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Thread: LMM-commanded boost

  1. #11
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    Quote Originally Posted by bballer182 View Post
    Have you tried using B2232 and B2231 to isolate the problem.
    Setting the two tables with high mm3 values would eliminate the referencing of the vane tables and would only look at the desired boost.
    Conversely setting the two tables with low to zero mm3 values would make the ecm go solely off the vane tables and disregard the desired boost.

    (theoretically)

    I've done this a few times to isolate boost/vane issues that have arisen.

    Quote Originally Posted by killerbee View Post
    High? B2231 should be lowered, not increased, correct?
    The definitions of those two tables are a little hard to understand correctly and probably should say something to the affect of "it uses the vane tables when the main rate goes above X and uses the boost table when the main rate goes below X" you know something like that.

    But yeah what i did in order to eliminate the boost tables was set both tables at 200 so that the ECM would reference the vanes only and throw desired boost out the window and eliminating the possibility of getting a boost code too. so lowering them should net you the opposite result.

    without seeing your log vs. the tune i would bet that the vane and boost tables are mis-matched and the main rate is varying so the the ECM is falling in and out of the main rate that dictates whether or not it is supposed to use the vane tables or not.

    Just a guess.
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  2. #12
    Lifetime Member killerbee's Avatar
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    Lowering them did nothing for me, in fact, the logs above are with these tables lowered. It sounds like you have no boost control either then,

    This LMM has an endless number of frustrations. Do you really want to run on vane position? I am going to have to set up a separate weekly anger management session, just for this platform.
    Michael, Systems Engineer 04.5 D-max LLY, Phoenix, Arizona Email
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  3. #13
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    Quote Originally Posted by killerbee View Post
    This LMM has an endless number of frustrations. Do you really want to run on vane position? I am going to have to set up a separate weekly anger management session, just for this platform.
    I thought you drive off vain position anyway it's just a matter of how you get there. You are wanting boost to control vain position like it's sapose to and then you don't have to worry about target vain position.

    I read this, and maybe I am missing it but which one has final say on vain position, the target vain position table or the desired boost table. Why would you want a target vain position table?


  4. #14
    Lifetime Member killerbee's Avatar
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    The whole point of variable geometry, is MAP governed boost. Without the ability to regulate it, there is no point in even having a map sensor. For that matter, you may as well just throw on a wastegate. At this point, that is what is called for, unless there is a way to cap boost production.

    As far as final say on vain position, that is mute at this point. Actual logged vane has no resemblence to what is entered in the tables.

    Max vane does seem to cap vane position, but as far as regulating boost, that is worthless. Max vane is necessary for transient considerations. It is very valuable in enabling quicker spoolup. If I reduce all those numbers, we get a slug performance-wise.
    Michael, Systems Engineer 04.5 D-max LLY, Phoenix, Arizona Email
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  5. #15
    Lifetime Member GMPX's Avatar
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    bballer182 is on the money with setting B2231 & B2232 high to stop the ECM trying to correct the boost away from the desired tables.
    With those set high it should just use Desired Boost + ECT Boost + IAT Boost as the determining factor. If commanded fuel is within the window of B2231 & B2232 then the ECM will still use the boost values but they are corrected using a PID controller routine, this is what will (should) be causing the erratic control based on what the desired boost values should be.
    Looking at the table values you can see that GM use the desired boost tables only when at idle, but about about 900RPM they use the correction.
    If someone is brave I can attempt to find and add in the PID control tables if someone want to play with them. PID loop calibration =

    Cheers,
    Ross
    I no longer monitor the forum, please either post your question or create a support ticket.

  6. #16
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    Baby steps, but I am will to help, you just have to let me know what you need from me and tell me how. LOL I can do logs etc etc.

    BTW I didn't know 2242 was a table, but I love it.

  7. #17
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    Quote Originally Posted by killerbee View Post
    The whole point of variable geometry, is MAP governed boost. Without the ability to regulate it, there is no point in even having a map sensor. For that matter, you may as well just throw on a wastegate. At this point, that is what is called for, unless there is a way to cap boost production.

    As far as final say on vain position, that is mute at this point. Actual logged vane has no resemblence to what is entered in the tables.

    Max vane does seem to cap vane position, but as far as regulating boost, that is worthless. Max vane is necessary for transient considerations. It is very valuable in enabling quicker spoolup. If I reduce all those numbers, we get a slug performance-wise.
    I understand the MAP governed boost. I thought if in fact the desired boost was "the table," then then when you stand on it, it should adjust the vains to make the boost accordingly. Guess that doesn't work like it should.

  8. #18
    Lifetime Member GMPX's Avatar
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    Quote Originally Posted by duramaximizer View Post
    BTW I didn't know 2242 was a table, but I love it.
    That eliminated one 'what the?' question on LMM boost control, I do remember adding that one in real time with someone testing on the other end!

    Cheers,
    Ross
    I no longer monitor the forum, please either post your question or create a support ticket.

  9. #19
    Lifetime Member killerbee's Avatar
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    Quote Originally Posted by GMPX View Post
    bballer182 is on the money with setting B2231 & B2232 high to stop the ECM trying to correct the boost away from the desired tables.
    With those set high it should just use Desired Boost + ECT Boost + IAT Boost
    Description of the table. Did I misinterpret this?

    "Based on the commanded main fuel rate and RPM, this table will enable the ECM to control boost pressure once the commanded fuel rate goes above the values in this table."


    I took this to mean that I needed low values in order to "control boost pressure"
    Michael, Systems Engineer 04.5 D-max LLY, Phoenix, Arizona Email
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  10. #20
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    Good Job, I think that was causing most of my wheel hop during shifts while truck pulling! I am willing to work with you on any LMM problems.

    I am willing to play with PID's. I know adding the files in the right spot can be a little tricky, but once over that, I can help. BTW I am running a public release, not the beta.

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