[Code of Federal Regulations]
[Title 40, Volume 17]
[Revised as of July 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR86.884-14]

[Page 71]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 86--CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND 
ENGINES (CONTINUED)--Table of Contents
 
Subpart I--Emission Regulations for New Diesel Heavy-Duty Engines; Smoke 
                         Exhaust Test Procedure
 
Sec. 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 Sec. 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:

Ns=100x(1-(1-Nm/100)Ls/Lm)

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 Sec. 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 Sec. 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 Sec. 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]