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Author Topic: Why does Actual AFR not match wideband gauge?  (Read 9166 times)
catbed
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« on: May 15, 2013, 06:42:06 PM »

My 018CH box's requested AFR is 14.7 at cruise and actual hovers around there, only deviating ~.5 AFR in either direction. However, my AEM UEGO gauge shows ~15.3 and rarely drops below 15.0. So my question is, which one is wrong? Both o2 sensors are brand new. UEGO replaced with a Bosch 17018 and the primary o2 replaced with a Bosch 17014. The primary is from a VW 1.8t so my next move was to compare LALIUS between the two files. However, I want to believe that the gauge is at fault.

I will connect the gauges analog out to the rear o2s and log voltage, but that won't happen until i figure out how to locate RAM addresses in IDA.
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userpike
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« Reply #1 on: May 15, 2013, 07:17:57 PM »

My 018CH box's requested AFR is 14.7 at cruise and actual hovers around there, only deviating ~.5 AFR in either direction. However, my AEM UEGO gauge shows ~15.3 and rarely drops below 15.0. So my question is, which one is wrong? Both o2 sensors are brand new. UEGO replaced with a Bosch 17018 and the primary o2 replaced with a Bosch 17014. The primary is from a VW 1.8t so my next move was to compare LALIUS between the two files. However, I want to believe that the gauge is at fault.

I will connect the gauges analog out to the rear o2s and log voltage, but that won't happen until i figure out how to locate RAM addresses in IDA.

Not sure how different the AEM gauge is but I have an Innovate MTX-L wideband and the instructions stated not to use a "noisy" ground or power source like where your radio is grounded or fed power. Also, how close in proximity is your WB sensor to your stock WB sensor location? I believe there will show a slight difference if they are far away from each other. My logic here is that fuel can still be burning in the DP  I think the farther away, a more complete burn will show up on the gauge. I could be wrong though.

I'm running a 1.8t with HSbox and I get pretty consistent AFR's between the precat sensor and the WB sensor for the Innovate gauge. I placed the sensor for the WB gauge very close to the same length from the turbo but at a different angle so the sensors wouldn't screw up exhaust flow for each other.
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catbed
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« Reply #2 on: May 15, 2013, 07:19:56 PM »

I will check the ground location.

The UEGO is 6 in away from the primary and 12 from the turbo. Both angled about the same.
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zillarob
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« Reply #3 on: May 15, 2013, 07:37:41 PM »

If they are both the same sensor, swap them and see what happens. Might narrow it down between a software scaling or sensor calibration thing.
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catbed
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« Reply #4 on: May 15, 2013, 07:42:29 PM »

Sensors are the same, connectors are different.

Just swapped gauges with my friend to see if it was the AEM controller. No luck, still reads the same.
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phila_dot
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« Reply #5 on: May 15, 2013, 09:24:31 PM »

It could just be the difference in logic. I'm sure that the external wideband has much simpler logic.

Is the external wideband mounted as recommended by the manufacturer?

Any exhaust leaks?
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userpike
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« Reply #6 on: May 15, 2013, 11:58:05 PM »

Sensors are the same, connectors are different.

Just swapped gauges with my friend to see if it was the AEM controller. No luck, still reads the same.

If you can put your friend's sensors on your car and get the same results I say your gauge wiring or if the AEM gauge can be calibrated, it needs to be done. (the Innovate WBs have a calibration sequence...requiring the o2 sensor outside the pipe in fresh air.) It would make sense to me about the sensor logic if you were trying to plug in the wrong sensor. Sometimes the plug is the same but the part is for a different application. but your part numbers are correct right?
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prj
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« Reply #7 on: May 16, 2013, 03:07:51 AM »

This is normal. The position of the sensor affects the reading somewhat.
There is a difference whether it is in the rear O2 or front O2 location...

I have once put three different widebands on a car, one in front WBO2 location, one in rear, and one in the tailpipe - all read slightly different.
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overspeed
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« Reply #8 on: May 16, 2013, 09:23:52 AM »

I guess it´s only sample rates diferences and precision.


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prj
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« Reply #9 on: May 16, 2013, 09:53:03 AM »

No, it is not sample or precision difference.
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