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I've noticed that many people are resetting their ECU after mods and since I do not know much about ECU I did some research and found this...

http://www.tmo.com/theory/myth/ecureset.htm

"Myth
There is quite a bit of mythology revolving around resetting the ECU. Many people mistakenly believe that they need to reset the ECU after installing major engine modifications. Others believe resetting will resolve engine problems. Neither are correct.

Reality
The ECU is always tracking the engine's sensors and actuators. Resetting the ECU does not cause the ECU to learn engine changes any faster. The ECU is always tracking the gradual changes in the engine sensors and actuators. The ECU never gets satisfied with a setting, and is always updating the trim values. It will discover whatever change you made to your engine and make the appropriate changes. In fact, unplugging the ECU will most likely increase the learning curve of the new part.

On a DSM, there are only two reasons why you would want to reset your ECU. One is to clear a CHECK ENGINE light or error code after fixing the problem that caused the error. The other is to reset the spark advance trim value. The advance trim controls how much the timing is retarded from what the factory engineers considered optimum. This particular trim value is the only one the ECU "resets" to a non-neutral MAX value. If you are driving on low grade gas, the pinging picked up by the knock sensor causes this trim value to be lowered, and your timing to be retarded. If you go to the track and put good gas in the tank, you might not want to wait for the ECU to learn about the new gas and advance the timing. So resetting the ECU in this case makes sense. However, in the process, you will lose your idle and fuel trims (probably not too important for drag racing, though).
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True to a great deal but this is what I recall reading from a Nissan source in the know, our ECU's have three settings – aggressive, medium and low (or whatever you want to call'em). When the ECU is reset, it starts with the highest most aggressive setting/timing but as soon as the ECU detects enough knocking/pinging (bad gas, too hot, etc), it goes one setting lower until it gets to the lowest and it is almost guaranteed that it will not go back higher without resetting. To make sure you are at the highest setting, resetting is needed.

Please, correct me if I'm mistaken.
 

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I will check with my tech on this,but when we once talked about this,he said a re set goes to factory setting.If you have factors that reduce mileage or performance and they are not corrected,the ECU will go back to pre re set levels in a day or two.+2 degrees is in until cleared.Performance mode gets back by aggressive driving...but I will verify this!
I do not believe 3 levels because the learn is too encompassing...fuel,timing maps etc,
 

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Certain settings such as A/F ratio and shift points will adjust based on driving habits/conditions but I should've been clear in stating that the three settings are related to timing. The lower the setting the more timing will be pulled. Then again, this still could be wrong due to bad memory/source.

brnjug said:
I will check with my tech...
Please do since this is an intersting point to some of us.
 

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"The ECU does have 3 timing maps, and the least aggressive map is the one that the car usually runs on. Whatever the factory settings is close to what the car will "learn" to run at. That is why over time, it will negate mods that are added to the car."

It is inappropriate to share the source on this..I also have a question into the regional super tech.

Key question is how it learns and where that takes itMy tech and I talked this morning and he and I believe that learning in the OBDII goes in both directions and is shown in Block learn and can be seen with a scan tool.

More to follow!
 
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