[sleeeper90]

I've been trying to do some tuning and work out some bov spring issues and come to find out I've got pretty low vacuum at idle, about -5hg, not enough to open the bov.. Does anyone know what a normal reading for vacuum is? I've got a Vargas vacuum adapter on the bottom of my throttle body and that's where I'm taking my reading and trying to run my bov from. I did a quick smoke test and really didn't see any action other than it coming back out of the turbo. I've been looking and I've seen a lot about bad pcv in the valve cover but isn't that like "unrelated' vacuum? And I'm thinking that the vacuum adapter would pull the same amount of vacuum from just behind the throttle body as if I were to drill and tap my manifold which I don't really want to do. Any thoughts on this or potential places to look that could cause low vacuum?

Thanks guys!!

[fastboatster]

there's not supposed to be much vacuum in the intake manifold even if there's no boost, the reason is throttle body is not used to regulate the airflow under most of the conditions - look up how the valvetronic functions. You need to use vacuum from the vacuum pump, there's a built in vacuum reservoir in the valve cover, you can splice into the vacuum hose for the exhaust flap.

[sleeeper90]

Are you talking about the vac line that comes off of the rear passenger side of the valve cover, it’s a hard line that then comes in front of the driver side strut tower? That had tons of vacuum when I tested it. But will that run the bov?

[fastboatster]

Yes, that’s the line I’m talking about. It’s up to you to find out if it has enough vacuum to run your bob

[sleeeper90]

Okay, yes. I can’t remember the exact number but it was over 20hg. Which would be more than the 18hg spring in my race gate. My understanding was that the bov needs vacuum/boost pressure to function and open and close with the throttle. If it’s off of the vacuum pump isn’t that only constant vacuum?