CFR > Title 40 - Protection of Environment > CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY > SUBCHAPTER U—AIR POLLUTION CONTROLS (Parts 1027–1074) > PART 1065—ENGINE-TESTING PROCEDURES > SUBPART G—Calculations and Data Requirements (§1065.601 to §1065.695) > 1065.670—NO X intake-air humidity and temperature corrections.

1065.670—NO X intake-air humidity and temperature corrections.

See the standard-setting part to determine if you may correct NOX emissions for the effects of intake-air humidity or temperature. Use the NOX intake-air humidity and temperature corrections specified in the standard-setting part instead of the NOX intake-air humidity correction specified in this part 1065. If the standard-setting part does not prohibit correcting NOX emissions for intake-air humidity according to this part 1065, first apply any NOX corrections for background emissions and water removal from the exhaust sample, then correct NOX concentrations for intake-air humidity. You may use a time-weighted mean combustion air humidity to calculate this correction if your combustion air humidity remains within a tolerance of ±0.0025 mol/mol of the mean value over the test interval. For intake-air humidity correction, use one of the following approaches:
(a) For compression-ignition engines, correct for intake-air humidity using the following equation:
Example:
xNOxuncor = 700.5 µmol/mol
xH2O = 0.022 mol/mol
xNOxcor = 700.5 · (9.953 · 0.022 0.832)
xNOxcor = 736.2 µmol/mol
(b) For spark-ignition engines, correct for intake-air humidity using the following equation:
Example:
xNOxuncor = 154.7 µmol/mol
xH2O = 0.022 mol/mol
xNOxcor = 154.7 · (18.840 · 0.022 0.68094)
xNOxcor = 169.5 µmol/mol
(c) Develop your own correction, based on good engineering judgment.

Code of Federal Regulations

[75 FR 23056, Apr. 30, 2010]