I am currently looking into buying the Synapse BOV and in the instructions it calls for a VAC ONLY source and a BOOST ONLY source. I remember there being a vac only source on the back of the UIM but where?

 

There is a very easy to use vac source right next to the BAC.

 

Doesn't that also allow boost if BAC is removed?

 

pretty sure the lowest nipple on the back of the UIM (towards the firewall) is a solid vac source

 

When the engine starts boosting, all 'dem nipples be seeing boost pressure.

On a series four, the bottom nipple is the only one that is true vacuum. Series four have either three or four nipples one above the other at the back of the throttle body. The lowest one is the only one that will see Vacuum off the metal nipple. Series five I suspect are the same dealeo.

Aw. I'm four minutes late with this post.

 

Yea, that's for the oil injectors if I recall correctly. You will need to T it off if you plan on keeping your Oil Injection system. Didn't read the post correctly the first time I suppose.

 

Thanks guys BUT I did some research on the Synapse forum and the BOV needs a BOOST only source, not what I originally posted. The Vac source for the bov CAN be a vac/boost source.

Thanks for your help guys and....Hailers, you losing your edge bro?

 

The stock BOV gets its vacuum/boost from the nipple just aft of the BAC on a turbo series four. That source come directly off the rear primary runner. That source sees vacuum most of the time and boost if your boosting.

The lower nipple on the back of the throttle body was dedicated to the water thermo valve and is the ONLY one that ever sees vacuum back there. But it also sees boost when you ...boost. The other three NEVER see vacuum from the metal nipple, but see air from the front of the primary throttle plates. Even those see Boost if you Boost.

So think a moment about where the stock BOV gets its vacuum/pressure from.

IF you tee into one of the top tees on the back, and you have a boost gauge connected to that tee, you'll NEVER see vacuum on your gauge. Only boost.