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Thread: DIY LTCC or similar system for LT1s

  1. #661
    Fuel Injected! spfautsch's Avatar
    Join Date
    Apr 2015
    Quote Originally Posted by kur4o View Post
    ... but it also provides power to auto trans solenoids.
    Ooh, that kinda sucks. I doubt everything in the trans draws more than 1 amp peak, until one of them shorts. I'm surprised GM did that.

    In light of that information a relay setup like you describe would be my choice on an auto car.

    Quote Originally Posted by kur4o View Post
    That 3 slots explains the counts inconsistency.
    I think the three slots are to give more light transmission for a cleaner high-speed signal at the phototransistor - as opposed to the low res side which switches very slowly by comparison.

    Quote Originally Posted by kur4o View Post
    I also found why opties fail so much. It is the only japanese part in the car. There is some dot welds that eventually will broke due to high frequency switching and cause signal loss. Not an easy fix since soldering wont last long there.
    I respect everything you take the time to post, but after spending plenty of time researching my personal opinion is that the phototransistor (receiver side) eventually shorts internally from temperature. All things aside, if you put a bunch of semiconductors on a chunk of aluminum that for all intents and purposes has 215F oil sprayed on it it's whole life, failure is inevitable, and I think it's no accident that phototransistor equipped sensors have been almost completely absent from the automotive industry for nearly two decades.

    Quote Originally Posted by kur4o View Post
    Is there a way to get feedback from coil if it is blown or not delivering spark for some reason.
    Unfortunately not. Unless these coils have some internal self-diagnostics that we're not aware of it would require monitoring current to each coil. There aren't enough adc channels to start with, and you would need current sensing shunts for each coil which would increase wire and part count immensely. Maybe if misfire detection works that would help diagnose, but I'm not optimistic it will (work). If GM is doing anything like this currently, keep in mind they have a slightly larger R&D budget than Scott's basement lab.

  2. #662
    Fuel Injected! spfautsch's Avatar
    Join Date
    Apr 2015
    Latest release 0.9.38

    Found incorrect sequence detection bug - although I did luck out yesterday and manage to log an instance, it would have been easy to find had I looked. Fallthroughs in sequence detection routines were returning 0 instead of -1 which means #1 is on compression stroke.

    int8_t detectSequence(uint8_t seqDegrees) {
      // note: returns the index of sequencer array, not cylNo
      if ((seqDegrees > 82) && (seqDegrees < 90)) {
        return -1;
      } else {
        if ((seqDegrees > 72) && (seqDegrees < 80)) {
          // next cyl #4
          return 2;
        } else if ((seqDegrees > 62) && (seqDegrees < 70)) {
          // next cyl #6
          return 4;
        } else if ((seqDegrees > 52) && (seqDegrees < 60)) {
          // next cyl #7
          return 6;
        } else if ((seqDegrees > 42) && (seqDegrees < 50)) {
          // next cyl #1
          return 0;
      return 0; // << plant forehead firmly in palm !!!
    Also added a state variable to handle stall detection instead of using the pin 13 state (drives the yellow led). Will allow for using the status led for other purposes in the future (i.e. kur4o's suggestion).

    This hasn't been road tested yet but I will report back if there are issues.

    Update: I've driven about 100 miles on this with no issues. I further simplified the sequence detection routines to eliminate the initial error catch and just let the fallthrough handle all oddball scenarios. I only have about 25 starts on this build so it's too early to make a determination, but so far zero no-start cranks.
    Attached Files Attached Files

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