How to test a turbo gate transducer ?

Discussion in 'Engine' started by Tony Russell, Sep 3, 2009.

  1. Tony Russell

    Tony Russell Active Member

    Messages:
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    Jul 21, 2009
    Location:
    Glasgow ish.
    Car:
    Vaneo. 1.7CDi. I know. Stop laughing ! I need an MPV and it had to be Mercedes. OK ?
    Hello,
    This regards an electrical component, but since it's sole purpose is to control the turbo, I'm posting it in here.


    There's a wee electricity to suction converter, a transducer, which controls the gate on the turbo in the diesel Vaneo / A-Class.
    It sits just under the brake fluid reservoir.

    I had mine replaced the other day, the only test being that it was swapped with one off another car, that worked, so it must be faulty. And this prognosis was quite correct - as it solved all the problems in a oner.

    There's only two terminals on the beast, so I'm thinking it's a fan creating a vacuum and this is merely voltage controlled by the ECU - the feedback being in the turbo or elsewhere ?

    Anyway, I'd have presumed the test was to apply a variable voltage to said terminals up to 12v, and note any increase in suction, if at all.

    Thing is, mine seemed to have been intermittently failing, then catastrophically , then kind of coming back.

    I'm going to open it tonight and do some testing (I have a new one fitted and it's going a treat), just wondered if anyone else had any comments on how they work, how to test etc.

    thanks,
    Tony
     
  2. lynall

    lynall MB Enthusiast

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    Location:
    Kent
    Car:
    The silver one.
    Without looking at it i would say its just a solenoid valve ie the vac is provided by the cars own vac pump and when told to the solenoid valve is opened thus activating the wastegate cylinder.

    Or it may work of the engines boost pressure and again opens when told to.

    My old TD5 worked on the boost system, so basically a small pipe from the main intercooler pipe to the sol valve to the wastgate, ecu provides power and the wastegate activates.

    This is meant to be more accurate than running straight of the boost pipe ie no valve and stops the wastgate creeping open.

    Be careful as a lot of stuff controlled by the ecu operates at 5 volts.



    Lynall
     
  3. OP
    OP
    Tony Russell

    Tony Russell Active Member

    Messages:
    139
    Joined:
    Jul 21, 2009
    Location:
    Glasgow ish.
    Car:
    Vaneo. 1.7CDi. I know. Stop laughing ! I need an MPV and it had to be Mercedes. OK ?
    Thanks for that Lynall.
    Didn't get around to opening it this evening. I'll get peace to do it tomorrow :)

    What you say makes perfect sense, since it looks to be fed off the main vac loop.

    Lovin' this thing now - kind of dipped my diesel and electric cherry and it's actually dead simple.



    Tony
     
  4. alexander patie

    alexander patie Active Member

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    sunny suffolk
    this part is actually a modulating vacuum valve working on pulse width modulation, quite a complex bit of kit after all ;)
     
  5. lynall

    lynall MB Enthusiast

    Messages:
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    Location:
    Kent
    Car:
    The silver one.
    Everythings dead simple when you know how and a little bit of googling:)

    Many many cars have similiar systems if not exactly the same.

    Pulse width equals length of elec pulse to the sol valve?



    Lynall
     
  6. alexander patie

    alexander patie Active Member

    Messages:
    606
    Joined:
    Aug 15, 2009
    Location:
    sunny suffolk
    pulse width moulation is a very clever way of regulating power supply without ballast resistance and consequent heat problems. also PWM can infinately control power instead of in steps.

    for instance the heater blowers inside cars use pwm to control blower speed, old systems had coiled wire ballast resistors placed somewhere they could keep cool. on cdi engines the m55 port shut of motor, pressure control valve and turbo wastegate all use pwm. on ME engines the throttle bodies use PWM.

    the basic way to think of it is a pulsing signal at, say, 50hz (i do not know exactly what hz they tend to use). the signal is square wave, with 12v when on and 0v when off. the signal on time vs off time is varied to control power supplied to compnents. eg an on time of 2ms and an off time of 18ms = around 11%, whereas an on time of 19ms vs an off time of 1ms = about 95%. the ecu will display the pwm out put of components like eg the pressure control valve on cdi engines in this on time% format when lookin at live data.

    i hope all that makes sense, i have not googled it though, so forgive me if i have got anything wrong. most of my info has come from hobbies and education with a large amount of specific MB info from wis-net.
     

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