Document ID: chunk:federal_register_of_legislation:F2021C01210:reg:90:p5
Version: federal_register_of_legislation:F2021C01210
Segment Type: reg
Provision Reference: reg 90 (pt 5/7)
Character Range: 78748–81664

repeated not less than six times in order to clear the exhaust system and to allow for any necessary adjustment of the apparatus. The maximum opacity values read in each successive acceleration shall be noted until stabilized values are obtained. No account shall be taken of the values read while, after each acceleration, the engine is idling. The values read shall be regarded as stabilized when four of them consecutively are situated within a band width of 0.25 m-1 and do not form a decreasing sequence. The absorption coefficient XM to be recorded shall be the arithmetical mean of these four values.
        2.7  Engines fitted with an air pressure-charger shall be subject, where appropriate, to the following special requirements:
        2.7.1 In the case of engines with an air pressure-charger which is coupled or driven mechanically by the engine and is capable of being disengaged, two complete measurement cycles with preliminary accelerations shall be carried out, the air pressure-charger being engaged in one case and disengaged in the other. The measurement result recorded shall be the higher of the two results obtained; and
        2.7.2 In cases where the engine has several exhaust outlets, the tests shall be carried out with all the outlets joined in an adequate device ensuring mixture of the gases and ending in a single orifice. Free acceleration tests, however, may be carried out on each outlet. In this case the value to be used for calculating the correction to the absorption coefficient shall be the arithmetical mean of the values recorded at each outlet, and the test shall be regarded as valid only if the extreme values measured do not differ by more than       0.15 m-1.

        3.   DETERMINATION OF THE CORRECTED VALUE OF THE ABSORPTION COEFFICIENT
        Applicable where steady speed absorption coefficient has been effectively established on the same engine derivative.
        3.1  Notation
                X M = value of the absorption coefficient under free acceleration measured as prescribed in paragraph 2.4 of this annex;
                X L = corrected value of the absorption coefficient under free acceleration;
                S M = value of the absorption coefficient measured at steady speed (annex 4, paragraph 2.1) which is closest to the prescribed limit value corresponding to the same nominal flow;
                S L = value of the absorption coefficient prescribed in annex 4, paragraph 4.2, for the nominal flow corresponding to the point of measurement which gave the value S M .
        3.2  The absorption coefficients being expressed in m -1 the corrected value X L  is given by the smaller of the following two expressions:

    or

Annex 6
SPECIFICATIONS OF REFERENCE FUEL PRESCRIBED FOR APPROVAL
TESTS AND TO VERIFY CONFORMITY OF PRODUCTION
Property Limits and Units ASTM Method 1/

                                         Density at 15C