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Tuning OBD1 Systems

  • Fuel related

  • Tuning OBD1 Systems

    Fuel Related
    • Injector Flow Rate: not what you think, it's only for DIC calculations for fuel economy. good for sticking in to remember what exactly something was tuned for though.
    • Injector Flow Rate for Alpha-N Idle: This is used for telling the ECM only the injector size while at idle if the alpha-N idle is specified.
    • Idle Fuel: idle fuel is a bit different than normal speed-density, but the values to enter it don't really have a reason to be messed with unless you have a wicked cam that happens to idle with a lot different vacuum and you want to keep idle fuel mode.
    • Hot/Cold Closed Loop Temps: sets thresholds for timers to allow closed loop operation. their overlap forms a "warm" zone, which is mentioned momentarily. normally you won't play with these, unless you live in some extreme climate.
    • Closed Loop Timers: cold/warm/hot: its how many seconds the ECM will wait before attempting to use the O2 to correct fueling. stock in BFBD, they are 180/84/2 seconds. I have personally seen the non-heated O2 ready in less than 90 seconds from a ~0*F start, so I changed it to 100 seconds for cold, left the 84 alone, and changed the 2 to 10 seconds since 2 seconds seems a bit too quick to me, but your mileage may vary. if you are methodical enough, you will be able to change them to within a few seconds of when the O2 becomes operative, helping your O2 diagnostic and saving fuel. keep in mind that these timers also apply to EGR as well.
    • Minimum MAT for closed loop: exactly as it sounds: the minimum air temp to allow closed loop.
    • Minimum coolant temp for closed loop: again, exactly. stock was 103.10*F, but I think that's too long considering my O2 is ready long before that. so I liked the idea of 50*F. works well. if you are trying to tune using a wideband, max this out to prevent going into closed loop.
    • O2 sensor not ready timer: this is how long the ECM will wait for the O2 to become 'active' after the appropriate closed loop coolant temp timer has expired, and the minimum coolant temp for closed loop has been reached before it will set an error code.
    • Idle O2 sensor not ready timer: same as above, but while at idle.
    • BLM disable above/below RPMs/MAP: for learn only, otherwise, the previously derived values will still be in effect.
    • INT Window: the INT's 'happy zone'. this is how far the BLM will allow the INT to move before correcting fuel.
    • Max/Min BLM/INT: exactly as they sound. they are in decent spots from the factory, if you need more room to tune, you need to learn more about tuning or are dealing with a VERY different combo than what the BIN is setup for.
    • Maximum AFR: exactly as it sounds: it's the maximum Lean AFR allowed by the ECM, regardless of what values are used for open loop or highway fuel.
    • Max/min async pulsewidth: async fuel is from AE/DE operation, this determines how much is too little to care or too much to be async.
    • Highway fuel MPH/AFR: when the vehicle is at a good speed and low load, the ECM can go into highway fuel mode and not run at the required (by EPA) 14.7:1 AFR. I like 16.2:1 AFR. the MPH thresholds can be tailored to match your vehicle.
    • Stoich AFR: match this to the fuel you are using, trust me, it will save headaches.
    • Closed to open loop blend rate: how quickly the ECM will filter in open loop fueling differences compared to the closed loop BPW it had before.
    • Min O2 error for INT: this is how far the average of the O2 voltage must be off before the INT will move in an attempt to correct it.
    • Rich/lean threshold at idle: makes sense, it's what the ECM targets as the average O2 voltage while in idle condition.
    • O2 references at idle: this is how the ECM determines if the O2 is working correctly or not. if the O2 doesn't swing out of those ranges, it isn't hot enough. the O2 swings due to the ECM varying between rich and lean firings and if it doesn't see what it likes, it will kick out of closed loop.
    • Min BPW for BLM learn: more hysteresis confusion: only should need changed if you go with significantly larger injectors, otherwise, no reason to play with it.
    • Prop gains: know how I mentioned the ECM commands slightly rich, then slightly lean to attain an average O2 voltage? well, this is how. more gain means larger swings.
    • Idle fuel settings: they were mentioned before, this is more requirements.
    • Fixing factor for injectors: ??? possibly to compensate for injector open/close times? doesn't usually get messed with.

    SAM (stay alive memory)
    SAM is how the ECM stores certain values after shutoff, like last BLM positions and IAC minimum positions.
    • BLM: simple enough, it's the limits it can reach. stock values are fairly tight and won't allow a lot of permanent learn, possibly to prevent junk O2s from messing with an otherwise good engine. there are coolant temp and runtime requirements to store BLM values in SAM to make sure everything is in normal condition before storing.

    Speed/Rev Limits
    • Speed/rev limiters: be sensible, that's it. this will cut fuel when you reach either.

    • AE: accel enrich is to compensate for the rush of air the engine sees during quick throttle transitions. going lean will produce a stumble and going too rich will cause a "too rich to burn" condition that will bog, but more AE will feel like a stronger motor until you reach that point, though emissions (and fuel economy) will suffer.
    • DE: decel enleanment is the exact same idea as AE, just the polar opposite. pulling more fuel will result in more dramatic changes and eventually you'll hit the point of lean misfires and potentially popping and backfires.
    • DFCO: cuts fuel flow to the motor in 'overrun' situations. basically, there is a LOT of vacuum, and the RPMs are fairly high. both variables are customizable, but know this: it works MUCH better for manuals than it does automatics. there are timers for short and long term DFCO.
    • PE: power enrich is what the ECM enters when enough throttle is applied and is basically going into a max power mode.

    IAC related
    • IAC Park Start-Up Position: something to change if your car starts and revs too high for your liking at all coolant temps. less steps means less air.
    • Initial IAC Minimum Value after NVM Power Loss: this can replace idle relearns so long as the engine isn't modified after its set correctly. the datastream pushes out this value, so make note of it after the car idles well.
    • Power steering cramp: if you turn the wheel too far, the PS pump can bog the motor down, which is the purpose of these settings.

    • EGR: DISABLE DURING TUNING! max the temp and forget about trying to compensate for it. afterwards, if you want it, enable it and tune the table meant for it.
    • Gear multipliers: good for curing some low-MPH bogs due to EGR action.
    • Requirements: they are there to minimize the effect EGR can have on drivability.

    • 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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