[Code of Federal Regulations]
[Title 40, Volume 30]
[Revised as of July 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR1048.310]
[Page 562-563]
TITLE 40--PROTECTION OF ENVIRONMENT
CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
PART 1048_CONTROL OF EMISSIONS FROM NEW, LARGE NONROAD SPARK-IGNITION
ENGINES--Table of Contents
Subpart D_Testing Production-line Engines
Sec. 1048.310 How must I select engines for production-line testing?
(a) Use test results from two engines for each engine family to
calculate the required sample size for the model year. Update this
calculation with each test.
(b) Early in each calendar quarter, randomly select and test two
engines
[[Page 563]]
from the end of the assembly line for each engine family.
(c) Calculate the required sample size for each engine family.
Separately calculate this figure for HC+NOX and for CO. The
required sample size is the greater of these two calculated values. Use
the following equation:
[GRAPHIC] [TIFF OMITTED] TR08NO02.004
Where:
N = Required sample size for the model year.
t95 = 95% confidence coefficient, which depends on the number
of tests completed, n, as specified in the table in paragraph (c)(1) of
this section. It defines 95% confidence intervals for a one-tail
distribution.
x = Mean of emission test results of the sample.
STD = Emission standard.
[sigma] = Test sample standard deviation (see paragraph (c)(2) of this
section).
(1) Determine the 95% confidence coefficient, t95, from
the following table:
------------------------------------------------------------------------
n t95 n t95 n t95
------------------------------------------------------------------------
2 6.31 12 1.80 22 1.72
3 2.92 13 1.78 23 1.72
4 2.35 14 1.77 24 1.71
5 2.13 15 1.76 25 1.71
6 2.02 16 1.75 26 1.71
7 1.94 17 1.75 27 1.71
8 1.90 18 1.74 28 1.70
9 1.86 19 1.73 29 1.70
10 1.83 20 1.73 30+ 1.70
11 1.81 21 1.72 ......................
------------------------------------------------------------------------
(2) Calculate the standard deviation, [sigma], for the test sample
using the following formula:
[GRAPHIC] [TIFF OMITTED] TR08NO02.005
Where:
Xi = Emission test result for an individual engine.
n = The number of tests completed in an engine family.
(d) Use final deteriorated test results to calculate the variables
in the equations in paragraph (c) of this section (see Sec.
1048.315(a)).
(e) After each new test, recalculate the required sample size using
the updated mean values, standard deviations, and the appropriate 95-
percent confidence coefficient.
(f) Distribute the remaining engine tests evenly throughout the rest
of the year. You may need to adjust your schedule for selecting engines
if the required sample size changes. Continue to randomly select engines
from each engine family; this may involve testing engines that operate
on different fuels.
(g) Continue testing any engine family for which the sample mean, x,
is greater than the emission standard. This applies if the sample mean
for either HC+NOX or for CO is greater than the emission
standard. Continue testing until one of the following things happens:
(1) The sample size, n, for an engine family is greater than the
required sample size, N, and the sample mean, x, is less than or equal
to the emission standard. For example, if N = 3.1 after the third test,
the sample-size calculation does not allow you to stop testing.
(2) The engine family does not comply according to Sec. 1048.325.
(3) You test 30 engines from the engine family.
(4) You test one percent of your projected annual U.S.-directed
production volume for the engine family.
(5) You choose to declare that the engine family does not comply
with the requirements of this subpart.
(h) If the sample-size calculation allows you to stop testing for a
pollutant, you must continue measuring emission levels of that pollutant
for any additional tests required under this section. However, you need
not continue making the calculations specified in this section for that
pollutant. This paragraph (h) does not affect the requirements in
section Sec. 1048.320.
(i) You may elect to test more randomly chosen engines than we
require. Include these engines in the sample-size calculations.