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S3 BAM boost log - can anyone shed some light please

Ashy>> Dec 30, 2017

  1. Ashy>>

    Ashy>> Member

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    So i picked up an s3 just before christmas. Good price but noticeable low boost.

    logged it a few times and it pinpointed MAF to me as the readings never got above 100.

    bought a new bosch maf yesterday and it has made it a lot better but still not boosting as i expect.
    had a run out for 5 mins with laptop plugged in today and here is my requested vs actual boost graph.

    does this look like air leak or N75 valve?

    near the end of the drive it started boosting really well as you can see so im puzzled.
    engine was a brand new rebuild less than 10k ago along with a rebuilt turbo with receipts.

    [​IMG]
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    any input welcome
     
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  3. <tuffty/>

    <tuffty/> Badger 5 Edition...Its all about the flow... Staff Member Moderator Audi S3

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    Fault codes?

    Actual logs? the graph doesn't give much context... need to see the logged data in context of rpm/boost request to make any sense of it.. ideally a third gear run from 2000rpm to as much as you can safely/legally get away with

    <tuffty/>
     
  4. Ashy>>

    Ashy>> Member

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    cheers mate, i will nip out and log again with rpm. is there anything else i could do with logging at the same time?
     
  5. Ashy>>

    Ashy>> Member

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  6. Stuart B

    Stuart B Well-Known Member

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    is it stock map?

    isn't 1900 mbar 900 actual = ~ 12.5PSI ?
    and 161 g/s 161/0.8 = 201BHP @ 5800
     
  7. Ashy>>

    Ashy>> Member

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    Yes I presume it's a stock map, it just seems to be holding back quite a bit. I think I need to do some better logs tomorrow and look into it more.
    I have some more from today where the GS only goes upto 120
     
  8. Stuart B

    Stuart B Well-Known Member

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    Is it different with the N75 unplugged, I'm no expert, but that is about 6psi and 120bhp is like driving with a handbrake on.
     
  9. desertstorm

    desertstorm Moderator Staff Member Moderator VCDS Map User Audi A4 Audi Avant Owner Group quattro TDi

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    Looking at your logs it seems as if the engine is OK at lower RPM but is having an issue at the top end. Could be a fuel problem. Has the fuel filter ever been changed ?. The fuel pump may be on it's way out. You could try logging the injector timing. Also check the fuel trims to see what they are.
    Every time you clear a fault code on the ECU the trims are zeroed so you need to drive the car for a few miles to get a meaningful reading if you have just cleared some fault codes.
    http://www.audi-sport.net/xf/threads/how-use-vagcom-vcds-to-test-for-boost-vac-leaks.106699/
    Here's some logs from my Bog standard BAM TT if they are any use. Gives you an idea what boost and MAF readings should be on a good standard engine with no issues. This was a 3rd gear acceleration run .
     

    Attached Files:

    Ashy>> likes this.
  10. Ashy>>

    Ashy>> Member

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    @desertstorm that is excellent, exactly what I'm looking for.

    Except how do you get the timings so close together, mine only seems to log far apart of you know what I mean.

    Not sure on fuel filter, but will check tomorrow
     
  11. Ashy>>

    Ashy>> Member

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    Will also try with n75 unplugged tomorrow, cheers mate
     
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  13. desertstorm

    desertstorm Moderator Staff Member Moderator VCDS Map User Audi A4 Audi Avant Owner Group quattro TDi

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    I used the ME7 logger off Nefarious motorsports site. Great piece of software. I use one of the cheap £5 KKL VAG-COM leads I use to use with my Passat B5.5. Unfortunately it's not straightforward to use, requires some knowledge and tinkering to get it too work.
    With VCDS don't try and log too many things at the same time and click the turbo button for the logging to get faster logging speeds.
     
  14. Fordy51

    Fordy51 New Member

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    Log 031 for fuel request/actual.

    If not following each other then suspect a bad fuel pump.
     
  15. badger5

    badger5 www.badger5.co.uk Site Sponsor

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    80%^ n75 duty cycle for 0.5bar boost screams weak actuator/turbo/big leak issue
     
  16. Ashy>>

    Ashy>> Member

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    im in the process of making a diy leak tester so should be able to check for leaks soon. On the plus side I found that the 3 way valve on the side of the rocker cover was twisted together due to the bottom breather hose being too long and also the pipe was off the vacuum reservoir thingy ontop of the last coilpack.
    I think i have a definite boost leak somewhere still, i just cant find it
     
  17. Stuart B

    Stuart B Well-Known Member

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    you can delete the N249 (which is what you are describing on top of the rocker cover) that will at least rule out that jungle
     
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  18. Ashy>>

    Ashy>> Member

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    Thanks Stuart. Just found some silicon hose in the shed and deleted the n249 system. It has definitely made a difference for the better.

    Still going to do a boost leak test asap but It is miles better now
     

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