UN R51 — Supplement 6 to the 03 series of amendments

Paragraph 2.26. now defines three conditions for stable acceleration. Paragraph 2.26.1. applies to all vehicles subject to this Regulation for low engine speed conditions, and eliminates power train reactions such as bumping and jerking. Paragraph 2.26.2. applies to vehicles of category M1, N1 and M2 < 3,500 kg technically permissible maximum laden mass. This condition avoids acceleration delays due to engine control application, at the moment when the acceleration unit is depressed. Paragraph 2.26.3., for the purpose of Annex 7, assumes a constant acceleration over the complete measurement distance between AA' and BB' plus the vehicle length. Before, paragraph 2.26.1. gave stable acceleration, where acceleration needs to be calculated, as a ratio between awot_testPP-BB and awot test of 1.2 or less.

For all points, stable acceleration according to the definition of 2.26.3. must be checked. The check compares the acceleration awot_test,AA-BB between line AA' and line BB' with the acceleration awot_test,PP-BB between line PP' and BB'. If the ratio awot_test,PP-BB / awot_test,AA-BB exceeds 1,20, the acceleration is calculated between line PP' and line BB'. If the ratio does not exceed or is equal to 1,20, the acceleration is calculated between line AA' and line BB'. Before, if stable acceleration according to 2.26.1. could not be achieved, awot_testPP-BB was calculated with the formula of paragraph 3.1.2.1.2 of Annex 3. For P1, the stable acceleration condition now refers to the definition of 2.26.1 instead of 2.26.2.1.

Gear ratio i now means a gear ratio with an acceleration within the 5 per cent tolerance of awot_ref, or greater than awot_ref. The definition of gear ratio i+1 now says an acceleration lower than gear ratio i, instead of an engine speed lower than gear ratio i. A sentence is deleted: for a vehicle not exempted from ASEP according to paragraph 6.2.3., gear i had to be tested for Annex 7. In the PMR formula, mro is now defined according to paragraph 2.4. of the main body, instead of paragraph 2.2.1. of this Annex. Paragraph 2.11.1. has a new rule for vehicles of categories M1, N1 and M2 < 3,500 kg having multiple propulsion sources. The position of the propulsion source having the highest power determines the reference point, and among sources of equivalent power the most forward prevails.

With exhaust outlets spaced more than 0.3 m apart or more than one silencer, one set of measurement is made for each outlet. Two or more exhaust outlets spaced 0.3 m apart or less and connected to a single silencer need only one set of measurement. For these outlets, the microphone is located relative to the outlet furthest from the vehicle longitudinal centreline, not nearest to one extreme edge. Paragraph 3.2.5.3.1.5. now also covers exhaust pipe reference points that are not accessible because of obstacles which form part of the vehicle. In these cases, the microphone must be at least 0.2 m from the nearest obstacle, including the vehicle body, and not under the vehicle. New Cases 1 and 2 set d1 and d2 when the exhaust outlet is more than 0.2 m from the other side of the vehicle.

Paragraph 3.2.6. now gives results for sound emitted by stationary vehicles, with separate rules for a single test position (outlet) and multiple test positions (outlets). The result for a test position (outlet) is the arithmetic average of the three valid measurements, mathematically rounded to the nearest integer value. With multiple test positions (outlets), the reported sound pressure level is for the test position having the highest average sound pressure level. If the vehicle has different modes according to the definition 2.25.1., the stationary sound must be determined for each mode. With multiple modes, the representative sound pressure level for the vehicle type and its registration papers is the highest reported level of all modes. Before, the maximum sound level, for all measurement positions, and of the three measurement results, was the final result.

New text covers vehicles with an engine speed that is a fixed value above or below the target engine speed, for example series hybrids. If the accelerator cannot adjust that fixed engine speed, the test must be carried out at the fixed engine speed. If the engine speed deviates from the applicable target engine speed, the speed used and the reason must be documented in the test report. They must also be documented at paragraph 2.2. of Appendix 1 to Annex 1. Paragraph 2.2. now has a mode entry for the sound level of stationary vehicle, and four more such lines are added. New paragraph 2.1.1. asks for the selected mode for tests of the vehicle in motion.

Annex 6, paragraph 2.1., changes the rules for vehicles of category M1, N1 and M2 ≤ 3,500 kg technically permissible maximum laden mass. For these vehicles, type approval mode, gear(s), k and kP may be used if the type approval test report gives them for the applicable variant. If the type approval test report does not give this information, it must be determined anew. The test report must document which way of data processing was selected. New paragraph 11.12. is a transitional provision for extensions of existing approvals originally granted before the date of entry into force of Supplement 6. Until 12 months after the date of entry into force of Supplement 6, Supplement 6 does not apply to such extensions.