Blow off valves

Hey everyone, im new to the website and proud to be apart of this. Now my question is, what is a blow off valve and what does it do for the car?Does it help performance wise or what? Do i need to add any thing else when you put the blow offf vavle in? Thanks https://www.thegalantcenter.org/styl...lt/biggrin.gif

Welcome to the club

Firstly BOV (blow off valves) are used in TURBO cars only

They are used to elimnate back pressure and keep the turbo spinning

If you havent a Turbo no point buying one as you can't fit it

welcome to the club and and nick is right about the BOV

There are actually 2 different kinds (BOV)

1) Blow off valve (BOV) = usually load and make very distinct sound

2) By-pass Valve (so technically not BOV) = this is what i have for my supercharger. doesnt make as much noise except for when i floor it and take my foot off the gause suddenly

when under boost, especially high boost, and you close the throttle plate, like when you shift, the air coming into the throttle body is suddenly shut off. so, you have a huge amount of air going nowhere. this sets off a reverse wave that goes back to the turbo, which is still spinning and pressurizing the intake. what happens is it tries to make the compressor wheel reverse direction immediatly, and it can damage the turbo.
the blow off valve is operated by intake vacuum, when the throttle plate shuts, vacuum is produced, which opens the blow off valve. compressed air in the intake then bleeds off back to the intake BEFORE the compressor, so no pressure wave is sent back to the turbo. depending on what type of metering system is used for air, like in the eclipse, which uses a karman type air mass sensor, this is air that has already been counted, and the ecu has made adjustments for. so, if it is vented to atmosphere, the car momentarily runs rich. the common symptom is the car will not idle and die.
i forgot to mention that with high boost, you need the bov to keep the turbo spinning, so when you get back on the gas, the turbo dont have to build boost back up. and then there is anti-lag

thanks for the info i thought i knew about BOV,, i guess i didnt

thanks

The best way to counter idle problems from atmospheric blow off valves would be to delete the MAFS with either a VPC or a stand-alone; 3-bar MAP sensor with an intake temp. sensor.

In all honesty if you are running any kind of air flow controller that is decent and has EIDS(I personally prefer the HKS AFR), you can minimize your idle problems if you set it right. Minimize is the keyword.

The Greddy Type-S sounds really good as well as the HKS Super-Sequential if you do plan on getting a BOV.

You can actually hear a few of them here:
http://alltrac.net/tuning/blowoffvalve.html

wait so i couldnt use an HKS SSBOV with a ripp supercharger?

that is a good question. i wonder if a different BOV can be used. mine isnt very loud. you can only hear when i really get on it and let off the gas

<div class='quotetop'>QUOTE(GTZ27)</div><div class='quotemain'>that is a good question. Â*i wonder if a different BOV can be used. Â*mine isnt very loud. Â*you can only hear when i really get on it and let off the gas</div>

how does the sound compare to a turbos BOV? does it have that same general sound? i know i'll be using a different BOV with my SC. prolly the greddy type-s.

face it, you just AINT gonna get much sound unless you are running more boost. a supercharger at 5-6 lbs probably doesnt even NEED a bov. sound is a secondary effect of the bov, the real reason for the bov is to avoid damage to the compressor. turbos spin a lot faster than superchargers. also, turbos are dependent on exh gasses to spin, so if the compressor gets slowed or stopped by backflow, it takes time to get back up to speed. the supercharger is driven off of the engine, it dont care if there is backflow, unless you are making lots of boost, but then, lots of boost would start the ole turbo vs supercharger, which is better.