Council Directive of 2 August 1972 on the approximation of the laws of the Member States relating to the measures to be taken against the emission of pollutants from diesel engines for use in vehicles (72/306/EEC) (repealed)

ANNEX IV U.K. TEST UNDER FREE ACCELERATION

1. TEST CONDITIONS U.K.

1.1. The test shall be carried out on the vehicle or engine which has undergone the test at steady speeds described in Annex III. U.K.

1.1.1. If the engine is tested on a bench the test shall be carried out as soon as possible after the test for measurement of opacity under full load at steady speed. In particular, the cooling water and the oil shall be at the normal temperatures indicated by the manufacturer. U.K.

1.1.2. If the test is carried out on a stationary vehicle, the engine shall first be brought to normal operating condition by a road run. The test shall be carried out as soon as possible after completion of the road run. U.K.

1.2. The combustion chamber shall not have been cooled or fouled by a prolonged period of idling preceding the test. U.K.

1.3. The test conditions described in Annex III, items 3.1, 3.2 and 3.3, shall apply. U.K.

1.4. The conditions described in Annex III, item 3.4, with regard to the sampling and measuring apparatus shall apply. U.K.

2. TEST METHODS U.K.

2.1. If the test is a bench test, the engine shall be disconnected from the brake, the latter being replaced either by the rotating parts driven when no gear is engaged or by an inertia substantially equivalent to that of the rotating parts. U.K.

2.2. If the test is carried out on a vehicle, the gear-change control shall be set in the neutral position and the engine in gear. U.K.

2.3. With the engine idling, the accelerator control shall be operated quickly, but not violently, so as to obtain maximum delivery from the injection pump. This position shall be maintained until maximum engine speed is reached and the governor comes into action. As soon as this speed is reached the accelerator shall be released until the engine resumes its idling speed and the opacimeter reverts to the corresponding conditions. U.K.

2.4. The operation described in item 2.3 above shall be repeated not less than six times in order to clear the exhaust system and to allow for any necessary adjustment of the apparatus. The maximum opacity values read at each successive acceleration shall be noted until stabilized values are obtained. No account shall be taken of the values read while the engine is idling after each acceleration. The values read shall be regarded as stabilized when four consecutive readings are situated within a band width of 0·25 m⁻¹ and do not form a decreasing sequence. The absorption coefficient X_M to be recorded shall be the arithmetic mean of these four values. U.K.

2.5. Engines fitted with an air supercharger shall be subject, where appropriate, to the following special requirements: U.K.

2.5.1. In the case of engines with an air supercharger which is coupled with or driven mechanically by the engine and is capable of being disengaged, two complete measurement cycles with preliminary accelerations shall be carried out, the air supercharger being engaged in one case and disengaged in the other. The measurement result recorded shall be the higher of the two results obtained; U.K.

2.5.2. In the case of engines with an air supercharger which can be cut out by means of a driver-operated bypass, the test shall be carried out with and without the bypass. The measurement result recorded shall be the higher of the results obtained. U.K.

3. DETERMINATION OF THE CORRECTED VALUE OF THE ABSORPTION COEFFICIENT U.K.

3.1. Notation U.K.

X_M

=

value of the absorption coefficient under free acceleration measured as described in item 2.4 of this Annex;

X_L

=

corrected value of the absorption coefficient under free acceleration;

S_M

=

value of the absorption coefficient measured at steady speed (Annex III, item 2.1.) which is closest to the prescribed limit value corresponding to the same nominal flow;

S_L

=

value of the absorption coefficient (Annex III, item 4.2.) for the nominal flow corresponding to the point of measurement which gave the value S_M;

L

=

effective length of the light path in the opacimeter.

3.2. When the absorption coefficients are expressed in m⁻¹ and the effective length of the light path in metres, the corrected value X_L is given by the smaller of the following two expressions: U.K.

or