# Commission Delegated Regulation (EU) 2017/654 of 19 December 2016 supplementing Regulation (EU) 2016/1628 of the European Parliament and of the Council with regard to technical and general requirements relating to emission limits and type-approval for internal combustion engines for non-road mobile machinery, Division 2.2.2.2: Dilution factor

Extent: E+W+S+N.I.

The dilution factor D [-] (which is necessary for the background correction and the k w2 calculation) shall be calculated by means of equation (7-28):
D = F s c CO2,e + c HC,e + c CO,e × 10 − 4
(7-28)
where:
F S stoichiometric factor [-]
c CO2,e concentration of CO2 in the diluted exhaust gas on a wet basis [per cent vol]
c HC,e concentration of HC in the diluted exhaust gas on a wet basis [ppm C1]
c CO,e concentration of CO in the diluted exhaust gas on a wet basis [ppm]
The stoichiometric factor shall be calculated by means of equation (7-29):
F s = 100 × 1 1 + α 2 + 3,76 × 1 + α 4
(7-29)
Where:
α molar hydrogen to carbon ratio in the fuel [-]
Alternatively, if the fuel composition is not known, the following stoichiometric factors may be used:
F S (diesel) = 13,4
FS (LPG) = 11,6
FS (NG) = 9,5
FS (E10) = 13,3
FS (E85) = 11,5
If a direct measurement is made of the exhaust gas flow, the dilution factor D [-] may be calculated by means of equation (7-30):
D = q V CVS q V ew
(7-30)
Where:
qV CVS is the volumetric flow rate of diluted exhaust gas [m3/s]
qV ew = volumetric flow rate of raw exhaust gas [m3/s]

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Source: https://www.legislation.gov.uk/eur/2017/654/annex/VII/division/2/division/2.2/division/2.2.2/division/2.2.2.2 (the official version)
Page: https://openlegislation.uk/eu-regulation-2017-654/annex-VII/division-2/division-2.2/division-2.2.2/division-2.2.2.2
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.