1 Comments on the Ste 3 gearshift calculation tool from validation 2 participants Heinz Steven WLTP WLTP-DHC-16-03

Background 2 In order to take into account the technical progress and the increased variety of transmission design (e.g. 4-speed up to 7- speed gearboxes) shift points at fixed vehicle speeds are no longer appropriate. In order to reflect practical use as well as fuel efficient driving behaviour as much as possible, the prescriptions are based on the balance between the power required for driving resistance and acceleration and the power provided by the engine in all possible gears at a specific cycle phase. In order to cover the wide range of rated engine speeds (e.g to 8000 min-1) depending of the engine technology, a calculation tool was developed which is based on normalised engine speeds (normalised to the span between idling speed and rated engine speed) and normalised full load power curves (normalised to rated power) versus normalised engine speed.

Input data 3

Interim feedback from validation 2 participants 4 This calculation tool was used during validation 2 of the WLTP project. Some participants wanted to get the opportunity to choose n_min_drive values below the current limit, which is not possible in the current version. Another comment: Downshift to 1. gear should be avoided or minimised. This downshift is most probably caused by the definition of n_min for the 2. gear: n_min = 1,25*n_idle, which might be too high. A comment from one party: upshifts are too early, engine speeds are too low, shift behaviour not in line with practical use, A comment from another party tended into the opposite direction and requested also the use of n_min_drive values below the current limit curve.

Modifications performed during validation 2 5 The author concluded that the following modifications should be made in conjunction with the implementation of the modified cycle versions for low powered vehicles.  options for the choice of lower n_min_drive values (for gears >= 3),  Add an option for the choice of n_min values for the 2. gear.  A 3rd modification is related to the choice of the safety margin for the full load power curve.

Modifications 6 Modific. 0: Implementation of modified cycle versions for low powered vehicles (class 1 and 2), Modific. 1: n_min_2 was added as input parameter. n_min_2 is the minimum engine speed in gear 2. n_min_2 was defined as 1,25*idling_speed. It is now recommended to set n_min_2 to 1,15*idling_speed. The minimum value that can be used for the calculation is 1,1*idling_speed.

Modifications 7 Modific. 2: n_min_drive, the minimum engine speed for short trips in gears > 2, was limited to 0,125*(rated_speed - idling_speed) + idling_speed. The use of this value is still recommended, but lower values down to n_min_2 can be used for the calculation. Modific. 3: The safety margin accounting for the difference between stationary wot power curve and the power available during transient conditions could be chosen as input parameter in the previous version. The choice of 90% was recommended. The safety margin is now set to 90% and cannot be changed any more.

Further comments 8 These modifications were implemented in an updated version of the tool (reference date ) which was then distributed and used for validation 2. Further comments on the calculation tool were made by the following participants:  ACEA members Daimler, Delphi, PSA  India,  Japan

Comments from Daimler 9 prevent backshifting, because a scenario with reduced downshifting/backshifting points is closer to real driving behaviour, It increases driveability during test procedure, Backshift to „Gear 1“ often not necessary as long as vehicle is in motion, Average engine speed is only slightly reduced by the modification, Suggestion for improvement of Gearshift Calculation Approach “Steven” ：  Possibility to define „n_min_drive“ for single gears individually.

Comments from Delphi 10 The Delphi comments were also delivered as presentation and can be summarised as follows: Downshifting to 1st gear:  We observe that the speed decrease sharply during the downshifting with the risk of missing the target speed. Feedback from drivers who had tested the cycle:  It’s hard to follow the cycle in 1 st gear  Downshifting frequently to 1 st gear isn’t totally representative of a real drive on the road

Comments from Delphi 11 Proposal for improvement:  Not engage the 1 st gear when the vehicle is still moving,  Let the 2 nd gear engaged,  At the time when the 1 st gear is engaged, disengage the clutch,  Re-engage the clutch when the vehicle speed will increase again Benefits:  The vehicle speed is closer to the target than before  The risk of driver violation is decreased

Comments from Delphi 12 Feedback from drivers:  The cycle is easier to follow  The time spent on the slip point is decrease because the the downshifting to 1st gear requires more time on this point than the re-engagement of the 2nd gear Other effects:  Time spent without a gear engage is increased

Comments from PSA 13 The approach is too much aiming at economic driving, The number of shift points is too high, The current proposal disadvantages gasoline engines.

Comments from India 14 No. of Gear Shifts (Stevens) vs PMR  Gear shifts are higher than proposed by Japan,  With reduction of Safety Margin from 90% to 80% the cycle is expected to become stringent on the lower PMR Range,  Use of Moderated Cycle 5.1 will compensate for this effect as shown in the chart in WLTP-DHC Safety Margin on Full Load Power Curve  Steven’s Gear Shift is based on the assumption of 90% Safety Margin of Power Available.  The actual power available at Wheel is 80%. Hence for actual safety margin, the criteria should be modified to 80%. (20% margin),

Comments from India 15  For new vehicles tested for COP will have lesser Power Availability due to Higher Engine Friction Losses. The proposed criteria of 80% barely meets requirements of new vehicles.

Comments from Japan 16 The Japanese colleagues sent analysis results for 8 different vehicles including low powered N1 vehicles. The results are summarised in the following table.

Comments from Japan 17

Summary of discussion points 18 Input data:  Default values for the full load power curve and for driving resistance coefficients should not be provided in a final version.  The safety margin for the full load power curve needs to be updated/improved, the input data for the curve need to be simplified.  Uniform input data for a vehicle family. Downshifts:  Downshift to 1. gear: Although the number of downshifts to the 1. gear within a short trip were reduced with version 2 compared to version 1, there is still a need for further improvement.  Downshifts by more than 2 gears.

Summary of discussion points 19 Approach  The current approach aimes at a compromise between economic driving and representativity with respect to in- use data,  The current n_min_drive concept is a bit more favourable for Diesel engines compared to Petrol engines As a consequence the number of shift points is higher compared to a vehicle speed based system. It should be assessed, how the number of shift points correlates with the in-use data and whether or to what extent it could be reduced by an increase of engine speeds.