Forge BOV

GTI-R Nath

New Member
hi was having a look at my car tonight and noticed that my BOV is open when the car is idling, is this meant to be like this ? i would of thought is should be closed at idle

i just took it apart to have a look and is got the Blue spring - 14-16 psi and the cars running 1 bar boost
 

skiddusmarkus

Active Member
It will make your car run like crap.I had a leaky old HKS one years back and once swapped for a new SQV I must have regained 50bhp that I'd lost.

Is the spring knackered?Forge are pretty good at replacing things like this for free.
 

Gaz gtiR

New Member
yes its normal thats how they used to be on my old renault 5 turdo's. it stays open to equal out the air flow on idle as there is equal preasure at vac side & boost side to draw air in to your inlet as your air filter is goes to your turbo & has a big boost circuit to get round so cos ur not on boost & theres minimum persentage of air getting threw on idle it sources it when your dump valve is open! then it closes when your driving as the preasure from your turbo is forcing it shut so you dont lose boost & your getting a sufficiant percentage of air threw your inlet! if it was open when driving & u were losing boost it would be down to a sticky piston or ripped diaphram in your dump valve.

as an N/A car your air filter is close to your inlet!
 
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PobodY

Moderators
Staff member
Do you have any issues with a high idle? It shouldn't really be open because that's letting unmetered air back into the inlet manifold; I had a Bailey one that was doing that, and replacing it fixed my idle issues.

Really it should only open when the pressure of the boost on one side plus vacuum on the other is enough to pull the piston back; if there's no boost at idle then the spring should hold it closed.
 

GTI-R Nath

New Member
It will make your car run like crap.I had a leaky old HKS one years back and once swapped for a new SQV I must have regained 50bhp that I'd lost.

Is the spring knackered?Forge are pretty good at replacing things like this for free.
iv just took it apart cleaned it and re greased it and everything looks fine inside
 

GTI-R Nath

New Member
I had a look when i put it back on, and noticed that the big silver piston opens at idle but the small plastic one stays closed, so it isn't actually open even tho it looks open
 

PobodY

Moderators
Staff member
That's exactly what it's supposed to do! - It's the single piston ones that tend to cause problems.
 
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