# 40 CFR § 86.884-14 - Calculations.

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§ 86.884-14 Calculations.

(a) If the measured half-second opacity values were obtained with a smokemeter with an optical path length different than shown in the table in § 86.884-8(c), then convert the measured half-second values or the original instantaneous values to the appropriate equivalent optical path length values specified in the table. Convert the opacity values according to the following equations:

${N}_{s}=100×\left({1-\left(1-{N}_{m}/100\right)}^{{L}_{s}/{L}_{m}}\right)$

Lm and Ls must use consistent units in the above equation
Where:
Nm = Measured half-second value for conversion, percent opacity
Lm = Measuring smokemeter optical path length, meters
Ls = Standard optical path length corresponding with engine power, n
Ns = Standard half-second value, percent opacity

(b) Average the 45 readings in § 86.884-13(d)(3) or the equivalent converted values from paragraph (a) of this section if appropriate, and designate the value as “A”. This is the value for the engine acceleration mode.

(c) Average the 15 readings in § 86.884-13(d)(4) or the equivalent converted values from paragraph (a) of this section if appropriate, and designate the value as “B”. This is the value for the engine lugging mode.

(d) Average the 9 readings in § 86.884-13(d)(5) or the equivalent converted values from paragraph (a) of this section if appropriate, and designate the value as “C”. This is the value for the peaks in either mode.

(e)

(1) If multiple smokemeters were used, the half-second values for each mode from each smokemeter shall be combined and the calculated average based upon the total number of combined values.

(2) For example, if two smokemeters were used for acceleration mode data, 45 half-second values in each data set from both smokemeters would be combined to form a data set of 90 values, which would then be averaged.

[62 FR 47123, Sept. 5, 1997, as amended at 69 FR 2441, Jan. 15, 2004]