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MTU series 2000 M94 Secondary turbos coming in and out?

Discussion in 'Engines' started by Cawley, Dec 17, 2019.

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  1. Pascal

    Pascal Senior Member

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    Every month or two, I take pictures of the Engine displays underway at the typical cruise RPM. I save them to a folder on my phone so I can spot trends over time. I guess you can do it the old fashioned way writing in a log .... but recording all pressures, fuel flow, load, boost is very helpful. Especially gear temps while are always the first sign that the cooling system need attention, before coolant temp
  2. Fiammetta42

    Fiammetta42 Member

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    Could it be a bit of radial play and or turbo bearing wear ?
    More so with the 2nd turbo in the sequence .....it can’t catch as easy as when it was new .
    A slight misaligned of just one bearing or two makes it hesitant reaching its full rpm /boost .
    This just gets ever so slightly worse and worse the rpms flicker momentarily until it’s overcome.
    Caused by basically oil heat soaking and baking , breaking down the oil .
    Begs the question on the actual oil used at service .This May be different to what’s appeared on the invoices .
    Last edited: Dec 18, 2019
  3. Cawley

    Cawley New Member

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    Good idea... I will make this part of my routine...
  4. Cawley

    Cawley New Member

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    We just the secondary turbo rebuilt.... No change... They did use the right oil because I saw the pales it came in. Thank you to everyone for your suggestions. There is a lot of useful info here. I will keep you all posted. Merry Xmas and Happy new year to all.
  5. Capt Ralph

    Capt Ralph Senior Member

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    The turbos are staged on inlet pressures per performance required. Anybody looked at the first turbos yet?
    If the primary turbos are bouncing around, on higher air demands they could be an issue also.
  6. Cawley

    Cawley New Member

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    Not yet, everyone focussed on the secondaries... I will bring this up at our next meeting with the techs. Thank you.....
  7. Capt J

    Capt J Senior Member

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    Is it both engines or just 1 engine? What does it do if you run it up on both throttles and not the synchronizer? Does one engine lag behind the other?
  8. Fiammetta42

    Fiammetta42 Member

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    Ah , would have been nice to have mentioned that in the opening post ....current state of play re what’s been chucked at it .
    In that case as per Capt Ralph it’s the primary’s bearings .I,am not familiar with the exact airflow routing .
    What causes the “ bearing bake “ now improper oil is eliminated......is excessive EGTs .
    This is more likely to be the first turbo .
    You are not imagining this btw , the turbo hesitation it’s typical of bearings on there way out .Obviously sequentiality mounted turbos just doubles the headache in definitive diagnosis.
    Not laptop will diagnose frying of turbo bearings .
    So what’s caused the excessive EGTs = overloads ......begs the question how often the stern gear has been cleaned before a good run out .Can you elude a bit of your stern gear hygiene routine ?
    You see the 24 knot cruise is poor if 1/2 loaded with fluids so it’s easy to push on with dirty / fouled sterngear from 21/22 knots back up to the regular 24 ......because it did 24 2 weeks ago or what ever .
  9. Fiammetta42

    Fiammetta42 Member

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    Additionally not mentioned is the ECU history .
    Need to know if anyone has messed around with the engine (s) ECU,s ?
    Sometimes with upgrades or reboots or programming adjustments and such like the tech empties the software from the master and slaves .....makes the alteration then up loads it all back .
    All is well and good at the first test no error codes etc etc job done .

    But occasionally there’s a glitch and this does not show up on the subsequent diagnostic software run by the tech investigating an issue .
    Which is what you might have here ?
    You know temporarily running outside a parameter at a certain rpm / condition reducing fuelling .....but the diagnostic software can’t see it after the ECU,s been messed with .Or reports “ implausible signal “ or such like which the tech dismisses?


    So if it’s not a mech turbo bearing it’s a hidden ECU glitch .
    So is there any tech ECU history stuff ?
    It’s not like the same techs are gonna be quick in coming forward with this either .
  10. f3504x4ps

    f3504x4ps Member

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    Cawley,

    Did you get a resolution on your issue, did you take 2" pitch out of the props as suggested, what about checking the primary turbos as suggested.
    Rich