Searched forums, couldn't find much on this.

http://www.gofastbits.com.au/

"Leaking factory (BOV) valves: Some factory valves have systems designed into them to crack open at high boost, in order to protect the engine from boost spikes. They do this by designing the pressure to be unequal on the top an bottom of the valve, thereby overcoming the spring at a certain pressure.

If you are intentionally raising the boost level, this is bad news as the valve will begin to leak pressure. Examples of factory valves which exhibit this behaviour are the Subaru WRX MY95-98, and MY01-04, Mitsubishi Lancer GSR, and Nissan 200SX to name a few. Replacing these valves when increasing the boost is a good idea."

I thought (loud) aftermarket BOV's are a load of wank, we all know they don't do anything for hp but do some stock bov actually leak (on purpose) under higher than stock boost (due to mods)? Never knew this...

I'm just starting to mod my car but don't want to waste money...according to the aformentioned paragraphs, the stock bov in my MY00 will be fine...

Just wont be a "car that goes psssh"

Have most people got an aftermarket BOV regardless of other mods? Is it purely for show? Just seems to me it's a mod that is easy and cheap, adds no performance and one that the cops will take pleasure putting on a sticker for. Doesn't make sence!

Its for wank factor, if anything the car will run worse when it goes "PSHH".

Logically speaking, the car running worse has nothing to do with the fitment of a atmospheric-style BOV... as other's have stated, it's your tuning!

I believe that BOV are a good safety precaution (turbo cavitation protection). It's very difficult to totally prove how they effect outright performance etc, but as long as it works effectively, any brand- even factory will do IMO.

I know there's the age old debate about using or not using one... happens over and over on other forums! The usual argument is:

"I've been running no BOV for years with my TD05 and it's fine"... however, as soon as you point out what can happen to say a VF22 (bent and broken impeller blades etc) the usual reply is"

"yeah, well you'd have to be stupid to run a VF22 without a BOV.. those turbos are a lot weaker!"

Here lies the irony of their statement, they seem to be missing the point... all things being equal, a turbo doesn't just fall apart because it's just simply a 'weaker design', it falls apart because there's some bloody huge backpressures acting on the weaker designed turbo!
By admitting that some turbos cannot be run without a BOV only strengthens the overall argument of indeed using some form of pressure-bypassing device!! /rant off.

I've been using a gfb Stealth FX for a few years now. Great unit because they are designed well (acetyl piston rings etc), can be serviced locally- I get mine done approximately each year, are the largest diameter port in the range, and can run silent or vented to atmosphere. I generally run it closed, only opening for events as I find it gives 'audible feedback' as to where boost is etc at different throttle positions/ different corners etc.

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"...even my Grandma can drive fast in a straight line"

True, but there are negative affects

Use a modified stock BVP or an aftermarket BVP...
What is the function of a bypass valve (BPV)? To release pressure from the intake tract of a turbo car when the throttle closes. It is a vacuum-actuated valve designed to recirculate the air back into the intake before the turbo inlet, but after the airflow sensor.

There is no need to release to atmosphere, none at all

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Mazda CX-7
Mitsubishi Evo X MR

While most of us know the whole atmo thing is more for the BLING factor, some may argue that recirculating the pressurised air can often raise inlet temps. Eg- the charged hot air fed back into turbine compressor again is going to be warmer than uninterupted cooler air coming straight from air filter etc. Of course, this may not be that significant and so in either case the intercooler may take care of the added temperature... but it is a 'worthy' argument to investigate.

As I mentioned before, having an audible reference point (vented to atmosphere) can often reveal a few things I find useful out on the track.

As far as the negative effects... AGAIN I'll just re-iterate, this has nothing to do with whether a BOV is plumbed back or vented to atmosphere! It is related to your ECU and it's tune. So yes, fitting an atmo to your existing factory ECU setup will increase fueling... but if you had an aftermarket ECU, you can tune to suit open or closed... no need to blame it on the BOV!!!

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"...even my Grandma can drive fast in a straight line"

I wasn't aware it was possible to tune the BOV issues out. How can the ECU accommodate for the missing air? Was pretty sure that was impossible, but happy to be proven wrong.

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Mazda CX-7
Mitsubishi Evo X MR

Yeah will run rich if you still rely on factory computer and AFM.. .once u go MAP you can PSSHHHH alll you like.

In fact my car ran perfectly on MAP even with a totally burst intercooler pipe silicone joiner.

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[url]http://img514.imageshack.us/img514/6284/evobeatsstiug6.gif[/url]

you can modify the stock bov to not break open at high boost,
once modified they will hold endless boost and cannot leak.
this is mainly due to the diaphram design of the stock bov being back pressurised by the manifold.

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Long live the WRC

Is there a "Tuna Tech" update on this? Would be a good mod. I have heard the Rally Guys have been doing this for years.

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Speak to Shane @ SMC Tyres, Unit 6/385 Sevenoaks St Beckenham WA 6107. Mobile 0413 128 087. Tell him Maddog sent you!

stace - when would you mod you BOV say like past 18 pound?