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Hi Hussein

 

Did some calculation. The ECU reads an AFR wich is exactly 0.4 AFR to high.

That's why it stabilze at an AFR of 12.3 while the actual AFR is 11.9.

I tested the rear lambdasensor channel of the ECU on the bench. When grounded to the the ECU ground it reads exactly the right value, while grounded to the sensor negative pin of the ECU it exactly reads 0.2 volt to much (an offset of 0.2 volt).

The range of the wideband sensor is 0 volt@ 10 AFR to 5 volt@20 AFR so that's 0.5 volt per 1 AFR. An offset of 0.2 volt therefore represents a mismatch of 0.2/0.5=0.4 AFR which is exactly your mismatch.

The sensor therefore probably isn't grounded correctly. Best you connect the ground of the WB sensor directly to the ground of the ECU.

When that doesn't help ... move over to the much less troublesome tank pressure sensor :)

This problem can't be resolved by changing the conversionfactor in he ADX, while despite you might get correct readings that way, the ECU still sees an incorrect value for the AFR and the achieved AFR will not be matched correctly with the requested AFRs in the VE table.

 

Piet

 

 

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This problem can't be resolved by changing the conversionfactor in he ADX, while despite you might get correct readings that way, the ECU still sees an incorrect value for the AFR and the achieved AFR will not be matched correctly with the requested AFRs in the VE table.

Piet, can you explain further? I've tested the rear O2 input with an adjustable bench supply while in the car, and I found the voltage offset to be linear and equal to 0xA (.196V), throughout the entirety of the voltage range. The bench supply was grounded to a common ground, and not the rear O2 sensor ground.

I'm not sure why changing the .adx conversion factor, or, in the case of wideband regulation, the .bin conversion factor wouldn't eliminate the error. 

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I've tested it on the bench (I will post some pictures of it later on),  also with a (extra)  bench supply connected .

If the extra  supply is connected with it's ground to the signal min of the rear sensor  then there is an (linear, indeed) offset of 0.2 volt..

With the ground of the supply connected to the ECU ground on the other hand, there definitely wasn't any offset at all !

 

With changing the .adx conversion factor you will get the right AFR reading, but the ECU will still see 0.2 volt to much and stabilizes therefore at an AFR of  0,4 to high.

To get that right,  the conversion factor in the bin itself has to be changed also, but that's exactly what I like to avoid, keping things uniform and simple without complicating things by introducing al kinds of unnecessary scalars and tables.

It just is possible to connect the wideband sensor without introducing an offset, that's in my opinion the right way to go.

Edited by Piet
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I've tested it on the bench (I will post some pictures of it later s.

It just is possible to connect the wideband sensor without introducing an offset, that's in my opinion the right way to go.

​OK  -so I need to change the WB02 ground to the ECU ground, and change the conversion factor to the correct (uncorrected) formula.

Edited by lookforjoe
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Sorry to butt in here but are you guys basically replacing the stock front o2 sensor with a Wideband o2, grounding it to the ecu instead and then using a conversion formula to use it in all the fueling maps, part load, wot etc.??

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​OK  -so I need to change the WB02 ground to the ECU ground, and change the conversion factor to the correct (uncorrected) formula.

​Hi Hussein,

I remember I had a question about this a few months back; we determined the WB ground (minus input) should be connected to sensor ground of ECU (e.g. pin A18) rather than A19.  Did you have yours connected to A19?  That will definitely give you an offset.

^ What avinitlarge did works too of course!

Edited by gdog
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Mine wasn't connected to A19, it was simply connected to ground in the pass compartment (aux ground in accessory connector found on all x70 98)

What's curious is that the AFR discrepancy varied: (no WOT, as I need to resolve the rich condition first) about 24psi here

Screenshot%202015-06-02%2021.42.28_zpsug

Screenshot%202015-06-02%2021.38.37_zpskf

Screenshot%202015-06-02%2021.44.43_zpsox

Anyway, I have moved the AEM controller ground to the ECU ground, and will test it tomorrow

 

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Mine wasn't connected to A19, it was simply connected to ground in the pass compartment (aux ground in accessory connector found on all x70 98)

What's curious is that the AFR discrepancy varied: (no WOT, as I need to resolve the rich condition first) about 24psi here​

 

Aha, that's not unexpected then.  Connecting a sensor like a WB to a ground far from the ECU sensor ground reference would give you inconsistent results.  As currents vary through the different connecting ground paths, you'll get different voltage drops between that aux ground point and the ECU sensor reference.  Hopefully it will work better now.

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Sorry to butt in here but are you guys basically replacing the stock front o2 sensor with a Wideband o2, grounding it to the ecu instead and then using a conversion formula to use it in all the fueling maps, part load, wot etc.?

You need a WBO2 controller - the ECU cannot govern the sensor, just accepts the 0-5v analog output from the controller as opposed to the nerst signal.

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The AFR will never

What's curious is that the AFR discrepancy varied: (no WOT, as I need to resolve the rich condition first) about 24psi her

 

The actual AFR will never always exactly be  the same as the requested AFR., but will be oscillating somewhat around the requested AFR, ihherent to a feedback (closed loop) regulation. 

Edited by Piet
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