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Thread: 2 bar tune for Turbo LT1 F-body possible with '93 ECM? DA3

  1. #31
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    Quote Originally Posted by steveo View Post
    i can dig into other stuff that uses map to see if adjustment is necessary

    i'd like to say we can set baro to a static value for a boosted engine, assuming it isnt going cross country (or maybe even if it is)
    Thank you, thank you , thank you SteveO and Xnke for thinking about / looking into this for me. Looks like there's a few items in there to get me in trouble!

    So you could potentially set baro = 100 manually, but I'd still use the 2 bar MAP and set all the tables as such, where 55kpa = 100 in reality?


    I don't have much to offer in the way of solutions, as I just don't understand the code and how it works. (but I can test it! ) Is there somewhere you would suggest that I could learn up on this?
    J. Moen
    91 Camaro - NASA American Iron Road Racer #91 "The Menace", carb'd 350, FloTek heads, "because racecar"
    91 Camaro RS - '93 LT1 /T56 swap, 224/224, 32lb D3, LTs, garage ported

  2. #32
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    Quote Originally Posted by steveo View Post
    $003F is the memory address of baro pressure volts

    at C366, we see:

    C366 : LDAA $00DA
    C368 : STAA $003F

    00DA is the map pressure (isn't it cool they put a speed density ECM's MAP memory address the same as its mask? im probably the only one that finds this cool.)

    this is probably inside the barometric update subroutine, now just need to analyze the conditions and branches that reach this code to figure out how to disable.

    or be super evil and just patch 'er like this:

    C366 : LDAA $003F
    C368 : STAA $003F

    also found this,

    E5E4 : LDAA #$FF
    E5E6 : STAA $003F

    this is probably a barometric initializer, sets baro to max, perhaps set this to $7F for a 2 bar system?

    more research required.
    Like all this, how do I learn about all the code etc.? Might as well be Chinese.
    J. Moen
    91 Camaro - NASA American Iron Road Racer #91 "The Menace", carb'd 350, FloTek heads, "because racecar"
    91 Camaro RS - '93 LT1 /T56 swap, 224/224, 32lb D3, LTs, garage ported

  3. #33
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    Quote Originally Posted by hotrodf1 View Post
    Thank you, thank you , thank you SteveO and Xnke for thinking about / looking into this for me. Looks like there's a few items in there to get me in trouble!

    So you could potentially set baro = 100 manually, but I'd still use the 2 bar MAP and set all the tables as such, where 55kpa = 100 in reality?


    I don't have much to offer in the way of solutions, as I just don't understand the code and how it works. (but I can test it! ) Is there somewhere you would suggest that I could learn up on this?
    if running fixed baro i think you'd set it to something like 50kpa (7F)

    these are all motorola 68k instructions, look up a tutorial on 68k (aka 68000) assembly code online somewhere, there are lots of them

  4. #34
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    Quote Originally Posted by steveo View Post
    if running fixed baro i think you'd set it to something like 50kpa (7F)

    these are all motorola 68k instructions, look up a tutorial on 68k (aka 68000) assembly code online somewhere, there are lots of them
    Ok Iíll check it out.

    And the ecu currently reads 55.4 kpa as the baro reading. So if we set it to that my current tune and all would remain valid I think.
    J. Moen
    91 Camaro - NASA American Iron Road Racer #91 "The Menace", carb'd 350, FloTek heads, "because racecar"
    91 Camaro RS - '93 LT1 /T56 swap, 224/224, 32lb D3, LTs, garage ported

  5. #35
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    Quote Originally Posted by steveo View Post
    i can dig into other stuff that uses map to see if adjustment is necessary

    i'd like to say we can set baro to a static value for a boosted engine, assuming it isnt going cross country (or maybe even if it is)
    Hello Steveo,

    I've been looking at the disassembly some with the code you referenced in previous posts. I can at least find it in there, big step for me LOL. Currently reading up on the Motorola 68k stuff. Learning curve for me, I'm certainly not a programmer.

    Where do we go from here?
    J. Moen
    91 Camaro - NASA American Iron Road Racer #91 "The Menace", carb'd 350, FloTek heads, "because racecar"
    91 Camaro RS - '93 LT1 /T56 swap, 224/224, 32lb D3, LTs, garage ported

  6. #36
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    More parts have showed up. Hotside stuff will all be here in a couple days.

    Any time to look into the baro update deal Steveo?
    J. Moen
    91 Camaro - NASA American Iron Road Racer #91 "The Menace", carb'd 350, FloTek heads, "because racecar"
    91 Camaro RS - '93 LT1 /T56 swap, 224/224, 32lb D3, LTs, garage ported

  7. #37
    Fuel Injected! steveo's Avatar
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    i took that DA3 xdf and added a patch for what we discussed earlier, so apply that patch, then modify the scalar named ** BAROMETRIC INITIALIZER

    i -think- that will force whatever initial baro value you set. please test it, even key on engine off just to see if the initializer holds.

    i also noticed that the xdf is a bit error prone, for example the map threshold for PE entry had no conversion on its value (i added a conversion), just be wary of any MAP related parameters that dont max out at ~105kpa, they might not have their math done properly.
    Attached Files Attached Files

  8. #38
    Fuel Injected! steveo's Avatar
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    just to detail what we're doing with this hacky fixed baro patch (want to modify as little as possible)

    - @0xC366 instead of setting baro=map during its update routine if conditions are met, it simply sets baro=baro and moves on.

    - @0xA3CF during the keep-alive (or other update) routine (which ensures map never exceeds baro), it compares map to baro, but doesn't actually store the value (i just changed STAA to LDAA, so it's loading the value again and continuing on)

    - @0xE5E4 we override the initial value for BARO (0xFF / 104.5KPA) to a new fixed value (about half of that for your two bar thing)

    keep in mind the bin offset is 0x8000 and disassembly addresses are relative to 0x0000.. so if you're looking at the bin, subtract 0x8000 from the addresses above

  9. #39
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    You da man Steveo!

    Thank you for the help. I have found a couple resources for operations / coding / instruction for the 68HC11, but still so much to learn. The computer science stuff I took in college was FORTRAN, and I remember about none of it LOL. So cool you are able (and willing!!) to help me out and make this work. I still can't believe TunerPro is out there, and these files are available, basically for free.

    Anyhow, tonight I got it loaded onto the EEPROM per your instructions, and tried key on engine off first. Baro was showing 54.63, which is what I had set it to in the scalar var. you put in the XDF ( ** BARO INITIALIZER ). So far so good . . .

    Then decided to start it, and see what happens. No drama! She starts and drives just like before. I didn't have the wideband on it, so not sure if the A/F ratio is right where it was, but it seems close enough for now. After driving for a bit, some cruising, some WOT stuff, etc., the BARO was still the same. So it appears that is working.

    So, is there anything to worry about here, with setting the baro manually like we have? If the weather changes etc., altitude changes, will I have issues with the A/F ratio getting thrown out of whack? I'm sure the Baro reading has a strong influence on the fuel delivery calculation. I have no idea how "sensitive" to a small change in actual Baro it would be. Remember I'm in open loop, so there's no BLMs at work here.

    Also, should I expect to get the "high MAP sensor" code 33 when I go into boost? Obviously can't try that just yet.

    Some of the stainless hotside mandrel bends showed up today. Gettin ready to get serious, not lacking much now.
    Last edited by hotrodf1; 1 Week Ago at 06:56 PM.
    J. Moen
    91 Camaro - NASA American Iron Road Racer #91 "The Menace", carb'd 350, FloTek heads, "because racecar"
    91 Camaro RS - '93 LT1 /T56 swap, 224/224, 32lb D3, LTs, garage ported

  10. #40
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    So, is there anything to worry about here, with setting the baro manually like we have? If the weather changes etc., altitude changes, will I have issues with the A/F ratio getting thrown out of whack? I'm sure the Baro reading has a strong influence on the fuel delivery calculation.
    hell no, a 2 bar map with an 8 bit scale isn't nearly accurate enough for weather barometrics! the stock sensor is about 0.5kpa resolution. with your division you're more like 1kpa per step now.

    think about it, what is your summer to winter kpa variation anyway? now divide it by two since you halved your kpa, i bet it's 0.02 or less.

    tune for high air density, and when air density drops a bit from the weather, the extra juice wont hurt anything.

    large altitude changes are an issue, but keep in mind even if you DID have baro update on startup, you'd have to pull over and restart the car every time you changed altitude, agin, that's why lots of factory turbo cars have a second sensor for baro pressure

    boosted engines don't mind being a bit rich in the short term, all that extra combustion pressure and heat will burn off the excess no problem.

    Also, should I expect to get the "high MAP sensor" code 33 when I go into boost? Obviously can't try that just yet.
    i doubt it ...? but we could just disable that code. i don't think most speed density ECMS throw a default on map errors (if it did, it would probably be pretty nasty in this case)

    if i have more time i'll trace all your map sensor code too and see if i can find anything like that, or other variables that need to be /2

  11. #41
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    Alright, well if you get time to dig further in that would be fantastic. Would be nice to be warm and fuzzy that nothing stupid (or detrimental to the motor) will happen when I get into boost, which will hopefully be graceful and easy to start off with.

    At this point, I'm going to get ready to start fabbing this setup. Hopefully it won't take that long. Famous last words. . . .

    Thank you again for sharing some of your time and knowledge to further the hobby and help me out!
    J. Moen
    91 Camaro - NASA American Iron Road Racer #91 "The Menace", carb'd 350, FloTek heads, "because racecar"
    91 Camaro RS - '93 LT1 /T56 swap, 224/224, 32lb D3, LTs, garage ported

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