6.3.2. Calculation of Bessel averaged smoke

Directive 2005/55/EC of the European Parliament and of the Council of 28 September 2005 on the approximation of the laws of the Member States relating to the measures to be taken against the emission of gaseous and particulate pollutants from compression-ignition engines for use in vehicles, and the emission of gaseous pollutants from positive-ignition engines fuelled with natural gas or liquefied petroleum gas for use in vehicles (Text with EEA relevance) · European Union

The proper cut-off frequency fc is the one that produces the required filter response time tF. Once this frequency has been determined through the iterative process of Section 6.1.1, the proper Bessel algorithm constants E and K shall be calculated. The Bessel algorithm shall then be applied to the instantaneous smoke trace (k-value), as described in Section 6.1.2: The Bessel algorithm is recursive in nature. Thus, it needs some initial input values of Si-1 and Si-2 and initial output values Yi-1 and Yi-2 to get the algorithm started. These may be assumed to be 0. For each load step of the three speeds A, B and C, the maximum 1s value Ymax shall be selected from the individual Yi values of each smoke trace.

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Source: EUR-Lex (Cellar) · retrieved 2026-11-01 · Text as adopted (Official Journal); later amendments are not incorporated in this text.