Chris Gregg

iTrader: (59)

I know, seems like a stupid question and I would agree. The BOV is installed and has been running for weeks. The Type-s has two vacuum lines coming out. I originally left the lower, smaller line open but noticed that the smaller line moved air while the engine was running. I plugged the line with a dead end vacuum hose and the car ran/idled a bit better.

Here's my issue though. The valve came with nothing that explained the two lines. Greddy's website fails to address this as well. I can't find information on this anywhere! What do I need to do with this second line? Is is supposed to hook up to something else? Why would Greddy put a second line for nothing? Is it supposed to be "Y'd" into the other line?

Any guidance would be helpful. Just wanting to make sure everything is hooked up and operating like it should. If no response, I'm just going to leave as is.

abci30

iTrader: (11)

the second port is to help the bov open quicker i believe. If you aren't running another vacuum line to it, i think it's supposed to be left open.

Chief Brody

iTrader: (2)

Yup, that's right. Except you would hook a boost only (pre throttle bod) source for the smaller port.

Chris Gregg

iTrader: (59)

Clarification: Does the second line 1. Get left open 2. Get a vacuum signal such as from intake manifold (when throttle closed) or 3. Hook up to pre-throttle body which is pressurized? If the original line is vacuum from manifold when the throttle is closed, then why would the second line be pressure from pre-throttle body? Please explain!

abci30

iTrader: (11)

whoops, thats what i meant. You can either leave the second port open or hook it up to a boost source. The second port is only to help the bov open quicker

Latinmax2

I have it run to the port on the SC. All it does is make it responde much quicker.

Chris Gregg

iTrader: (59)

Thanks for the quick response guys. Still interested in knowing why the larger line is for vacuum and the smaller hooks up to a pressurized line? Do both ports not connect to the same thing inside?

Latinmax2

No there is a diaphram in the middle so that when there is boost in the charge pipe then there will be the same amount of preassure on the diaphram to keep the BOV closed. When boost is gone (vacum) then the diaphram will allow the BOV to open. the additional line just provides boost on the other side to slam it open.

Chris Gregg

iTrader: (59)

Got it! Will remedy this weekend. Of course no issues, but would like to see if it affects response/drivability.

One more question: Is there any way to determine at what PSI the BOV is set to release? My Greddy is adjustable and I originally thought it opened about 5-6psi. However, recently upped boost to about 7-8psi and held that pressure. I can hear the BOV open when coming off boost/changing gears even at 5psi. So, how can I make sure it's set properly? Thanks again for all the feedback. There is not a good local source to refer to for this information and is my first turboed car...still learning!

Latinmax2

It just almost self ajust... not realy, but based on the example above. While there is boost on the other side the vacuum will never open the BOV until the boost is gone. I did not have to ajust the BOV and any boost.
I think the set screww will change the bleed off if you just leave the other line disconnected or to the atmosphere

Chief Brody

iTrader: (2)

BOV do not open up at at certain psi. Wastegates do that to regulate boost. BOV open when there is vacuum. When you shift gears and the throttle plate closes the vacuum opens the BOV diaphram. In this way the built up pressure in the intake tube has a place to go other than slamming back into the compressor.

The screw setting atop the type S is sets how "hard" or "soft" the BOV will operate. It really just adjusts the spring preload. The harder setting won't open as much as a softer. You want to find the sweat spot in the middle where it doesn't let too much air out, but doesn't cause any compressor surge--the fluttering sound.