On-road comparison of a portable emission measurement system with a mobile reference laboratory for a heavy-duty diesel vehicle

On-road comparisons were made between a mobile emissions laboratory (MEL) meeting federal standards and a portable emissions measurement system (PEMS). These comparisons were made over different conditions; including road grade, vibration, altitude, electric fields, and humidity with the PEMS mounted inside and outside of the tractor's cab. Brake-specific emissions were calculated to explore error differences between the MEL and PEMS during the Not-To-Exceed (NTE) engine operating zone. The PEMS brake-specific NOx (bsNOx) NTE emissions were biased high relative to the MEL and, in general, were about 8% of the 2007 in-use NTE NOx standard of 2.68 g kW(-1) h(-1) (2.0 g hp(-1) h(-1)). The bSCO(2) emissions for the PEMS were also consistently biased high relative to the MEL with an average deviation of +4% +/- 2%. NMHC and CO emissions were very low and typically less than 1% of the NTE threshold. This research was part of a comprehensive program to determine the allowance when PEMS are used for in use compliance testing of heavy-duty diesel vehicles (HDDVs). (C) 2009 Elsevier Ltd. All rights reserved.