Speedo correction after leader gear install

Discussion in 'Z32 Technical' started by Mitch, Apr 14, 2019 at 9:21 PM.

  1. Mitch

    Mitch Has one gear: GO

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    I've installed a 4.1:1 final drive gearing to the R230 (Leader gears). Speedo now reads approx 10% higher than actual speed (110km/h on speedo is approx 100km/h actual).

    What's the options for correcting the speedo? I'm running a TT 5 speed gearbox.
    1) Will a replacing a NA speed sensor work (not sure if these are a different tooth count, or even if interchangable at all?)
    2)Can I modify the speedo cluster with a suitable potentiometer to modify signal?
    3) Is there something off the shelf to correct this, while maintining a factory look? (no HUD type speedos)
     
  2. Fists

    Fists Well-Known Member

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    1 definitely works, just swap the plastic gear on the sender or the whole sender if easier and you're done. The cluster does have some capacity for trimming the output but I'm not sure how far it goes.
     
  3. rob260

    rob260 Moderator Staff Member

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    NA speed sensor but big $$ if new. And you have to buy the cog separately...

    I don’t think the cogs are interchangeable but don’t quote me.
     
  4. Fists

    Fists Well-Known Member

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    Hmm, the senders always looked identical to me but looking at their listings with different part numbers maybe there's an offset for the different gears.
     
  5. Mitch

    Mitch Has one gear: GO

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    Interesting. I did look at the sensors, and they are quite pricy.
    Any ideas if it's a 0-5V DC signal to the speedo, or some kind of funky PWM?

    There is a black box solution at Jaycar that will intercept / modify a speedo signal, and only $40, so might be a good option.
     
  6. Chrispy

    Chrispy Pretentious Upstart

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    I understood it to be a square wave output. NA gear or that Jaycar box sound like the way to go.
     
  7. J3bba

    J3bba He Who Struggles

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    Pretty sure it works by pulse. As the sensor gear rotates it goes in and out of continuity causing a pulse signal. The faster the pulses the higher the speed.

    Best and simplest bet would be a black box style thing.
     
  8. MagicMike

    MagicMike Mod and Event Coord [QLD] Staff Member

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    The old 300km gauge faces, some came with a trimpot to wire in to correct the reading.

    I did always think an NA cog swap worked, but I have it in my head that they chew themselves up over time. Some ki d of misalignment issue. Can't confirm however.
     

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