Question & AnswerQ&A (LTO MEMORANDUM CIRCULAR NO. 94-208)
The main purpose is to establish interim emission standards for used imported motor vehicles subject to inspection prior to initial registration, in accordance with DENR Administrative Order No. 24, Series of 1994.
The standards took effect on September 1, 1994.
The maximum CO limit is 3.5% volume and the maximum HC limit is 500 ppm, both measured using an analyzer and idling test/NDIR method.
The maximum allowable smoke opacity is 50% HSU (Hartridge Smoke Units) or 40% Bosch, measured during free acceleration from low idle engine speed using a Hartridge or Bosch smoke meter.
For spark-ignition gasoline vehicles, an idling test with an NDIR analyzer is used for CO and HC. For diesel vehicles, a free acceleration test from low idle speed is used with an opacimeter (Hartridge or Bosch smoke meter) to measure smoke opacity.
This test measures smoke opacity for in-use diesel vehicles equipped with compression-ignition engines using the method of free acceleration from low idle speed, on a stationary vehicle at normal operating temperature.
The engine must be at normal operating temperature, the combustion chamber not cooled or fouled by prolonged idling before the test, the exhaust system must be free of leaks or orifices, and the vehicle must be stationary with the handbrake engaged and transmission in neutral.
The procedure includes warming up the engine, inserting the probe at least 30 cm into the tailpipe, accelerating the engine quickly to maximum delivery from the injection pump, maintaining that speed until stabilized, and recording maximum smoke readings until three consecutive stabilized values are obtained.
The full load screw of the injection pump/delivery system must be sealed to prevent tampering after a pass-test.
Annex 2 outlines the procedure for measuring exhaust CO and HC emissions at idle speed, including vehicle preparation, use of NDIR analyzers, engine speed adjustments, and data collection from multiple exhaust outlets if applicable.
Instruments must be calibrated (span and zero calibration) within 4 hours before use, checked for leaks and cleanliness, maintained per manufacturer instructions, and calibration must be done away from running engines if manual compensation is needed.
If the in-use emission standard of the country of origin differs, the stricter standard shall be the basis for approval for initial registration of the used imported vehicle.