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Overboost but not overboost

Discussion in 'TD5' started by tom1979, Jun 18, 2022.

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  1. tom1979

    tom1979 Well-Known Member

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    I can get the MAF eliminated from the equation quite simply but would not want to just take the easy route to mask a problem. I know the limiters in EU3 maps use the AAT which Nanocom does not see.
     
  2. sierrafery

    sierrafery Well-Known Member

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    The AAT is used only for smoke limiters it can't cause your symptom and if it was that unplugging the MAF would have had no effect, as long as the problem goes away by unplugging the MAF the problem is on that path
     
  3. tom1979

    tom1979 Well-Known Member

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    This is taken from a well-known source. It shows the turbo overspeed limiter.
    turbo overspeed.JPG

    I will try and run some data logs (if the Nanocom doesn't have a fit before I hit save!) and see what airflow readings I am getting.
     
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  4. sierrafery

    sierrafery Well-Known Member

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    Yes, i forgot about that, though if you take that formula apart as in the complete article you'll see that the AAT has effect in the air flow ratio calculation ... though you might have a point and be the first i see who has an issue with the AAT with that symptom, take a log and if the MAF reading never drops to 0 while the symptom occurs then eventually unpin the AAT wire(green/blue) from the sensor's plug and see then... would be a revelation
     
  5. tom1979

    tom1979 Well-Known Member

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    I am clutching at straws a bit to be honest but a faulty AAP sensor which incorporates the AAT can't be ruled out - I have never changed it. I'll try and catch it in a log at some point and go from there.
     
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  6. sierrafery

    sierrafery Well-Known Member

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    You gave me some food for thought with that AAT thing which is a good point even if very uncommon... i'm watching now with interest the outcome but the brute logic is that if the symptom is caused by turbo overspeed protection due to wrong AAT input it should occur with unplugged MAF too as the default for MAF open circuit should not disable the overspeed protection as the fuelling goes to a kind of Eu2 calculation and there is overspeed protection in that ecuation too without AAT involvment .... though the reality might contradict that logic, fortunately the 4 pin AAP/T sensors are affordable compared to the 3 pin AAPs
     
    Last edited: Jun 23, 2022
  7. tom1979

    tom1979 Well-Known Member

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    I would also expect some sort of recognition in the ECU fault codes that the overspeed protection had occurred but then it does not go into full limp mode which you don't always get a logged fault for
     
  8. tom1979

    tom1979 Well-Known Member

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    I’ve tried several times today and the fault has not reappeared o_O
     
  9. sierrafery

    sierrafery Well-Known Member

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    If it was with MAF connected then i'm affraid it can be a bad contact somewhere or intermittent boost leak and that's a nightmare to troubleshoot :(
     
  10. Discodevon

    Discodevon Well-Known Member

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    Any luck tom?
     
  11. tom1979

    tom1979 Well-Known Member

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    No mate, but I did notice on Friday when I was rummaging around that my ITG air filter had seen better days so I chucked a cheap paper filter in.
     
  12. tom1979

    tom1979 Well-Known Member

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    Little update, sort of... The ITG air filter I took out looked a bit grubby so I put a cheapo paper air filter in and plugged the MAF back in. Fine for a day but then yesterday started playing up again so I unplugged the MAF again and no problem since. Given it has had two new VDO MAF's I reckon it's probably the wiring. I do have a spare engine sensor loom but for now I will just keep the thing unplugged.
     
  13. sierrafery

    sierrafery Well-Known Member

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    You really need to save a log from a drive with MAF connected to catch the symptom on file cos if the air flow drops to 0 from above 600 under load then i doubt that the problem is with the wiring... or at least let nanocom connected and watch the air flow live on instrument mode when the symptom occurs... though that AAT thing is still something to be ruled out if the MAF reading is normal cos once the MAF is unplugged the default is a kind'a Eu2 fuelling which neglects the AAT input
     
  14. tom1979

    tom1979 Well-Known Member

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    I have a log from yesterday and I noted the times it did it, but it was captured using the app on my Android head unit and it records the raw values so I will have to convert them all. https://github.com/hairyone/TD5Tester
     
  15. tom1979

    tom1979 Well-Known Member

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    I could not link from our server - here is the Excel spreadsheet on WeTransfer : https://we.tl/t-ja7vGUPe8d

    The issue occurred at around:
    0944hrs
    0954hrs
    1008hrs

    It is not a very clear set of data when you're used to the Nanocom!
     
  16. sierrafery

    sierrafery Well-Known Member

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    You are right, i can't figure out much from there :confused:
     
  17. tom1979

    tom1979 Well-Known Member

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    Little update....

    I was thinking along the lines of pedal problems as I have just once had a driver demand fault logged. I was sat with the Nanocom playing with the pedal and bingo, "Problems detected with driver demand (logged)". The readings I have got are:

    Acc Way 1 0.759v (3.9v when pressed)
    Acc Way 2 4.301v (1.256v when pressed)
    Acc Way 3 4.682v (1.202v when pressed)
    Acc Supply 5.020v (5.026v when pressed)

    There are slight variations in the above, but looks like it could be the pedal ?

    Taken from a previous @sierrafery post I believe good readings should be:
    ACCEL. WAY 1 - about 0.3V with the pedal released, about 4.7V with pedal to the maximum position
    ACCEL. WAY 2 - about 4.7V with the pedal released, about 0.3V with pedal to the maximum position
    ACCEL. WAY 3 – this track must have values very near to the second track.(only 15P-16P engines)
    ACCEL. SUPPLY – this value must stay between 4.9 a 5.1
    * an up to +0.5V for WAY 1 and -0.5V for WAY 2 are accepted
     
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