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Thread: Tach Issue on LS1 Swap-Miata tach too fast

  1. #1
    Potential Tuner
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    Oct 2018
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    Tach Issue on LS1 Swap-Miata tach too fast

    I put together my LS1 miata a couple years ago, been driving and enjoying for a while but my tach has never worked correctly. I have read a multitude of people having success or failures with it, but I have not had a complete version of either. My car has a 2002 LS1 from a Camaro SS, using the computer from the same car. I have disable VATS/EGR/O2 sensors...etc. I wired in the white signal wire to my miata tach, but my tach reading is too high, id guess 150-200% of the actual engine speed. Plenty of people have been able to solve tach issues by using a resistor T'd into the signal wire from a switched source, but that hasn't solved my issue. I have recently read about how there is a tach signal "pullup" feature that can be modified in the computer. I have recently bought an MVPI2 setup and am definitely learning slowly, can anyone tell me if this is something possible to modify with my setup?

    Thank you in advance!

  2. #2
    Tuner in Training
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    Nov 2018
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    I did an LM7 swap which is a 5.3 vortec from a 2003 Silverado into a jeep TJ.

    I purchased an Tach Emulator from Novak Adapters which allowed me to connect my tach signal from my P59 ECU to my Crank and Cam inputs on my jeep ECU. In order for the emulator to work correctly I needed to change my VCM Editor view to Advanced in order to view my output setting for the P59 ECU Tach Settings. Once I was in advanced view in the editor I could view and change my tach setting in Engine>General>Tach Output. for me I had to change the High and Low resolution from 3 over 3 to 6 over 6. The pullup type is also listed in the tach output settings.

    Hope this helps.
    Last edited by CaliberConcepts; 01-11-2019 at 04:19 PM.

  3. #3
    Potential Tuner
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    Oct 2018
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    Quote Originally Posted by CaliberConcepts View Post
    I did an LM7 swap which is a 5.3 vortec from a 2003 Silverado into a jeep TJ.

    I purchased an Tach Emulator from Novak Adapters which allowed me to connect my tach signal from my P59 ECU to my Crank and Cam inputs on my jeep ECU. In order for the emulator to work correctly I needed to change my VCM Editor view to Advanced in order to view my output setting for the P59 ECU Tach Settings. Once I was in advanced view in the editor I could view and change my tach setting in Engine>General>Tach Output. for me I had to change the High and Low resolution from 3 over 3 to 6 over 6. The pullup type is also listed in the tach output settings.

    Hope this helps.
    My tach is currently working just not at the correct speed, but I appreciate the info. I actually spent more time with the search function and figured out the info about the high/low resolution. I have yet to mess with it but that is my next plan.

    Thanks

  4. #4
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    Oct 2018
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    Well I will call it a success. I was able to go in last night and modify the resolution values to 6/6 and the tach slowed down. I wasn't able to actually verify against what the computer said the RPM's were because for some reason it wasn't showing RPM's when I ran the scanner afterwards, but just running the car for a while it seemed to be much more reasonable on the gauge.

    Thanks for the help