1. General approach
1.1. The shifting procedures described in this annex shall apply to vehicles equipped with manual and automatic shift transmissions.
1.2. The prescribed gears and shifting points are based on the balance between the power required to overcome driving resistance and acceleration, and the power provided by the engine in all possible gears at a specific cycle phase.
1.3. The calculation to determine the gears to use shall be 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.
1.4. This annex shall not apply to vehicles tested according to Annex 8.
2. Required data
The following data is required to calculate the gears to be used when driving the cycle on a chassis dynamometer:
(a) , the maximum rated engine power as declared by the manufacturer;
(b) , the rated engine speed at which an engine develops its maximum power. If the maximum power is developed over an engine speed range, s is determined by the mean of this range;
(c) , idling speed
(d) , the number of forward gears;
(e) , minimum engine speed for gears when the vehicle is in motion. The minimum value is determined by the following equation:
(1) Higher values may be used if requested by the manufacturer;
(f) , the ratio obtained by dividing n in min-1 by v in km/h for each
gear , to ;
(g) , test mass of the vehicle in kg;
(h) , , , driving resistance coefficients as defined of Annex 4 in N, N/(km/h), and N/(km/h)² respectively;
(i) is the full load power curve, normalised to rated power and (rated engine speed – idling speed), where .
3. Calculations of required power, engine speeds, available power, and possible gear to be used
3.1. Calculation of required power
For every second of the cycle trace, the power required to overcome driving resistance and to accelerate shall be calculated using the following equation:
(2) where:
is the road load coefficient, N;
is the road load parameter dependent on velocity, N/(km/h);
is the road load parameter based on the square of velocity, N/(km/h)²;
is the required power at second j, kW;
is the vehicle speed at second j, km/h;
is the vehicle acceleration at second j, m/s², ; is the vehicle test mass, kg;
is a factor taking the inertial resistances of the drivetrain during acceleration into account and is set to 1.1.
3.2. Determination of engine speeds
For each km/h, the engine speed shall be set to and the gear lever shall be placed in neutral with the clutch engaged.
For each km/h of the cycle trace and each gear i, to , the engine speed shall be calculated using the following equation:
(3) All gears i for which are possible gears to be used for driving the cycle trace at .
If ,
;
if and ,
;
if , the clutch shall
be disengaged.
if ,
3.3. Calculation of available power
The available power for each possible gear i and each vehicle speed value of the cycle trace shall be calculated using the following equation:
(4) where:
and:
is the rated power, kW;
is the percentage of rated power available at at full load condition from the normalised full load power curve;
is a safety margin accounting for the difference between stationary full load condition power curve and the power available during transition conditions. SM is set to 0.9;
is the idling speed, min-1; is the rated engine speed.
3.4. Determination of possible gears to be used
The possible gears to be used shall be determined by the following conditions:
(a) ;
(b)
The initial gear to be used for each second of the cycle trace is the highest final possible gear . When starting from standstill, only the first gear shall be used.
4. Additional requirements for corrections and/or modifications of gear use The initial gear selection shall be checked and modified in order to avoid too frequent gearshifts and to ensure driveability and practicality.
Corrections and/or modifications shall be made according to the following requirements:
(a) First gear shall be selected one second before beginning an acceleration phase from standstill with the clutch disengaged. Vehicle speeds below 1 km/h imply that the vehicle is standing still;
(b) Gears shall not be skipped during acceleration phases. Gears used during accelerations and decelerations must be used for a period of at least three seconds (e.g. a gear sequence 1, 1, 2, 2, 3, 3, 3, 3, 3 shall be replaced by 1, 1, 1, 2, 2, 2, 3, 3, 3);
(c) Gears may be skipped during deceleration phases. For the last phase of a deceleration to a stop, the clutch may be either disengaged or the gear lever placed in neutral and the clutch left engaged;
(d) There shall be no gearshift during transition from an acceleration phase to a deceleration phase. E.g., if and the gear for the time sequence and is i, gear i is also kept for the time
, even if the initial gear for would be ;
(e) If a gear is used for a time sequence of 1 to 5 s and the gear before this sequence is the same as the gear after this sequence, e.g. , the gear use for this sequence shall be corrected to .
Example:
(i) a gear sequence , , is replaced by , , ; (ii) a gear sequence , , , is replaced by , ,
, ;
(iii) a gear sequence , , , , is replaced by ,
, , , ;
(iv) a gear sequence , , , , , is replaced by , ,
, , , ;
(v) a gear sequence , , , , , , is replaced by ,
, , , , , .
For all cases (i) to (v), must be fulfilled;
(f) A gear sequence , , , shall be replaced by , , , if the following conditions are fulfilled:
(i) Engine speed does not drop below nmin; and
(ii) The sequence does not occur more often than four times each for the low, medium and high speed cycle phases and not more than three times for the extra high speed phase.
Requirement (ii) is necessary as the available power will drop below the required power when the gear , is replaced by ;
(g) If, during an acceleration phase, a lower gear is required at a higher vehicle speed for at least 2 seconds, the higher gears before shall be corrected to the lower gear.
Example: . The
originally calculated gear use is 2, 3, 3, 3, 2, 2, 3. In this case the gear use will be corrected to 2, 2, 2, 2, 2, 2, 2, 3.
Since the above modifications may create new gear use sequences which are in conflict with these requirements, the gear sequences shall be checked twice.