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Thread: Barometric pressure question

  1. #1
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    Barometric pressure question

    Baro pressure at cold, key on engine off is reading 32.5inhg. My baro pressure is 29.98 today, I'm located at 30 feet above sea level, temperature is 75


    The engine is a 6.2L hellcat, the PCM is a factory unlocked Hellcrate PCM with nothing tuned in it yet.

    As a side note I also have 32% fuel trim for both long terms.

    My thoughts on this is that the barometric pressure sensor thats built into the PCM is reading incorrectly. I think the PCM thinks its at -2000 feet

    What are your thoughts about the baro sensor reading?

  2. #2
    Quote Originally Posted by Shizzbee View Post
    Baro pressure at cold, key on engine off is reading 32.5inhg. My baro pressure is 29.98 today, I'm located at 30 feet above sea level, temperature is 75


    The engine is a 6.2L hellcat, the PCM is a factory unlocked Hellcrate PCM with nothing tuned in it yet.

    As a side note I also have 32% fuel trim for both long terms.

    My thoughts on this is that the barometric pressure sensor thats built into the PCM is reading incorrectly. I think the PCM thinks its at -2000 feet

    What are your thoughts about the baro sensor reading?
    Barometric pressure reported by your weather station is corrected. The one reported by your ECU is actual.
    You're after "station pressure" from your weather source if you can get it.
    If its not broke, just give it time.

  3. #3
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    second run after key cycle and pedal was good.hpl

    do you feel these map and baro readings are correct for 32 feet, 75 degrees outside?

    See file

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    Quote Originally Posted by Steven@HPTuners View Post
    Barometric pressure reported by your weather station is corrected. The one reported by your ECU is actual.
    You're after "station pressure" from your weather source if you can get it.
    This is where I got my local pressure. I believe its not corrected. Please let me know if that's not the case

    https://w1.weather.gov/obhistory/KCRQ.html

  5. #5
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    Factory ECU is set to learn the baro pressure overtime. There are a number of factors that come into play that could cause the baro to be learned WRONG, including boost/vacuum leaks, clogged air filter, and any air mods done, such as pulley, exhaust, etc. Most tuners turn off baro learning to avoid all the bad inputs to the tune.

    That said, being off 3in/hg isn't going to make your fuel trims be +32.

    What other mods are done to the car?

  6. #6
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    Its a Hellcat with the hellcrate ECU, headers and while I wont call it cold air intake it looks like one. I have a second issue I will post in a separate question to keep them apart.

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    Sounds like fuel system. What pump/s and how are you controlling them?

  8. #8
    Advanced Tuner Blue Bee's Avatar
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    Doesn't the Hellcrate PCM have the baro on/in the PCM?

  9. #9
    Advanced Tuner Blue Bee's Avatar
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    Considering sea level is 29.92inhg I'm not sure where you are getting the -2000 feet at?

  10. #10
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    The baro is reading 32.5inhg

  11. #11
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    Quote Originally Posted by Blue Bee View Post
    Doesn't the Hellcrate PCM have the baro on/in the PCM?
    The hell cat uses GPEC2A controller which does not have a built in baro sensor. Only controller I have heard about having an onboard baro sensor is the 8GMx. See page 20 in PDF link below.

    http://perception.fcaperformanceinst...84/0121716.pdf

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    Quote Originally Posted by Shizzbee View Post
    The baro is reading 32.5inhg
    What is the manifold pressure when the key is on but the engine is not running?

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    Quote Originally Posted by Homer View Post
    What is the manifold pressure when the key is on but the engine is not running?

    22.4
    Attached Files Attached Files

  14. #14
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    Quote Originally Posted by unicornpower View Post
    Sounds like fuel system. What pump/s and how are you controlling them?

    hellcrate fuel module, Walbro pump, regulator set to 80psi

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    Quote Originally Posted by Shizzbee View Post
    22.4
    Somethings not right, your baro (110kPa) and MAP (76kPa) are off by more than 40%? 32feet is 95.7kPa and neither of the readings are close.

    I have checked my logs on my boosted 5.7 and both baro and MAP at key on are identical and both are very close to the typical barometer reading for my area. Can you post the tune that came with the crate PCM? Nevermind saw it in your other post.

    I see baro learn is enabled, have you tried disabling?
    baro.JPG
    Last edited by Homer; 05-03-2019 at 11:13 AM.

  16. #16
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    Quote Originally Posted by Homer View Post
    Somethings not right, your baro (110kPa) and MAP (76kPa) are off by more than 40%? 32feet is 95.7kPa and neither of the readings are close.

    I have checked my logs on my boosted 5.7 and both baro and MAP at key on are identical and both are very close to the typical barometer reading for my area. Can you post the tune that came with the crate PCM? Nevermind saw it in your other post.

    I see baro learn is enabled, have you tried disabling?
    baro.JPG
    I haven't tried that yet. I'll give that a try too and see.

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    Quote Originally Posted by Shizzbee View Post
    I haven't tried that yet. I'll give that a try too and see.
    Make the change, clear the adaptives and see if at least MAP and Baro are the same at key on. If they are the next thing to do is make sure your MAP is reading the correct ambient temp at key on. If it is off, then something is wrong with the sensor (although I thing the 6.2 used two) or the transfer function. Also, log your MAP voltage as a sanity check.
    Last edited by Homer; 05-03-2019 at 04:02 PM.

  18. #18
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    Quote Originally Posted by Homer View Post
    The hell cat uses GPEC2A controller which does not have a built in baro sensor. Only controller I have heard about having an onboard baro sensor is the 8GMx. See page 20 in PDF link below.

    http://perception.fcaperformanceinst...84/0121716.pdf
    Well that's funny because I have a 2016 HC PCM (GPEC2A) sitting here opened I'm unlocking right now and it has a BARO on the board as most Dodge PCM's do. #MPXHZ6115A to be exact, I was questioning if the Hellcrate had one, or which PCM it is exactly, I already know the rest do.

    Posting a FCA training workbook. Come on, you think they tell you everything? I was level 4 (when they had it) and SRT. That would be like going to a class and asking the instructor how the Neural Network worked...haha. Most of the "instructors" were college grads that had never even worked on a Dodge. They honestly knew less...in general.
    Last edited by Blue Bee; 05-05-2019 at 12:55 AM.

  19. #19
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    Quote Originally Posted by Blue Bee View Post
    Well that's funny because I have a 2016 HC PCM (GPEC2A) sitting here opened I'm unlocking right now and it has a BARO on the board as most Dodge PCM's do. #MPXHZ6115A to be exact, I was questioning if the Hellcrate had one, or which PCM it is exactly, I already know the rest do.

    Posting a FCA training workbook. Come on, you think they tell you everything? I was level 4 (when they had it) and SRT. That would be like going to a class and asking the instructor how the Neural Network worked...haha. Most of the "instructors" were college grads that had never even worked on a Dodge. They honestly knew less...in general.
    I am really glad you confirmed the baro sensor being in the GPEC2A...at least the HC version. Now I wonder if non-HC versions have it as well?

    As for the FCA workbook...that's all us DIY'ers (I design MEMS devices for a living) have available. I would love to get my hands on more reputable literature on dodge controllers and their programming but where can that info be found? This whole, trial and error approach to tuning is PITA. If it wasn't for this site I would be clueless.

  20. #20
    Advanced Tuner Blue Bee's Avatar
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    So I think the problem especially on the 392 cars is it at whether it is in the PCM or HPT the Baro and map settings are linked or being linked so if you go to a bigger map sensor you inadvertently change the Baro settings. So in that case you have to go back, as long as your map sensor settings are correct, go back to Baro settings and change them until it lines up.