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The future worldwide emission regulations will request a drastic decrease of Diesel engine tailpipe emissions. Depending on the planned application and the real official regulations, a further strong decrease of engine out emissions is necessary, even though the utilized exhaust after-treatment systems are very powerful. To reduce NOx emissions internally, the external exhaust gas recirculation (EGR) is known as the most effective way. Due to the continuously increasing requirements regarding specific power, dynamic behavior and low emissions, future air path systems have to fulfill higher requirements and, consequently, become more and more complex, e.g. arrangements with a 2-stage turbo charging or 2-stage EGR system with different stages of cooling performance.

This paper describes research and development activities dealing with a technique which allows the measurement of gaseous and particulate concentrations inside the combustion chamber. This so-called fast-timed gas sampling technique was used for both the observation of the development of gaseous pollutants and soot during combustion and expansion and for getting information about the particle size history. The system has been applied to a modern passenger car DI diesel engine (Volkswagen). The investigation covers the early combustion phase beginning with the start of combustion and throughout the expansion phase until exhaust valve opening. Particles with a size of about 10 nm up to 1 μm were found. Slight variations in the smaller size classes could be observed during the combustion and expansion process.