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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.

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.

VOLKSWAGEN has conducted a number of investigations on a Multi Fuel Vehicle (MFV), designed for variable fuel operation, to determine the influence of fuel composition and clean fuels on exhaust emissions, mainly on ozone forming potential. Results of the tests indicate a small advantage of Phase II Reformulated Gasoline and a greater one for for methanol fuel M85, compared to today's gasoline. For M85 there is an about 25 % lower ozone forming potential. The most critical components in the exhaust of methanol fueled vehicles (M85) are unburned methanol and formaldehyde, forming more than 60 % of the total ozone forming potential. Therefore improvement of cold start and warmup driving during the first two to three minutes is of great importance, because in this time about 90 % of the mentioned components are formed.

Since about four to five years car manufacturers are concerned with measurements of particulate matter in the diesel exhaust gas and with possible measures to control and re duce these substances. This paper discusses the technical approaches to the problems of sampling and determination of the diesel particulates on a mass basis. In detail the paper includes 1) results from experiences with the instrumentation for sampling and weighing particulate matter: manual sampling set-up, automatic sampling apparatus, filter holder., filter material, and microbalance; 2) results of the investigation of the main test parameters: sample flow rate, background particulate level, filter conditioning and efficiency. Further, a specific area of concern was the uncertainty of the measurements especially the variability and correlation of test results.