Narrowband AFR Comparison

I made a couple of logs this afternoon to look into an apparent difference in the narrowband O2 sensor readings reported by ME7Logger and VCDS.

Narrowband O2 sensor readingThe VCDS data is B1S1 and B2S1 in the legend and also has fewer sample points on the chart.  ME7Logger uses OSVoltageSensor1/2 in the legend.  The wideband sensor is an Innovate LM-1 with tailpipe probe so the readings are post catalytic converter.

The VCDS logged event showed a slightly leaner AFR on the wideband which should have translated into some difference in the narrowband readings, the question is if the scale of difference in narrowband readings is appropriate for the different wideband measurements.

I also logged a slightly different boost profile as I work on trying to have an acceptable temporary tune on the car.  This presented another opportunity to look into how the compressor absolute pressure relates to the manifold absolute pressure.

Revised LDRXN boost profileIn hopes of getting some additional insight I looked at the pressure readings at idle.  How much of this difference is due to pressure drop and how much to senor differences will have to wait for another event, next I’ll try logging both sensors with the engine off.

PSIa in the legend corresponds to the Turbo’s Compressor Absolute Pressure (CAP).

Absolute pressure at Idle
Absolute Pressure readings taken at Idle