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New European emissions legislation (Euro5) specifies a limit for Particle Number (PN) emissions and therefore drives measurement of PN during vehicle development and homologation. Concurrently, the use of biofuel is increasing in the marketplace, and Euro5 specifies that reference fuel must contain a bio-derived portion. Work was carried out to test the effect of fuels containing different levels of Fatty Acid Methyl Ester (FAME) on particle number, size, mass and composition. Measurements were conducted with a Cambustion Differential Mobility Spectrometer (DMS) to time-resolve sub-micron particles (5-1000nm), and a Horiba Solid Particle Counting System (SPCS) providing PN data from a Euro5-compliant measurement system. To ensure the findings are relevant to the modern automotive business, testing was carried out on a Euro4 compliant passenger car fitted with a high-pressure common-rail diesel engine and using standard homologation procedures.

In light of forthcoming particle number legislation for light-duty passenger vehicles, time-resolved Particle Mass (PM) and Particle Number (PN) emissions over the New European Drive Cycle (NEDC) are reported for four current vehicle technologies; modern diesel, with and without a Diesel Particulate Filter (DPF), Direct Injection Spark Ignition (DISI) gasoline and multi-point Port Fuel Injection (PFI) gasoline. The PN and PM emissions were ordered (highest to lowest) according to: Non-DPF diesel ≻ DISI ≻ PFI ~ DPF diesel. Both the non-DPF diesel and DISI vehicles emitted PN and PM continuously over the NEDC. This is in contrast with both the DPF diesel and PFI vehicles which emitted nearly all their PN and PM during the first 200 seconds. The PFI result is thought to be a consequence of cold-start mixture preparation whilst several possible explanations are offered for the DPF diesel trend.