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Thread: MAF Timing LB7

  1. #1
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    Default MAF Timing LB7

    Ok, i have searched high and low through various sites and forums and can not find an answer to my problem. i am trying to set up my 2004 LB7 duramax to use the MAF for timing. i have rescaled the MAF voltage (B0201) & Map (B0802) so as to work within the max 32 grams/sec limit in the MAF/MAP selection table (B0901-B0904). i have set my three timing tables based on the Excel timing calculator, and done a bunch of logging to see where my air flow grams/sec is at for different RPMs and loads.

    i then set up the tables (B0902-B0904) with new numbers 0, 7, 13, and MAP to MAF. went out and logged again it and it seemed that it was not moving to the other timing tables and was stuck on table A (B0908). i then adjusted the B0902-B0904 tables lower and it was still stuck in timing table A. i even set the grams/sec numbers to 0, 0.1, 0.2, so even at idle it should be using table C, but sure enough it was still using table A. i also set the MAF table A (B0902) to 32 grams/sec so it would have to use timing table B or C but it didn't budge from table A

    through logging i have confirmed that the ECM is seeing the gram/sec correctly per my rescaling

    i have put table (B0901) back to MAP and it will then correctly use timing table C.

    i dont know if this is an EFI Live issue and maybe a question for Ross, but i have almost given up trying to use MAF for timing

    anyone know what else to do? if i need to i can always attach logs and tun file for you guys to check out

    thanks Jason

  2. #2
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    HI!
    I had same kind of issues, when I was using MAF it never worked correctly, so I was returned using MAP.
    LB7 2001, EfiLive DSP5 , AirDog II, Afe intake , Summit 4"exhaust

  3. #3
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    That is why i was thinking that this may be a question for Ross. thinking that it may be a programming issue from GM or EFILive.

    Ross has an excellent comment here: http://forum.efilive.com/showthread....MAF-for-timing under post #2

    i was hopping to be able to take advantage of the MAF timing, better MPGs and faster turbo spool

    if anyone ever got this to work or knows how i would like to hear from you.

    Thanks Jason

  4. #4
    Forum tyhee Site Admin GMPX's Avatar
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    Wow, it's been 5 years or so since I looked at LB7, I didn't even remember you could switch between MAP and MAF. I find it funny that the gas guys are busting to run off a MAP sensor and ditch the MAF, your quest is the opposite.


  5. #5
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    well it seems to me that you could have the best of both worlds when it comes to turbo spooling and MPGs with MAF timing. with timing table A you could set the low fuel MM3 areas to a higher timing value for light cruising, then set the higher MM3 to a lower timing value to spool the turbo when you stomp on the go pedal. when the turbo spools and the air flow goes up the ECM will switch over to the next timing table (B or C depending on how you set it up) and raise the timing again. or with different combinations of these one could make a tune that will work well for light cruising and for heaving towing, etc.

    i am just having trouble getting it to switch over to the next timing table

  6. #6
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    so i did some testing and more logging yesterday evening, and it appears that when any of the cells B0902, B0903 or B0904 have any value other then "0" the ECM will only use timing table A. if they are all set to "0.00" then the ECM uses timing table C.

    more testing...

    Jason

  7. #7
    Lifetime Member GMC-2002-Dmax's Avatar
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    Quote Originally Posted by LB72004 View Post
    so i did some testing and more logging yesterday evening, and it appears that when any of the cells B0902, B0903 or B0904 have any value other then "0" the ECM will only use timing table A. if they are all set to "0.00" then the ECM uses timing table C.

    more testing...

    Jason
    The DSP1 timing tables are described as follows and 2-4 also have the same description:

    This is the base start of injection (injection timing) table if MAF flow is within the range of {B0904} "Injection Timing (MAF Map C)" or barometric pressure is within the range of {B0907} "Injection Timing (Baro Map C)" and if the user selected EFILive DSP5 program #1 is running.
    This table is based on fuel delivery per stroke (mm3) and RPM.

    When not running the DSP program the ECM will use {B0910} "Injection Timing Base (C)".

    See also:
    - {B0901} MAP or MAF Injection Timed
    - {B0915} Injection Timing ECT (C)
    - {B0917} Injection Timing IAT
    - {B0919} Injection Timing Fuel Temp
    www.mscservices.net


    Tuner of many, many Duramax and Cummins Diesels.


  8. #8
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    Quote Originally Posted by GMC-2002-Dmax View Post
    The DSP1 timing tables are described as follows and 2-4 also have the same description:

    This is the base start of injection (injection timing) table if MAF flow is within the range of {B0904} "Injection Timing (MAF Map C)" or barometric pressure is within the range of {B0907} "Injection Timing (Baro Map C)" and if the user selected EFILive DSP5 program #1 is running.
    This table is based on fuel delivery per stroke (mm3) and RPM.

    When not running the DSP program the ECM will use {B0910} "Injection Timing Base (C)".

    See also:
    - {B0901} MAP or MAF Injection Timed
    - {B0915} Injection Timing ECT (C)
    - {B0917} Injection Timing IAT
    - {B0919} Injection Timing Fuel Temp

    for my tests i was running with the DSP in the "off" or "0" position. i have been running with the DSP5 for some time now with my own programming. when i have the B0901 set to MAF the ECM will only use timing table "A" if anything other then "0" is put in B0902/3/4, regardless of my DSP5 setting. if i have the cells B0902/3/4 set to all to "0" then it will only use timing table C.

    is there a PID or something that will tell me what timing table the ECM is using so i dont have to keep cross checking between the RPMs and MM3s with the timing to see what table it matches with?

  9. #9
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    Do any of you super EFI Live gurus have any insight on this? i would have thought, being that it is an LB7 just about everything would have been done, but there seems to be little information on the internet about this.

    if all else fails i guess i could always use the DSP output wired to a relay and set up to turn on when it sees xx number of lbs boost. the relay could then be wired into the DSP switch so as to automatically switch between two diffident tuns. this would almost do the same thing but you would only get two timing tables to switch between instead of three. on the plus side i would be able to have other parameters that i could change ie: MM3, fuel MPA, etc that would automatically change when i stomp on it and the boost comes up.

    now that i think of it, one could just use more then one pressure switch and several relays/resisters to switch between all of the DSP programs and have five timing tables that automatically switch. but this would be over kill and not likely to ever be needed

    please let me know if any of you know how to get the LB7 to work on MAF timing, otherwise i will end up trying the relay option

    thanks Jason

  10. #10
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    I myslef personally do not see any reason as to why you would need to change this. It is pretty easy to set up a timing table to allow for good milage(high timing in the cruise area), and then set it up for fast turbo spool(moderate timing in teh low RPM power areas). I just don't see any advantage to setting it up so as to change timing tables based on MAF flow. I know I have played quite a bit with timing, and found with the LB7's larger injectors they don't take as well to really high timing at lower RPM's like the LLY+ does(I saw a drop in milage at more than about 6.5 degrees of cruise timing whereas the LLY guys will go up to around 8-10 at cruise). And I have found that a little more timing over stock helped my spool up some. Also just because the option is there to change timing, it doesn't mean the rest of teh code in the ECM will fully support the changes. There is alot in the ECM we cannot see, so like you posted above there could very well be some other hidden tables that need to be opened up to get this to work. Then again, if they open the tables who is to say it will be beneficial. I know i for one like teh MAP based timing as I have been up in altitude ab it and found it to work quite nice with the changed timing at altitude.
    1995 GMC 2500 SUBURBAN powered by 01 DURAMAX/ALLISON, little of this, a little of that,
    DIAMONDEYE 4" exhaust, CORSA muffler, AFE stage 1 dry filter, custom tuning by me, KENNEDY single pump and pump rub kit.

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