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Thread: 95 LT-1 Idle Cell Comparison - Humidity?

  1. #91
    Fuel Injected! spfautsch's Avatar
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    I'm honestly baffled by what it's wanting. I started suspecting offsets because my alternator isn't maintaining the battery charge.

    But, get this: I've tried changing the cranking AFR from 10:1 to 16:1 for the 80c row of the cranking AFR table and it wants to crank until it switches to using the MAF and then it fires immediately.

    Once the coolant temp starts to dip below 75c it starts firing sooner and when below 72c it fires immediately pretty much every time. I think I'm going to look at the end of injection table and see if it may be involved, but I'm sweaty and tired.

    The injectors I have are GM 12561462. I need to look at the datasheet I used to interpolate the offsets from. It's been 2+ years and I honestly don't remember.

    Incidentally, what would I be able to do with the low slope on these? I was under the impression $EE could only handle low pulsewidth adders for injectors that flow less below the knee point. It was my understanding that all the Gen 3 bosch injectors flow more on the low slope.

    I've hung up my hat for the day before I brick my ecu or burn my starter up.

    Edit: The more I think about it, the more I'm considering zeroing all the cranking tables above 50c and see if it starts reliably. I'm a firm believer that having oil pressure before fire is a good thing, and this may be an idiot's way to make that happen. Obviously I may have problems if the MAF dies - guess I better test with and without it.

  2. #92
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    I think Gm made it start hot from maf reading, and it starts hard hotter in stock applications too. I too think that it starts longer when it gets hotter, above 80 degrees.

    There are 2 tables that set engine run flag. When it is set it calculates fuel from maf.
    $122b4 are the rpm above which the flag is set. The scalar for the table is x*12.5, on the xdf is set at x*25, so fix that first to get accurate readings.
    At 80* you can lower the rpms to 160-180.

    Than the other table is $122bd. This is a counter of how many cycles the routine will run with the rpm target reached, before the engine run flag is set.
    Set it to 0 above 80 degrees.


    The injectors are from 01-02 ls6 vette. I will dig a bin and see what are the stock offsets.
    You can even try the ls1 patch if we score some good data. The fuel flow is linear with vacuum manifold so it won`t be hard to interpolate.

    The low pulse slope is very important, when you have that much low pulse driving, below 4ms the flow is not linear and needs adjusting, usually adding time.

    The end of injection target is pretty much the same above 44*.

  3. #93
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by kur4o View Post
    I think Gm made it start hot from maf reading, and it starts hard hotter in stock applications too. I too think that it starts longer when it gets hotter, above 80 degrees.
    I don't recall anything like this before the stroker build. Whatever the case, as long as it starts reliably I'm happy.

    I guess I need to put a test light on one of the injectors and see if they're being pulsed at all before the engine run flag is set.

    Quote Originally Posted by kur4o View Post
    The injectors are from 01-02 ls6 vette. I will dig a bin and see what are the stock offsets.
    You can even try the ls1 patch if we score some good data. The fuel flow is linear with vacuum manifold so it won`t be hard to interpolate.
    Wasn't that a 4 bar application? If so the offsets would be different for 3 bar.

  4. #94
    Fuel Injected! spfautsch's Avatar
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    Here's the datasheet I found (somewhere????) for the modified LS6 injectors. As with all Bosch datasheets it specifies 39.15 psi as the target pressure.

    I'll work over this tomorrow to see if I adjusted the offsets for 3 bar or just copied + pasted.
    Attached Files Attached Files

  5. #95
    Fuel Injected! spfautsch's Avatar
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    I think my prime pulsewidth foolishness might revolve around the $12680 multiplier that I'd completely forgotten about. It looks like we talked about this a couple years ago here, and I'd just blocked it out of memory.

    I'd completely forgotten changing this multiplier because I didn't put it in the Startup AFR category in my .xdf, but it would explain why it wouldn't start with the stock injectors. This multiplier would give a lot more resolution for these prime pulsewidth tables so I suppose I need to figure out how it works so I can account for it in my spreadsheet.

    Edit: take a look - the table on the left is what the default parameter for the 12691 table gives (1.5625*X). The one on the right is using the 12680 multiplier X*($12680*0.00015625). The conversion formula is suspect but I believe the prime pulsewidths I was using from the stock bin were way off so fuel mass conversion was equally way off.

    prime-pulse-comparison.PNG

  6. #96
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    That scalar is used to convert 8bit value to 16 bit BPW. AT stock it is $6666.
    It will definitely offset the pw to hell if you had it set at that value all the time.

    SUb_7781 is where the conversion takes place. It is something like $6666 [66{=a}66{=b}]
    c= 8bit value from table. It is something like (c*a) + (c*b)

    Revert to stock and start from there. I just run a hot restart and it started immediately.
    With that lower scalar it could be sub 1 ms pw you are getting.

    EDIT: the calculation formula is a little different
    You take from C*A only the first byte if the result is 00CC you take 00 and add it to c*b

    $05 8 bit value will be converted like this 05*66{b}= $01FE
    05*66{a}=1FE +01 =1FF * 0.0152587891= 7.7972412301ms

    If you change the scalar follow the rule to change it like $5555 or $4444 , than set your own scalar calculations in tuner pro for PW to see the corrected results.

    edit2:
    (c*a) + (c*b) should be c*b + c*a
    Last edited by kur4o; 09-30-2019 at 02:53 PM.

  7. #97
    Fuel Injected! spfautsch's Avatar
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    Looks like by scaling the table at 12691 I had 2s in the 80c and hotter rows. With the multiplier I had in 12680 that resulted in 2.7ms prime pulses. Not too short to fire the injector, but an awful lot less fuel mass.

    I guess it never occurred to me back in 2017 when it was being discussed that the 12691 and 12682 tables were presented in the wrong units in the xdf. I've created new definitions for them showing the decimal value and with a big "DO NOT EDIT" note.

  8. #98
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    So you got this injectors redrilled.
    here

    The datasheet you have are for some ford injectors which some belief are the same one. I will rip some bins to get you the offsets. Hope they don`t change with the redrill and are coil dependant. Some testing will prove it.

  9. #99
    Fuel Injected! spfautsch's Avatar
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    I just noticed your math on the base pulsewidth scalar - very interesting. Confounding actually. No idea how to pull the MSB and LSB out of a table value in a xdf definition.

    Quick question on a related subject, does anyone know if the injector offsets are applied to the prime pulses? I'm guessing that's handled in the processor we don't have the ROM for because I'm not finding any references to the table address in the public disassembly?

    Edit: So if I'm following you correctly, you're saying the pulsewidths in the left table of the screencap in post #95 were correct for 0x6666 scalar? I'm struggling to understand why this scalar is used like this and why the limitation of having 0x3333, 0x4444, 0x5555.

  10. #100
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    It is 8bit processor calculating 16bits value. I too haven`t found way to get a usable decimal scalar out of it.

    It is just easier to calulate it that way, you can throw any number in there but the first byte is the most important. You can rescale the PWs with new scalar but have to find how to convert it to decimal. I guess it is compromise between low resolution and max usable value. If you lower the scalar you can get better resolution but will loose the max possible value.
    01*6666 = $66
    02*6666 = $CC
    03*6666 = 1+ 132= $133
    ff*6666= $65+$659a=$65ff

    01*5555= $55
    02*5555=$AA
    03*5555= $FF
    FF*5555=54+54ab=$54FF

    01*4444=$44
    02*4444=$88
    03*4444=$CC
    ff*44444=43+43bc=$43ff

    to convert the results to bpw ms the scalar is x*0.0152587891
    SO with different scalar the minimum step will be
    $66[102]*0.0152587891 =1.556316ms resolution
    $55[85]*0.0152587891 = 1.29693 ms
    $44[68]*0.0152587891 = 1.007028ms

    and the max usable value will be
    $65ff[26111]*0.0152587891 = 398ms
    $54ff[21759]*0.0152587891 =331 ms
    $43ff[17407]*0.0152587891 =265ms

    I just noticed that the 1 resolution is really close to the scalar in the xdf (1.562500 * X) + 0.000000 vs 1.556316ms
    Actually the numbers missed the rounding so it it is a close match.

    I guess you need to find the 1 resolution for the scalar and use it as a conversion factor in the tables.
    Last edited by kur4o; 10-01-2019 at 10:31 AM.

  11. #101
    Fuel Injected! spfautsch's Avatar
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    I'm not sure it makes complete sense to me yet but thanks for looking into it!

    I've already found by hand that 0x44(44) puts me 2% rich of target so that should be close enough. I was just laboring under the false assumption that this was a 16 bit scalar when in fact it's 8 bit and optimized somehow (for speed?)? I don't really want to delve into motorola machine code but why couldn't something like 0x4646 be valid?

    I don't think it's a problem losing maximum possible value - the only reason to change this is to accommodate larger injectors so a tuner theoretically shouldn't need the ability for larger maximum PWs here.

    Will give it a try tonight.

    I was able to test with your fork of eehack last night and think I must have been mis-using the trims initially. It wasn't clear to me at the time that the ram table needed to be populated manually before enabling it. I know it would be an undertaking, but some of that stuff deserves a bit of a how-to write up in the readme or something. There's only so much intelligence that can be squeezed into the mouse-over tool tips.

    Edit: Whatever the case, I suppose the parameter definition for 12680 should be setup as a two byte table instead of a 16 bit scalar.

  12. #102
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    Quote Originally Posted by spfautsch View Post
    It wasn't clear to me at the time that the ram table needed to be populated manually before enabling it. I know it would be an undertaking, but some of that stuff deserves a bit of a how-to write up in the readme or something.
    It wasn`t supposed to but there was some bug in the patch. I am doing a reworked version that will fix some stuff and adds off idle cyl trim corrections.
    Definitely a guide of how to will be needed.

    Ok follow this guide.

    Set the scalar to $4444

    Set the conversion factor of the prime pw tables in the xdf to
    (1.007028* X) + 0.000000

    Now it will be pretty close.

    It could be $xx xx for linearity in the calculations.

  13. #103
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by kur4o View Post
    It wasn`t supposed to but there was some bug in the patch. I am doing a reworked version that will fix some stuff and adds off idle cyl trim corrections.
    You're really a glutton for punishment!

    I'm not that worried about seeing what calculated PW the .xdf shows me - I'm more interested in how it works. But if it does maybe it's worth letting people know about.

    Incidentally I found a 2002 ls6 bin here. I haven't been able to find a definition file to look at it with but maybe I have one in Jet DST. I think I deleted the virtual I had it installed on so I'll have to find the cd and build a new VM.

    Also, the engine was exceptionally quiet last night for some reason when I first started it and I think I might have heard a faint pecking sound near the edit: right collector. I'm going to pull the clamp loose tonight and see if there's any carbon in any of the reliefs.

  14. #104
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    I already had posted a printout of the bin here here

    You can search it for injection or injector to find the offset tables.

  15. #105
    Fuel Injected! spfautsch's Avatar
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    Hot restart seems to be cured as far as I can tell. I didn't get a chance to test thoroughly last night or the night before, and a front moved in today so the summer like weather seems to have moved south (at least for now). But I should be able to tell from a warm restart in a few hours if it's right. How's yours - I thought you'd mentioned having sluggish starts after cooling for 4-5 hours?

    Question on your fork of eehack - should the MAF indicator on the dashboard go "off" when switching to SD mode? I'm currently running a MAF tune and clicked the SD button before starting it this morning, but I was seeing airflow from the MAF and the green indicator was lit the entire time. The engine also stayed running and showed no signs of change when I toggled back to MAF at idle. I'm just curious if my log that was supposed to be for tuning VE is going to be useful.

    Quote Originally Posted by kur4o View Post
    I already had posted a printout of the bin here
    Sorry, had completely overlooked that. Thank you! Interesting - GM's using some really low offsets in the 14v row compared to what the datasheet shows. 10v is pretty close though. Corrected high slope is also a good bit different, so I have to question the accuracy of the Ford Racing injector data.

    I'm starting to think I just need to build my own injector flow bench and figure all this out on my own.

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