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Old 09-26-2012, 09:38 AM   #10
Cobb Tuning
Member#: 4803
Join Date: Mar 2001
Location: Austin, TX

Originally Posted by tiled00dles View Post
Can someone explain to me what the a/f learning is. Mine is always in the high positives, but when I look at other stage 1 data logs, they always have negative numbers.
A/F Learning 1 is a long-term correction to fueling based on patterns of fueling errors that the engine control unit (ECU) sees based on front o2 sensor feedback. The idea is that the ECU can get you closer to the intended fuel target faster. A/F Learning 1 is made up of 4 different values (A,B,C,D), which you can view individually ("A/F Learning 1" in your log is simply the current one that is being applied).

The learned values can alternate between positive and negative - there's a margin of error here and it isn't always precise. There are also variances in the ethanol content of fuel that impact these trims. A general rule of thumb is that they all should be within about +/- 5%. If you are well outside of this, then you may have a mechanical fueling issue. If not, then it is not something to be concerned with, regardless if they are all positive or all negative, or a mix of both.

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