4.

PREPARING THE TEST 4.1. Setting of brake 4.1.1. The brake shall be so adjusted as to reproduce the operation of the vehicle on the level at a steady speed of 50 km/h. 4.1.2. For this purpose the vacuum shall be measured at the engine intake during a road test carried out at 50 km/h in third gear, or using the gears specified in item 1.3, the vehicle being loaded to its reference weight and the tyre pressure being that indicated by the manufacturer. The vacuum shall be measured when a steady speed on the level has been maintained for at least fifteen seconds. To take account of the effects of wind, the average of the results of measurements made twice in each direction shall be taken. 4.1.3. The vehicle shall then be placed on the dynamometer bench and the brake so adjusted as to obtain the same vacuum at the intake as that recorded in the road test referred to item 4.1.2 above. This brake setting shall be maintained throughout the test. 4.1.4. This setting is appropriate for brakes of hydraulic type. For other types it may be necessary to make sure that the setting so obtained is appropriate for other intermediate states between idling and the maximum speed in the cycle. If necessary, an average setting shall be adopted. 4.2. Adjustment of equivalent inertias to the vehicle's translatory inertias A flywheel shall be used enabling a total inertia of the rotating masses to be obtained proportional to the reference weight within the following limits: >PIC FILE= "T0002126"> 4.3. Conditioning of vehicle 4.3.1. Before the test the vehicle shall be kept at a temperature of between 20º and 30º C for at least six hours. The cooling-water and engine-oil temperatures shall be measured before the test to make sure that they are between 20º and 30º C. 4.3.2. The tyre pressure shall, as in the case of the preliminary road test for brake adjustment, be that indicated by the manufacturer. However, if the diamter of the rollers is less than 50 cm, the pressure in the tyres shall be increased by 30-50 % to prevent damage to the tyres. 4.4. Check of back-pressure During the preliminary tests a check shall be made to ensure that the back-pressure set up by the sampling device does not exceed 75 mm water gauge, measurements being performed at the various steady speeds prescribed in the cycle. 4.5. Conditioning of bags 4.5.1. The bags shall be so conditioned, particularly with regard to hydrocarbons, that hydrocarbon losses over a period of 20 minutes do not exceed 2 % of the initial content. This conditioning shall be carried out during preliminary tests conducted at temperatures close to the extreme temperatures encountered during the various tests. 4.5.2. Losses shall be measured as follows. When the engine is running at a constant (rpm) speed the hydrocarbon content of the gases entering the bag shall be measured continuously until the bag has been filled. The content, when filling is completed, must be the average of the contents recorded during filling. The bag shall be emptied by the analyser pumps and the content recorded continuously or at fixed intervals. If after twenty minutes the content has varied by more than 2 %, the bag shall be emptied and then refilled for a second measurement. This cycle shall be repeated as many times as is necessary to saturate the walls. 4.6. Calibration of analytical apparatus 4.6.1. Calibration of analysers. The quantity of gas at the indicated pressure compatible with the correct functioning of the equipment shall be injected into the analyser by means of the discharge gauge and the pressure-reducing valve mounted on each bottle. The apparatus shall be adjusted to indicate as a stabilised value the value shown on the standard-gas bottle. Starting from the setting obtained with the maximum-content bottle, the curve of the analyser's deviations shall be drawn as a function of the content of the various standard-gas bottles used. 4.6.2. Overall response time of the apparatus. The gas from the maximum-content bottle shall be injected into the end of the sampling probe. A check shall be made to ensure that the indicated value corresponding to maximum deviation is attained in less than one minute. If this value is not attained, the analysing circuit shall be inspected from end to end for leaks. 4.7. Adjustment of volume-measuring device The bag shall be filled during the preliminary tests and a check made to ensure that the volume can be measured with the desired accuracy. If necessary, a suitable (gas) gauge shall be selected in each case.

← 3. · All articles · 5. →

Source: EUR-Lex (Cellar) · retrieved 2026-11-01 · Text as adopted (Official Journal); later amendments are not incorporated in this text.