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Clearly the difference can be seen between the two sensors. The original VW sensor outputs a slightly higher output voltage, which will produce a higher airflow reading in the ECU. At 350kg/hour the curves seem to be closer than at 200kg/hour, but still the TDI ECU will calculate a difference of about 25kg/hour.(7% difference) Also remember that the readings above 200kg/hour are done on the road. These will be less accurate as conditions will never be perfectly the same. The output voltage of the CDI MAF is calculated by reading the RPM and actual MAF value and by the use of the known Bosch TDI MAF curve.

The picture below shows a typical VAGCOM logging results (Fourth gear, WOT). One is with a CDI MAF, the other with a TDI MAF. The time scale is corrected (time shifting) for one logging to get a good comparison. Two things are clear (I think).

  • 1.

    The MB CDI MAF outputs a lower reading. This is in agreement with the curve above.

  • 2.

    As RPMs climb at the same rate, there's no significant difference in engine power in this condition.

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