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2.0EFi 'O' engine transmission transducer - what does it do ?

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  • 2.0EFi 'O' engine transmission transducer - what does it do ?

    I was delighted when I used my AR Speed Check for the 1st time (properly ) to see all the correct lights appearing. The transducer light showed that there was some issue with that unit. I recently changed the speedo cable and that fixed the previous one's habit of dancing around the speedometer it's still showing an optimistic reading, for example when speedo shows 100KPH it's actually only doing about +- 90KPH. Would the transducer be responsible for that ? The speedo cable goes directly to the traansducer. I do have a spare transducer. Any info or help much appreciated, Chris

  • #2
    I am quite sure that the transducer is only there to provide a road speed signal to the ECU, which processes it to allow fuel cutoff on the overrun under certain conditions. You should find a second shorter cable going from the transducer to drive the speedometer: all Maestros and Montegos with analogue instruments use a mechanical speedometer.

    Digidash cars have a speed transducer mounted on top of the gearbox.

    Incidentally, the transducer you have will not provide a correct signal to run a digital speedometer: I tried this on an MG Montego many moons ago and I seem to remember it over-read considerably.

    Your speedometer error seems to be just about within the +10% tolerance. Are you running the standard tyre size and how much tread is left on them?

    1983 (Y) MG 1600
    1985 MG EFi with digital dash (owned since 1987)
    1987 700 City 1.6 Van
    1988 Tandy camper 2.0D
    1990 Advantage, just 29k on the clock
    1990 Clubman D
    1990 MG 2.0i (spares donor)

    (all Maestros)

    Daily drive: Rover 25 GTi

    Weekend rave: Honda Civic Type R GT

    Current projects: Allegro 1100 deluxe, Maestro 1.3HL

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    • #3
      Originally posted by digital efi View Post
      I am quite sure that the transducer is only there to provide a road speed signal to the ECU, which processes it to allow fuel cutoff on the overrun under certain conditions. You should find a second shorter cable going from the transducer to drive the speedometer: all Maestros and Montegos with analogue instruments use a mechanical speedometer.

      Digidash cars have a speed transducer mounted on top of the gearbox.

      Incidentally, the transducer you have will not provide a correct signal to run a digital speedometer: I tried this on an MG Montego many moons ago and I seem to remember it over-read considerably.

      Your speedometer error seems to be just about within the +10% tolerance. Are you running the standard tyre size and how much tread is left on them?
      I've have an old/new stock transducer that I'll fit, I replaced the speedo cable as it was playing up. I run a standard tyre and they are fairly new, the oldest will have done 15.000kms and the newer less than 8.000kms.

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