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  1. #1
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    DME Questions/Flash Tune

    Hi Guys,

    I got some questions about the DME as it pertains to flash tuning. Posted it over at N54tech, but figured this would be a good place too:

    Load:

    • How is load calculated? Does the DME use DME PSI and pedal position to infer
      load?
    • Is max load then equivalent to when DME PSI is at 9psi or so (stock max) and
      the pedal is floored?
    • Can load be logged by the JB4?
    • What happens when you exceed the max load in the tables (if possible)
    • What does the load target table refer to? Is that the max load target at a
      given rpm assuming WOT? If so is the load target then scaled down linearly with
      pedal or throttle?
    • What is the load to torque limits and why are there 3 tables when everything
      else is in pairs based on banks?
    • What is torque limit cap?


    Advance:

    • What tables affect advance? Is it only load/rpm, open loop, and then the
      spool table, or are there others?
    • What determines when the other tables are active and when they are active is
      it that their values take over entirely, blend, or are added to the base
      ignition timing table? For instance if you are in spool does the DME add the
      spool timing to base timing, or simply switch from the base timing table to the
      values in the spool table?
    • How do trims change advance? I thought advance was load/rpm based (at least
      that's what the tables seem to show), but Terry made a comment that seemed to
      indicate trims were involved in timing advance.


    AFR/Fuel:


    • What tables affect AFR besides bank 1 and 2 main fuel tables?
    • What is open loop, how does it affect fuel calculations, and when is it
      active?
    • I see fuel AFR max target is 14.7:1 or so, but I know the fueling goes
      leaner than that at times. What is driving this?


    Lastly, is there a table that shows the calculations/formulas that link tables to each other? Its nice having the raw
    data, but it would be great to know when one table is being called upon and when it is being ignored for something else.

    Thanks!

  2. #2
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    Someone want to take up this homework assignment?

  3. #3
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    1 out of 1 members liked this post. Reputation: Yes | No
    Bump. Update with some questions I was able to answer through Terry and experimenting... need more answers...

    Load:


    • How is load calculated? Does the DME use DME PSI and pedal position to infer
      load?
    • Is max load then equivalent to when DME PSI is at 9psi or so (stock max) and
      the pedal is floored?
    • Can load be logged by the JB4? No, but COBB can.
    • What happens when you exceed the max load in the tables (if possible) Assumes highest/last value on the table
    • What does the load target table refer to? Is that the max load target at a given rpm assuming WOT? If so is the load target then scaled down linearly with pedal or throttle?
    • What is the load to torque limits and why are there 3 tables when everything else is in pairs based on banks?
    • What is torque limit cap?


    Advance:


    • What tables affect advance? Is it only load/rpm, open loop, and then the spool table, or are there others?
    • What determines when the other tables are active and when they are active is it that their values take over entirely, blend, or are added to the base ignition timing table? For instance if you are in spool does the DME add the spool timing to base timing, or simply switch from the base timing table to the values in the spool table?
    • How do trims change advance? I thought advance was load/rpm based (at least that's what the tables seem to show), but Terry made a comment that seemed to indicate trims were involved in timing advance.


    AFR/Fuel:


    • What tables affect AFR besides bank 1 and 2 main fuel tables?
    • What is open loop, how does it affect fuel calculations, and when is it
      active? This is actually pretty basic. Open loop is active once the motor has gotten to heat. Are there other times when the DME goes back into closed loop? I don't know.
    • I see fuel AFR max target is 14.7:1 or so, but I know the fueling goes
      leaner than that at times. What is driving this?

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