WLTP OIL #6, annex 2, section 2 Use of the gearbox, required data

Detailed issue descriptions 2 OIL #6, use of the gearbox, required data can be split into the following subsections: 1.the definition of n min_drive should be modified in order to make it more appropriate for modern engines and to make manipulations more difficult. 2.n max needs to be added to section 2, required data and needs to be amended, because the current definition is not appropriate for low powered vehicles. 3.section 2 (i), P normwot (n norm i, j ) should be replaced by P wot (n i, j ), since there is no need for the normalisation.

Definition of n min_drive 3 The issue of an amendment of n min_drive is by far the most complex and controversely discussed issue. The chairman prepared WLTP-GS-TF-13 for the further discussion and distributed it at This document compared 4 different proposals for modified n min_drive determination methods. Based on his assessment he proposed to continue the further discussion with proposals 3 and 4 of this paper. But the group should of course get time to assess WLTP-GS-TF-13.

Definition of n min_drive 4 In the meantime one group member came up with an additional proposal based on the engine speed in the highest gear at the maximum cycle speed:  n min_drive = n idle + k * ndv_ng max * 131,3 This proposal is simple to calculate, independent from engine rated power and considering drivetrain layout. It was agreed that this proposal should be included in the further investigations. The GS-TF asks the WLTP IG for an extension of the time schedule for this issue in order to allow more detailed discussions and assessments. A final amendment proposal from the group should be ready till end of February 2015 latest.

Definition of n min_drive 5 But apart from this, the text in annex 2 of the GTR needs to be amended with respect to n min_drive for clarity reasons. Section 2 required data, bullet point (e) should be amended as follows: (e)n min_drive, minimum engine speed when the vehicle is in motion for n gear = 1, n min_drive = n idle, for n gear = 2, n min_drive = 0,9 x n idle, for ngear > 2, n min_drive is determined by : n min_drive = n_ idle ×(s-n idle )(1) Higher values may be used if requested by the manufacturer.

Definition of n min_drive 6 This proposal is already implemented in WLTP It should be discussed and adopted at WLTP IG #8.

Definition of n max 7 The current definition in the GTR is n max = 1,2*(n rated – n idle ). India requested to come back to the previous definition n max = 0,9*(n rated – n idle )+n idle, if ng < ng vmax. A new proposal for n max was introduced by the chairman: If ng < ng vmax. n max is the minimum engine speed, where 95% of rated power is reached, else n max is limited by v_max of the WLTC. ng vmax is the gear number, in which the maximum vehicle speed is reached. Figure 1 shows a comparison of the values requested by India (n_max_old) and the new proposal by the chairman.

Definition of n max 8 Figure 1

Definition of n max 9 The chairman’s proposal was discussed and adopted by the group. It is already implemented in WLTP This proposal will be brought to the WLTP IG in order to be discussed and adopted at meeting #8.

P normwot (n norm i, j ) -> P wot (n i, j ) 10 During the development process of the gearshift prescriptions normalised full load power curves versus normalised engine speeds had to be used in order to assess the results for different engine and powertrain combinations. For a particular vehicle under test the use of normalised curves is an unnecessary burden, because the current prescriptions in annex 2 require a denormalisation. Therefore the group proposes to amend the text in annex 2 accordingly. It is already implemented in WLTP This proposal should be adopted at WLTP IG #8.