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Blowoff Valve Threads


EricF

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what do you mean it didn't make a difference on the dyno? what do you think a blowoff valve does? btw you should post pics in the showroom

If operating properly, the location of the BOV doesn't mean stuff when you're on the throttle. It's closed. It only matters when you let off the throttle, which is behavior that a dyno doesn't record. :huh:

Instead of arguing where you should put your bypass valves, instead argue how much air you should be flowing out of it. The turbo cares about that, and it actually makes a difference when you get back on the throttle ;)

And Eric, it's ok, you can tell us how you really feel about BOVs :lol:

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You guys are so cute about this.

The CBV is located in a bad spot. A recirculation valve (the actual name for BOV's) dose the same thing, right back into the intake system. Back in the day when only the cool kids had BOV it was due to recalculating pressurized air would back up and because a surge. Messing up your turbo : ( . Also at this time the only kids rocking them had lots-o-boost and lots-o-power. Then DSM kids discovered how to make the stock 1g recirculation valve make the mad tite JDM sounds like racecars! Then they discovered how leak valves worked and smashed the top so they open later (under more pressure). and thus the BOV.

If you are worried about surge I'd get a surge valve, it works like a BOV but only opens (and stays open) under surge. You just set it higher then your boost level and when you get compressor surge it pops open.

Side note: wheels are tires are a performance mod, but not if they are PEGS that are super heavy and not wide.

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You guys are so cute about this.

The CBV is located in a bad spot. A recirculation valve (the actual name for BOV's) dose the same thing, right back into the intake system. Back in the day when only the cool kids had BOV it was due to recalculating pressurized air would back up and because a surge. Messing up your turbo : ( . Also at this time the only kids rocking them had lots-o-boost and lots-o-power. Then DSM kids discovered how to make the stock 1g recirculation valve make the mad tite JDM sounds like racecars! Then they discovered how leak valves worked and smashed the top so they open later (under more pressure). and thus the BOV.

If you are worried about surge I'd get a surge valve, it works like a BOV but only opens (and stays open) under surge. You just set it higher then your boost level and when you get compressor surge it pops open.

Side note: wheels are tires are a performance mod, but not if they are PEGS that are super heavy and not wide.

speaking of cute...you spell "does" funny

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  • 2 weeks later...

If you are running higher than stock boost levels than you may want to look into a CBV rebuild kit from Quickbricks.com. The original stock diaphram most likely won't be able to withstand the raised boost level due to age(worn out). This kit comes with a new diaphram and 5 shims to allow a 20 psi set up. I purchased this because mine was leaking at 19psi and all I can say is that it does what is said, and install is very simple.

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to continue answering the question that was originally asked...

The richness cause as a result of the loss of metered air will result in some carbon build up in you exhaust system due to combustion occurring there. The likelihood of methodical damage to your CAT is also negligible (opinion only) because this occurs under low pressures and doesn't generate the kind of temperatures that combustion chambers create (compressed combustion). Your CAT is exposed to much higher temperatures based on spirited driving EGTs alone.

On an application such as a Volvo, nice as they are, they don't usually make GOBS of power, and thus, a BOV isn't necessarily more useful than a BPV. They are, for this application, pretty noises for you to listen to.

In a different application, like a 2006 Subaru STI, a BOV can provide a much needed RAPID venting off of pressure. I was having a problem with over-revving on up-shifts when my boost was not lowering fast enough THROUGH the BPV. I would lift at 6900rpm and RPM would jump to 7300(then immediately die down) due to the pressure not venting rapidly enough. After installation of a hybrid (~50/50 recirc/vent) valve, my boost declines rapidly upon lifting and I do not overrev on shifts any longer.

This adds HP to my car in that my car will continue to work in the future!!! When broken HP = 0. When operating HP = 350. My hybrid BOV nets me 350HP by keeping my car from eating itself!

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to continue answering the question that was originally asked...

The richness cause as a result of the loss of metered air will result in some carbon build up in you exhaust system due to combustion occurring there. The likelihood of methodical damage to your CAT is also negligible (opinion only) because this occurs under low pressures and doesn't generate the kind of temperatures that combustion chambers create (compressed combustion). Your CAT is exposed to much higher temperatures based on spirited driving EGTs alone.

On an application such as a Volvo, nice as they are, they don't usually make GOBS of power, and thus, a BOV isn't necessarily more useful than a BPV. They are, for this application, pretty noises for you to listen to.

In a different application, like a 2006 Subaru STI, a BOV can provide a much needed RAPID venting off of pressure. I was having a problem with over-revving on up-shifts when my boost was not lowering fast enough THROUGH the BPV. I would lift at 6900rpm and RPM would jump to 7300(then immediately die down) due to the pressure not venting rapidly enough. After installation of a hybrid (~50/50 recirc/vent) valve, my boost declines rapidly upon lifting and I do not overrev on shifts any longer.

This adds HP to my car in that my car will continue to work in the future!!! When broken HP = 0. When operating HP = 350. My hybrid BOV nets me 350HP by keeping my car from eating itself!

I have a 99 Volvo S70 glt with the lpt 13G turbo.

I have intake and exhaust and an st stage 2 tune. I plated off my cbv, and added a turbo xs bov. When I first installed it when I let off the throttle my car would die. I shimmed it up, and now it doesn't die, but it has turbo flutter at the lower boost settings....and everytime it blows off it fills the cabin with a horrible exhaust smell.

Any tips or ideas?

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  • 1 month later...

Just to be clear, a BOV doesn't add performance! A BOV is designed to help keep the turbo spooled and reduce stress between shifts when the throttle plate is closed. When the throttle is closed the compressed and metered air comes to a temporary halt which ends up pressurizing the piping which slows the compressor down until the throttle plate is opened again. In engines that have MAF systems like ours the metered air isn't routed to the atmosphere but rather piped back into the system. Think of it as air that has been accounted for. This prevents a rich condition as the ecu has already altered the duty cycle of the injectors to add more fuel. This is why you see MAF cars with atmospheric BOVs puffing black smoke between shifts or see a sooty residue on their bumpers above the exhaust.

A BOV ideally should be mounted close to the turbo where it can vent the pressurized air before it reaches the compressor. Look at any Pro drag car that's turbocharged and if it's done right they are running one or two BOVs close to the turbos 6-12". So BOVs aren't stupid on auto tranny car because it's serving a function. Just ask the sub 8-second 1200hp turbo cars that use powerglides if they are stupid.

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I thought this would be interesting to add in there. People claim that the BOV doesnt add performance. The link above is on a MS3 they just switch out the stock BOV for an Aftermarket. I know its not CBV to BOV but I thought this was an interesting Video.

So he had a boost leak they fixed it and the car made more power? HOLY SHIT! CANIHAZ2PLEEZ?

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