Speedo correction after leader gear install

Discussion in 'Technical' started by Mitch, Apr 14, 2019.

  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 Moderator 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.
     
  9. Zeo

    Zeo Active Member

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    I have some info somewhere about applying a square wave, changing resistors etc. I will see if I can find it.
     
  10. JT

    JT Track Addict

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    You need the NA speed sensor and NA gear. I think its a red gear from memory, different colour to the TT one. Did this years ago and my speedo is spot on.
     
  11. East Coast Z

    East Coast Z Well-Known Member

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    Agree with JT.
    Replace the TT sensor & gear with NA items, simplest & easiest solution.
     
  12. beaver

    beaver southern zeds

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    Or you could just use a speedo corrector, cheep, easy install, matchbox size, auto calibration.. that's if the na bits prove elusive.
     
  13. MagicMike

    MagicMike Moderator Staff Member

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    I have it in my head that the NA sensor/gear has a marginally different length/location of the gear, which can chew up the plastic gear when used in a TT box.

    Happy to be wrong, been a long time.
     
  14. rob260

    rob260 Moderator Staff Member

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    Did some reading on tt.net.

    The pinion axle is offset on the TT sensor, which allows the the two sensors to be interchangeable despite the two pinion gears being different sizes.

    So in sum using an NA pinion gear on a TT sensor will result in the gear being offset incorrectly, which is probably what leads to premature failure.

    Geoff's suggestion use a signal bender and calibrate the speedo on a dyno sounds good as the NA gear is expensive to buy new.
     
    Last edited: May 3, 2019
  15. beaver

    beaver southern zeds

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    You dont really need a dyno rob, although its safer for sure.. when I had the corrector in place for the 3000k speedo dial face thingy
    calibration,
    I used an app called speed glow, I confirmed the app was accurate by playing it off

    against a late model fords speedo, while in cruse control, and it was.
     
  16. East Coast Z

    East Coast Z Well-Known Member

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  17. Martin Williams

    Martin Williams Well-Known Member

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    ECZ is correct, buy the correct part from whoever. It will work. I know they are not cheap but what $/hr price do you put on your own time?
     
  18. JT

    JT Track Addict

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  19. East Coast Z

    East Coast Z Well-Known Member

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    According to Nissan FAST.
    The sensor (25911-40P10) used in a manual TT gearbox is NOT the same as used in an NA box.
    The only parts that are common to the TT & NA concerning the sensor are the O-ring seal & the external circlip that secures the pinions on the shafts.

    The concept that you can purchase the sensor, gear & circlip as a complete assembly is incorrect.
     
  20. ZDUCTIV

    ZDUCTIV Active Member

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    You can run the NA pinion on the TT sensor without swapping the sensor because the offset is not large enough to be an issue according the some of the bigger names over at TT.net
     

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