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Tuning OBD1 Systems

  • Spark Related

  • Tuning OBD1 Systems

    Spark Related
    • Initial advance: hint: don't mess with it, it effects global advance calculations.
    • Spark reference angle: also effects global calculations and unless you are sticking this on something that was definitely not intended for it, leave it be.
    • Main spark extension breakpoint: this is at what RPM to quit adding advance as added by the below value.
    • >4800RPM Spark Adder: exactly as it sounds: it adds this many * of advance per 1K RPM over 4800RPM.
    • Max spark advance/retard relative to TDC: you should never need to mess with these as they are set very generously from the factory.
    • TPS and MPH requirements for idle spark: the ECM uses a hysteresis to go on idle or main spark, these are usually set well.
    • EST RPM/kPa Requirements: if the ECM detects values outside of these, it will transfer control of the amount of advance to the ICM.
    • Bias (EGR SA, base coolant advance, TCC locked retard, initial spark timeout): the ECM uses a bias to generate negative values (if necessary) to allow for more versatility. Most if not all should be accounted for in the equations of the tables.
    • RPM/MPH/coolant temp/time/voltage requirements for ESC: ESC is the knock sensor, and if below certain values, any "knocks" detected are disregarded.

    A/C Related
    • A/C Disable constants: compressors don't like to spin very fast, that's why these exist. There are also a few n/v and TPS related disables that exist to stop the compressor from sapping power from the motor.
    • A/C Pressure constants: these determine when to allow compressor clutch action and fan controls. Generally, they shouldn't be messed with unless you know there are problems.
    • A/C idle steps: MPH constants to add IAC steps for idle stability purposes.

    Shift light related
    • Shift light requirements: easily explained, though if you're smart about it, shift light constants can be used to control things other than shift lights....
    • Shift light n/v: n/v is a ratio of engine RPM to vehicle speed. Now, the ECM will look at the n/v and know which gear it is in based on these numbers. Changing tire sizes or gear ratios can affect these, but not much else.

    CCP Related
    • CCP Enable Temp: the minimum coolant temp to allow CCP to be purged. This should be turned off while tuning to eliminate any variables. Disable it by turning the temp to maximum (304.25*F). Re-enable if desired when you're happy with your results.
    • Other CCP requirements: CCP CAN cause a rough and rich idle, which is why these exist. The duty cycle multiplier can be useful though, to get it to ramp up to 100% or down to 0% quicker, depending on what you want to do.

    TCC Related
    These can completely change the way your vehicle behaves in 3rd gear and above (possibly 2nd if you play with the settings enough and bypass a check. take caution when changing them. a LH0 feels even more gutless without TCC lockup at higher speeds.
    • TPS Required for TCC lock in Converter Melt-Down Mode: this is referring to catalytic converter meltdown, not the TCC. Simple enough.
    • Delays: exist to stabilize the engine a bit before allowing lockup. The global delay is simple, high delta TPS unlock is also simple; quick throttle change but still in lockup range will cause an unlock for this period of time. 4-3 downshift unlock is for a regular downshift from 4th, and since we're usually dealing with a 4T60, it's based on a mechanical equation involving trans fluid pressure, throttle position(via the TV cable) and MPH.
    • Unconditional lock/unlock: the LH0 isn't a high-rev motor, and locking the TCC will bring down the RPMs for a given MPH, which will bring it into its powerband and hold it there longer. Keep in mind the TCC can only withstand so much HP though without slipping. But at stock settings in BFBD, 88MPH, in 3rd gear you would be at roughly 3750RPM with 26.3" tires, which is slightly after the torque peak.
    • TCC TPS/MPH thresholds: easy to set with a good calc, like the moonwell gear ratio calculator and just realizing how it feels. The 4T60 uses an accumulator to soften the TCC apply; unlike the later transmissions that used PWM apply operation.
    • Meltdown mode: if the engine coolant temp reaches a certain point (250*F in BFBD), you'll get lockdown mode TCC operation, which can lock the TCC in any situation that meets its criteria, including 2nd gear IIRC.
    • TCC declutch: looks to be something the factory never implemented.

    Fan Settings
    • Fan Temps (with or without a/c): I like them set 15*F above my thermostat temp to avoid thermal cycling, which can seriously FUBAR your motor if it happens enough. I set fan #2 about 3* above fan#1 to avoid too much of a draw on the electrical system at once. I set the turn off points about 3* away from each other as well. Fan #1 off at ~5*F above the thermostat temp.
    • Fan MPH cutoffs: above certain MPHs, the airflow coming through the radiator is more than enough to cool off the motor without the help of the fans. They can potentially hinder airflow as well, so unless you can find out the exact CFM ratings of the fans, the MPH constants should probably stay as-is.
    • Turn on delays: these work to help stop a flaky CTS and air pockets from kicking the fans on and off constantly.
    • IAC steps added: if you have anything else triggered by fan relays or swap to different fans, or they just have gotten old, then you can use the IAC to compensate for the large amperage draw that would otherwise drop the RPM unnecessarily.

    Cat Protect
    • Cat settings: there are settings in the tune to richen up the AFR while in high load to cool off the cat. I personally don't care for the converters, and heating them up enough WILL burn off contaminants, so I disable the routine by setting the enable temps to their maximum and I'm done.

    • Divert: it seems that only manual trans vehicles got AIR pumps, but "diverting" is when the solenoid to control whether to pump air into the atmosphere or exhaust is sent to exhaust. Copying values from an auto BIN will disable it.

    Launch mode/shift energy
    • Launch Mode: this is normally used in factory tunes to spin up the torque converter faster than normal by adding a bit more spark advance. However: for the higher HP/lower traction cars, you can add a few degrees to the bias, and then it becomes a spark retard, allowing you to pick up traction. Nifty little idea.
    • Spark retard: this is to help keep the trans alive during some abuse by removing some advance during shifts.

    • SappySE107
      SappySE107 commented
      Editing a comment
      Needs updated! Links are broken for freescan and all moates products. Also, tunerpro can scan most of our OBD1 systems.
    Posting comments is disabled.

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