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Thread: Speedo giving incorrect reading

  1. #21
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    On my 6 (running on 225/45s) the speedo overreads by 3 or 4kmh at 100. Compared to GPS. So going past the Holland Park speed cameras on the freeway at a GPS indicated 101 or 102 the speedo reads about 105. No pictures in the mail yet!

  2. #22
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    Quote Originally Posted by armthehomeless View Post
    Wouldn't want them to do that to me! My GPS proudly displays a top speed of 217km/h

    (on a private road ofcourse)
    Must have been a very long private road...
    2009 VW Passat R36 - 220KW of German engineering.
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  3. #23
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    Quote Originally Posted by Swallowtail View Post
    Must have been a very long private road...
    Yeah and it ran out pretty quick!

  4. #24
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    So to keep it on-topic, what was your speedo reading when the GPS was saying 217? ...

  5. #25
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    Probably ~240km/h indicated i'd say..

    I've seen an indicated 255km/h on my private course before

  6. #26
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    Quote Originally Posted by Swallowtail View Post
    So to keep it on-topic, what was your speedo reading when the GPS was saying 217? ...
    Yeah I'd say it was pretty close to 240. Although, I wasn't really looking. I was trying to keep it straight! Haha. And work out when to start braking!
    2014 Mk7 Golf R | DSG | Reflex Silver | Leather | Drive Assist | Bi-Xenon Headlights
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  7. #27
    HellionXR6T Guest

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    Haven't tested mine. Although Dee's Mazda 2 Genki was about 4 kms off @ 100, GPS was saying 96 to 97kmh.

    Isn't this fairly common across almost all makes and models?

  8. #28
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    Quote Originally Posted by HellionMPS View Post
    Haven't tested mine. Although Dee's Mazda 2 Genki was about 4 kms off @ 100, GPS was saying 96 to 97kmh.

    Isn't this fairly common across almost all makes and models?
    Sure is, but 7-10% is a bit annoying. Generally it's 3 or 4.

    First time I drove it on brisneyland arterials I couldn't figure out why everyone was speeding.

  9. #29
    HellionXR6T Guest

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    I'll have to test it out

  10. #30

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    in england all speed cameras or officers expect a 10/15 % speeding offence anything over is considered a offe3nce to be dealt with. I can tell you this after 3 years service....

    But its better to get it sorted as it no excuse that you speedo is wrong "Offficer"! no defence really????

    good luck

  11. #31

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    Quote Originally Posted by Jeev View Post
    The MPS3 Speedo is out by ~10% when on 215/45 R18 tyres. Putting 225/45 R18 tyres on will take that back down to ~8%, but it's roughly the same on every car. I think the problem itself is in the instrument cluster, as my ScanGuage II gives the correct speed readout. Makes you wonder how many km your car has really done though... 10% out puts my car at 70,000 not 77,000km.
    If you're scanguage is reading the correct speed, it's obviously getting the readings from the computer, which would also be feeding the odometer. The actual guage being out by 10% is just a calibration in the actual arm, I doubt very much that as a manufacturer, Mazda would be allowed to have a 10% tolerance on an odometer. I can't be certain, but I've heard somewhere along the lines that they'll accept 2% max on an odometer.
    Last edited by mpsJOE; 15-04-2009 at 05:46 PM.
    .

  12. #32
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    Well, I had the entire dash replaced a few weeks back now.
    Have'nt had a the chance to check it on the same PGS I was using before, but it definately seems to be a lot better.
    Will hopefully have an answer for you this weekend...

    Took alot of complaining and heated discussions with the state Mazda Rep, but they finally agreed to do it for me.

  13. #33
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    yeh my casr also seems 10% out, this also suggests that my car is travelling a far more dstance than i really am, eg, i travel 500kms, the car will read 520kms

  14. #34
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    Quote Originally Posted by Mr Nasa View Post
    yeh my casr also seems 10% out, this also suggests that my car is travelling a far more dstance than i really am, eg, i travel 500kms, the car will read 520kms
    I've done a 5K speedo check and while the speedo was out by the expected margin, the odo was within 5m over 5Km = 0.1% tolerance. Someone correct me if I'm wrong, but OBD diags will report the correct speed, and the odo is just displaying a value in the ECU memory. The speedo error is just the analogue guage, I believe.
    Last edited by Nexus; 18-04-2009 at 04:06 PM.

  15. #35

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    Quote Originally Posted by Nexus View Post
    I've done a 5K speedo check and while the speedo was out by the expected margin, the odo was within 5m over 5Km = 0.1% tolerance. Someone correct me if I'm wrong, but OBD diags will report the correct speed, and the odo is just displaying a value in the ECU memory. The speedo error is just the analogue guage, I believe.
    is my post invisible?
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  16. #36
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    Quote Originally Posted by mpsJOE View Post
    is my post invisible?
    No, just reinforcing the point and stating the result from an actual test...again. Not the first time I've said this either.

    Quote Originally Posted by Nexus View Post
    last time I did a speedo check with the stock tyres on and the odometer was accurate to within 5m over 5Km, so the odometer is probably right...but having said that the very first time I did a speedo check the odo was out around 300-400m over 5Km. I think they changed something with the infamous first flash.
    Raises the question - Is there anyone still on the original firmware and have you done a speedo check? There's a 5K trap on the gatton bypass with markers at every 1K.
    Last edited by Nexus; 19-04-2009 at 02:34 PM.

  17. #37
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    Another thought I just thought to mention is that I don't think it's a % error as such. Below 110K with 225/45 it seems to be approx 7Km/h across the board. i.e. 60 indicated 53 actual, 110 indicated 103 actual.

  18. #38

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    Quote Originally Posted by Nexus View Post
    Another thought I just thought to mention is that I don't think it's a % error as such. Below 110K with 225/45 it seems to be approx 7Km/h across the board. i.e. 60 indicated 53 actual, 110 indicated 103 actual.
    But wouldn't a larger diameter tyre change the speed as a percentage, not a constant? I can understand that different brands have different properties e.g wall sizes, but in general, this should not provide a constant speed difference, it should be a varied speed difference, which leaves the only other alternative being the fact that the needle on the speedo is calibrated incorrectly, obviously from factory as it is common on all cars.

    ---------- Post added at 10:54 PM ---------- Previous post was at 10:51 PM ----------

    Quote Originally Posted by Nexus View Post
    No, just reinforcing the point and stating the result from an actual test...again. Not the first time I've said this either.
    Fair call
    .

  19. #39

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    I think I have this problem as well on my MPS 3. Anyone found out what the problem is yet? Can Mazda fix this under warranty?

  20. #40

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    From what I have read, car manufacturers only have to be within 10% of actual speed.

    To combat this nearly all manufacturers set their cars up to the lower side to avoid customers complaining about speeding fines.

    Mazda sets theirs pretty close to 10% under on most of mazda range from what I know.

    As far as it being a set rate of difference instead of a percentage...well...I have no explanation for that one.

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