The V8 Owners Forum -

not sure if I have fitted mine correctly or not,
BUT at idle its open and venting that correct?

Thats the only time I would expect to see this operating Tony. !!
Excess boost being dumped at low rpm.

Ta Pel

im reading conflicting stories regarding this valve,
Which way round should it be plumbed in?

should the boosted air be entering at the bottom of the valve under the writing (bosch) in the picture or the side port?

Judging by the construction I would assume that its air in the bottom and out the side.

It looks like a spring loaded diaphragm valve which I guess will alos act as a non return valve. Have you tried blowing into it?

well that's the way I have it connected,
reason I asked as others on forums I have looked on said they go the other way round and others have said this way round,

if I pull the vac line off while at idle while connected your way Pel the valve shuts, put it back on and it opens and vents,

others have said it goes the otherway round and the air pushes the valve shut and the vacuum opens it, bit confussed now

When under vacuum the valve opens, when under boost its held shut.

Have read you can have the valve either way round but think its normal to have the in at the bottom eg the same as a dump vale.

Any reason you have gone for a recirculating valve?

it came with the old charger Reg so thought may as well use it lol,
what are you using? bov?

Sorry!!
Have I mis read this??

Is this a dump valve or is it some sort of by pass valve?

How does this connect into the system?

I thought this was to get rid of excess pressure under low rpm conditions?

But then thinking about this again, what manifold pressure do you have at idle and low rpms?

Mine always runs in a vacuum at idle and low rpm until the engine is under load. When I do a burnout im still seeing vac in the manfold. It does not make boost until I load the transmission on the foot brake at 2000rpm. And even then its a max of 2-3psi.

Is there a vacuum signal pipe for this unit? I'm lost on this idea for a blower setup mate. Sounds like its something to get rid of turbo lag??

Hopefully one of the guys can shed some light on the need for this thing?

Pel

I am using a Forge BOV as there is no need to recirculate as we are not using air flow meter.

As soon as you shut throttle depending on the vacuum it will open valve to release any excess boost.

Don't think mine is open at idle but will check for you.

after asking a few questions, (thanks Phil)
it seems I don't need a recirc but just a bov,
any recommendations please? im new to this supercharging lark

single or double piston??

Manifold pressure either opens or closes the valve, with the assistance of spring pressure.

So boost goes directly opposite the signal line. And yes on a supercharged application, if your throttle blade is shut, then the air must have an escape path so as not to cause damage to the blower.
SC's dont suddenly stop moving air when you close the throttle like in a turbocharged setup.

Unless you want something fancy, just stick with what you have.

And in general, if you hear a fluttering noise when you close the throttle, you are not venting enough air, as the air is trying to go back out through the impeller.

As steve says you want to be venting any pressure that the charger is producing against your closed throttle. Turbo setups need them too as they will still produce boost against the closed throttle.
Even on my automatic setup - where you don't snap the throttle closed to change gear, I still found I needed one because the turbo's were producing more air than was required at mid throttle/cruise. You could hear the air making a funny noise as it rushed back past the compressor to the filters.

With the dump/bypass/bov/recirc valve you get air flowing out of that in situations where there is more air being produced than is required. I'm pretty sure my valve is open at idle too.

You typically only need to recirculate the air if you are running a MAF, also the OEM's do it to AVOID the "Pssttt" sound.

cheers Stevie/Elliot
im going to run the recirc for now as its in the pipe, I like the no psssst sound too so looks like it may end up staying lol,

Hi Tony,
I just have a dump valve with a filter on the end of it (Im not a teenager any more so dont want the noise) and this vents at idle. In fact it can be adjusted to be open until close to boost pressure, which is how I have mine.

One thing for certain is a dump valve is needed to get rid of the boost when you shut the throttle. A recirc valve wont react quickly enough I think.

Personally I cant see the point in a recirc valve unless you are using a AFM.
Phil