EGR & NOx Emissions: Test Results & Explanation

  • Thread starter Thread starter Ali Durrani
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SUMMARY

The discussion focuses on the unexpected increase in NOx emissions observed during Exhaust Gas Recirculation (EGR) tests at 8% loading conditions on an engine test bench. It highlights the relationship between NOx production and the Stoichiometric ratio, emphasizing that variations in Air-Fuel Ratio (AFR) can occur due to the Engine Control Unit's fuel map, which may have limited resolution. The recommendation includes utilizing a wideband O2 sensor and an Exhaust Gas Temperature sensor to further analyze the mixture and identify contributing factors to the emissions results.

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  • Understanding of Exhaust Gas Recirculation (EGR) systems
  • Familiarity with Stoichiometric ratios and Air-Fuel Ratio (AFR)
  • Knowledge of Engine Control Unit (ECU) mapping techniques
  • Experience with wideband O2 sensors and Exhaust Gas Temperature sensors
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  • Learn about Stoichiometric ratio calculations and their impact on emissions
  • Investigate advanced ECU mapping strategies for improved performance
  • Explore the use of wideband O2 sensors for accurate AFR measurement
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Engineers, automotive technicians, and emissions specialists involved in optimizing engine performance and reducing NOx emissions through EGR systems.

Ali Durrani
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Hello
i have done tests on Exhaust gas re circulation on my engine test bench and these are the results, i don't know what's wrong? but at 8% loading conditions i am getting some weird results
the trendlines in the graph shows an increase in NOx with EGR
is there any explanation for this ? thanks
 

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Do you have access to the fuel map for the engine you are using? NOx production is indirectly related to the Stoichiometric ratio. At different volumetric efficiencies the AFR tends to migrate. This is often due to the Map used in the Engine Control Unit. Some of them use a grid as small as 16x16 to cover all load and RPM conditions. This can lead to wandering results which are occasionally cyclic.
I would suggest running tests with a wide band O2 sensor to evaluate mixture and again with an Exhaust Gas Temperature sensor to look for variations and effects that may be contributing.
 

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