaru
    they will be here this thursday, ill let yall know, anyone that says you will lose hp and torque with this style header is ****ing retarded.
    hmm. that's nice. got a dyno sheet to back up your butt dyno? i've seen many. they all show varyind degrees of torque loss / shifting. still haven't seen one for the megan headers... so take it easy on the "retarded" comments.

    bov's are generally worthless performance wise we discourage them b/c we like to see suby tuners worrying more about going fast, cornering faster, and stopping quicker. psshht! = teh ghey

    there are a few different types of MAFs.

    intakes are not NECESSARY until later in the mod curve. anyone worth their salt will tell you they're fine in the right conditions. without a dyno tune (and the right intake) many dyno tuners will tell you that they are more trouble than they are worth.

    stinky cats STINK!

    that is all.

    dR

  5. #4414
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    oops...
    Last edited by BigClunke; 11-08-2004 at 06:16 PM. Reason: double post

  6. #4415
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    Quote Originally Posted by dark_rex
    bov's are generally worthless performance wise we discourage them b/c we like to see suby tuners worrying more about going fast, cornering faster, and stopping quicker. psshht! = teh ghey
    they might be worthless for performance but so are a whole lot of mods endorced by the clubwrx constituency.
    from a mechanical perspective: Psshht=L0gikk re-circulting=teh ghey
    its only because you associate them with rice that you have a problem, that is how a turbo should sound. youve gone to too much trouble otherwise.

    there are a few different types of MAFs.
    really? i was only taught about the ones that used a hot wire to get a read out. of course, some different output depending on the type of engine management system.

    remember, people value your opinion alot more than mine; you have a responsibility to make sure everything you say is true and relivant if you seek to combat a valid statement...
    http://www.kemparts.com/TechTalk/tt06.asp

    intakes are not NECESSARY until later in the mod curve. anyone worth their salt will tell you they're fine in the right conditions. without a dyno tune (and the right intake) many dyno tuners will tell you that they are more trouble than they are worth.
    i wouldn't ever dispute that, but it is a problem when people remain are alowed to remain under the impression that they will ruin your engine. they dont do anything dramatic eitherway you look at it.
    though i need to inquire, what trouble have they caused (or what problems have you heard about)?

  7. #4416
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    Quote Originally Posted by BigClunke
    they might be worthless for performance but so are a whole lot of mods endorced by the clubwrx constituency.

    from a mechanical perspective: Psshht=L0gikk re-circulting=teh ghey
    its only because you associate them with rice that you have a problem, that is how a turbo should sound. youve gone to too much trouble otherwise.
    which parts if you dont mind me asking?

    turbos arent supposed to sound any particular way. they would be that way from the factory if so.

    not everyone here thinks BOV=Rice...

    most do agree it is just plain unnecessary until youre at least running upgraded IC, Turbo, & all corresponding mods.
    Vanitas vanitatum...et omnia vanitas

  8. #4417
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    Quote Originally Posted by BigClunke
    I feel that this is an issue that seriously needs to be addressed because of the sheer number of useless opinions on the topic.
    Things that are not ok in this post.
    Flaming
    Hearsay
    Blunt ignorance (it is better to have people think you are an idiot, than to open your mouth and remove all doubt)

    A Blow Off Valve (aka bypass valve or show off valve) is an essential part of a turbocharged engine. It relives the excess pressure created by a turbo immediately when opens. The energy created by the turbo cannot be destroyed, so it must be redirected. Without a blow off valve, your engine would continue to rev even when the clutch is depressed. Iím sure you can see why that might be bad thing.

    Wrong! Your engine would not continue to rev without a BOV. Your throttle plate is closed, so you are not gonna force air into the engine to keep it spinning. Instead, the air would back up in the post turbo intake tract and cause your turbo to try and spin the worng way. Good way to break your turbo.

    The stock bypass valve is re-circulating, that means that that pressure is released back into the intake. Now from the KISS (keep it simple stoopid) this is a stupid idea. Your adding in an unnecessary step that only aids in emissions (turbos reuse exhaust gasses, therefore, what is blown off is a mixture of re-circulated gasses and fresh air). I feel that it is most likely reason for Subaru choosing a re-circulating bypass valve is to cut back on emissions.

    Wrong! First, turbos DO NOT recirculate exhaust gasses. You obviously don't know how a turbo works to make a statement like this. The exhaust gasses pass through the turbine housing of the turbo and exit into the exhaust system. The compressor side of the turbo draws ALL of it's air from the intake through the MAF sensor. Subaru (and every other OEM turbocharged car that I know of) use a recirculating BOV (actually refered to as a Bypass Valve since it recirculates) because the air in the post turbo tract has already been metered by the Mass Air Flow (MAF) sensor. If they didn't recirculate, then they would have the rich condition you talk about below, right from the factory!! You're right that from a KISS standpoint recirculating the air seems unneeded... So then why does every manufacturer use that setup?! It's not for emmissions as you stated, so what is it? Hmmmm...

    Aftermarket BOV's have a variety of designs that range from 100% atmospheric vent to 100% re-circulating vent (like stock) and some are even adjustable.
    These BOV have the same function as the stock bypass valve but you get the "Show Off" noise in between shifts because of the air being forced outside through the valve (often times shaped to accentuate the noise).
    (I expect that many of you already know that, so now it is time for debate...)

    Since some designs do not re-circulate this air; they alter the normal operation of the engine, the potential negative and positive effects need to be weighed before coming to any conclusions about BOV (admittedly they are very few to reach).

    The most common problem addressed with the use of a 100% atmospheric BOV is a "rich condition" in between shifts. Those conditions ruin the catalytic converter and it can smash apart and ruin your turbo

    Rich conditions can be troublesome when your dealing with a catalytic converter because the more rich the condition, the harder the catalytic converter has to work. The harder it has to work, the more energy created. The more energy created the greater the heat created. Etc...

    Catalytic converters are not a frequent maintenance item; meaning they are intended to last the life of the car. They are resilient and designed to take into account a variety of conditions.
    The ideal combustion ratio for gasoline is 14.7:1. For those of you with tuning experience, you know that turbocharged engines are usually around 10:1-11:1 and something that high would cause catastrophic failure. A turbocharged engine creates an enormous amount of heat and to control that heat a rich condition is necessary.

    That means, our engines are already putting more stress on the catalytic converter than any normally aspirated engine would. Clearly, our cats are engineered tough to withstand the harsh conditions that a turbocharger creates.
    When a catalytic converter fails it is usually know by everyone around you, it smells awful and hurts your performance because it is restricted with build up. I really hadnít heard of a cat shattering and flying into the turbo before a fellow board member introduced the concept to me. So I would be interested in hearing first-hand experiences.

    The rich condition created by atmospheric BOV's is momentary. While that may be slighty detrimental to performance, the amount of fuel that we're talking about is rediculously small and will be burnt by the catalytic converter before it has a chance to accumulate and do damage. I have never heard of a Cat breakup in a subaru engine. If someone knows of one, please share. In any event the thing to worry about more than rich conditions is lean conditions which can raise exhaust gas temp dramatically, something much more detrimental to the life of a catalytic converter than a little extra fuel. A properly working BOV will never cause a lean condition. So in that aspect, your cats are safe.

    It has been established that a rich condition is created because air that would normally be re-circulated and mixed with fuel, is blown off but the ECUís fuel compensation remains. This does create a rich condition, but you need to consider how little effect that can really have on performance. Our engines are rotating about 600-700 times a minute at idle and much more when you apply throttle. As soon as a revolution is complete the gas leaves the combustion chamber and is expelled or collected and re-circulated (turbocharged). For a few revolutions that rich condition might exist, but will be expelled very quickly. So quickly that a performance increase or decrease would be undetectable and the rich condition would only be momentary.

    Have you actually had an atmospheric BOV to make this statement? You said above that you wanted no speculation... I have tried 3 different bov's on my car (APS dual vent, Forge Atmospheric, and WORX) and I can say without a doubt that the performance difference is not only there, but noticeable. Any one with a utec and a wideband that can do some logs can prove this as I've seen it many times as well as felt it. I took off the forge from my car for this exact reason. Depending on how much air needs to get vented (based on your turbo efficiency and the boost you're running) the rich condition may be more or less pronounced, but it is there.

    The bottom line is an aftermarket BOV cannot ruin your engine unless there is a problem elsewhere. It might wear on your cats a bit more but certainly not enough to justify failure. Any failure attributed to a BOV is a confusion of causation with correlation and should be treated as such, not encouraged by the ďanti-riceĒ members.

    Agreed, a properly functioning BOV cannot do any damage to your engine or cats.

    100% atmospheric BOV are a much simpler design than stock. Some aftermarket valves even reverse the valves operation to eliminate to problems with the stock valves ability to hold boost (negligible point unless you have a big aftermarket turbo).
    Conclusions:
    You do not need an aftermarket BOV on even the majority of heavily modified wrxís. They will not help performance. They will not ruin your cat or engine. They will make noise that a lot of clubwrx members donít like.

    The main problem with the stock BPV is that it starts to leak. For some it leaks as early as 18psi. Mine started leaking at 18.5psi roughly. So yes, there is a reason and justification to use an aftermarket unit. And yes, a non leaking BOV will definitely help you performance wise.

    Put the money towards something that will help performance, if you got one for free put it on, it wonít hurt.
    This post is my theory of refusal. I am certainly open to hear others well thought out opinions because we really need to stop demonizing these valves, even if you think they are annoying, we have a goal of objectivity. That truly what sets us apart from the ďsports compactĒ scene.
    See my comments above in the quoted post in bold.

    Let me just say that I'm not someone who thinks BOV's are just noise makers and are rice. I think they have their place and can be useful. I do however also think that someone who grabs a BOV as one of their first mods should understand that it's not gonna do anything good for them but make a cool noise and may possibly slow them down. Although, on a stock car at stock boost levels, the rich condition is minimal and the stock turbo is still in boost after shifts so it's really not noticeable.
    Last edited by MidKnight; 11-08-2004 at 06:40 PM.
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  9. #4418
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    Quote Originally Posted by BigClunke
    really? i was only taught about the ones that used a hot wire to get a read out. of course, some different output depending on the type of engine management system.

    There are two basic types of mass airflow sensors: hot wire and hot film. In the first type, a very thin wire (about 0.2 mm thick) is used as the heated element. The second type uses a nickel foil sensor..

    There is also a difference in the structure. it can be either a "vane type" or a "wire type". the vane type is actually not temp related, but a "sail" of sorts, that swings a distance depending on the mass / velocity of the intake air.

    Quote Originally Posted by BigClunke
    remember, people value your opinion alot more than mine; you have a responsibility to make sure everything you say is true and relivant if you seek to combat a valid statement...
    http://www.kemparts.com/TechTalk/tt06.asp
    thanks. while it's important not to trust everything you see on the web, i try to live up to that standard. autozone's website has some details on MAFs, the types, how to test, replace and inspect. check it out.



    Quote Originally Posted by BigClunke
    though i need to inquire, what trouble have they caused (or what problems have you heard about)?
    dan at godspeed, as well as phil at element (and txs) and many others have spoken of the dangerous lean conditions, and unpredictable tuning resulting from CAIs and some brands of intakes.

    dR
    Last edited by dark_rex; 11-08-2004 at 06:48 PM.

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  11. #4420
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    Theres just too much focus on the BOV as a necessity. It is not a necessity. It is supplementary to have 100% atmospheric BOV when you're not running the conditions which is is is necessary for. If you are running engine management and around 20lbs of of boost, then it becomes a necessity, but I always suggest to allocate funds to more important things that cost the relatively same amount but dramatically improve performance, i.e. Downpipe, Up pipe, Intercooler hoses, or ECU reflash. Don't flame those who have BOV's, the money could've been put elsewhere, that is their loss whatever, who cares, move on.
    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!

  12. #4421
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    I am really not trying to say that a bov or Cai are necessary or even worthwhile mods. i am trying to put perspective on the ills associated with them.
    and i must appolegise for that attack dark_rex, i havent encountered any maf's that look like the vane type. i dont remember them being discussed in diagnostics and tune up... my mistake.
    what types of cars use a vane typed meter?
    (btw, i am very aware of most internals and usually reference my textbook, i cant find it at the moment)

  13. #4422
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    Truthfully, i am very new to the turbo charging process. i hadn't even considered it until i purchased a wrx. So i am still trying to catch up.
    When I made my post, i did not understand the part about, the exhaust spinning then it sucking fresh air in (kind of like a water wheel), thanks for adding that clarification.
    (I had the wrong impression that, the gasses were collected at the wastegate, compressed in turbo, passed through intercooler, directed into intake manifold and the intake and tb were separate. Now everything is making sense )

    my point about bov's is still true, it doesnít hurt so people should stop filling up every post about a bov with crazy anecdotes or just mean spirited comments about how stupid 100% atmospheric bov's are.

    I have had experience with a hks bov. I purchased my wrx used and it had a hks bov on it. it was crap at first and operated terribly and I listened to others on the forum and just accepted its poor performance and replace the valve. Then I started messing around with the spring tension and realized it wasn't the bov's fault; it was my incompetence. It functions great now.

    EtherealWRX:
    I donít think there is a focus on BOV's being a necessity, almost every post about them is full of people flaming them.

    Again to clarify, this post is about bov "not hurting" more than it is about helping; I donít want the misunderstanding to get out of hand.

  14. #4423
    Moderator MidKnight's Avatar
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    Quote Originally Posted by BigClunke
    Again to clarify, this post is about bov "not hurting" more than it is about helping; I donít want the misunderstanding to get out of hand.
    Again, a BOV won't hurt your engine, but it can hurt performance. The rich condition an atmospheric bov creates is real. A lot of people don't care, but it is there.
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  15. #4424
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    are you sure that the powerloss is caused by the momentairly rich conditions?
    it would seem to me that a change in the speed of the valves operation due to varying spring tensions would be the more likely reason for any noticeable loss. i really have a rough time accepting that this change accounts for enough of difference to be apreciable.
    i am not disputing any noted difference between bovs from different manufactures; rather, pinning the problem on the function of bov. like i said mine operated much worse before i started to play with the spring tension.

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    still doesn't solve the problem of bov melting ur up cat

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