Bag Mini-Diluter System Diagnostics

Automakers in the United States have started using bag mini-diluters (BMD) for developing, testing and certifying vehicles, to meet PZEV and SULEV regulation requirements. The BMD system which is a new technology developed by AIGER, is being used as an alternative to the traditional CFV/CVS system for accurate ultra low-level emission measurement. BMD system has shown to have considerable advantage over CFV/CVS system, especially at ULEV/SULEV emission levels. This paper details modifications and diagnostic checks conducted with the existing BMD system at the DaimlerChrysler Tech Center emissions facility, Auburn Hills, Michigan. This paper also discusses possible scenarios where the BMD system at DaimlerChrysler could give erroneous results due to system setup, optimization issues and equipment limitations. Trouble shooting processes to debug and resolve the identified problems are discussed along with the effect of sample time delay and length of sample line on emission constituents. It was found that the bag fill mass flow controller range of operability affected the CO2 and fuel economy correlation. The BMD sample line length had a substantial effect on recovered BMD bag NOx emissions. Results from vehicle testing to demonstrate the aforementioned scenarios are included. The issues discussed in this paper apply mainly to the BMD system used by DaimlerChrysler.