Abstract
In the last 5 - 10 years advances previously considered impossible have been made in reducing the emissions of diesel engines. Development and optimisation was carried out mainly under steady-state conditions and the final tuning under the transient conditions of the transient certification test cycle of the relevant country, i.e. until recently just the USA. With the introduction of EU4 in 2005, the Japanese transient test from 2005 and the likely introduction of the World Harmonised Transient Cycles (WHTC) with EU6, development will concentrate more on transient operation and steady-state optimisation will reduce in importance. This trend will become more pronounced as emission standards are reduced still further and will also lead to changes in the development methods employed for some areas.
In the following, the existing and future transient tests will be analysed and the consequences on the development processes used and the technologies selected are discussed. The lower the emission limits, the greater the divergence between the results of steady-state and transient optimisation. The characteristics of the transient test itself thereby play an important role since the divergence increases with the proportion of part load operation in the test.