Verification of a Gaseous Portable Emissions Measurement System with a Laboratory System Using the Code of Federal Regulations Part 1065

This paper summarizes the validation testing of the Horiba Instruments OBS-2200 gaseous portable emissions measurement system (PEMS) for in-use compliance testing per Title 40 of the Code of Federal Regulations (CFR) Part 1065.920 (Section 1065.920). The qualification process included analyzer verifications as well as engine testing on a model-year 2007 heavy-duty diesel engine produced by Volvo Powertrain. The measurements of brake-specific emissions with the OBS-2200 were compared to those of a CFR Part 1065-compliant CVS test cell over a series of not-to-exceed (NTE) events. The OBS-2200 passed all linearity verifications and analyzer checks required of PEMS. Engine test validation was achieved for all three regulated gaseous emissions (CO, NMHC, and NO_X) per 40 CFR Part 1065.920(b)(5)(i), which requires a minimum of 91 percent of the measurement allowance adjusted deltas to be less than or equal to zero. The PEMS correlated much better to the laboratory than was necessary to satisfy the verification criteria with 100 percent of the measurements passing for all constituents. The average brake-specific CO₂ and NO_X values both fell within five percent of the laboratory values, while the CO and NMHC levels were both below three percent of the 2007 standard as measured by both systems. Several different time alignment techniques for adjusting the alignment of the engine electronic control module (ECM) parameters, gas concentrations, and exhaust flow signals are discussed as well as the CO₂ and NO_X measurement sensitivity to misalignment. A one second difference in time alignment between gas concentration and exhaust flow was found to change the brake-specific emissions by as much as ten percent for a single NTE event and five percent for an average of all NTE events.