The effects of diesel fuel density on fuel consumption measurements of portable in-use emissions measurement systems

Emissions produced by heavy duty diesel engines (HDDE) have been a constant source of pollution to air, water, and soil. In October 1998, a court settlement between the US Environmental Protection Agency, California Air Resources Board, US Department of Justice, and the major diesel engine manufacturers was reached on the issue of high NOx emissions during certain in-use operation of HDDE used in on-road vehicles. A requirement of this court settlement was the implementation of an in-use emission measurement program that obligated the HDDE manufactures to measure emissions from their engines during actual vehicle operation using on-board, portable emissions measurement systems (PEMS). The accuracy of the PEMS suffers due to the miniaturization of the system and the lack of redundant systems used in a laboratory system. However, the engine's electronic control unit (ECU) provides outputs that can be used with the PEMS as a quality assurance. Specifically, HDDE broadcast a fueling rate which can be compared to a carbon balance of the exhaust constituents.;The purpose of this research effort was to examine the effects fuel properties had on reported ECU fueling. Specifically, the variation in specific gravity was examined from 153 in-use vehicles and the difference between ECU-reported fueling and fuel recovery though an exhaust carbon balance was determined.;The ability of a PEMS to measure emissions was determined by a comparison with laboratory grade analyzers. The PEMS results were on average within 0.4% of laboratory measurements. Laboratory measurements of NOx and CO2 agreed to within 5.3% and 6.1% of MEMS results.