barrywayne

okay i was told that i could hook the boost gauge bov and wastegate up to any vacuum line, well i have all 3 hooked to the same vacuum line and my bov isnt opening and my boost gauge is only reading vacuum not boost. can someone help me please, and it is on a d15b7 so i dont have a huge selection of vacuum lines to choose from.

Fabrik8

Who told you that? That's like saying you can install a car alarm by tapping into any wires on the factory harness.

All vac lines are not created equal, and they aren't attached to the same locations. There are some on the intake manifold side of the throttle body, some on the valve cover, you get the idea. You want the boost gauge to come from the intake manifold somewhere, the BOV to come from the intake manifold somewhere, and the wastegate to come from the piping between the intercooler and the throttle body. You can also come off of the turbo side of the piping but then the wastegate won't compensate for pressure drop across the intercooler.

barrywayne

well i see where i went wrong then i have all the lines coming off of the intake mani instead of just the boost gauge and bov. damn, well ill try and figure out a way to do that. thanks man

Fabrik8

Hopefully you didn't destroy your wastegate by hooking it up to manifold vacuum. If you aren't building boost, the gauge wouldn't read any boost (obviously) and the BOV would open but you wouldn't be able to hear it because it wouldn't be venting anything.

barrywayne

Okay, so I took the wastegate line and hooked it in between the intercooler and tb and it works and I kept the boost gauge and bov on the same vacuum, and the boost gauge and wastegate work but the bov still isn't opening. Could it be because the bov spring is stiffer then the wastegate spring??

Fabrik8

The BOV doesn't really work the same way. The wastegate works off of the pressure difference between the atmosphere and the intake piping, so it regulates boost (which is just pressure above atmosphere). The BOV works off of the pressure difference between the intake piping and the intake manifold, so it opens when throttle plate closes (manifold vacuum). That being said, there are a few things that can affect whether the BOV works properly or not.

First, there is often a preload adjustment that changes how much pressure difference there needs to be on either side of the BOV actuator/diaphragm before it opens (one side is the intake piping, the other side is the vac line port). So that preload adjustment could be set really high, and in that case you wouldn't have enough boost and enough vacuum (at the same time) to get the BOV actuator/diaphragm to open. Go to the website of whatever brand you bought and look up the procedure for setting that. Some vendor websites have that info too, so see what Google comes up with.

Oh, try to stay away from Tees and things like that on the BOV vac line. Tees are often pretty small inside, and don't do great things for pressure drop. The boost gauge doesn't need any flow to make it work properly, but the BOV does. It's kind of like electricity. Something that draws current will make a voltage drop across a wire that is too small, but it doesn't matter with a voltage gauge or multimeter because it takes a really tiny amount of current to make them work. No current draw, no voltage drop. With the vacuum line, no flow means no pressure drop.

Second, make sure the vacuum line going to the BOV is not too small and not too long, because that can make a lot of pressure drop and can affect how well the BOV works. That's not generally an issue though, because any vac line that properly fits on the BOV nipple and isn't strung all over the engine bay is generally more than adequate. The preload adjustment is the likely cause of your problem.

barrywayne

Okay, i opened up the bov to find that it had 2 springs inside of it instead of just one. Now i tried adjusting the preload spring and it goes from one extreme to another, the bov either opens to easily, or its too stiff and wont open. My bov and boost gauge are both tee'd into the same vacuum line so from what you are saying, the tees are restricting the airflow to bov and not allowing it to work properly. im not sure what to do because my intake mani doesnt have but like 2 vacuum lines