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Go Back   E46Fanatics > Tuning & Tech > Driveline, Engine & DME Tuning

Driveline, Engine & DME Tuning
Talk about driveline improvements, NA tuning and DME tuning your E46 BMW here. This includes diffs, intakes, exhausts, chips, software and OBD tuning.

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Old 10-11-2016, 09:07 PM   #1
e46partsguy
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O2 sensor voltage readings.

I just recently repaired some vacuum leaks on a 2004 m54. I reset the adaptations, and currently the pre cat o2 stay at 1.5 volts with little fluctuations. I was wondering what the allowed voltage range was at idle and 3k to see if i still have any leaks. I smoked my intake system with no leaks found. I repaired three leaks before considering it good. Car seem to run excellent. I believe it's MS43. Input is greatly appreciated! Thanks fanatics
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Old 10-14-2016, 11:20 AM   #2
rkneeshaw
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I thought a 2004 M54 is going to have a MS45.1 DME, and therefore wideband O2 sensors in the pre-cat locations.

My 2003 ZHP has the M45.1 DME.

You should verify this first, as that will change what voltage readings you should expect to see.

I've been able to find a transfer function to convert the wideband O2 voltage to an AFR.
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Last edited by rkneeshaw; 10-14-2016 at 11:22 AM.
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Old 10-14-2016, 02:46 PM   #3
e46partsguy
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I thought the same thing, what I can say is ms45.1 uses a six wire maf while ms43 uses a four wire maf . This car has the six wire maf so I do believe it to be using wideband o2. Just wondering what optimal readings would be for both systems?
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Old 10-17-2016, 09:06 PM   #4
rkneeshaw
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The wideband pre-cat O2 sensor voltage will range from around .2 volts (super rich) to 4 volts (super lean). Approximately 1.5 volts = 14.7 or so AFR.

The transfer function looks like this in excel, assuming your pre-cat O2 bank 1 sensor voltage is in cell N5 and your pre-cat O2 bank 2 sensor voltage is in cell M5:
=(0.684562+(((N5+M5)/2)*0.205987))*14.7

I arrived at this formula after hours of testing and data logging using an Innovate LM-2 wideband kit and Bytelogger to dump the DME pre-cat O2 sensor values.
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Last edited by rkneeshaw; 10-17-2016 at 09:06 PM.
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Old 10-19-2016, 02:39 PM   #5
e46partsguy
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That is awesome. If i !ay ask why did you need to record your o2 sensor values. Are you tuning?
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Old 10-19-2016, 08:42 PM   #6
rkneeshaw
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Yeah, I wanted to be able to check my AFR after updates to my tune from ESS without having to install an aftermarket wideband O2 sensor, controller, and gauge.

Those of us with MS45 have the advantage of the built-in wideband.
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