Appendix D to Subpart S of Part 51 - Steady-State Short Test Equipment
40:2.0.1.1.2.16.11.25.27 : Appendix D
Appendix D to Subpart S of Part 51 - Steady-State Short Test
Equipment (I) Steady-State Test Exhaust Analysis System
(a) Sampling system - (1) General requirements.
The sampling system for steady-state short tests shall, at a
minimum, consist of a tailpipe probe, a flexible sample line, a
water removal system, particulate trap, sample pump, flow control
components, tachometer or dynamometer, analyzers for HC, CO, and
CO2, and digital displays for exhaust concentrations of HC, CO, and
CO2, and engine rpm. Materials that are in contact with the gases
sampled shall not contaminate or change the character of the gases
to be analyzed, including gases from alcohol fueled vehicles. The
probe shall be capable of being inserted to a depth of at least ten
inches into the tailpipe of the vehicle being tested, or into an
extension boot if one is used. A digital display for dynamometer
speed and load shall be included if the test procedures described
in appendix B to this subpart, paragraphs (III) and (V), are
conducted. Minimum specifications for optional NO analyzers are
also described in this appendix. The analyzer system shall be able
to test, as specified in at least one section in appendix B to this
subpart, all model vehicles in service at the time of sale of the
analyzer.
(2) Temperature operating range. The sampling system and
all associated hardware shall be of a design certified to operate
within the performance specifications described in paragraph (I)(b)
of this appendix in ambient air temperatures ranging from 41 to 110
degrees Fahrenheit. The analyzer system shall, where necessary,
include features to keep the sampling system within the specified
range.
(3) Humidity operating range. The sampling system and all
associated hardware shall be of a design certified to operate
within the performance specifications described in paragraph (I)(b)
of this appendix at a minimum of 80 percent relative humidity
throughout the required temperature range.
(4) Barometric pressure compensation. Barometric pressure
compensation shall be provided. Compensation shall be made for
elevations up to 6,000 feet (above mean sea level). At any given
altitude and ambient conditions specified in paragraph (I)(b) of
this appendix, errors due to barometric pressure changes of ±2
inches of mercury shall not exceed the accuracy limits specified in
paragraph (I)(b) of this appendix.
(5) Dual sample probe requirements. When testing a
vehicle with dual exhaust pipes, a dual sample probe of a design
certified by the analyzer manufacturer to provide equal flow in
each leg shall be used. The equal flow requirement is considered to
be met if the flow rate in each leg of the probe has been measured
under two sample pump flow rates (the normal rate and a rate equal
to the onset of low flow), and if the flow rates in each of the
legs are found to be equal to each other (within 15% of the flow
rate in the leg having lower flow).
(6) System lockout during warm-up. Functional operation
of the gas sampling unit shall remain disabled through a system
lockout until the instrument meets stability and warm-up
requirements. The instrument shall be considered “warmed up” when
the zero and span readings for HC, CO, and CO2 have stabilized,
within ±3% of the full range of low scale, for five minutes without
adjustment.
(7) Electromagnetic isolation and interference.
Electromagnetic signals found in an automotive service environment
shall not cause malfunctions or changes in the accuracy in the
electronics of the analyzer system. The instrument design shall
ensure that readings do not vary as a result of electromagnetic
radiation and induction devices normally found in the automotive
service environment, including high energy vehicle ignition
systems, radio frequency transmission radiation sources, and
building electrical systems.
(8) Vibration and shock protection. System operation
shall be unaffected by the vibration and shock encountered under
the normal operating conditions encountered in an automotive
service environment.
(9) Propane equivalency factor. The propane equivalency
factor shall be displayed in a manner that enables it to be viewed
conveniently, while permitting it to be altered only by personnel
specifically authorized to do so.
(b) Analyzers - (1) Accuracy. The analyzers shall
be of a design certified to meet the following accuracy
requirements when calibrated to the span points specified in
appendix A to this subpart:
| Channel |
Range |
Accuracy |
Noise |
Repeatability |
| HC, ppm |
0-400 |
±12 |
6 |
8 |
| as hexane |
401-1000 |
±30 |
10 |
15 |
|
1001-2000 |
±80 |
20 |
30 |
| CO, % |
0-2.00 |
±0.06 |
0.02 |
0.03 |
|
2.01-5.00 |
±0.15 |
0.06 |
0.08 |
|
5.01-9.99 |
±0.40 |
0.10 |
0.15 |
| CO2, % |
0-4.0 |
±0.6 |
0.2 |
0.3 |
|
4.1-14.0 |
±0.5 |
0.2 |
0.3 |
| NO, ppm |
0-1000 |
±32 |
16 |
20 |
|
1001-2000 |
±60 |
25 |
30 |
|
2001-4000 |
±120 |
50 |
60 |
(2) Minimum analyzer display resolution. The analyzer
electronics shall have sufficient resolution to achieve the
following:
| HC |
1ppm HC as hexane. |
| CO |
0.01% CO. |
| CO2 |
0.1% CO2. |
| NO |
1ppm NO. |
| RPM |
1rpm. |
(3) Response time. The response time from the probe to
the display for HC, CO, and CO2 analyzers shall not exceed eight
seconds to 90% of a step change in input. For NO analyzers, the
response time shall not exceed twelve seconds to 90% of a step
change in input.
(4) Display refresh rate. Dynamic information being
displayed shall be refreshed at a minimum rate of twice per
second.
(5) Interference effects. The interference effects for
non-interest gases shall not exceed ±10 ppm for hydrocarbons, ±0.05
percent for carbon monoxide, ±0.20 percent for carbon dioxide, and
±20 ppm for oxides of nitrogen.
(6) Low flow indication. The analyzer shall provide an
indication when the sample flow is below the acceptable level. The
sampling system shall be equipped with a flow meter (or equivalent)
that shall indicate sample flow degradation when meter error
exceeds three percent of full scale, or causes system response time
to exceed 13 seconds to 90 percent of a step change in input,
whichever is less.
(7) Engine speed detection. The analyzer shall utilize a
tachometer capable of detecting engine speed in revolutions per
minute (rpm) with a 0.5 second response time and an accuracy of ±3%
of the true rpm.
(8) Test and mode timers. The analyzer shall be capable
of simultaneously determining the amount of time elapsed in a test,
and in a mode within that test.
(9) Sample rate. The analyzer shall be capable of
measuring exhaust concentrations of gases specified in this section
at a minimum rate of twice per second.
(c) Demonstration of conformity. The analyzer shall be
demonstrated to the satisfaction of the inspection program manager,
through acceptance testing procedures, to meet the requirements of
this section and that it is capable of being maintained as required
in appendix A to this subpart.
(II) Steady-State Test Dynamometer
(a) The chassis dynamometer for steady-state short tests shall
provide the following capabilities:
(1) Power absorption. The dynamometer shall be capable of
applying a load to the vehicle's driving tire surfaces at the
horsepower and speed levels specified in paragraph (II)(b) of this
appendix.
(2) Short-term stability. Power absorption at constant
speed shall not drift more than ±0.5 horsepower (hp) during any
single test mode.
(3) Roll weight capacity. The dynamometer shall be
capable of supporting a driving axle weight up to four thousand
(4,000) pounds or greater.
(4) Between roll wheel lifts. These shall be controllable
and capable of lifting a minimum of four thousand (4,000)
pounds.
(5) Roll brakes. Both rolls shall be locked when the
wheel lift is up.
(6) Speed indications. The dynamometer speed display
shall have a range of 0-60 mph, and a resolution and accuracy of at
least 1 mph.
(7) Safety interlock. A roll speed sensor and safety
interlock circuit shall be provided which prevents the application
of the roll brakes and upward lift movement at any roll speed above
0.5 mph.
(b) The dynamometer shall produce the load speed relationships
specified in paragraphs (III) and (V) of appendix B to this
subpart.
(III) Transient Emission Test Equipment [Reserved] (IV) Evaporative
System Purge Test Equipment [Reserved] (V) Evaporative System
Integrity Test Equipment [Reserved] [57 FR 52987, Nov. 5, 1992, as
amended at 58 FR 59367, Nov. 9, 1993]