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Thread: DIY LTCC or similar system for LT1s

  1. #241
    Fuel Injected! vilefly's Avatar
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    I just hope that the code 41 doesn't make the ecm lock the ignition timing.

    I have 2 more spare arduino 328P pro mini's at my disposal. I bought 5 for halloween animated eyes that I made so I could teach myself about these things. So no need to recompile.

    I need to get a hold of 8 ls1 coils still.

  2. #242
    Fuel Injected! spfautsch's Avatar
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    It doesn't seem to have any effect on timing, it's just an ECM diagnostic to let ppl know their EST wire is broken / disconnected. It would be simple enough to just disable the test in the calibration (if possible) but I'm trying to work around it electrically.

    I've found that a 470 ohm resistor is enough load on this pin to prevent the code, at least while cranking. Unfortunately it pulls the voltage down enough the arduino isn't seeing the pin go high. So it might require a schmitt trigger or ???

    I got a bit sidetracked trying to fix this issue and got off the task of posting the sketch. Will try to get it on github in a bit.

  3. #243
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    Here are some info on dtc 41 and 42.

    It is triggered during cranking when the voltage on the line exceed 4.6 volts. Normal value is between 0.5 to 4.5 volts.
    On the calibration you can disable dtc 42.
    For DTc 41 you can only raise the voltage threshold. It is located at byte_12037. It is set at 4.6volts. Raising it to Max value will likely disable DTC 41.

    I still can`t be sure, does the PCM provides power or ground path on the IC line?
    Attached Images Attached Images

  4. #244
    Fuel Injected! Terminal_Crazy's Avatar
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    Just watched the videos. Looking Good.

    Will this allow the motor to rev over 7K or is that limited by the PCM ?

    Thanks
    Mitch
    '95 Z28 M6 -Just the odd mod.
    '80 350 A3 C3 Corvette - recent addition.

  5. #245
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    Quote Originally Posted by Terminal_Crazy View Post
    Just watched the videos. Looking Good.

    Will this allow the motor to rev over 7K or is that limited by the PCM ?

    Thanks
    Mitch
    The PCM will freak out at 7228 rpm. Beyond that the opti signal might be too corupt or the PCM too slow to read it.
    Most of the tables will be maxed at 6000-6400 rpm too.
    The opti signal is capped at 7228 rpm and the injectors at 7245 rpm in the code. These limits can be raised but the engine operation might become unstable.

  6. #246
    Fuel Injected! Terminal_Crazy's Avatar
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    Quote Originally Posted by kur4o View Post
    Here are some info on dtc 41 and 42.

    It is triggered during cranking when the voltage on the line exceed 4.6 volts. Normal value is between 0.5 to 4.5 volts.
    On the calibration you can disable dtc 42.
    For DTc 41 you can only raise the voltage threshold. It is located at byte_12037. It is set at 4.6volts. Raising it to Max value will likely disable DTC 41.
    FYI (anyones) On my '95 LT1 PCM ($EE 16188051) is it set to 10.43 for the stock Z28 and the LT4 .bin i have.

    Mitch
    '95 Z28 M6 -Just the odd mod.
    '80 350 A3 C3 Corvette - recent addition.

  7. #247
    Fuel Injected! Terminal_Crazy's Avatar
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    Quote Originally Posted by kur4o View Post
    The PCM will freak out at 7228 rpm. Beyond that the opti signal might be too corupt or the PCM too slow to read it.
    Most of the tables will be maxed at 6000-6400 rpm too.
    The opti signal is capped at 7228 rpm and the injectors at 7245 rpm in the code. These limits can be raised but the engine operation might become unstable.
    I've just checked my logs from today.
    I thought i was abusing the motor but i only just managed to turn 5500 whilst logging for the VE tables.


    Mitch
    '95 Z28 M6 -Just the odd mod.
    '80 350 A3 C3 Corvette - recent addition.

  8. #248
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    Quote Originally Posted by Terminal_Crazy View Post
    FYI (anyones) On my '95 LT1 PCM ($EE 16188051) is it set to 10.43 for the stock Z28 and the LT4 .bin i have.

    Mitch
    The conversion on the xdf is wrong. It should be
    x*0.019607843

  9. #249
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by kur4o View Post
    I still can`t be sure, does the PCM provides power or ground path on the IC line?
    The PCM drives the EST line low, or in other words its an open collector output.

    I'd rather stay away from tuning requirements, and I think I can - connecting the EST line to ground through a 470 ohm resistor seems to prevent the DTC. I just need to figure out this voltage comparator circuit so the microcontroller can see the signal.

    This won't increase any inherent RPM limitations, but it should give stronger spark than the opti above 4500 RPM.

  10. #250
    Fuel Injected! spfautsch's Avatar
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    Initial code commit - diy-ltcc-0.9.0

    Hope to have time this week to work up a partial schematic.

    Been banging my head against the wall with this EST line / DTC 41. Replacing the 10k pullup resistor with a 470 ohm pull-down allows cranking without setting the code, but with the side effect of the microcontroller not catching the falling edge (and no spark). I've tried a LM339N comparator, a 7407 buffer and a 2501 optocoupler. The optocoupler showed promise but nothing close to success. I'll have to do some bench testing on this one because it's really difficult getting useful test data cranking (but not running).

  11. #251
    Fuel Injected! vilefly's Avatar
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    ebay has a nice deal on the arduino 328P pro mini (5v version) 5 + 1 programmer unit for $16.84
    https://www.ebay.com/itm/5Pcs-Atmega...IAAOSwoAxZrwyA

  12. #252
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    What happens when you turn off the code?

  13. #253
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by kur4o View Post
    Here are some info on dtc 41 and 42.
    Interesting - do you know what year that info pertains to? Because the code certainly triggered the MIL while this document states it won't. I immediately noticed there was a code because the fans were running on high right after startup. I was freezing my kiester off what with the garage door half open and 15 degree air coming in while the cooling fans were blasting my legs with not-so-warm air as well.

    Quote Originally Posted by lionelhutz View Post
    What happens when you turn off the code?
    Haven't tested that yet, saving as a last resort. I'm hoping to come up with an electrical workaround so this mod remains a bolt-on affair.

    I went dumpster diving in the recycling bin and located a 7414 schmitt trigger ic on an old switch card. Going to give that a shot tonight.

    It's supposed to get even colder tonight - man do I hate winter. Anyone have some swamp land in Florida they'd sell me cheap?

  14. #254
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    It is from 94 f-body manual.
    Whenever the voltage on the est line is higher that 4.6 volts the error will trigger.
    You can monitor the ICM voltage on the eehack AD tab, hacker label ADCHANNEL_02B5.
    $eb gives you 4.6volts threshold.

    94 and 95 calibrations are all set with these settings.
    Last edited by kur4o; 01-15-2018 at 02:31 PM.

  15. #255
    Fuel Injected! vilefly's Avatar
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    I wonder if you could just cheat and leave the ignition module hooked up (but not to the coil) and tap into the wiring (use optoisolator only if needed). If not,
    I will have to run a scope pattern to see what how much the voltage shoots up when terminal "b" on the ignition module when it is unplugged. That way, I might be able to match the impedence by wiring the EST signal through the center tap of a 10K potentiometer in which one side is tied to 5v and the other is grounded. May need to be higher in resistance, also.

    est biasing idea.pnggoing to be zero degrees F tomorrow, so don't hold your breath, as I am working out in the open. Can't spare the shop room at work, too busy. But I will try sometime.
    Last edited by vilefly; 01-15-2018 at 06:11 PM.

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