40 C.F.R. § 1066.610

Current through September 30, 2024

Section 1066.610 - Dilution air background correction

(a) Correct the emissions in a gaseous sample for background using the following equation:

Where:

x_{[emission]dexh} = measured emission concentration in dilute exhaust (after dry-to-wet correction, if applicable).

x_{[emission]bkgnd} = measured emission concentration in the dilution air (after dry-to-wet correction, if applicable).

DF = dilution factor, as determined in paragraph (b) of this section.

Where:

x_CO2 = amount of CO₂ measured in the sample over the test interval.

x_NMHC = amount of C₁-equivalent NMHC measured in the sample over the test interval.

x_CH4 = amount of CH₄ measured in the sample over the test interval.

x_CO = amount of CO measured in the sample over the test interval.

[ALPHA] = atomic hydrogen-to-carbon ratio of the test fuel. You may measure [ALPHA] or use default values from Table 1 of 40 CFR 1065.655 .

[BETA] = atomic oxygen-to-carbon ratio of the test fuel. You may measure [BETA] or use default values from Table 1 of 40 CFR 1065.655 .

(c) Determine the dilution factor, DF, over the test interval for partial-flow dilution sample systems using the following equation:

Where:

V_dexhstd = total dilute exhaust volume sampled over the test interval, corrected to standard reference conditions.

V_exhstd = total exhaust volume sampled from the vehicle, corrected to standard reference conditions.

(d) Determine the time-weighted dilution factor, DF_w, over the duty cycle using the following equation:

Where:

N = number of test intervals

i = test interval number

t = duration of the test interval

DF = dilution factor over the test interval

Example:

N = 3

DF₁ = 14.40

t₁ = 505 s

DF₂ = 24.48

t₂ = 867 s

DF₃ = 17.28

t₃ = 505 s

40 C.F.R. §1066.610

79 FR 23823, Apr. 28, 2014, as amended at 86 FR 34583, June 29, 2021