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Thanks for the posts.
ECU learning… The OE ECU doesn’t adapt to a Unichip tune… remember the OE ECU doesn’t even know the Unichip is installed so there’s nothing to relearn. What may need to be relearned, however, are trims already in the OE ECU.
Remember, the OE ECU constantly learns…with the correct data in the Unichip, the values it learns are just very close to zero. Let’s say, for example you have a CAI and no Unichip and have driven the car long enough so the OE ECU is fully adapted.
With a correctly programmed Unichip installed, the data to eliminate those fuel trims is programmed into the Unichip so the learning drives the trims near zero. However, if they already existed and aren’t reset when you install the Unichip, it takes them a little time to get there.
If you disconnect the battery for a few minutes, the ECU’s volatile memory dumps (which contains the fuel trims) and when everything is reconnected, the trims are zero, the learning is near zero, and the solution is stable.
If you don’t disconnect the battery, the previously learned trims will be “relearn” down near zero. This process happens over the course of about a week just like when the trims originally built… once the learning gets the trims back near zero, the solution again becomes stable.
Ignition timing changes between the -, ~, and + maps… remember, values read with a scan tool are from the OBD2 data stream which doesn’t reflect the Unichip changes for ignition timing. What we change is the arrival time of the crank sensor pulse… what the factory computer does remains exactly the same…but it does that either earlier or later than “it should” because the Unichip causes the trigger to arrive either early or late.
Cheers
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