[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: 40CFR1051.310]
[Page 622-623]
TITLE 40--PROTECTION OF ENVIRONMENT
CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
PART 1051_CONTROL OF EMISSIONS FROM RECREATIONAL ENGINES AND VEHICLES
--Table of Contents
Subpart D_Testing Production-line Engines
Sec. 1051.310 How must I select vehicles or engines for production-line
testing?
(a) Use test results from two vehicles or engines for each engine
family to calculate the required sample size for the test period. Update
this calculation with each test.
(1) For engine families with projected annual sales of at least
1600, the test periods are consecutive quarters (3 months). If your
annual production period is less than 12 months long, define your test
periods by dividing your annual production period into approximately
equal segments of 70 to 125 calendar days.
(2) For engine families with projected annual sales below 1600, the
test period is the whole model year.
(b) Early in each test period, randomly select and test an engine
from the end of the assembly line for each engine family.
(1) In the first test period for newly certified engines, randomly
select and test one more engine. Then, calculate the required sample
size for the test period as described in paragraph (c) of this section.
(2) In later test periods or for engine families relying on
previously submitted test data, combine the new test result with the
last test result from the previous test period. Then, calculate the
required sample size for the new test period as described in paragraph
(c) of this section.
(c) Calculate the required sample size for each engine family.
Separately calculate this figure for HC, NOX (or
HC+NOX), and CO (and other regulated pollutants). The
required sample size is the greater of these calculated values. Use the
following equation:
[GRAPHIC] [TIFF OMITTED] TR08NO02.008
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 (or family emission limit, if applicable).
[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] TR08NO02.009
Where:
Xi = Emission test result for an individual vehicle or
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.
1051.315(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 vehicle or engine tests evenly
throughout the rest of the year. You may need to adjust your schedule
for selecting vehicles or engines if the required sample size changes.
Continue to randomly select vehicles or engines from each engine family;
this may involve testing
[[Page 623]]
vehicles or 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 HC+NOX), or CO (or other
regulated pollutants) 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. 1051.325.
(3) You test 30 vehicles or 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 fails 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 does not affect the requirements in section Sec. 1051.320.
(i) You may elect to test more randomly chosen vehicles or engines
than we require. Include these vehicles or engines in the sample-size
calculations.