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The accuracy of low-level emission measurements has become increasingly important, due to the development and implementation of ULEV, SULEV, and PZEV vehicles. Measurement of these decreasing levels of automotive emissions requires new sampling and measuring techniques. Several alternative emission sampling techniques have been investigated to minimize measurement variability and maximize system repeatability. An alternative technique to obtain accurate low-level emissions measurement from SULEV vehicles is the Bag Mini-Diluter, which uses a proportional signal from an Exhaust Volume Measurement Device to sample vehicle exhaust. Crucial to successful proportional sampling of vehicle exhaust flow is the performance of the Exhaust Flow Measurement Device. This study evaluates an Exhaust Volume Measurement Device commonly used with a Bag Mini-Diluter.

Automobile Particulate Matter (PM) Emission regulation requires gravimetric determination of PM collected on filter media under simulated driving conditions in the laboratory traditionally in a full flow Constant Volume Sampling (CVS) dilution tunnel. There have been discussions about whether current sampling and measurement practices are sufficiently accurate in quantifying PM at the upcoming 1mg/mi PM emissions standards of CARB LEV III. Sampling technique alternative to a CVS such as a Partial Flow Dilution (PFD) system has already been developed and is acceptable for certification testing. Lower dilution ratios and higher filter face velocity (FFV) are options to load traceable amount of PM on filter in case of light duty vehicle (LDV) testing. On the other hand higher dilution ratios and lower FFV are required for heavy duty engine (HDE) testing to keep the PM loaded on filter <400μg.