Ginerbolox

This dump valve is on the car I recently bought.
Now though it is really starting to annoy me,every time I change gear it goes off and people stare.
Does this thing actually have any benefit to the car or is it purely a noise maker?

Carlh

Reduce lag. My car has been mapped to a DV and when I changed my Forge one back to the original recirc I got all sorts of breathing problems with the scoob. Ive since changed it to a HKS and its a lot less noisy and sounds better too, buts its not cheap.

You could always buy a 2nd hand OEM recirc valve. What model and year have you got?

Ginerbolox

bugeye wrx my01

Ginerbolox

Car has not had a remap though.It is standard apart from the dv and a afterburner vortex system with decat pipe.
Been thinking about a remap,but only just got the car a few weeks ago.

Brun

I can see this being a 3 pager

performance sti

taken from scoobypedia

The dump valve is also called a blow off valve and air by-pass valve. Replacing your OEM dump valve with an aftermarket one is a common tunning mod. Some tuners claim replacement dump valves have the following benefits:

improves pick-up, through reduced turbo lag
sounds good when it vents to the atmosphere (read: loud)
helps regulate the boot pressure better than OEM valve

How it works

What a dump valve does is allow the pressurised air to vent, either to atmosphere (aftermarket values), or back through the intake plenum (OEM is a recirculating system - as per Impreza). This reduces the restriction on the turbo impeller allowing it to spin almost freely and therefore retain momentum. If you then re-apply the accelerator soon after (such as during a gear change) the butterfly opens and dump valve closes and the turbo still spinning at quite a high speed. It takes much less time to spin up to full boost and thus creates less lag. If the dump valve should leak it will not allow full boost to be applied to the engine.

Aaron1978

iTrader: (12)

Noise maker.

Source a OE one and bin it!

Oh and Brun, I see your 3 and raise you 4

Aaron

alcazar

iTrader: (2)

Not going to comment: apparently they are OK, according to the last know-nothing that posted about them............

midnight

iTrader: (10)

That is taken from scoobypedia describing the operation of a bov on a turbocharged car,what it has not taken into account is that a car equipted with a mass air flow meter measures the amount of air passing through it and the ecu compensates this by adding fuel.Once the bov has vented the air it is not in the system and the turbo will take a little while longer to spin up due to less pressurised air .

This explains it better ,taken from the Impreza Web Owners Club:

Dump Valves/Blow off valves (BOVs)


Firstly you have to ask yourself, "Why do you want an after market unit?" The Impreza is equiped with a satisfactory DV as standard.
The blow off valve does not increase performance. In fact the best performance increase can be gained by not having one altogether, the WRC cars do not run one.
BUT...
...the main advantage of the blow off valve is to reduce stress upon the turbo blades when you lift off of the accelerator to lets say change gear. The turbine is still spinning and thus pumping gas into the input...but the engine is off power. So what to do with the excess. A blow off valve set to a certain pressure releases this excess. A vent to atmosphere allows it to go to air giving the characteristic pfffft, a recirculating one feeds it back into the input of the turbo thus keeping the system pressurised. When you hit the accelerator the vented system then needs to momentarily build up the pressure again whilst the recirculating system doesn't.
Without a BOV the turbine can actually stall or air is drawn back through the wastegate in the wrong direction. The turbine is spinning but there are no exhaust gases coming out of the engine, so it either stalls or draws airthrough the wastegate from the exhaust side.This is the chirp you hear on the WRC cars. The stress on the bearings is quite substantial and in a completely different direction to that which the turbo is designed. The turbo in the WRC cars has a 360 degree bearing surface to counter this (and the turbo is changed and refurbished per rally if not sooner), the road going turbo does not.
After market BOVs are adjustable, and the pressure at which they blow can be set higher than standard which means that there is more pressure retained at gear change.... BUT how high can you go, what is a safe setting and will it ultimately shorten the life of the turbo?
The other reason an aftermarket BOV is selected is if the system is running more boost than stock and the stock BOV can not operate at the elevated levels.
Finally the main reason I can see a BOV is fitted is because people want that characteristic PFFFT! which probably loses them performance rather than gain it as they are dumping turbine pressure everytime they change gear. One other negative thing about vent to atmosphere BOVs is that the ECU monitors the air into the system via the MAF. This is in the input before the recirculating pipework reintroduces the gases back into the system. Thus the ECU takes into account this recirculated air in its calculation for fueling, and ultimately over fuels for a VTA-BOV and won't do the turbo much good or any following catalyst in the exhaust.

Personally i have fitted 5 different bov's to my impreza over the last 2 years: baileys,forge,gfb,turbosmart & a blitz,and in all honesty the car has run much sweeter with the std recirc on. If on the other hand you have your car mapped with one fitted ,then at least the mapper can compensate for the overfuelling.

astra_dave

iTrader: (1)

i've got a baileys unit on mine, and part throttle the car feels like its surging. its going as soon as i can afford to get rid of it

SpecDscooby

Does nothing but make a noise, is a personal choice thingy....imo.....but wait for it.....3 more pages to follow.....everyone has an opinion but in truth the only opinion that matters is the car owners......if ya like a woosh keep it on, dont....take it off!....

midnight

iTrader: (10)

+1 ,Your car ,your choice,good luck

alcazar

iTrader: (2)

Right! Go for it! Keep it! Dump that metered air straight to atmosphere!

After all, it's not like it could cause overfuelling, borewash or play havoc with any cats, is it now?

chopperman

Make's your car sound chavy.

Ginerbolox

Then if they do not benefit the car,what's the point?? . Its going ill buy a used one from ebay.Because to be honest its starting to pisshhhttt me off.Then put the baileys on ebay after i have fitted the OEM.