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01-18-2015, 09:16 PM | #1 |
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oem dv leaking at idle
Hey guys, I'm running oem DV vent to atmosphere and I've noticed that at start up and idle they are blowing air, at start up its bad to the point where it feels like a fan and then when the car warms it they leak, if you put your hand you can barely feel it. Here's a picture with a shop towel that I placed in the front, you can see where the towel is being blown compared to the right side. Is this normal or did I damage them running higher boost.
https://flic.kr/p/qRDLzr
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01-19-2015, 01:23 PM | #3 |
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I bet your vacuum res lines are melts near the valve cover/solenoids area.
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01-19-2015, 09:08 PM | #6 |
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+1
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01-19-2015, 10:17 PM | #7 |
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Which plug exactly? Also if it was sucking air, why when I put a paper or small towel it blows out rather than suck in? Because at start up it blows like a damn fan haha
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01-20-2015, 06:45 AM | #8 |
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I may have viewed the picture wrong. If you're venting to atmosphere, you need to cap the hole where the flex tube from the DVs plug into the recirculation plumbing. I assumed you felt the air rushing out of those holes. Is the air coming out of the DVs?
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01-20-2015, 09:54 AM | #9 |
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Those holes are plugged, both of them, and yes the air is coming out if the dvs, I can feel it on both of them at start up and idle, unless they were to close when I hit bpost and then open up when I let off?
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01-20-2015, 07:43 PM | #10 |
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Perhaps a video would help illustrate your problem better?
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01-21-2015, 07:36 AM | #11 |
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Engine is sitting in a vacuum state at idle, so it's normal for them to be pulled open at idle. Once you get on the throttle at all they should seal right up. Completely normal. I was concerned about this with the BOV on my M3, until I put all the pieces together and it makes sense.
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01-21-2015, 02:15 PM | #13 | |
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01-21-2015, 05:21 PM | #14 |
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^
The fact the manifold is in a state of vacuum is what has me puzzled? I would expect to feel air being sucked into the open DVs. I may have to pull my DV hose this weekend and see if it blows air at cold start-up. |
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01-21-2015, 05:50 PM | #15 |
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However one thing that would make sense is that they are open and im feeling the air from the turbos spinning at idle, because at cold start they blow alot! (I.e because the turbos are spinning faster) can you try it and let me know
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01-21-2015, 08:29 PM | #17 |
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Yep. Intake is pulling vacuum on the diverter diaphragm, thus opening it. Air from the turbos blowing into the throttle is escaping through the valves..
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01-21-2015, 09:03 PM | #18 |
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Wait no, because the way diveter valves open is when boost forces them to open after boost can't go into the TB, thus oping the valve, if vacuum is opening them up, how is that working since the valve can't be opened from sucking the valve in, that wouldn't make no sense because how would the air be going out yet have enough vacuum to open the valve up
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01-21-2015, 09:37 PM | #19 | |
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01-21-2015, 10:13 PM | #20 |
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hmm? boost pressure is what opens them up, when boost needs to escape it is either shot out or recirculated back into the intake, or i am wrong, unless a dv works differently than a bov
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01-21-2015, 10:50 PM | #21 |
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When you lift off the throttle, the throttle plate shuts but the engine still acts as an air pump creating suction (i.e a vacuum in the space between the back of the throttle plate and manifold). This vacuum opens the DV. Since the turbos are still spinning and creating boost, the open DVs allows the boost to recirculate through the intake system or in your case vent to atmosphere. If the DVs did not open, the boost would slam into the face of the closed throttle plate and cause a pressure wave to bounce back against the turbos' compressor wheels causing them to slow or even stop. This can seriously damage the turbos.
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01-22-2015, 02:18 AM | #22 | |
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