86.1243-96—Calculations; evaporative emissions.
(a)
The following equations are used to calculate the evaporative emissions from gasoline- and methanol-fueled vehicles, and for gaseous-fueled vehicles.
(b)
Use the measurements of initial and final concentrations to determine the mass of hydrocarbons and methanol emitted. For testing with pure gasoline, methanol emissions are assumed to be zero.
Where:
(B)
VFn =Net enclosure volume, ft 3, as determined by subtracting 50 ft 3 (1.42 m 3) (volume of vehicle with trunk and windows open) from the enclosure volume. A manufacturer may use the measured volume of the vehicle (instead of the nominal 50 ft 3) with advance approval by the Administrator: Provided, the measured volume is determined and used for all vehicles tested by that manufacturer.
(D)
VE =Volume of sample withdrawn, ft 3. Sample volumes must be corrected for differences in temperature to be consistent with determination of Vn, prior to being used in the equation.
(M)
MCH3OH,out =mass of methanol exiting the enclosure, in the case of fixed volume enclosures for diurnal emission testing, µg,
(N)
MCH3OH,in =mass of methanol entering the enclosure, in the case of fixed volume enclosures for diurnal emission testing, µg,
Where,
(B)
CHC =FID hydrocarbon concentration as ppm carbon including FID response to methanol (or methane, as applicable) in the sample.
(D)
Vn =Net enclosure volume ft 3 (m 3) as determined by subtracting 50 ft 3 (1.42 m 3) (volume of vehicle with trunk and windows open) from the enclosure volume. A manufacturer may use the measured volume of the vehicle (instead of the nominal 50 ft 3) with advance approval by the Administrator, provided the measured volume is determined and used for all vehicles tested by that manufacturer.
(1) k=2.97; and
(2) For SI units, k=17.16.
(M)
MHC,out =mass of hydrocarbons exiting the enclosure, in the case of fixed-volume enclosures for diurnal emission testing, g.
(N)
MHC,in =mass of hydrocarbons entering the enclosure, in the case of fixed-volume enclosures for diurnal emission testing, g.
(iii)
For variable-volume enclosures, defined in § 86.1207(a)(1)(i), the following simplified form of the hydrocarbon mass change equation may be used:
(2)
For running loss testing by the point-source method, the mass emissions of each test phase are calculated below, then summed for a total mass emission for the running loss test. If emissions are continuously sampled, the following equations can be used in integral form.
Where,
(C)
Vmix =total dilute sample volume, in ft 3, calculated as appropriate for the collection technique used.
(D)
CCH
[=E T=0362]3
OH,rl =methanol concentration of diluted running loss sample, in ppm carbon equivalent.
Where,
(C)
Vmix =total dilute sample volume, in ft 3, calculated as appropriate for the collection technique used.
where MDI=mass emissions from the diurnal emission test (see § 86.1233), g.
where MHS=mass emissions from the hot soak test (see § 86.1238), g.
where MRL=mass emissions from the running loss test (see § 86.1234), g.
(ii)
The adjusted total mass emissions for the running loss test, on a grams per mile basis=MRL /DRL, where DRL =miles driven for the running loss test (see § 86.1234-96(c)(6) ).
(2)
For the supplemental two-diurnal test sequence, there is one final result to report: the sum of the adjusted total mass emissions for the diurnal and hot soak tests (MDI MHS ), described in §§ 86.1233-96(p) and 86.1238-96(k), respectively.