http://www.scoobyparts.com/acatalog/WRXSTEALTHFX.jpgGFB WRX STEALTH FX BOV - 1007
This fantastic GFB (Go Fast Bits) WRX Stealth FX BOV (Blow Off Valve) is a direct bolt-on replacement for New Age Impreza (2001 onwards).
Utilising a unique twist adjust feature allowing you to go from silent to ear shattering in a matter of seconds!
By utilising a unique air diverting system you control exactly how much air you dump to the atmosphere for noise, or the inlet for silence. By sending the vented
air back to the inlet (rather than muffling it), there is no restriction and the valve still operates at maximum efficiency. For cars with sensitive air flow meters, the valve can be tuned to vent just enough air back to the inlet to prevent backfiring whilst giving the loudest possible blow-off noise.


As this can recircultate as much as you like. If it was set to about 80% recirc and 20% atmopsheric would it benefit in any way. I don;t like the "Full on" Dump sound, but a subtle one would be nice when driving hard. Also would it help with spool up ect and reduce any turbo lag.

I have heard may reports that say a Dump valve will damage a Turbo and almost as may repots that say it wont and that it improves performance. So what is the truth ????????? after all the Rally car dumps atmospherically !

 

No it doesn't.

 

which bit are you referring to ?

 

WRC cars dont dump at all, they have a closed system and anti-lag.

If you use a vta, when it opens the car will over-fuel. It's already counted that air you just threw away so puts fuel in for it.

Over a long time this will foul the cats, if you have them. If you don't have any you can get pops bangs and the odd flame out the exhaust.

Some people claim that it will cause bore wash, but I'm yet to hear of an engine failure purely as a dump valve was fitted. IMO thats not an issue.

You won't get any performance gain as the std dump valve works perfectly well. It's all down to whether you like the noise or not.

 

I think the anti-VTA dump valve school of thought has been amply represented across many SN threads. Essentially if it ain't broke, don't fix it. Of course this doesn't address the issue that many people actually like the sound of a dump valve venting at full boost.

Anyway, I should imagine there is a boost level at which the factory recirculating dump valve either starts to break under the strain or can't dump enough of the charge quickly enough to do its job properly. However, I've no idea how much boost you'd need to run before you get to this stage. There seem to be a lot of people running 300 - 400bhp Scoobs on the standard valve. Mine runs 1.4 bar of boost and I've no problems with the factory dump valve.

 

As said earlier about the ECU already accounting for the air that is dumped, this is only true if you have a airflow sensor if you have done or are going to do any ECU work that will mean the car uses a Manifold air Apressure sensor then this is not the case. As the dump[ valve only works when the throttle is closed then surly the ECU will know that the throttle is closed via the TPS so would not inject fuel even though the airflow meter says a lot of air is sucked in. Can anyone else shed light on my last bit cheers Steve

 

It's not quite that simple.. The ecu knows the throttle is closed and it is fueling on over run, but it needs to keep enough fuel to keep the mixture rich enough to prevent detonation and keep the engine smooth. It fuels for this airfuel ratio based on various things including the air flow meter, which has given a wrong reading due to the dump valve opening.

The most common ecu upgrades at the moment are the Ecutek remap, and Apexi power FC. Both of which retain the MAF sensors function.

If you do use a map based ecu then the dv you use makes no difference.

 

btw 360ste, which impreza do you have? I live in lossie (not often there mind you) wonder if i've spotted you around.

 

Just for my own peace of mind - and cos I can't help it -

Why do these type of threads say ...thinking of fitting a dump valve.... or ... do dump valves work on these cars... etc ?

The car already has a d/v - all stock turbo imprezas have one. Surely it should be ...I'm thinking of replacing the dump valve....

For example, this thread states ....I've heard that dump valves will damage a turbo..... If anything, its quite the opposite....

A small point maybe (And I'm not having a go at anyone here), but it doesn't seem to be one that's addressed properly - I'm sure that a lot of people asking the question don't realise that the car is fitted with a valve already....

Mark

 

think thats a good point mark, ill be honest i didnt know untill a few months back that imprezas had a d/v already fitted

 

I think that its a selling point of the VTAs to be honest - the marketing tells you that the D/V is good for spool up etc - and that's true, but it doesn't tell you that the one already fitted on the car does all that already - except it doesn't hiss a lot !

I guess that some people like the noise - but I wonder whether they really like it, or are actually after a WRC type chirp - and this is as close as they get.

For the last six months of ownership, I ran my 98 UK without a D/V at all (Prodrive grp N inlet pipe, with no D/V takeoff) on a TD05. It ran fine, didn't hiss, didn't suffer on spool up and made a noise chirrup too... (Though the noise was incidental - I'm a function over form kind of guy...)

Don't get me wrong here, I'm not suggesting that everyone remove the D/V, but I wonder why no-one makes a VTA that actually makes the 'right' noise - or have the 'hiss' merchants made the general public think that this IS the right noise ?

Mark

 

Well then go away and read up on turbo cars!

http://auto.howstuffworks.com/turbo.htm

 

i ran with no dump valve for about a week and did not like it at all! the spool up on gear change was sooooo slow put it back on, mine didnt come with a standard one so put a vta i do like them, and i can drive in town without setting it off

 

I found that when I fitted a vta to my old sti 4, it was very jerky, especially if you 'feathered' the throttle.

 

Thanks for all the comments, very useful indeed. I have decided to stay with the Standard Valve.