revhrdls

1 Why does the Greddy type-S BOV have two ports??? what's their purpose?

2 Where's that link for the Special on the Greddy oil catch can under 90???

Mikex25

I wonder that my self also

DirtyLude

It's a push pull type BOV. One of the ports goes to a boost source before the throttle body, one goes to a source after the throttle body. The vacuum pulls it open while the boost pushes it open.

DirtyLude

Okay, since you asked for more info.

My car has been in for a rebuild for the last 3 weeks. From what I remember the top port is vacuum and the bottom port is boost.

You can test it. Get a vacuum line and idle your car, place it on the top port and pull it off. You should hear the plunger pull up and drop back.

You can hookup one or the other, or both if you want. The BOV should be filtered, since at idle and the vacuum line is connected, it's wide open and most of the idle air will be pulled in through the BOV instead of through the turbo.

The bottom port on mine is hooked up to the port off of the turbo compressor.

TurboInteg95

I dont think the BOV will work without the top port hooked up to vac. the bottom port is a vent. Think about it, if there's a diaphram in there, there has to be a vent for it to work properly.

DirtyLude

Huh? I have no idea what you're talking about with a vent. It's sounds like you think when not using one of the ports you block it off somehow; you don't, you leave it open. The top port gives access to the top of the diaphram and the bottom port gives access to the bottom of the diaphram.

The top port hooked to vacuum will pull on it from the top. If it's the only thing hooked up, that's all it gets is pulled on and the plunger opens, fine. If the bottom port is hooked up to boost, it gets pushed on from the bottom which opens the plunger. Both ports where exactly the same, but from two different directions.

If you only hook up the boost port the BOV is going to work like a normal BOV. It will only open when boost reaches a level to overcome the diaphram spring and let out the extra air. If you only hook up the vacuum the plunger is pulled open whenever there's enough vacuum in the plenum, which means whenever the throttle plate is closed or almost closed while the car is running. The two work well together, but can work seperately as well.

TurboInteg95

What are YOU talking about? you are confusing two ideas, you'r talking about a popoff valve and a blow off valve. When using the Type S as a BOV you hook the top port up to vac and the bottom port is a vent, it does not need to be hooked up to boost. In any sealed system where a diaphram is present one side has to be vented or else it will not function properly. It would be like blocking off the top port of a wastegate. Hooking the bottom up to boost is pointless.


[Modified by TurboInteg95, 9:38 AM 10/13/2001]

DirtyLude

The instructions that came with my Type-S BOV where very clear. The bottom port even has a bead specificly for connecting to a 4mm line. If this port was not supposed to be hooked to anything this obviously would not be the case.

Hooking a boost source to the bottom port DOES NOT BLOCK THE PORT. I don't understand your reasoning behind this. Air still gets in and when hooked to a boost source it acts very much like a pop off valve, blowing the plunger open while the vacuum pulls it open. The only way this possibly could be a hinderance is if you somehow had vacuum coming from your turbo port fighting the vacuum from the plenum.

I understand that's it's not needed to hook up the bottom port, but it does help and doesn't reduce the effectiveness of the BOV at all, in fact it aids it.


[Modified by DirtyLude, 1:29 PM 10/13/2001]

TurboInteg95

a pop-off valve and blow off valve are two completely different things. a popoff valve is used to prevent overboost or in extreme cases I've seen it used in place of a wastegate. I will say it again, in the case of a BOV, the top gets hooked up to vacuum and the bottom port is left open. Who here hooks there bottom port up to boost?