Evaluation of Improved Bag Mini-Diluter System for Low Level Emissions Measurements

General Motors Corporation has installed its first production Bag Mini-Diluter Emission Test Site. This site is capable of conducting chassis dynamometer tests in either traditional CFV mode, or BMD mode, and a combination mode in which both technologies sample simultaneously. This paper discusses ambient interferent (Hydrocarbon and humidity) contamination issues which impact data resolution and measurement accuracy as emission standards are lowered. Solutions are recommended which compensate for these effects. This document examines new technologies required for accurate BMD measurements, and presents data obtained from running the site in the dual sampling mode utilizing a four-cylinder PZEV vehicle.