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Thread: 1996 LT1 to 12200411 PCM conversion help

  1. #16
    Fuel Injected!
    Join Date
    May 2020

    Cool LT1 0411 tuning quest continues.....

    Hello everyone! I’m still trying to wrap my head around this project,
    it feels more like I’m getting “Wrapped around the axle” I’m reading more
    about spark tables and advancing/retarding the timing according to
    map-vs.rpm’s-vs.temp, etc. I found an online calculator that helps you
    start initial spark tables, perhaps one of you guy’s can look this over and
    see if it comes close. It’s from a site that uses “microSquirt” efi.
    It ask’s specifics like:

    Cylinder Bore: inches millimeters
    Combustion Chamber Type: open chamber - little or no quench 2-valve closed chamber w/ optimized quench 3 or 4 valve engines, w/ swirl&tumble
    Fuel: regular (87 octane) mid-grade (91 or 92 octane) premium (94+ octane) E85
    Compression Ratio: < 9.0:1 9.1:1 to 10.0:1 10.1:1 to 11.5:1 > 11.6:1
    Idle Vacuum: in·Hg
    Maximum boost level:
    (0 for naturally aspirated,
    max. boost (psi) for turbo/supercharged)
    (21 psi maximum)
    Maximum RPM: RPM
    Idle RPM: RPM
    Spark advance table dimensions: 8×8 12×12 16×16 24×24 MS-I uses 8×8 tables;
    MS-II, MicroSquirt, and the Sequencer use 12×12 tables.

    if anyone has a different calculator or spreadsheets that can help us “Noobies” Please share,
    I really want to understand the flow of how everything works together.
    thanks again!
    have a great day!
    Ben Smith
    “He who lives by the Sword, gets Shot by those who don’t”

  2. #17
    Fuel Injected!
    Join Date
    May 2020
    Hello all!
    Just thought I’d post an update to my project. After chasing gremlins for the better part
    Of the last week, I figured out two problems with my setup.
    1.) I’m sure everyone has witnessed “broken MAP sensor connector locks breaking” Well, mine
    Was no better. Since I had a couple spare connectors handy, I un-pinned the wires from the
    connector, but “ failed to mark each Wire location” ( the middle one was easy, the light green sensing wire)
    But I managed to swap the 5v ref. Wire with the ground and, the readings I got confused the hell out of me.
    When I back probed the connector of the gray 5v ref wire, it was right on, and the ground as well,
    But when I installed the connector on the sensor, well you know the rest: my 5v ref signal was reading 1.745volts-
    Wtf? And my Map sensor read 25 KPA all the time, regardless of engine rpm’s. I finally gave in and broke out
    the schematics (again) to verify the order of wires to the map connector ( insert bone head mistake of the year award here) 1E2ADEF1-37F3-43CD-BBF6-9EFB2B62423B.gif
    After I corrected that, my MAP sensor reads spot on now,
    And the engine is Idling smooth again.

    My second problem was my TPS sensor would not adjust to .5volts, I even elongated the mounting holes,
    I finally had to bend the tab on the Throttle body (at the adjustment screw) in order to get my adjustment right.

    So now, I have no DTC’s and I can proceed with data logging and fine tuning this beast. (Just in time to put it away
    for winter) dang.......
    It's been a real learning curve to say the least, but as they say: “ Knowledge is power” I’ve never “thrown in the Towel” on any project I’ve started , and I don’t intend to start now!
    Well, work calls so have a Great Day!
    Ben Smith
    Attached Images Attached Images
    “He who lives by the Sword, gets Shot by those who don’t”

  3. #18
    Fuel Injected!
    Join Date
    May 2020
    Hello everyone!
    Just wanted to update everyone on what I’ve accomplished so far. I finally found the reason
    my engine was running so rough, and I am embarrassed to say, I had a “Brain Fart” while re pinning
    my harness....I’m sure most, if not all have found the retaining clip on the MAP sensor is prone to breaking
    Off. I had an extra connector laying around and decided to unpin the wires and simply swap the connector.
    Well, I didn’t mark the locations and mixed them up (the light green sensing wire was easy, since it was in the
    center, but I had the 5v ref. And ground swapped) so I kept getting weird reference voltage readings like 1.73 volts
    But everything is good now, with the exception of a bad O2 sensor ( and I just replaced with new Delco sensors)

    So, I wanted to post my data log here for everyone to review and feel free to make any suggestions to what I need to change/modify to get this beast “dialed in”!
    One thing I noticed while driving the car: at deceleration, it backfires Through the exhaust, and randomly while driving.
    I’m sure that bank two O2 sensor is causing that. I also noticed my speedo was off, it was reading “30 mph” when it was more like “60 mph” likely the VSS pulse count need changing.
    So, here is the data logs I have made so far, and I’ll get more done later after I replace that O2 sensor.
    Ben Smith
    Attached Files Attached Files
    Last edited by Snipescastle2; 6 Days Ago at 02:04 AM. Reason: Changes
    “He who lives by the Sword, gets Shot by those who don’t”

  4. #19
    Fuel Injected!
    Join Date
    May 2020
    Hello again! I’ve replaced my non functioning O2 sensor(bank 2 sensor 1) and I’m going to
    do more data logging tomorrow. While driving the other day, and even when the engine was
    idling, it was “Back Firing” through the exhaust, not sure if the bad O2 sensor might have contributed
    to this. I’m sure my timing needs addressing, as the car doesn’t have much power while “Rowing
    through the gears” well, I’ll post more logs when I record them.
    Have a good one!
    Ben Smith
    “He who lives by the Sword, gets Shot by those who don’t”

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