| Summary: | Particle number (PN) emissions and particle mass (PM) emissions have been evaluated from a diesel passenger car with diesel particulate filter (DPF) and seven gasoline direct injection passenger cars. PN and PM at upstream of DPF were also measured to evaluate DPF filtering efficiency. Particle mass emissions were obtained with photoacoustic soot measurement method. Particle number emissions were measured using a method which is adopted to European type approval tests for vehicles emissions, but cut-off diameter of this method changed to 10 nm from 23 nm. PN at upstream of DPF in cold start mode was higher than that at downstream of DPF. DPF reduced PM and PN almost zero level. PN and PM results with gasoline direct injection vehicles indicated that 6×1011 #/km of PN is almost equal to 0.1 mg/km of PM. According to this relationship, PN regulation in Europe (6×1011 #/km) is stricter than PM regulation in Japan (5 mg/km).
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