X-Nico

Portable emissions measurement system

On the other hand, fleet emissions deduced from laboratory measurements can be subject to significant inaccuracies if the selected engines and operating conditions were not representative of the fleet, or if deliberate anomalies (i.e., dual mapping of the ECU) were not demonstrated during laboratory testing.

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Also, PEMS testing identified several engine “anomalies” where fuel-specific NOx emissions were two to three times higher than expected during some modes of operation, suggesting deliberate alterations of the engine control unit (ECU) settings.

see also