260z speedo cable RPM | The Z Club of Great Britain
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260z speedo cable RPM

Discussion in 'Drivetrain' started by Russell, Dec 28, 2016.

  1. Russell

    Russell
    Z Club Member

    I don't suppose anyone knows the rpm of the speedo cable at max speed?

    I am going to convert my original speedo to GPS but need to know how fast it needs to be turned.

    Or if someone has a speedo they would like to donate so I can build it on the bench without taking mine apart it would be gratefully received!


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  2. Moriarty

    Moriarty Well-Known Forum User

    And "max speed" is ?

    GPS takes a timing signal from multiple satellites and is stand alone
    Sorry for being thick but If your converting to GPS then please explain what that has got to do with the rpm of the cable ?
     
  3. jonbills

    jonbills
    ZClub Administrator
    Moderator

    I think there must be an add-on gps unit that drives oem speedos via the cable drive thingy.
     
  4. Russell

    Russell
    Z Club Member

    There are aftermarket ones in the US it they are really expensive. I was planning on using an arduino connected to a GPS receiver. Based on how fast the speedo drive needs to turn, the arduino will spin a stepper motor to move the needle. Probably going to put that on the back burner and use a cable and correct cog in the Gearbox. Have enough work to do with the 1JZ for now


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  5. jonbills

    jonbills
    ZClub Administrator
    Moderator

    Are you experienced with arduino development work? I'm thinking of trying to make a spark knock buzzer with one.
     
  6. Russell

    Russell
    Z Club Member



    I have made a few projects with them. The last one was a PWM Controller for my marine fish tank.

    Like anything, breaking it down into smaller chunks makes it easier and most of the code for the smaller chunks is a mere google away.

    What you are trying to do wouldnt be hard. The hardest bit would be getting the arduino to read the signal from a knock sensor. Once it reads the signal you just tell it to act upon a threshold - sound a buzzer, display a message on an LCD etc.


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  7. jonbills

    jonbills
    ZClub Administrator
    Moderator

    Thanks, that's what I thought. I did see that they have a sample for a knock sensor.
    Will be a fun project. perhaps :)
     
  8. uk66fastback

    uk66fastback
    Z Club Member

    I'm always massively impressed by this kind of stuff. I wish I understood any of the above ... I did google aduino so at least I am a bit informed, but I still don't really understand! I know there is a conference going on starting tomorrow though in Las Vegas!

    http://www.arduino.org
     
  9. Russell

    Russell
    Z Club Member

    I had a quick look and the code uses a Piezo element.

    Not sure how waterproof they are but are very cheap. stick to the side of the engine and set the Arduino to listen for the specific "knock" frequency.

    I don't know enough about the frequencies produced when the engine knocks though so that may be a bit more complicated.

    There would be enough space left to add additional features to it as well, maybe some sort of failsafe that it cuts fuel or ignition if it detects knock over a certain amount of time etc.
     
  10. jonbills

    jonbills
    ZClub Administrator
    Moderator

    I already ordered some random car knock sensor from ebay (£2.99 I think), I'm assuming there'll all piezo at heart - I may learn different. I guess it would be pretty easy to open a relay switch to cut ignition or fuel as you say.

    :cheers:
     
  11. Russell

    Russell
    Z Club Member



    Agree it would be easy to make the outputs do whatever you want. The problem is getting the arduino to understand when the engine is knocking. Modern cars with knock sensors are calibrated to the exact engine and location.
    Not sure how you would get it to identify a knock from normal running, hitting bumps, alternator and other environmental noise.


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  12. jonbills

    jonbills
    ZClub Administrator
    Moderator

    yes, I guess I'm looking for the tell tale frequency and duration of the knock. I was thinking if I can get it first up to just show what the sensor is seeing, and if I hear it knocking, I might be able to spot the signature.
    Hopefully before anything bad happens :rolleyes:
     
  13. johnymd

    johnymd
    Z Club Member

    You will see knock as it will be a big spike amongst all the noise. Knowing the level of knock to set your limit at will need to be desired by yourself.

    I've enabled knock control on my life ecu and using 2 sensors the monitor the 6 cylinders. I've set the thresholds quite low so it does retard ignition under some conditions. I've setup the 2 sensors to use different thresholds per cylinder per sensor based on the different distance from each sensor me general noise around each cylinder. That way the ecu can identify knock per cylinder and only retard ignition on the cylinder with knock. It's currently set to retard the amount of ignition based on level of knock and return ignition over the next 4 engine revolutions. Takes a lot of configuration and data loggin to get the highest ignition without entering into detonation.
     

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