[pjr710]

I’m chasing 30ff someone mentioned my DV valves. I realized i dont fullly understand how they work. I replaced vac lines, boost solenoids, and did a pressurized boost leak test from intake onward with DV return ends capped off. I didn’t hear any leaks.

I guess this gentlemen’s thought was my DVs May not be holding the boost (not leaking from the connection point.

So I’m wondering how do our DVs work? And also what told do the vacuum lines play on them? Because doing the pressurized boost test the car was off (so not under vacuum) which i wonder would affect their function.

[tylerboland01]

When the throttle shuts vacuum is generated in the intake manifold, pulling the DVs open which recycles the pressurized air in the charge pipe back into the intake. This prevents backflow through the turbo aka turbo flutter.

[pjr710]

Originally Posted by tylerboland01

When the throttle shuts vacuum is generated in the intake manifold, pulling the DVs open which recycles the pressurized air in the charge pipe back into the intake. This prevents backflow through the turbo aka turbo flutter.

that makes sense but isn't vaccuum constantly applied to them anyway since they are connected to the main vacuum pipe/lines? That's what I get confused on

[Sbar]

Just a thought as I was recently chasing the same code around, check your charge air pipe just under the air box if you haven't already had it replaced. Mine blew off recently upon very light acceleration (about 2500rpm). I noticed it when I was replacing the vacuum lines that go over the top of the engine and behind the oil cooler. Couldn't get the thing to stay connected but found that I had an extended warranty by BMW for 10 yrs or 120K miles. Replaced it for free, did another recall, and cleared all the codes. Runs like a stuck pig again!

[arkie6]

Originally Posted by pjr710

that makes sense but isn't vaccuum constantly applied to them anyway since they are connected to the main vacuum pipe/lines? That's what I get confused on

No. The "vacuum" line to the DVs is connected to a nipple on the plastic intake manifold. It is separate from the vacuum lines downstream of the vacuum pump. That DV line senses pressure between the intake valves and the throttle plate. At idle there is weak to moderate vacuum there. As the throttle plate opens, the vacuum signal gets less and goes to positive pressure under boost which holds the DVs closed. With moderate to high RPM and the throttle plate abruptly closes when the throttle is lifted, high vacuum exists in the intake manifold allowing the DVs to dump excess boost pressure back into the turbo inlets.

[TemjinX2]

the dv's themselves have rubber gaskets. Theres another thread where someone found some rubber gaskets online thats the same size as oem and replacement. I believe there around $0.20 each...worth a shot to replace as well.

also check the vaccum cannisters, there known to leak over time as well.

[pjr710]

Originally Posted by Sbar

Just a thought as I was recently chasing the same code around, check your charge air pipe just under the air box if you haven't already had it replaced. Mine blew off recently upon very light acceleration (about 2500rpm). I noticed it when I was replacing the vacuum lines that go over the top of the engine and behind the oil cooler. Couldn't get the thing to stay connected but found that I had an extended warranty by BMW for 10 yrs or 120K miles. Replaced it for free, did another recall, and cleared all the codes. Runs like a stuck pig again!

yea mines good I pressurized the system and didn't hear any leaks at all.

Originally Posted by arkie6

No. The "vacuum" line to the DVs is connected to a nipple on the plastic intake manifold. It is separate from the vacuum lines downstream of the vacuum pump. That DV line senses pressure between the intake valves and the throttle plate. At idle there is weak to moderate vacuum there. As the throttle plate opens, the vacuum signal gets less and goes to positive pressure under boost which holds the DVs closed. With moderate to high RPM and the throttle plate abruptly closes when the throttle is lifted, high vacuum exists in the intake manifold allowing the DVs to dump excess boost pressure back into the turbo inlets.

Hmm ok .. so yea the nipple they connect to from the drivers side is throwing me off. But yea if it's a separate system then that makes a lot of sense.

So in that case .. if i pressurized my charge pipe with DVs on and return lines capped off to 6PSI and it held like a champ .. my DVs are good to go then right?

Originally Posted by TemjinX2

the dv's themselves have rubber gaskets. Theres another thread where someone found some rubber gaskets online thats the same size as oem and replacement. I believe there around $0.20 each...worth a shot to replace as well.

also check the vaccum cannisters, there known to leak over time as well.

yea everything else is good. I think my actuator arms are the culprit

[TemjinX2]

are you tuned? are you looking at your logs?

[pjr710]

Originally Posted by TemjinX2

are you tuned? are you looking at your logs?

I’m not tuned. I am looking at Mhd monitoring logs. From what I’ve deduced my wgdc hits 100 and boost builds slow

[TemjinX2]

Originally Posted by pjr710

I’m not tuned. I am looking at Mhd monitoring logs. From what I’ve deduced my wgdc hits 100 and boost builds slow

do you ever hit your boost targets?

[pjr710]

Originally Posted by TemjinX2

do you ever hit your boost targets?

Here’s my latest pulls. I didn’t hit 30ff https://datazap.me/u/pjr710/no-30ff-logs?log=0&data=5-6-15-23

I can make 30ff happen whenever i want it’s a mix of rpms, gear, peda positon. I can “hack” my way around it as you can see with those logs.

I do hit target but you can see it takes a bit of time. And i don’t believe that is the norm from what i have researched.

[TemjinX2]

Originally Posted by pjr710

Here’s my latest pulls. I didn’t hit 30ff https://datazap.me/u/pjr710/no-30ff-...data=5-6-15-23

I can make 30ff happen whenever i want it’s a mix of rpms, gear, peda positon. I can “hack” my way around it as you can see with those logs.

I do hit target but you can see it takes a bit of time. And i don’t believe that is the norm from what i have researched.

hmmm...your right..you seem to have some kind of boost leak...its taking way too long to get near your boost targets.


if you have a aftermarket charge pipe, check your connectors...if you have extra silicon hoses, you can try bypassing the vaccum cannisters to see if they helps. Some times the vaccum cannisters will develop leaks over time.

[pjr710]

Originally Posted by TemjinX2

hmmm...your right..you seem to have some kind of boost leak...its taking way too long to get near your boost targets.


if you have a aftermarket charge pipe, check your connectors...if you have extra silicon hoses, you can try bypassing the vaccum cannisters to see if they helps. Some times the vaccum cannisters will develop leaks over time.

I adjusted my actuator arm and fixed the 30FF code!

https://datazap.me/u/pjr710/3rd-gear...5-6-9-15-23-24