car tachometer

Discussion in 'The Projects Forum' started by mozikluv, Jun 24, 2007.

  1. mozikluv

    Thread Starter AAC Fanatic!

    Jan 22, 2004
    1,437
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    hey guys,

    does anybody know how to convert a 4,6,8 cylinder analog tach into a 3 cylinder tach? this will be connected to a 3 cylinder suzuki 6 valve engine.

    i have been mulling the idea of swithching it to 6 cylinder function and then have its output pass thru a divide by 2 logic circuit. but then i don't know how to do the circuit. 2ndly am not sure if it would give an accurate rpm reading.

    your help would be greatly appreciated.

    moz
     
  2. Gadget

    Distinguished Member

    Jan 10, 2006
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    0
    If its an Analogue Tach, then surely its more a matter of calibration... ??
     
  3. mozikluv

    Thread Starter AAC Fanatic!

    Jan 22, 2004
    1,437
    1
    hi gadget,

    thanks for the reply, this is an old tach which i have set aside and i no longer have the installation instruction. the last tach i installed in my pickup was also an analog but it had a selector for 4, 6, or 8.

    i'll try to open this thing and see if there's also a selector. but if there's none then i will go along as what you have suggested. but then again i don't know how to recalibrate it.:(

    moz
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    For 3 cylinders, the reading will have to be twice that for 6. If the tach is accurate, you can either multiply the reading in the 6 position by 2, or adjust the meter, if it has the range. If the engine is idling at 800 RPM, the tach should read 400. The adjustment might let you tweak it up to 800. If not, you can at least adjust to the original idle indication.

    Another dodge is to pull the meter open and change the scale numbers to agree with what they should be for 3 cylinders.
     
  5. mozikluv

    Thread Starter AAC Fanatic!

    Jan 22, 2004
    1,437
    1
    thanks beenthere,

    so my previous assumption that if i set it to 6 cyl i would have to divide it by 2 was wrong.

    there's a hitch here. thru expereience i would know when an engine is idling at 600 or 800 or even 1000. but it is based on a 4, 6, & 8 cyl cars. this is the 1st time that i hae acquired a 3 cyl vehicle and i don't have any idea how it purrs say at 600 or 800. right now it is set at a certain rpm based on the air con turned on. i guess i have to presume that its idling at 800:confused:

    i like the idea of changing the face plate to correspond with the reading.:)

    again thanks beenthere

    moz
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Sure moz - that's what they make white-out for.
     
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