Just wondering. I've had mine hooked up after the TB, but someone was saying it needs to have a pressure source from in front of the TB, which is it?

If it was before the TB it wouldn't ever open, right?

 

Needs to be AFTER the TB.
If it goes before the TB, it will never open.


-Ted

 

K, that's what I was thinking too, just wanted to make sure I was right.

Thanks!

 

Well, if you've got a fancy BOV (such as the Greddy S), that has two nipples, it can use both, but most often BOV's will use the one AFTER the plates (this is, that when the plates close, it creates vacuum, which helps open the valve), the Greddy's have an extra nipple on the bottom that uses boost as well to push the valve open, while using vacuum at the same time.... Just in case anybody was wondering....

 

And if you try and use the bottom fitting with the stock AFM with the BOV open-vented, you just created an intake leak. :P

Don't bother with the lower fitting if you're going open vented.

You should try and blow into it and hear where it comes out.


-Ted

 

Where's it come out? Mine didn't leak at all, not that I used it, but on my mitivac it wasn't leaking any air

 

what do you mean by after the throttle body? like on the upper intake manifold? shouldnt it be between the intake side of the turbo and the throttle body so that bostt from the turbo that gets shut out by the throttle body can leave through the blow off valve?

 

That's where the BOV should be, but I was asking where the vacuum line for the BOV should be plumbed to.

 

It comes out the discharge?
Were you "sucking" on it or pressurizing it?


-Ted

 

Pressurizing, wouldn't doubt if it's clogged or bent or something, it was used and for free, so I can't complain.

 

oh okay, this thread makes sense again. i mustve missed the 'pressure source' part the first time.

 

Nah, you gotta "suck" on it.
Intake leak problems are usually under vacuum, so you gotta suck on the fitting.


-Ted

 

Haha, got a point, I figured the purpose of it was to have boost press on it, so that's all I tested

 

Yeah, under boost, the + pressure is supposed to keep the valve from opening, but it still leaks (well, unless mines was not supposed to leak in the first place?).
I assumed this was only for if the BOV discharge was plumbed back into the intake when you're using an AFM.
I tried to hook mines up (GReddy Type-S, JDM black top though ), and the car wouldn't idle. :P


-Ted

 

BOVs use vacuum in the intake manifold to know when the throttle plate is closed... because closing the throttle plate creates vacuum (more sucking from the engine than can get around the closed or almost closed throttle) and a restriction of air that could go back into the turbo, and thats why we have blow off valves - to let the pressure go somewhere so the turbo doesnt get potentially hurt by it.

So yeah, now you know how it works