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  1. #26
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    great advice. thanks.

    Click here to enlarge Originally Posted by JoshBoody Click here to enlarge
    If you suspect a boost leak, really need to confirm hardware:
    1. WG vacuum... simple check is to correlate known WGDC to pump vacuum. For example 50% to around 25"Hg from the pump should yield maybe >16" (always higher then DC%). If you are close, prob good. If not then start checking lines... you can put vac pump on solenoid inlet line, cap the side not testing and cap the outlet to the booster with your thumb; any bleed should be very slow or none at all. Then check from solenoids to WG... again basically no bleed should be present. For solenoids you can isolate each one again referencing to WGDC at idle.
    2. Post turbo plumbing. Start with cap on IC inlet... I used pvc with tapped quick connect (Sniz DIY is good). Should hold 20psi with slow bleed... any leaks will be easily found. Unless its an obvious leak it doesn't have a huge effect on holding boost. Likely plumbing can be checked visually, while checking tightness of connections clamps. Tight worm clamp can have a hard to find, without compressor, slow leak but this does NOT greatly effect holding boost.
    3. DVs. Check vac tubing as mentioned. There's a couple DIYs on testing these with compressor. I just test with vac pump checking that diaphragm moves smoothly and holds vac.
    2011 335is DCT, moving to Italy, looking for new car friends Click here to enlarge

  2. #27
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    This car has stock DV and they worry me. I took mine off my 335i almost as soon as i got it. I'm going to talk the owner into some Forge DV soon Click here to enlarge

    Click here to enlarge Originally Posted by SCGT Click here to enlarge
    With a cobb flash I had trouble triggering a 30FF code despite diverter valve(s) that were sticking open and a car that didn't want to go past 5psi until I was at 4500+ rpm. I mean, I stood on it and it wouldn't throw a 30FF. It finally did it in 4th gear at around 130 mph, which took about 2 hours to get to at 5psi. Oddly enough, I had a vac line break right at a diverter valve months later and it threw a 30FF within seconds of me driving aggressively on the highway. Usually the ECU is good but there are clearly circumstances, however rare, where a significant boost leak will evade throwing a code for whatever reason for a lot longer than seems reasonable. This one, she is fickle.
    2011 335is DCT, moving to Italy, looking for new car friends Click here to enlarge

  3. #28
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    well, loaded up 20D and still underboosting.
    2011 335is DCT, moving to Italy, looking for new car friends Click here to enlarge

  4. #29
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    Click here to enlarge Originally Posted by zeel Click here to enlarge
    I've noticed this behavior where the first gear I start a pull with will be about 1psi under target and as soon as I upshift it will then be right on target. Currently on iso22 here.
    That is normal, including if you start a run in 2nd gear on higher powered cars. Turbos need some time to get up to target, however in 3rd gear it should hit target pretty much instantly.

  5. #30
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    Click here to enlarge Originally Posted by bigdnno98 Click here to enlarge
    well, loaded up 20D and still underboosting.
    cool, at least you ruled out the software then, time to go checking the vacuum lines / solenoids.

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