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Old 02-01-2008, 04:31 PM   #1
Toolz
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Default AFR logging with stock sensor?

Can some tell me the reason why the stock o2 sensor is not reliable? So logging ,A/F Sensor #1 (AFR) and A/F Learning #1 (%) are not useful in determining how lean/rich you are running?

Thx
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Old 02-01-2008, 04:56 PM   #2
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It is located pre-turbo is why. It is only accurate near stoich. The JDM twinscrolls are post turbo, but I have only tuned one of those and I used my own WB just because (time constraint).

Gabe
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Old 02-01-2008, 05:34 PM   #3
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The 16 bit ecu O2 sensors are also different than the later ones used on 32 bit ecu. The newer type are referred to by Denso as Planar Wideband and theoretically would work post turbo like in JDM twinscroll applications but there are other factors that may affect its accuracy.

Since you have a 16 bit ecu, I don't think your O2 sensor would work that well post turbo regardless. This is based on the lambda vs mA chart that's included in Denso's paper.
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Old 03-30-2008, 09:43 AM   #4
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So are these values worth anything on stock sensor in determining rich/lean condition?
I am seeing 11.25 at WOT,with learning at -7.81 and then between 12.x - 14.x, at part throttle. But when throttle is let off showing zero in log it shows 23.x-24.x!?

Thx
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Old 03-30-2008, 12:14 PM   #5
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The AFR Learning can be a problem. You should check that with a WBO2.
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Old 03-30-2008, 01:55 PM   #6
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Quote:
Originally Posted by mickeyd2005 View Post
The AFR Learning can be a problem. You should check that with a WBO2.
Hey thanks for the reply, but can you explain please?
Thx
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Old 03-30-2008, 02:14 PM   #7
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I don't know if your car has been tuned or not.

Most of the time, the WOT is tuned when AFR Learning D is 0% because the ecu was reflashed. Over time, the ecu will adjust AFR based upon what it learns from the 50-70 g/s range.

So, now you are running -7.81% less fuel than when you were tuned.
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Old 03-30-2008, 02:42 PM   #8
Toolz
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I was running osecu Stg 1 map, now I am just running the boost values from stg 1 on the stock map. And recently started logging the AFR values, and was not sure how to interpet them.. or if they were even reliable.?
-7.81 means ecu is reducing fuel beause it is richer than the target?

Thanks again.
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Old 03-31-2008, 01:16 PM   #9
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The reason the stock sensor is not good to log is because it is a narrowband sensor. It is only accurate around the stoich areas. Like 15.5-13.5. Anything else and I wouldnt trust it.
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Old 03-31-2008, 03:03 PM   #10
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That's not quite true.

Even if you put a WBO2 in the front O2 position, it would still be inaccurate due to the high exhaust pressure.

Jon[in CT] posted the technical paper for the 32 bit front O2 sensors. Theoretically, it can read down to AFR 11.
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Old 03-31-2008, 04:21 PM   #11
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Here's the paper:
Development of Planar Air Fuel Ratio Sensor

The sensors were designed to distinguish air/fuel ratios down to 10:1.

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Old 03-31-2008, 04:25 PM   #12
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I did not know that. It definately doesnt read accurately though.
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Old 04-03-2008, 10:54 PM   #13
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wolfplayer has some tables to re-calibrate the front 02 to make it read very close to a wideband down to 11.8:1. This is for the 32 bit ECU's though so YMMV with the 16bit.
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