Proposal to replace 3 s rule by 2 s rule WLTP-08-15e OIL #8, annex 2, section 4b Proposal to replace 3 s rule by 2 s rule 01.11.2014 1

Review 3 s rule for acc phases This issue was requested by a N1 manufacturer, because the 3 s rule could lead to too high engine speeds for vehicles with „short“ transmissions, especially for the 1. gear. The TF discussed this issue extensively and came up with the proposal to change the 3 s rule to a 2 s rule already in an early stage of the discussions, because this change could ease the prescriptions significantly with respect to other requirements (e.g. skipping of gears) and does not lead to significant changes in the engine speed distributions. One member of the group expressed concerns, that the 2 s rule will influence the number of gear changes in the wrong direction. 2

Review 3 s rule for acc phases Concerning the number of gear changes calculations were performed for 243 class 3 vehicles with maximum vehicle speeds between 136 km/h and 244 km/h. The results can be summarised as follows: The number of upshifts varies amongst the 243 vehicles for the 3 s rule between 44 and 82 (average 60), 2 s rule between 44 and 85 (average 60,5) 3

Review 3 s rule for acc phases A direct comparison leads to the following distribution of differences in upshifts between the 2 s rule and the 3 s rule (see also figure 1): +3, 6 vehicles, +2, 10 vehicles, +1, 54 vehicles, 0, 173 vehicles The average engine speed (excluding the stop phases) decreases with the 2 s rule by 0,15% on average and 1,3% at maximum. 4

2 s rule vs 3 s rule Figure 1 5

Review 3 s rule for acc phases The TF concluded that these results would not justify a reopening of the discussion, especially because the change to the 2 s rule will make the assessment of the possibility of skipping of gears during acceleration phases unnecessary. The proposal is already implemented in WLTP-08-15. The proposal will be brought to the WLTP IG #8 for discussion and adoption. 6