Tips on installing HKS BOV in recirc mode? - struggling to get the thing to activate.

[Mike B]

Hi All,

 

Do any of you have any advice for correct fitting of these things - specifically which is the best vacuum point on the manifold to get the crispest (or any atm) activation of the BOV. Also any tips on the type of vacuum hose to use? I had a bit re-plumb and tidy up of all the vacuum systems (changed some routing and renewed hose) and even after fitting a brand new BOV, linked directly to the main vacuum pipe just behind the throttle body, I just cant get the thing to activate.

 

I had an old HKS BOV on the car which is wired up in re-circ mode to make it nice and quiet. I started to get a bit of noise through the turbo on throttle closing a while ago, so I stripped it down (it is old) and lubricated what I could - internal membrane was stiff but not breached - and I managed to get it to work for 2-3 drives and then it stopped all together. The internal bushings on the thing felt incredibly sticky. I then ordered a new one and fitted it at the same time I tidied up all the hoses and now... nada.

 

Is it possible that there are better takeoffs from the manifold than others?

Is it possible that my silicon hose is weak walled and collapses under vacuum? (it does feel pathetically flimsy)

Boost gauge is reading -0.8 bar of vacuum when the throttle body shuts under normal driving.

 

I'm scratching my head :-/

[np89]

Id just T it into the boost gauge line usually, if it still isnt dumping at that then I'd say the valve is gone or else there isnt enough pressure to open it. Some of the old HKS ones were adjustable and only opened at really high boost

[Mike B]

valve is ok, I have an old one and a new one to test - neither work.

cant see why there would not be enough vacuum in the manifold, -1 bar prob at peak. They dont open on boost though, only on lift off, which is quite the opposite, and why big boost should produce so much more vacuum, hmm.. I doubt it would be much more.

old bov was adjustable, new one is locked - I did try and adjust the old one.

I have new tube coming better qual, and I'll try some different locations.

[np89]

Yea but its a push-pull relationship. The vacuuming of the trigger tube signals the diaphram to open and by proxy the pressure within the system is able to push the valve open and escape hence the dump. I do agreee though, it seems strange. Are you testing it in the road and just listening for it to open or how do you know its not opening? A problem i had with 2 ssqvs on mine was that they leaked and never dumped because the plunger wasnt sealing correctly. They are an inferior valve as the components are plastic and warp and dont seal say in comparison to the greddy type valves that have metal components

[Mike B]

Yea but its a push-pull relationship. The vacuuming of the trigger tube signals the diaphram to open and by proxy the pressure within the system is able to push the valve open and escape hence the dump.

That is a good point - I had not considered that it was pressure sealing and the pressure itself was contribution to the way it was activating from the pressured side..

I can tell it's not working as I get compressor stall on throttle close - you can hear it clear as day. When it was working the system was silent.

I can only test it driving, spool is excellent so I'm sure it's sealing, just not releasing.

I will change the hose & change the connection on the inlet manifold, see what comes.