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Two different implementations of Partial Flow Dilution (PFD) methodology designed for gravimetric particulate matter (PM) sampling are evaluated for applicability to light-duty chassis emissions testing. Filter PM measurements were collected and compared to constant volume sampler (CVS) full dilution tunnel PM filter measurements and other real-time PM measurement technologies, using gasoline vehicles generating a range of 0.1 to 10.0 mg/mile PM. Exhaust samples were collected for each phase of the Federal Test Procedure (FTP-75) with a fourth filter sample collected for the US06 supplemental cycle. Both PFDs satisfactorily met proportionality criteria for conventional combustion engines, but some improvements are needed for hybrid electric vehicles (HEVs). The PM mass collected scaled linearly with the CVS tunnel samples, with slopes of 1.03 and 0.74 for the two PFDs.

Four vehicle fleets, consisting of 3 to 4 vehicles each, were emission tested on a 48″ roll chassis dynamometer using both the FTP urban dynamometer driving cycle and the REP05 driving cycle. The REP05 cycle was developed to test vehicles under high speed and high load conditions not included in the FTP. The vehicle fleets consisted of 1989 light-duty gasoline vehicles, 1992-93 limited production FFV/VFV methanol vehicles, 1992-93 compressed natural gas (CNG) vehicles and their gasoline counterparts, and a 1992 production and two prototype ethanol FFV/VFV vehicles. All vehicles (except the dedicated CNG vehicles) were tested using Auto/Oil AQIRP fuels A and C2. Other fuels used were M85 blended from A and C2, E85 blended from C1, which is similar to C2 but without MTBE, and four CNG fuels representing the range of in-use CNG fuels. In addition to bag measurements, tailpipe exhaust concentration and A/F data were collected once per second throughout every test.