A/C No. MC-3A
united states Office of November 2, 1982
Environmental Protection Air. Noise and Radiation Paee 1 of 7
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Agency Washington. DC 20460
&EPA OMSAPC
Advisory Circular
SUBJECT: Criteria for Determining the Acceptability of Service Accumulation
on an Outdoor Chassis Dynamometer
I. Purpose
The purpose of this advisory circular (A/C), No. MC-3A, is to update
the general criteria that are to be used to determine if service accumulation
on a chassis dynamometer is adequately similar to service accumulation on a
road route. This A/C supersedes A/C No. MC-3.
II. Background
A. Paragraph 40 CFR 86.426-78(a) specifies the use of prescribed road
course durability driving schedules but allows the use of other service
accumulation procedures which are approved in advance by the Administrator.
Criteria for the approval of modified procedures which utilize chassis
dynamometer simulators were published in the form of an A/C, No. MC-3, which
was published on February 10, 1977. Authority for the approval of such
procedures was subsequently transferred to the manufacturers in an EPA letter
which was disseminated on March 16, 1981.
B. A/C No. MC-3 incorporated the approval criteria which had been
adopted for light-duty vehicles on April 2, 1979 by the publication of A/C No.
35A. These criteria were subsequently revised for light-duty vehicles by the
publication of A/C No. 35B on April 30, 1982. The changes in the evaluating,
operating, monitoring and reporting requirements which were implemented for
light-duty vehicles at that time have been incorporated in this revised
motorcycle A/C, No. MC-3A.
III. Applicability
A. The provisions of A/C No. MC-3A are effective immediately and are
applicable to gasoline-fueled motorcycles. The provisions apply to the use of
an outdoor chassis dynamometer on which certification vehicles accumulate
service.
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B. The use of indoor chassis dynamometers for service accumulation is
not approved.
IV. Discussion
A. As discussed in II.A. above, an applicant is no longer required to
obtain EPA approval to use an outdoor chassis dynamometer for service accumu-
lation. Instead the applicant can use the criteria which are set forth in
this A/C to make engineering judgments regarding the accuracy with which a
chassis dynamometer and its related systems simulate the temperature and load
conditions that are experienced by a driver-controlled vehicle which is
operated on a road route that meets the requirements of 40 CFR Part 86,
Appendix IV.
B. There are many vehicle characteristics which can prevent the main-
tenance of representative temperatures and engine loads during operation on
the chassis dynamometer. The applicant is responsible for assuring that the
service accumulated on the chassis dynamometer is representative of service
accumulated over the road route. This A/C contains only the basic parameters
upon which each applicant will base engineering judgments regarding the
similarity between chassis-dynamometer and a road-route service accumulation.
V. Minimum Demonstration Vehicles Needed to Support Similarity Between
Chassis Dynamometer Operation and Road Route Operation
A. The applicant will obtain data (see paragraph VI) from at least
one vehicle for each engine displacement class.
B. At a minimum, the applicant is to consider the following basic
vehicle characteristics in selecting demonstration vehicles.
1. Catalyst or thermal reactor usage,
2. Catalyst or thermal reactor location,
3. Engine configuration (i.e., number of cylinders, in-line or
V-type, water-cooled or air-cooled, 2-stroke or 4-stroke,
displacement),
4. Vehicle shape and ground clearance,
5. Inertia weight class.
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C. An applicant whose product line is very diverse needs to obtain
data on as many vehicles as engineering judgment indicates is appropriate.
(In the past, EPA selected a maximum of three vehicles per application.)
VI. Minimum Data Requirements Needed to Support Similarity Between Chassis
Dynamometer Operation and Road Route Operation
A. In order to qualify a chassis dynamometer system, similarity must
be shown in the data recorded from the demonstration vehicle(s) when driven on
an existing approved test track route for at least three laps (laps 2, 9, and
11 for Class I and II vehicles and laps 4, 8, and 11 for Class III vehicles)
of the Durability Driving Schedule, 40 CFR Part 86, Appendix IV, and when
operated on a chassis dynamometer representative of the system(s) to be used.
(The similarity in vehicle data may be determined on the basis of data
recorded on one day or for a longer period.)
B. Data plots or recordings of the variables listed below shall be
obtained continuously (or at intervals which are close enough to evaluate
transient conditions) on a vehicle which is driven on an acceptable road route
and on the chassis dynamometer:
Variable
1. Temperature
Parameter to be Measured
a. Cooling air
b. Engine inlet air
c. Engine oil
d. Transmission oil
e. Spark plug seat
(air-cooled
engine)
f. Coolant (liquid-
cooled engine)
g. Catalyst container
(if applicable)
Location of Thermocouple
At front axle centerline (either side)
At the clean side of the air filter
In sump, at drainplug or near dipstick
In sump, at drainplug or near dipstick
One required for each spark plug
(unless otherwise specified by EPA)
At both inlet and outlet of engine
Skin at inlet and outlet
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h. Exhaust pipe Skin near connection to cylinder head
(one required for each pipe unless
otherwise specified by EPA)
i. Muffler Skin at outlet
2. Manifold vacuum, wheel (or dynamometer) torque, throttle posi-
tion, or other indications of engine load
3. Vehicle speed or wheel speed
4. Engine speed
C. Data plots or recordings of the above variables shall be maintained
as long as the data generated by these vehicles are used to satisfy 40 CFR
Part 86 data requirements and shall be made available to EPA upon request.
VII. Minimum Acceptable Criteria
A. It is generally recognized that two drivers operating the same
vehicle over the same test route and using the same prescribed driving
schedule will show variations in driving patterns as reflected in manifold
vacuum, acceleration rates, and temperature transients. It is, therefore, not
necessary that the values of these parameters obtained on the dynamometer
exactly duplicate the values obtained on the road. In addition, exact
mechanical precision on the part of the road simulator is not considered an
accurate simulation of the driver-controlled vehicle since few, if any,
drivers are capable of accelerating, decelerating or driving a steady speed
over a variable road terrain without random variations in the load-speed
pattern. Therefore, the demonstrated simulated load-speed traces should show
normal variations similar to, but not necessarily an exact replica of, those
shown on the actual road-driven route.
B. The difference in temperature between road and dynamometer opera-
tion which are allowed will depend on the system being tested and the location
of temperature-sensitive components. Generally, temperature versus time
curves should agree within 5°C (10°F) for temperatures up to 40°C (100°F) and
within 10 percent for temperature above 40°C (100°F).
C. The relation between engine speed and vehicle (or wheel) speed,
both on the road and on the dynamometer, must be established in order to
ascertain that transmission shift points on the dynamometer essentially
duplicate the pattern observed on the road.
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D. There is no specification in 40 CFR Part 86 relative to grade or
condition of the road terrain, and a wide variety of grade and terrain condi-
tions exist in the durability routes described by applicants in their applica-
tions for certification. A road simulator matching any approved durability
route is satisfactory.
VIII. Authorization to Use Chassis Dynamometers
A. Each applicant will be responsible for determining whether the
service that is accumulated on a chassis dynamometer is representative of road
route operation. Paragraphs V, VI, and VII of this A/C set forth the minimum
criteria upon which such a determination is to be made.
B. When an applicant has determined that there is adequate similarity
between dynamometer and road-route operation, such determination is to be
noted in the application for certification. The applicant should maintain the
data and information used to make such determinations for as long as the
information is applicable to a vehicle which was used to generate data to
satisfy 40 CFR Part 86. In addition, these data and information must be made
available to EPA upon request so that EPA can determine if data generated in
support of certification was valid.
C. Applicants are reminded that, when an approved chassis dynamometer
is used for service accumulation, the road route/dynamometer schedule used
must be designated in the application for certification.
IX. Vehicle Operation on the Dynamometer
A. When a dynamometer system which controls manifold vacuum (or
throttle position) is used, periodic checks must be made to determine if the
manifold vacuum (or throttle position) as controlled on the chassis dyna-
mometer continues to correspond to the actual load requirements on the road.
These checks should be made at least once at an intermediate point during
service accumulation. Discrepancies revealed by these checks must be
corrected before service accumulation is continued.
B. Malfunctions to vehicles accumulating service on a chassis dyna-
mometer must be recognized with no more time lag than would occur if the
vehicle were accumulating service on the road.
1. Since the road simulator causes the driver to be eliminated
from the feedback network, the applicant may utilize some type of monitoring
system to detect any potential vehicle or dynamometer malfunction. This
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approach is particularly desirable for a road simulator installation in which
auxiliary power (electric motor or equivalent) is used to simulate inertia or
downhill operation. With this type of installation, auxiliary power may
compensate in case of vehicle malfunction or general vehicle deterioration by
"driving" the crippled vehicle. If the applicant does not utilize such a
detection system, frequent on-the-road evaluations must be made. These
evaluations shall be made at the midpoint (+ 250km) of each service accumula-
tion interval. Exhaust gas analysis is not an acceptable technique for
determining vehicle or dynamometer malfunctions.
2. The provisions of §86.429-78(a)(l)(ii) require an overt indica-
tion of malfunction in order to justify unscheduled maintenance. A vehicle
malfunction detected during dynamometer operation, can be verified either on
the dynamometer or by an on-the-road evaluation to determine the need for
unscheduled maintenance. If the verification is to be performed on-the-road,
the test vehicle must be driven on an approved service accumulation road route.
C. The applicant has the option of alternating between an approved
chassis dynamometer system and an approved service accumulation road route.
However, a change from one system to the other must be recorded on the
vehicle's service accumulation record and is to be made available to EPA upon
request.
X. Data to be Recorded
A. For all vehicles accumulating distance on a chassis dynamometer,
the following data shall be recorded by the manufacturer and maintained as
long as the data are used to satisfy 40 CFR Part 86 data requirements:
1. A continuous record of vehicle speed versus time. This record
will serve the same purpose as a tach-o-graph from a test vehicle operated on
the road and must reflect the service accumulation route which is submitted in
the application for certification. This record is not necessary if the appli-
cant can assure that the system design provides adequate safeguards that the
dynamometer will follow the correct driving schedule throughout all service
accumulation.
2. On chassis dynamometers which do not control manifold vacuum or
wheel (or dynamometer) torque, a check of the engine load indicating para-
meter^) is to be made at least every two hours. This record is to verify
that this simulation of the original road-load requirements has been main-
tained. Any maintenance or load setting adjustments made to maintain this
relationship must be indicated on vehicle data sheets kept by the applicant.
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B. These data shall be made available to EPA upon request. If the
data do not meet the requirements of this section, EPA will determine if modi-
fications in the procedure need to" be made, service on the chassis dynamometer
is to be discontinued, or the vehicle must be disqualified.
Director
llson
Office of Mobile Sources
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