Silencing the Atmo Blow off Valve

[Ronin 09]

I am interested in putting a switchable system in the car, whereby by switching a solenoid a valve will effectively 'turn off' the BOV. Why - as my HKS SSQV is hidden behind the bumper, if i am stopped by cops then i can switch off the BOV avoiding defect.

Some basics on BOVs:

BOV is triggered by a boost feed from the inlet manifold, when idling or accelerating, the pressure on both sides of the throttle are equal, therefore the BOV remains closed. When there is boost and the throttle is snapped shut, there is vacuum in the intake manifold vs. boost on the turbo side, therefore the BOV opens.

So, if I can install a vacuum hose that always sees turbo side pressure, and have the BOV feed to be switchable between the inlet manifold side and turbo side vacuum hose pressures, then when

1. it sees the intake manifold pressure it will operate

2. it sees the turbo side pressure it will remain closed at all times.

My questions are:

1. is this actually possible (switchable in cabin)

2. where would i take the turbo side vacuum hose from?

3. does anyone know if i can get a switchable valve ie. a t-piece that can be electronically switched so it is possible to switch between the inlet manifold side and the turbo side pressure hoses?

4. does anyone actually understand what i am talking about?!?!

Thanks, and I hope that is clear!!

[cameron]

dont think its possable ?

i think the incabbin switch is out of the question ?

correct me if im wrong ?

[BHDave]

You can fit a Tee in the line that gives the bov a signal and a tee in one of the lines coming off the comp cover and link them with a solenoid in the middle. Switch it open/closed as required and your valve wont open when the solenoid is open as it will be seeing the same pressure on both sides of the piston.

This is fine if you have a factory airbox which will muffle the sound of reversion.

If you have a pod you will hear the lovely reversion flutter which may be louder than your bov anyway.

So basically, yes you can do it but it may not be worth the effort.

[BHDave]

You'd also need a solenoid in the bov line that is open when the other one is closed and viceversa to maintain the positive pressure at the bov when you want to deactivate it.

[dojobi]

Another option would be to get a GFB Stealth FX and rig up something that would adjust it. NFI how to do that though.

[Guest RedLineGTR]

nah the GFB Stealth FX u have to adjust with your hands. even if the cops see a bov with a trumpet they will assume it vents to atmosphere. but if they cant see it then they get u to rev it and hear nothing u will be in the clear.

Try mucking around with different hoses etc see what the car reacts too. But i've seen cops find bov in bumpers, hiden behind airboxs etc..so they might find it anyways.

[dojobi]

So there's no way you could mod the SFX to be electronically adjustable with a solenoid? I'm just tossing up ideas really. I'd have no idea at all how to do it.

[Guest INASNT]

a even easier option - get a plumb back bov with the rice effect

[Ronin 09]

Try mucking around with different hoses etc see what the car reacts too. But i've seen cops find bov in bumpers, hiden behind airboxs etc..so they might find it anyways.

What gives them the right to feck about with whats under the hood? If they change something that makes it defective, isn't that just dodgy as hell? I wouldn't be letting any cop mess with hoses under the bonnet... In a diplomatic way of course.

[Guest RedLineGTR]

i dont mean the cops to mess around with hoses..i mean for you too...to see which hoses may stop the bov from venting etc.

But i've seen cops find bov in bumpers, hiden behind airboxs etc..so they might find it anyways.

[Ronin 09]

oh sorry mate :confused:

a friend of my mechanic thinks there is an easier option - i'll post it when i get to speak to him.

[riceline]

Hey mate - have you managed to find out about that other option yet?

[JimX]

Isn't the defect for the bov just for the fact that it's installed, not for whether or not it's doing anything? Either way I'm sure the cop would just assume it was there and working, if they saw it, even if you tried to prove that it was off.

[Ronin 09]

riceline - the guy is still on holidays.

JimX - i want to do this more for if i get RBT'd, or i see a police car in traffic, then i can switch it off and hopefully not draw any (more) attention.

[JimX]

Ah fair enough. I'm lucky that my bov doesn't go off at low boost, so whenever I see a cop I just drive sedately and he hears nothing You'd also have to do an indepth search to find it, so if I did get pulled over I don't think I'd get done (touch wood).

[Ronin 09]

yeah well mine is behind the front bar, just under the headlight (basically a mirror of where the factory cooler would sit). You can just see it if you're looking for it

[AutoTrust]

Ronin 09 go and see a LPGas workshop and get a high flow solenoid, fit this in-line on the existing vac/boost hose to your BOV. When energized the BOV will operate normally when swiched off the bov will cease to operate. I'm sure this would work..... Give it a go!

[Ronin 09]

Danny, don't you need to show the BOV line the same pressure as what the diaphram is seeing (ie pressure of the intake pipes) to keep it closed? I'm not sure what you mean by the high flow solenoid being energized..?

[AutoTrust]

I thought so too, but if you get a set of pliers in one hand and squeeze the hose on the BOV while revving the motor with the other you get no psssshhhh, let the pliers off and rev...psssshhhhh! if you fit a highflow gas solenoid to this hose when it has no power the solenoid is closed so there will be no pssshhh. when you power it up (energize) the solenoid opens and allows the BOV to operate normally. so you would use an ignition power supply via a switch to the solenoid and the other solenoid wire to earth. Make sense??

[Ronin 09]

yes mate, thanks.

will give it a go