BOV

[EJL1985]

What is the second vacuum connection for, and what runs to it?

[zach-Ka]

One on top is vacuum ( top right nipple in the TB.) and the bottom needs direct boost... i.e. anywhere on your intercooler piping. I have the same BOV sounds great.

[EJL1985]

thanks!

[Justin35ll]

Just leave the bottom one unhooked. All it does is cause a leak

[zach-Ka]

Really! Im gonna have to test that.

[EJL1985]

should I at least cap it? or is it better to leave it open?

[Justin35ll]

Well hook them both up first. Then when the car is running put your hand over the part that the air blows out of and see if your hand gets sucked in by the vacuum leak while at idle.That's what it did on mine at least. So I just unhooked it and left the top one connected. It won't make a difference if you cap it off or not

[vr446]

Have the same sweet BOV too, and mine is unhooked for over 4 yrs now...so far so good no probs

[EJL1985]

it doesn't seem to matter whether it's open or not, so I'm just leaving it open! Does anyone have low RPM whistling coming from the BOV?

Well hook them both up first. Then when the car is running put your hand over the part that the air blows out of and see if your hand gets sucked in by the vacuum leak while at idle.That's what it did on mine at least. So I just unhooked it and left the top one connected. It won't make a difference if you cap it off or not

[Seishuku]

The bottom port is for faster boost release, only connect it if you are recirculating.Top goes to a vacuum/boost source, the bottom goes to a boost only source (hot or cold pipe).

What happens, is when the throttle closes, the pressure in the charge piping spikes and puts that pressure to the lower port, while the vacuum is being drawn on the top port, opening the BOV quicker.The down side is that you will no longer have the boost holding the valve closed (equal pressure on both sides of the diaphragm), so you have to tighten it up a lot more or put in a larger spring. It can also hold it open while under vacuum only, so you must recirculate it or run with a blowthrough MAF or MAP setup.

[EJL1985]

The bottom port is for faster boost release, only connect it if you are recirculating.Top goes to a vacuum/boost source, the bottom goes to a boost only source (hot or cold pipe).

What happens, is when the throttle closes, the pressure in the charge piping spikes and puts that pressure to the lower port, while the vacuum is being drawn on the top port, opening the BOV quicker.The down side is that you will no longer have the boost holding the valve closed (equal pressure on both sides of the diaphragm), so you have to tighten it up a lot more or put in a larger spring. It can also hold it open while under vacuum only, so you must recirculate it or run with a blowthrough MAF or MAP setup.

I understand, so if the valve is a door, then it's opening up too easily on the low pressure side. Unless you counterbalance the pressure on the weak side, it will open with little force.