4. Test Procedures and Smoke Opacity Measurement
a) Follow the opacimeter manufacturer's instruction for on the proper
installation, operation/use and checking the accuracy and calibration before
and after each test.
b) Set the vehicle gear-change control in the neutral position and the handbrake
effectively engaged.
c) Start the engine and warm it up to its normal operating temperature.
d) Accelerate the engine two to three times (2-3) prior to smoke sampling in
order to remove deposits of soot and other carbon particles in the tail pipe.
e) With the engine idling, depress the accelerator quickly, but not violently, to
obtain maximum delivery from the injection pump. Maintain this position until
maximum engine speed is reached for about two (2) to four (4) seconds and
the governor comes into action. As soon as this speed is reached, release
the accelerator until the engine resumes its idling speed. Record the
maximum reading of the smokemeter.
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f) The operation described in paragraph (4)(e) shall be repeated not less than
six (6) times in order to clear the exhaust system and to allow for any
necessary adjustment of the apparatus. The maximum opacity values read
in each successive accelaration shall be noted until stabilized values are
obtained. The values read shall be regarded as stabilized when four (4)
consecutive readings are within a hand width of 0.25 m-1 and do not form a
decreasing sequence. The arithmetic mean of the four stabilized values shall
be the test result for the concerned vehicle.
g) For motor vehicles designed with several exhaust outlets that are individually
connected from paired exhaust ports, the free acceleration test shall be
carried out on each outlet. In this case, the values used for calculating the
correction to the absorption coefficient shall be arithmetical meanvalues
recorded at each outlet and the test shall be valid only if the extreme values
measured do not differ by more than 0.15m-1
For motor vehicles designed with several exhaust outlets connected from one
exhaust pipe coming from the engine's exhaust manifold collector, the free acceleration
test shall be carried out only on one exhaust outlet, the other outlets effectively blocked
to prevent leaks.
h) Seal the full load screw of the injection pump/delivery system of the motor
vehicle after a pass-test to prevent tampering;