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AFR up and down

Discussion in 'FAST Support Forum' started by crash520, Apr 2, 2018.

  1. crash520

    crash520 Member

    Joined:
    Dec 16, 2016
    hi gents
    In the attached log, immediately after a wot hit through first and second I’ve noticed my AFR, goes between 13 and 15.94 every .2 seconds, would this be normal?
     

    Attached Files:

  2. Denis

    Denis Member

    Joined:
    Dec 2, 2009
    Location:
    Mendocino County, Northern Calif
    It is not normal. I looked at a number of my logs and did not see anything like what you are getting. The closed loop gain table could be the culprit. If there is too little gain the response to excessively rich or lean becomes sluggish and does not respond as quickly causing it to overshoot and undershoot the target A/F. In theory excessive gain can cause instability and cause a similar problem but I have not experienced it with my XFI. Attached is a screen shot of my Closed Loop Gain table that I have been using for several years with no issues. The bottom row in my table is higher than it needs to be but it only comes into play during deceleration and I just want maximum O2 response to lean things out. I also made the bottom row in my target A/F table 15.1 so that the O2 sensor would lean things out on deceleration to stop backfiring. I did not make VE table numbers in the bottom row of the VE table a lot smaller as there was some transition issues when I went from deceleration to acceleration with bottom row numbers that were much lower than the second row numbers.
     

    Attached Files:

    Last edited: Apr 9, 2018
  3. crash520

    crash520 Member

    Joined:
    Dec 16, 2016
    Thanks Denis, I’ll take this on board, I do have some tuning issues to sort through, appreciate the response
     

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