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Particulate emissions from VW and Audi diesel vehicles ranging from 230 to 1000 mg/mi were analysed by different analytical techniques. The results from the classical elemental analysis shows that the particulate matter consists up to 90 % of carbon. For the determination of metals the X-ray fluorescence method was used, but only traces were found. Methods for the measurement of particle bound organics based on organic extraction and thermogravimetry. Results so far obtained indicate an organic fraction between 20 and 70 %. Sulfates were also determined in a portion of 2 to 4 % using the BCA method.

Besides regulated components VW's research program in the field of characterization of diesel emissions comprises a detailed analysis of the particulates and a comprehensive study of a number of unregulated gaseous compounds. The following chemical compounds and classes of compounds are measured: particulates, traces of metals, major elements, sulfates, sulfur dioxide, hydrogen sulfide, hydrogen cyanide, aldehydes, ammonia phenols, individual hydrocarbons, and odor (DOAS). The test fleet of this investigation included a number of VW and Audi cars equipped with 4-, and 5-cylinder diesel engines (naturally aspirated and turbocharged). All measurements were performed on a chassis dynamometer in accordance with the specification of the known US-test-procedures: Federal Test Procedure, Sulfate Emission Test, Fuel Economy Test. For sampling, in principle, the dilution tunnel technique was used combined with an automatically working collection system.