Thread: BOV Question *searched* NEED HELP!

*I did search...but couldn't find the exact answer I was looking for.*

I am running a BB motor, 10PSI, with a draw through MAF (I know ) and a Greddy Type S BOV. Now, this is sort of a two (or more) part question.

1) Someone mentioned to me that my car has a lot of compressor surge. I know it does...would this have anything to do with my BOV being recirc? I mean, is it to restrictive to let all the pressure out?

1a) Would it be better to just run the BOV atmospheric?

2) I noticed today that the upper nipple () on the BOV (on the purple part) doesn't have a vacuum line. So, I looked up an installation guide and it says that there MUST be a line there running to Manifold Vacuum (I.E. after the TB). Would this also be a cause to my surge problem?

2a) Where can I run that vacuum hose to? (pics would be helpful)

Thanks, in advance, for anyone's help. All helpful tips are appreciated!

Absolutely your problem.

Your BOV is not opening at all because you don't have a vacuum signal to the correct nipple.



Once you do that you'll be in better shape. If compressor surge does not go away completely, adjust the screw until it does.

1. Normally you wouldnt have compressor surge at 10psi. I think what is the problem is that your BOV is not adjusted properly.

2. You can run open but it will run a bit rich during shifts when draw through.

3. That smaller nipple is for increased BOV response. it doesnt need to be hooked up

I think that's the only one he has connected.

Thanks for the info. But looking at the above picture, the top nipple is the one that isn't connected. I know that the bottom one doesn't need to be, but it is.

BenFenner, thanks for the pic. That's very helpful. I'm going to take a closer look at the vacuum line routing when I leave work and see where that lower hose is actually going. But where is the best place to run the upper hose to? Is there like a spot that "everyone" uses? Like a common manifold vacuum line?

Thanks agian guys.

you need to connect the larger nipple to a source that sees both boost and vacuum. There should be either a place to connect it to on the IC piping or the manifold.

Yeah, I'll take a pic when I leave work to clarify. But that is correct.

Ah, ok. I'll take a look. Thanks.

Pretty sure it must get a vacuum signal from inside the manifold, after the throttle body. If not you won't get the pressure differential needed to open the BOV properly. You can't just connect it to a source in the IC piping.

On my USDM engine I put a "T" vacuum fitting into the line that runs from the manifold to the charcoal canister for my BOV and wastegate signals. Seems to be working just great.

Top nipple to boost/vac source (before throttle plate, mind you)

EDIT: To clarify, before throttle plate should probably read "after" the throttle plate. Run your signal from the vacuum line for the fuel pressure regulator.

Bottom is not necessary and hardly used, unless you have extremely low vacuum to begin with.

People tend to confuse themselves with BOV's and WG's. WG's dont use the top nipple, unless they're using a boost controller.