The exhaust gas flow shall be determined by one of the methods described in this section and conform to the tolerances of table 3 in appendix A to subpart D:
(a) Measurement of the air flow and the fuel flow by suitable metering systems (for details see SAE J244. This procedure has been incorporated by reference. See Sec. 89.6.) and calculation of the exhaust gas flow as follows: GEXHW = GAIRW + GFUEL (for wet exhaust mass) or VEXHD = VAIRD + (-.767) x GFUEL (for dry exhaust volume) or VEXHW = VAIRW + .749 x GFUEL (for wet exhaust volume)
(b) Exhaust mass calculation from fuel consumption (see Sec. 89.415) and exhaust gas concentrations using the method found in Sec. 89.418. [59 FR 31335, June 17, 1994. Redesignated at 63 FR 56996, Oct. 23, 1998]