Exhaust Back Pressure

Wideband Lambda sensors primarily count oxygen atom numbers through measuring the oxygen ion current within the sensors pump cell. The exhaust gas pressure affects this oxygen ion current – more pressure means more atoms per unit volume and a higher pump current at the same Lambda.i.e will cause the sensor to read farther from stoichiometric

  • A rich reading will appear richer than it really is.
  • A lean reading will appear leaner than it really

This predominantly becomes an issue in Turbocharged applications. This is the main reason you should position the sensor after the turbo where exhaust back-pressure is lowest.

When measuring Exhaust Back Pressure an Absolute Pressure Sensor MUST be used. (i.e do not used a Gauge Pressure Sensor)

The ECU can applied EMAP correction when enabled.  This ONLY applies when the Internal LSU4.9 control is used. This correction is not available to data on  Analog inputs or CAN channel as it requires precise correction the sensors Pump Current.

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