WLTP-08-20e
Road load family, draft
v1, 31.10.2014: Initial draft by Christoph Lueginger
X.
Road load family
Vehicles identical with respect to the following characteristics shall be considered to be part
of the same road load family:
(a) Transmission type (e.g. manual, automatic, CVT) and transmission model (e.g. torque
rating, number of gears, number of clutches, etc.);
(b) n/v ratios (engine rotational speed divided by vehicle speed). This requirement shall be
considered fulfilled if, for all transmission ratios concerned, the difference with respect to the
transmission ratios of the most commonly installed transmission type is within: [25] per cent;
(c) Number of powered axles;
(d) [RESERVED: family criteria for EVs];
(e) The range between the vehicle with the lowest energy demand over a full WLTC class 3
and the vehicle with the highest energy demand shall not exceed [5] MJ.
===================
Annex 4, 4.2.1. Test vehicle
A test vehicle (vehicle H) shall be selected from the CO2 vehicle family (see paragraph 5.6.
of this gtr) with the combination of road load relevant characteristics (i.e. e.g. mass,
aerodynamic drag and tyre rolling resistance) producing the highest cycle energy demand.
At the request of the manufacturer, the CO2 interpolation method may be applied for
individual vehicles in the CO2 vehicle family (see paragraph 1.2.3.1. of Annex 6 and
paragraph 3.2.3.2. of Annex 7). In that case, the road load shall also be determined on a test
vehicle (vehicle L), and vehicles H and L shall have having a combination of road load
relevant characteristics producing respectively producing the highest and lowest cycle
energy demand required for CO2 interpolation.
At the request of the manufacturer the road load values for the vehicles H and L of a CO2family within one road load family are calculated using their H and L properties as individual
input parameters according to the paragraphs 3.2.3.2.2.- 3.2.3.2.2.4. of Annex 7.
In this case for road load determination the test vehicle H (and L) shall be the vehicle with the
road load combination producing the highest (and lowest) cycle energy demand within the
road load family.
For the road load family the criteria from paragraph [X, TBD] shall apply.
Each test vehicle shall conform [...]
WLTP-08-20e
Annex 7
3.2.3.2.2.
Road load calculation for an individual vehicle
3.2.3.2.2.1.
Mass of an individual vehicle
The test masses of vehicles H and L shall be used as input for the
interpolation method.
TMind
is the individual test mass of the vehicle according to
paragraph 3.2.d. of II. Text of the global technical regulation, kg.
If the same test mass was used for test vehicles L and H, the value of
TMind shall be set to the mass of test vehicle H for the interpolation
method.
3.2.3.2.2.2.
Rolling resistance of an individual vehicle
The actual rolling resistance values for the selected tyres on test
vehicle L, RRL, and test vehicle H, RRH, shall be used as input for the
interpolation method. See Annex 4, paragraph 4.2.2.1.
If the tyres on the front and rear axles of vehicle L or H have different
rolling resistance values, the weighted average of the rolling
resistances shall be calculated using the following equation:
RR x = RR 𝑥,FA ∗ mp𝑥,FA + RR 𝑥,RA ∗ (1 − mp𝑥,FA )
where:
RR x,FA
kg/tonne;
is the rolling resistance of the front axle tyres,
RR x,RA
kg/tonne;
is the rolling resistance of the rear axle tyres,
mpx,FA
is the percentage of the vehicle mass on the front axle;
𝑥
represents vehicle L, H or an individual
vehicle.
For the tyres fitted to an individual vehicle, the value of the rolling
resistance RR ind shall be set to the class value of the applicable tyre
rolling resistance class, according to Table A4/1of Annex 4.
If the tyres have different rolling resistance class values on the front
and the rear axle, the weighted average shall be used, calculated with
the equation above.
If the same tyres were fitted to test vehicles L and H, the value of
RR ind for the interpolation method shall be set to RR H .
3.2.3.2.2.3.
Aerodynamic drag of an individual vehicle
The aerodynamic drag shall be measured for each of the drag
influencing options at a certified wind tunnel fulfilling the
requirements of paragraph 3.2. of Annex 4.
At the request of the manufacturer and with the agreement of the type
approval authority an equivalent method (e.g. simulation) can be used
for the determination of a defined and limited number of options.
Evidence of equivalency has to be shown to the authority.
The responsible authority shall verify if the wind tunnel facility is
qualified to
accurately determine the ∆(Cd × Af ) for options
and/or body shapes that differ between test vehicle L and H. If the
wind tunnel facility is not qualified, the Cd × Af for vehicle H shall
(27)
WLTP-08-20e
apply for the whole CO2 vehicle family.The aerodynamic drag of
options on the exterior of an individual vehicle shall be calculated
according to the following equation:
∆[Cd × Af ]ind = ∑ni=1 ∆[Cd × Af ]i
(28)
where:
Cd
is the aerodynamic drag coefficient;
Af
is the frontal area of the vehicle, m2;
∆[Cd × Af ]ind is the difference in aerodynamic drag between an
individual vehicle and test vehicle L, due to options on
the vehicle that differ from those installed on test
vehicle L, m2;
∆[Cd × Af ]i
is the aerodynamic drag difference due to an individual
feature i on the vehicle (∆[Cd × Af ]i is positive for an
option that adds aerodynamic drag with respect to test
vehicle L and vice versa), m2;
n
is the number of options on the vehicle that are different
between an individual vehicle and test vehicle L.
The sum of all ∆[Cd × Af ]i between options installed on the test
vehicles L and H shall correspond to the total difference between the
Cd × Af values for the test vehicles L and H, referred to as ∆[Cd ×
A f ]LH .
The sum of all ∆[Cd × Af ]i , expressed as Δf2 , between options
installed on the test vehicles L and H shall correspond to the
difference in f2 between the test vehicles L and H.
If the same options on the vehicle were also installed on test vehicles
L and H, the value of ∆[Cd × Af ]ind for the interpolation method shall
be set to zero.
3.2.3.2.2.4.
Calculation of road load for individual vehicles in the CO2 vehicle
family
The road load coefficients f0 , f1 and f2 (as defined in Annex 4) for test
vehicles H and L are referred to as f0,H , f1,H and f2,H ,and f0,L , f1,L and
f2,L respectively. An adjusted road load curve for the test vehicle L is
defined as follows:
∗
∗
FL (v) = f0,L
+ f1,H × v + f2,L
× v2
(29)
Applying the least squares regression method in the range of the
∗
reference speed points, adjusted road load coefficients f0,L
and
∗
∗
f2,L shall be determined for FL (v) with the linear coefficient f1,L set to
f1,H . The road load coefficients f0,ind , f1,ind and f2,ind for an individual
vehicle in the CO2 vehicle family are calculated as follows:
f0,ind = f0,H − ∆f0 ×
(TMH ×RRH −TMind ×RRind )
(TMH ×RRH −TML ×RRL )
(30)
or, if (TMH × RR H − TML × RR L ) = 0, the equation below shall
apply:
f0,ind = f0,H − ∆f0
(31)
f1,ind = f1,H
(32)
f2,ind = f2,H − ∆f2
(∆[Cd ×Af ]LH −∆[Cd ×Af ]ind )
(∆[Cd ×Af ]LH )
(33)
or, if ∆[Cd × Af ]LH = 0, the equation below shall apply:
f2,ind = f2,H − ∆f2
(34)
WLTP-08-20e
where:
,
∗
∆f0 = f0,H − f0,L
(35)
∗
∆f2 = f2,H − f2,L
(36)