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Thread: Barometric compensation

  1. Default Barometric compensation

    Tried looking up how to enable this in the manual, but can't find it. I'm having a really bad time trying to get my A/F's to stay steady. One minute they're good, the next I'm running pig rich.

  2. #2

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    I think this is related to this email which has the background: I have a map ecu and am having issues. I was stationed in South Carolina and other
    than running a little rich in the winter no big deal. I had to move out to New
    Mexico which is about 4,000 ft higher in elevation and am having all kinds of
    problems, especially now that it's colder. I will be cruising at 2,500RPM and my
    A/F is like 10 on my wideband.
    I leaned out the cells and it will be fine for awhile and then back down into the
    10 range. I'll come to a stop and the car dies because it's too rich. I've leaned
    out the idle to around 14 as well and it will be good, then rich and then lean.
    Yesterday I was driving and all of a sudden my A/F went to at least 17 (as high as
    my gauge goes).

    Is there something possibly wrong with my unit? Also, I have the sensor installing
    in my intake pipe right before the throttle body.


    Sorry, thought this was a MAP2 not a MAP1. There is no seperate baro comp on a MAP1. Is it possible this is related to IAT temps rather than baro? The IAT in before the throttle body could be suffering heat soak. We usually place it after the air filter near outside air as much as possible.

    The MAP sensor in the MAP-ECU is an absolute type so it should compensate for altitude. Can you check the "Output" readings and perhaps a log or some reading from the vacuum gauge will help.
    MAP-ECU Support

  3. Default

    I originally had it somewhat like you said, though it wasn't in the intake. I couldn't install it in the pipe because OEM is rubber. Before moving out to NM and having these issues I had the sensor installed in the engine bay and had no issues. Once I started having issues I assumed it was because it was just "chilling" in the engine bay. A guy on a forum I frequent said he had his sensor right next to his filter and had no issues. Not sure if it matters, but it's on a AWD Stealth TT. Are you familar with any speed shops that specialize in the MapECU in New Mexico?
    Last edited by Stealthman93; 11th-December-2011 at 09:48 AM.

  4. #4

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    I cannot see how it would just change unless an input changes radically. The MAP-ECU is pretty simply. The inputs are vacuum/boost and RPM which causes it to lookup the values in the fuel table. For the output to change radically and go really rich, either vacuum or RPM has to change. I suspect you are using different zones in the fuel table which were not used in SC because your vacuum will be different at 4000ft. I re-read your original post and I wonder if you are now fighting the OEM O2 sensor which is making the OEM ECU retune AFR's in closed loop causing the problem. Since you have a 93 you should be able to disconnect the OEM O2 sensors and clear the OEM ECU memory so it is not adjusting as well. BTW, make sure there are no zeros in the fuel table, the lowest value should be 16.

    It would be helpful you you could upload the base table from your MAP-ECU and let us know you vacuum reading at idle and cruise. A log file would be ideal. Thx
    MAP-ECU Support

  5. Default

    I'm out of state right now, but will get you the info. What size and thread pitch is the sensor that I have screwed into the intake? I may go back to the way I had it and put a plug in the hole.

  6. #6

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    The IAT has a 1/8"-27 NTPF thread.
    MAP-ECU Support

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