WLTP-08-14e_clean
This document is a proposal for a fundamental amended annex 2 of the GTR. The
amendments cover the following issues:
1. Revised text in order to improve the comprehensibility and the unambiguity; this
required sometimes additional sections and modifications in the rank order of
requirements,
2. A new definition of nmax, this parameter was also added to section 2, required data,
3. The replacement of the normalised full load power curve versus normalised engine
speed by the full load power curve versus engine speed, because the normalisation is
obsolete,
4. An additional subsection in section 1 for vehicles with a two range transmission,
5. The implementation of an additional safety margin for the calculation of the available
power,
6. The proposal to replace the 3 s rule for acceleration phases by a 2 s rule,
7. The possibility to skip a gear at transitions from acceleration to cruise is not
necessary any more because it is covered by the revised prescriptions,
8. More precise prescriptions for downshifts.
The remaining open issues, which still need further discussions and consideration are:
1. Amendment of the definition of nmin_drive,
2. Criteria for crawler gears, that should not be considered for the gear use calculation.
The revised text as well as more precise descriptions for downshifts were elaborated by the
chairman and were not yet discussed in the TF. Since the chairman did not get requests for
modifications from the TF, he aims at adoptions of points 1 to 8 at WLTP IG #8.
Colour code:
Added text
Modified text
Annex 2
Gear selection and shift point determination for vehicles
equipped with manual transmissions
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 engine
speeds and full load power curves versus speed.
1.4
For vehicles equipped with a two range transmission (low and high),
only the range designed to normal on road operation is considered for
the gear use determination.
1.5.
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)
Prated , the maximum rated engine power as declared by the
manufacturer;
(b) s, 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 minimum of this
range;
(c)
nidle , idling speed;
(d) ng max , the number of forward gears;
(e)
nmin⁡_drive , minimum engine speed when the vehicle is in motion
For ngear = 1, nmin_drive = nidle,
for ngear = 2, nmin_drive = 0,9 x nidle,
for ngear > 2, nmin_drive is determined by :
nmin_drive = nidle + 0.125⁡ × (s − nidle )
Higher values may be used if requested by the manufacturer;
(f)
ndvi , the ratio obtained by dividing n in min-1 by v in km/h for
each gear i, i⁡ = ⁡1 to ng max ;
(g)
TM, test mass of the vehicle in kg;
(h)
f0 , f1 , f2 , driving resistance coefficients as defined in Annex 4 in
N, N/(km/h), and N/(km/h)² respectively;
(i)
ngvmax, the gear number, in which the maximum vehicle speed is
reached. ngvmax is determined as follows:
vmax(ngmax) is the vehicle speed at which the required road load
power equals the available power Pwot in gear ngmax. vmax(ngmax-
(1)
1) is the vehicle speed at which the required road load power
equals the available power Pwot in the next lower gear.
The required road load power is calculated as
f ×v+f1 ×v2 +f2 ×v3
3600
Prequired = ( 0
)
(2)
If vmax(ngmax) ≥ vmax(ngmax-1) then ngvmax = ngmax,
else ngvmax = ngmax-1
(j)
nmax_95
nmax_95 is the minimum engine speed, where 95% of rated power
is reached.
(k)
nmax(ngvmax) = ndv(ngvmax) x vmax, cycle
vmax, cycle is the maximum speed of the vehicle speed trace
according to annex 1.
(l)
nmax = max(nmax_95, nmax(ngvmax))
(m) Pwot(n) is the full load power curve over the engine speed
range from idling speed to nmax.
3.
Calculations of required power, engine speeds, available power, and
possible gear to be used
3.1.
Calculation of required power
For every second j of the cycle trace, the power required to overcome
driving resistance and to accelerate shall be calculated using the
following equation:
3
f0 ×vj +f1 ×v2
j +f2 ×vj
Prequired,j = (
3600
)+
kr×aj ×vj ×TM
(3)
3600
where:
3.2.
f0
is the road load coefficient, N;
f1
is the road load parameter dependent on velocity,
N/(km/h);
f2
is the road load parameter based on the square of velocity,
N/(km/h)²;
Prequired,j
is the required power at second j, kW;
vj
is the vehicle speed at second j, km/h;
aj
is the vehicle acceleration at second j, m/s², a j =
TM
is the vehicle test mass, kg;
kr
is a factor taking the inertial resistances of the drivetrain
during acceleration into account and is set to 1.03.
(vj+1 −vj )
3.6
;
Determination of engine speeds
For each vj < 1 km/h the engine speed shall be set to nidle and it is
implied that the vehicle is standing still. The gear lever shall be placed
in neutral with the clutch engaged, except one second before
beginning an acceleration phase from standstill, where the first gear
shall be selected with the clutch disengaged.
(4)
For each vj ≥ 1 km/h of the cycle trace and each gear i, i⁡ = ⁡1 to
ng max , the engine speed ni,j shall be calculated using the following
equation:
ni,j = ndvi × vj
3.3
(5)
Determination of possible gears with respect to engine speed
boundaries
All gears i < ngvmax,
for which nmin_drive ≤ ni,j ≤ nmax_95,
and all gears i ≥ ngvmax,
for which nmin_drive ≤ ni,j ≤ nmax(ngvmax),
are possible gears to be used for driving the cycle trace at vj .
If aj ≤ 0 and ni,j drops below nidle, ni,j is set to nidle and the clutch should
be disengaged.
If aj > 0 and ni,j drops below 1,15 x nidle, ni,j is set to 1,15 x nidle and the
clutch should be disengaged.
3.4.
Calculation of available power
The available power for each possible gear i and each vehicle speed
value of the cycle trace vi shall be calculated using the following
equation:
Pavailable_i,j = Pwot (ni.j ) × (1 − (SM + ASM))
(6)
where Prated is the rated power, kW;
Pwot
is the power available at⁡ni.j at full load condition from
the full load power curve;
SM
is a safety margin accounting for the difference between
the stationary full load condition power curve and the
power available during transition conditions. SM is set
to 10%.
ASM
is an additional exponential power safety margin, which
may be applied on request of the manufacturer. ASM is
fully applied between nidle and nstart and exponentially
approaching almost 0 at nend as described by the
following requirements:
If n ≤ nstart, then ASM = ASM0,
If n > nstart, then
ASM = ASM0 x exp(ln(0,005/ASM0) x (nstart – n)/(nstart – nend))
ASM0, nstart and nend are defined by the manufacturer but must fulfill
the following side conditions:
nstart ≥ nidle,
nend > nstart.
3.5.
Determination of possible gears to be used
The possible gears to be used shall be determined by the following
conditions:
(a) The requirements of section 3.3 are fulfilled and
(7)
(b) Pavailable_i,j ≥ Prequired,j
The initial gear to be used for each second j of the cycle trace is the
highest final possible gear imax. 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.
In this context an acceleration phase is a time period of more than 3
seconds with a vehicle speed ≥ 1 km/h and with monotonic increase of
the vehicle speed. A deceleration phase is a time period of more than 3
seconds with a vehicle speed ≥ 1 km/h and with monotonic decrease of
the vehicle speed.
Corrections and/or modifications shall be made according to the
following requirements:
(a)
Gears used during accelerations must be used for a period of at least 2
seconds (e.g. a gear sequence 1, 2, 3, 3, 3, 3, 3 shall be replaced by 1, 1,
2, 2, 3, 3, 3, 3, 3). Gears shall not be skipped during acceleration phases.
(b)
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.
(c)
During a deceleration phase gears with n gear > 2 are kept as long as the
engine speed does not drop below nmin_drive. If a gear sequence is two
seconds or just one second, it must be replaced by gear 0 for the first
second and the next lower gear for the second time sample. The clutch
must be disengaged for the first second.
(d)
The 2. gear is used during a deceleration phase within a short trip of the
cycle as long as the engine speed does not drop below 0,9 x nidle. If the
engine speed would drop below nidle, the clutch should be disengaged.
(e)
If the deceleration phase is the last part of a short trip just before a stop
phase and the 2. gear would only be used for up to two seconds, the gear
is set to 0 and the clutch may be either disengaged or the gear lever
placed in neutral and the clutch left engaged. A downshift to the 1. gear
is prohibited for those deceleration phases.
(f)
If a gear i is used for a time sequence of 1 to 5 seconds and the gear
before this sequence is the same as the gear after this sequence, e.g. i-1
the gear use for this sequence shall be corrected to i-1.
Example:
(i)
a gear sequence i − 1, i, i − 1 is replaced by i − 1, i − 1, i − 1;
(ii) a gear sequence i − 1, i, i, i − 1 is replaced by i − 1, i − 1, i − 1, i −
1;
(iii) a gear sequence i − 1, i, i,⁡i, i − 1 is replaced by i − 1, i − 1,i − 1, i −
1, i − 1;
(iv) a gear sequence i − 1, i,⁡i, i, i, i − 1 is replaced by i − 1, i − 1, i − 1,
i − 1, i − 1, i − 1;
(v) a gear sequence i − 1, i,⁡i,⁡i, i, i, i − 1 is replaced by i − 1, i − 1, i − 1,
i − 1, i − 1, i − 1, i − 1.
For all cases (i) to (v), g min ≤ i must be fulfilled;
(g)
A gear sequence i,i − 1,i, shall be replaced by i,i,i, 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 i − 1, is replaced by i;
Example: vj < vj+1 < vj+2 < vj+3 < vj+4 < vj+5 < vj+6 . 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.
All rules are applied in succession, after the previous one has completely
finished scanning the gear-profile.