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Old 06-24-2012, 01:35 PM   #1
AuthenticAMD
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2008 Legacy Spec B
QSM (stage 3.5)

Default A/F Learning D

If you're running a stage 3 setup with greater than stock injectors / turbo, should the A/F Learning D value still be within 5%? Are the values determined by the rear O2 sensor? Just wanting to make sure a wideband isn't needed to determine the actual A/F of the tune during WOT conditions.
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Old 06-24-2012, 02:10 PM   #2
wildt267
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Yes you need a another wideband or to at least relocate the stock one to the downpipe. The pressure the stock one in the stock location is subjected to makes it read richer that what the actual af is.
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Old 06-25-2012, 08:45 AM   #3
Cobb Tuning
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Quote:
Originally Posted by AuthenticAMD View Post
If you're running a stage 3 setup with greater than stock injectors / turbo, should the A/F Learning D value still be within 5%? Are the values determined by the rear O2 sensor? Just wanting to make sure a wideband isn't needed to determine the actual A/F of the tune during WOT conditions.
During WOT (or other higher throttle/load conditions), you are in open loop which means that the ECU does not monitor your actual AFR anyway. It has no clue if you are hitting your target or not. Only in closed loop does it look at AFR and adjust short and long-term fuel trims appropriately.

The A/F Learning 1 values (long-term trims) are determined by the front o2 sensor and they should be reasonable regardless of the mods assuming a good tune and the car in good mechanical condition. The different stored (and applied) values are simply across different airflow ranges, with the "D" range determined in closed loop (in the highest range) but also applied in closed loop and open loop (i.e. even WOT). So, if you have a problem with the car/tune, "D" range has additional significance as it will also impact high load operation, whether there is a problem there or not.

Bill
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Old 06-25-2012, 10:59 AM   #4
AuthenticAMD
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Bill,

Thanks for the explanation. The reason I was asking about the D range was because in my current tune, it is -15%, which explains why it may be lean during WOT and thus knock.
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Old 06-25-2012, 11:05 AM   #5
Cobb Tuning
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Originally Posted by AuthenticAMD View Post
Bill,

Thanks for the explanation. The reason I was asking about the D range was because in my current tune, it is -15%, which explains why it may be lean during WOT and thus knock.
That is not good. I would not go WOT until you figure out what the cause is.

Bill
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Old 06-25-2012, 11:12 AM   #6
AuthenticAMD
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I log on a daily basis and have been running a safe map that is confirmed to have no knock with any significant load, even WOT. Getting a BPV relocation / leakdown check / retune this Thursday.
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