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Thread: 451 CDI too much boost

  1. #1
    Join Date
    Mar 2012
    Location
    Burnley
    Posts
    1,135

    451 CDI too much boost

    I seem to have eventually cured my problems apart from a recurring "check turbocharger" error. Most informative as usual for Star.

    When I got the car the wastegate arm was unfastened and I cannot find any instructions about how to set it correctly. I can boost to 2.6 bar, that is one atmosphere and 23 psi so way over what it should be.

    This only throws a fault on a long pull up a hill at which point the engine goes into safe mode (no engine light). It resets with an off/on of the key.

    Everything I read tells me that the ECU will learn over a few miles if the wastegate arm length is adjusted but this seems not to be the case.

    Next step please.

  2. #2
    Join Date
    Apr 2013
    Location
    the Netherlands
    Posts
    210
    Adjust (without preload) the arm, so the end( part with a hole in it ) is in line with the wastegate-axle.
    Now turn the end of the arm (part with the hole in it) 4 full turns, so the arm is getting shorter.

    try it out.
    If limpmode occurs , turn each time 1/4 or 1/2 a turn back (so the arm getting longer).

    I hope this would help.

  3. #3
    Join Date
    Nov 2007
    Location
    BANCHORY
    Posts
    3,018
    Yes, too much preload on wastegate actuator.



    Above photo shows turbo and wastegate actuator on my 450 Cdi. When I had overboost problems I reduced preload exactly as explained by Ossy in post above.

    Preload spring pulls rod towards the left keeping wastegate valve closed. Turbo boost pressure pushes rod towards the right once it has balanced out the preload.
    Drives a Smart Cdi - 65 to 85 MPG

  4. #4
    Join Date
    Mar 2012
    Location
    Burnley
    Posts
    1,135
    It is a total dog to get at on a 451. I have to spend some time working up to it, I have misplaced my double jointed fingers and wrists.

  5. #5
    Join Date
    Mar 2012
    Location
    Burnley
    Posts
    1,135
    So I got under there and adjusted it. Set it to three turns and it is worse than it was before for going into limp mode. Not had Xentry on yet, I think I will not bother but will just set it to two turns. I am not really bothered about getting all it can give so whatever stops the safe mode is good enough for me.

    I would like the boost to come in a bit earlier but probably wishing for the unobtainable with that desire.

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