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Jaycar Speed corrector in Ford AU

Discussion in 'Hobby Electronics' started by Davo, May 2, 2009.

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  1. Davo

    Davo Guest

    What about putting the correct size tyres on?
  2. atec 7 7

    atec 7 7 Guest

    Swap the gearbox sender to one which suites is much better.
  3. Uncle Al

    Uncle Al Guest

    Hi all,

    I've got an Ford AU3 Fairmont that has aftermarket rims/tyres.
    This throws the speedo out by about 10%.

    I am trying to sort out whether a Jaycar speed corrector
    ( will sort out the speedo error without
    incurring other issues.

    Other issues may be shift points for the auto transmission and/or
    problems with cruise control.

    I've hunted around the net looking for answers and came across a post
    where someone suggests that to control shift points it may require TWO
    speedo correctors.
    First corrector to drop the signal from the auto transmission to the
    speedo and the second corrector to increase the signal from the speedo
    to the ecu.

    Can any of you electronic boffins shed some light on this for me.

    I'm competent to assemble and install the kit but when it come to
    understanding electronics I'm lost.

    Thanks for reading.
  4. atec 7 7

    atec 7 7 Guest

    i assume it's much the same with drive running through an adaptor
    Well ask ford first , I have used after-market from the valley in
    I supplied the required information and he came back with the righ
  5. crazyclark

    crazyclark Guest

    Sure, that's always an option but given that the rims and tyres fall
    within the legal size for my car, it's good to individualise a little...

    Got a clue with regard to the question?
  6. That's interesting, thanks for that.

    In the past I've changed speedo gears in manuals but wasn't aware that a
    similar (if different) proposition was possible with auto's.

    Can you elaborate a little as to where I'd chase it up and what I'd ask
    for when I get there?

    (Is it simply a matter of saying that my speedo reads 10% high and could
    I have a speedo sender to suit, or is there more to it?)
  7. Mr.T

    Mr.T Guest

    Probably cheaper and far more accurate to just use a GPS unit for speed
    readout. And if your speedo reads 10% high, your just less likely to get
    booked anyway!
    (are you sure it's reading high though? IF your tyres are bigger
    circumference it will read low. If they are lower profile and the same
    width, then they would be smaller circumference and you would be correct of
    course. IF they are both lower profile and wider, as is often the case with
    aftermarket "upgrades", then the circumference is usually not 10% different)

    And the speedo reading has *ZERO* affect on your cruise control BTW. Are you
    really incapable of adding/subtracting 10% to the indicated speed when you
    set it?

  8. Franc Zabkar

    Franc Zabkar Guest

    Isn't the sensor a 3-wire Hall Effect type, in which case the signal
    would be in digital form? Wouldn't it be wired directly to the ECU?

    If the "someone" above is suggesting that the ECU should continue to
    see the actual speed of rotation of the transmission, regardless of
    road speed, then you would only need to connect the speedo corrector
    between the ECU speed output and the speedometer input, assuming the
    output is a pulse type.

    This could be the kit -- Super Speedo Corrector:

    - Franc Zabkar
  9. Franc Zabkar

    Franc Zabkar Guest

    If your car has an option for a lower ratio differential, then you
    could get the speedo sender that was designed to match it. IIRC,
    common ratios for other makes (in the 70s) were 2.92, 3.23, 3.50.
    These differ by about 10%.

    Doing this, however, may change the shift points for your automatic

    - Franc Zabkar
  10. Thanks mate, appreciate your input.
    I rem your nic from the old a2600w days - glad to see you're still
    contributing :)
  11. suss it out

    suss it out Guest

    Well... a bunch of assumptions based on what?

    If I only had one set of aftermarket rims in one size with one tyre
    profile and only drove it to the local shops then I may run with your
    line of thinking. That ain't the case.

    Obviously a closer reading of my op would clue you in that I wasn't
    suggesting that the speedo reading *did* have any effect on the cruise

    I don't know why whether or not I'd prefer my speedo to be accurate is
    worth you commenting about stuff of which you've no idea (my situation;
    my preferences; whether I have a gps; whether I have a clue about tyre
    sizes and speed differentials; at what speed I'm indicating a 10%
    difference; whether my calculating skills are adequate etc etc) but I
    guess if you've got time on your hands...

    Got any input about Jaycar speedo correctors?
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