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    Thread: VR6 Turbo Help?

    1. Member Roadhog_'s Avatar
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      1993 VW Corrado
      06-22-2015 12:27 AM #1
      Looking for some help with my new build. I seem to be having a few issues. Here is the rundown of what setup I have.

      93 VW Corrado, OBD2 swapped.
      UM #42 tune
      Precision 6262
      8.5:1 CR
      DRC 268 Cams
      Bosch 044 in tank
      Bosch 42# injectors
      3 bar fpr
      Water injection

      The first problem I am having is what seems to be low vacuum during idle. Only showing about -6 to -7 inHg. I'm pretty sure I don't have any vacuum leaks. I sprayed some carb cleaner around all the joints with it idling, then tried propane and the idle never changed any.

      The next issue is during idle the afr will slowly rise up to around 15-15.5 and it will start to idle a bit lumpy, for a few seconds, then the afr will drop back down to around 14.5-14.7. Rinse and repeat at random.

      Lastly, and my biggest concern is the in boost afr. It seems to run lean at lower boost pressures, around 7 psi, but seems to be about normal at higher boost pressures of around 15 psi. Also, seems to be lean at lower rpms too, and rich up top.

      Here are some logs I did of some third gear pulls. I am spraying water only with the smaller snow performance nozzle.


      Here is a photo of the setup.


      And a little video.

    2. Member suffocatemymind's Avatar
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      2003 Jetta Wolfsburg 20vT, 1994 Dusty Mauve Jetta 8v (sold)
      06-22-2015 07:31 AM #2
      I would pressure test the intake (see 1.8T FAQ, good write-ups in there) and spray every connection with soapy water. Make sure you connect your tester pre-turbo (but after the MAF) since your connection to the turbo inlet may not be perfect. This test will diagnose boost and vacuum leaks much better than squirting carb cleaner everywhere.

      I would then test for pre-primary O2 exhaust leaks with Seafoam (again, 1.8T FAQ has a nice write-up). It's a really easy way to see the leaks. Any leaks before the primary O2 can fuddle your tune.

      Once you've confirmed that you have no vacuum/boost/exhaust leaks, then start looking elsewhere. Performance cams will yield less vacuum at idle than stockers, so you're probably not gonna see 20 in/Mg. Injector seals? Fuel pressure? How's your pump?

      This should give you a good place to start.
      -Derek
      APR 93 | ITG | MMEvoDV | 034 Silicone + Catch Can | EuroSport 2.5" DP | BFI Stg 1 | BKR7EIX | NewSouth | VCDS | Bentley

      Stock(ish) been there, done that.

    3. Member NOTORIOUS VR's Avatar
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      D3 A8 4.2 - E36 Turbo
      06-22-2015 11:13 AM #3
      MAF sensors are very, very sensitive, especially with larger housings where air velocity is reduced and piping before and after has been changed and sub-optimally setup/positioned.

      The first thing that stands out to me is you have a 90 deg bend pretty much after the MAF and absolutely nothing on the front except for the filter right on the larger housing, universally that is pretty much the worst thing you can do on a MAF based setup..

      I would suggest you start by adding around 6" of straight pipe to the front of the MAF housing and then putting the filter on the end of that and see how it goes.
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    4. 06-22-2015 11:46 AM #4
      Have the same cams 15-15 hg is my normal. No leaks though.


      Pressure test the system, check the manifold flanges, also the injector seals. I've even checks the brake booster hoses. Seen leaks just about everywhere. Also the #42 file runs lean on low boost under 14 or so, that's just how it is. Lets see the engine bay, pictures tell 1000 words. Might be able to see something wrong.
      "I admit that I'm often...vexed by the behavior of my own people..." - Huey Freeman (The Boondocks)
      GTS Performance

    5. Member Roadhog_'s Avatar
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      1993 VW Corrado
      06-22-2015 02:11 PM #5
      You guys have been a great help so far! I pressure tested the intake system this morning, found a bunch of leaks. Most were fixed by tightening some clamps. The largest one was a large split vacuum line off the intake manifold. There's only one left that is a very tiny weld pinhole, which is so small it shouldn't cause any issues for now.

      Went for a little drive, runs SO much better! There's no more rev hang between shifts, and the throttle response is much better.

      Still have low vacuum at idle. -7 inHg. I need to put a manual gauge on it and see if its my gauge or what. Or the gauge reads psi in vacuum.. It's an aem truboost.

    6. Member suffocatemymind's Avatar
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      06-22-2015 04:38 PM #6
      Nice
      -Derek
      APR 93 | ITG | MMEvoDV | 034 Silicone + Catch Can | EuroSport 2.5" DP | BFI Stg 1 | BKR7EIX | NewSouth | VCDS | Bentley

      Stock(ish) been there, done that.

    7. Member Roadhog_'s Avatar
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      1993 VW Corrado
      06-27-2015 11:18 PM #7
      Having a few more issues it seems.

      First off, if you shut it off when the engine is hot, then go to restart, sometimes it will start for a split second, then stall and flood itself. Any attempts to restart after this will just cause worse flooding. If you stall the thing, you are also flooded.

      Last issue is still the lumpy idle. It will idle fine at 14.5-14.7 afr, then randomly jump up to 15-16 afr and idle rough for a few seconds, then go back to 14.5-14.7 afr. This seems to repeat over and over at random.

      I have a new MAF, new CTS, new Oxygen sensor, and new FPR.

    8. Member
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      06-28-2015 12:21 AM #8
      Quote Originally Posted by Roadhog_ View Post
      Having a few more issues it seems.

      First off, if you shut it off when the engine is hot, then go to restart, sometimes it will start for a split second, then stall and flood itself. Any attempts to restart after this will just cause worse flooding. If you stall the thing, you are also flooded.

      Last issue is still the lumpy idle. It will idle fine at 14.5-14.7 afr, then randomly jump up to 15-16 afr and idle rough for a few seconds, then go back to 14.5-14.7 afr. This seems to repeat over and over at random.
      i
      I have a new MAF, new CTS, new Oxygen sensor, and new FPR.
      The idle issue is common with running turbo chip tunes with the M5.9 ECU ,only standalone will rid this issue. Your not the only one...look at 2.0 Ho's - "Anyone else have problems with mis-fire at idle once warm - VR6 Pro Maf Setup" thread, and i myself and others have this issue too.

      Never had flooding issues like your's , try moving the DV discharge as close to the turbo inlet as possible and move the maf as far away possible.

    9. Member Roadhog_'s Avatar
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      1993 VW Corrado
      06-28-2015 12:36 AM #9
      Quote Originally Posted by 12V_VR View Post
      The idle issue is common with running turbo chip tunes with the M5.9 ECU ,only standalone will rid this issue. Your not the only one...look at 2.0 Ho's - "Anyone else have problems with mis-fire at idle once warm - VR6 Pro Maf Setup" thread, and i myself and others have this issue too.

      Never had flooding issues like your's , try moving the DV discharge as close to the turbo inlet as possible and move the maf as far away possible.
      That's unfortunate. I wish I knew of the issue before buying the tune.

      I'll have to see if I can somehow get the DV discharge closer to the turbo. Might work since it will un-flood itself and start with the maf unplugged and the throttle open.

    10. Member Roadhog_'s Avatar
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      Yesterday 02:14 PM #10
      Still having a hot start issue. Seems if you hold the throttle wide open if it fails to start it will fire after cranking for about 5 seconds. Have no ideas what could be causing this. :| If the engine is cold, it fires right up without even touching the accelerator.

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