{
  "url": "https://openlegislation.uk/eu-regulation-2017-654/annex-VII/division-2/division-2.5/division-2.5.2",
  "json_url": "https://openlegislation.uk/eu-regulation-2017-654/annex-VII/division-2/division-2.5/division-2.5.2.json",
  "legislation": "eur/2017/654",
  "legislation_title": "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",
  "legislation_url": "https://openlegislation.uk/eu-regulation-2017-654",
  "path": "annex/VII/division/2/division/2.5/division/2.5.2",
  "kind": "division",
  "number": "2.5.2",
  "heading": "Critical flow venturi (CFV)",
  "text": "Calibration of the CFV is based upon the flow equation for a critical venturi. Gas flow is a function of venturi inlet pressure and temperature.\nTo determine the range of critical flow, K V shall be plotted as a function of venturi inlet pressure. For critical (choked) flow, K V will have a relatively constant value. As pressure decreases (vacuum increases), the venturi becomes unchoked and K V decreases, which indicates that the CFV is operated outside the permissible range.\nThe airflow rate (qV CVS) at each restriction setting (minimum 8 settings) shall be calculated in standard m3/s from the flowmeter data using the manufacturer's prescribed method. The calibration coefficient K V K × m 4 × s ∕ kg shall be calculated from the calibration data for each setting by means of equation (7-72):\nK V = q V CVS × T p p\n(7-72)\nWhere:\nqV SSV air flow rate at standard conditions (101,325 kPa, 273,15 K) [m3/s]\nT temperature at the venturi inlet [K]\np p absolute pressure at venturi inlet [kPa]\nThe average K V and the standard deviation shall be calculated. The standard deviation shall not exceed ± 0,3 % of the average K V.",
  "extent": "E+W+S+N.I.",
  "status": null,
  "version": "current",
  "annotations": [],
  "outstanding_effects": [],
  "provenance": {
    "source": "legislation.gov.uk",
    "source_url": "https://www.legislation.gov.uk/eur/2017/654/annex/VII/division/2/division/2.5/division/2.5.2",
    "retrieved_at": "2026-11-01T14:45:01.864924+00:00"
  },
  "licence": "Open Government Licence v3.0",
  "licence_url": "https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/",
  "attribution": "Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives."
}