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Thread: 280ZX Speedometer - 85MPH?

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    Registered User jquigle1's Avatar
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    Post 280ZX Speedometer - 85MPH?

    Here is a tricky one! I'm confident some expert out there might know the answer.

    I have a 1983 280ZX 2+2....which has the digital dashboard. What I don't understand is that even with the pedal to the metal, the speedometer tops out at 85 MPH. Going downhill, with the pedal to the metal, I should certainly see a readout of higher than 85 MPH.

    I understand if it was only a two digit LED readout, that technically, it would top out at 99 MPH.

    Has anyone ever heard of this?

    Thanks for taking the time to reply.

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    1978 280Z (stock) TomoHawk's Avatar
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    You don't have a speedometer application on your iPhone??
    Drive Responsibly.
    enjoy classic Rock music.

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    Semi-retired admin Arne's Avatar
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    That was because the US regulations in the early '80s mandated that speedos not read higher than 85 MPH. Stupid, but true. This regulation was rescinded for the '84 model year.
    Arne - Former owner, HLS30-37705, 7/71, 905 Red
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    Former frequent poster sblake01's Avatar
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    Quote Originally Posted by TomoHawk View Post
    You don't have a speedometer application on your iPhone??
    I'm trying to get to what that would have to do with his question......anyway, only the 1979 280ZX had a 100mph speedo. On September 1, 1979, a regulation by the NHTSA required speedometers to have special emphasis on the number 55 and a maximum speed of 85 mph. Starting with the 1980 model year, all US 280ZX's went to an 85 mph speedo. 1983 was the only year that offered a digital speedometer but the 85 mph limit was carried over. Somewhere in the mid-80s that regulation was dropped.

    (Arne beat me to it)
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    On my 72 Z I have done 105mph and it was registered on the odometer plus a gps...... my cojones stop me but the Z felt like it had more in reserve.

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    Quote Originally Posted by 72 OJ View Post
    On my 72 Z I have done 105mph and it was registered on the odometer plus a gps...... my cojones stop me but the Z felt like it had more in reserve.
    Do you know TomoHawk?
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    It was a one and only one act of misconduct on my part, but I95 N was clear and in front of me a shiny silver 370Z.

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    You missed my point. I was poking fun because neither you nor TH gave a reponse that could really be thought of as an answer to the OPs question........
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    Is hard not to stick to the subject at times,fast reading and fast responses are the'" culpables""

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    Now I know how the Aflac duck feels.......
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    Registered User black gold man's Avatar
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    The answer is JIMMY CARTER.

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    1978 280Z (stock) TomoHawk's Avatar
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    From what I see on the streets, it seems that an iPhone is the answer to most things lately.
    Drive Responsibly.
    enjoy classic Rock music.

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    Look on the bright side, at least you can peg your speedo, I've seen 115. There ain't no way on gods green earth I'll ever see 160 cause at 115 thats all there is and there ain't no more.

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    Quote Originally Posted by TomoHawk View Post
    You don't have a speedometer application on your iPhone??
    To see how fast you are going as you hit the tree?

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    1978 280Z (stock) TomoHawk's Avatar
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    There is a video recorder application you can get that will record until just after it detects a high-G shock, assuming it was a collision of some kind.

    Otherwise, that's one way to eliminate one iPhone from circulation.
    Drive Responsibly.
    enjoy classic Rock music.

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    HS130-150591 4/79 zbane's Avatar
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    Back on track with the subject at hand...
    The speedometer is certainly reading the correct speed, but a circuit in the cluster isn't allowing the display to show it.
    It's been set up to display anything over 85 to be 85...
    85 mph=85 mph
    85+x=85
    85+(x+1,2,3,...)=85

    Find yourself an true electronics repair shop-one where they do the work on site, not shipped out for replacement.
    Download the schematics for the cluster, and take everything to the shop. They should be able to isolate the redundancy circuit and disable/remove it.
    David
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    Why??????
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    HS130-150591 4/79 zbane's Avatar
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    Stephan, I don't know why the original poster would need to do this either (unless there are track days in the car's future), but I wanted to at least try to answer the question with something not related to using a cell phone...
    David
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    Registered User black gold man's Avatar
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    About 7 years ago i made hi speed run thru DETROIT when i first got my 83zx 2+2.
    And thought 85 I was probably doing 110 at least.
    Without seeing an analog gauge it was hard to figure out what was going on.

    I was just enjoying a half hour run down the highway in my 83 today. I was working at a ford dealer and
    had many looks and comments.
    And got a roush performance banner big one.

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    Registered User Walter Moore's Avatar
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    The widely reported story at the time was that Joan Claybrook, who was the head of the NHTSA, believed that if the speedometer only went to 85 people would be more likely to obey the dreaded 55 mph national speed limit. You know, 55 is more than half of 85, so it looks similar to 70 on a 100mph speedometer... or some claptrap like that.

    Personally that was the era of my misspent youth, and I got even by keeping my 85 mph speedometer pegged as much as possible. (As my DMV history from the era shows...)

    Keeping up with traffic on most of the local interstates today, an 85mph speedometer would be nearly pegged most of the time.
    '71 240Z, Because any fool can drive fast in a straight line.

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    Former frequent poster sblake01's Avatar
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    Quote Originally Posted by zbane View Post
    Stephan, I don't know why the original poster would need to do this either (unless there are track days in the car's future), but I wanted to at least try to answer the question with something not related to using a cell phone...
    As far as that cell phone claptrap goes, all you have to do is consider who started it. Especially when he continued along that path even after the question was answered. I was just wondering why this went so far beyond the scope of what the OP asked.
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