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Emission Test Cycles

Worldwide Harmonized Light Vehicles Test Cycle (WLTC)

Time-speed data points: WLTC Class 3b | WLTC Class 3a | WLTC Class 2 | WLTC Class 1

Background

The Worldwide harmonized Light vehicles Test Cycles (WLTC) are chassis dynamometer tests for the determination of emissions and fuel consumption from light-duty vehicles. The tests have been developed by the UN ECE GRPE (Working Party on Pollution and Energy) group [2624]. The WLTC cycles are part of the Worldwide harmonized Light vehicles Test Procedures (WLTP), published as UNECE Global technical regulation No 15 (GTR 15) [3553]. While the acronyms WLTP and WLTC are sometimes used interchangeably, the WLTP procedures define a number of other procedures—in addition to the WLTC test cycles—that are needed to type approve a vehicle.

The WLTP will replace the European NEDC based procedure for type approval testing of light-duty vehicles.

The WLTP procedures includes several WLTC test cycles applicable to vehicle categories of different power-to-mass (PMR) ratio, Table 1. The PMR parameter is defined as the ratio of rated power (W) / curb mass (kg). The curb mass (or kerb mass) means the “unladed mass” as defined in ECE R83. The cycle definitions may also depend on the maximum speed (v_max), which is the maximum speed of the vehicle as declared by the manufacturer (ECE R68) and not any use restriction or safety based limitation. Cycle modifications are allowed to accommodate drivability problems for vehicles with power to mass ratios close to the borderlines or with maximum speeds limited to values below the maximum speed required by the cycle.

Table 1
WLTC test cycles
CategoryPMR, W/kgv_max, km/hSpeed Phase Sequence
Class 3bPMR > 34v_max ≥ 120Low 3 + Medium 3-2 + High 3-2 + Extra High 3
Class 3av_max < 120Low 3 + Medium 3-1 + High 3-1 + Extra High 3
Class 234 ≥ PMR > 22-Low 2 + Medium 2 + High 2 + Extra High 2
Class 1PMR ≤ 22-Low 1 + Medium 1 + Low 1

WLTC Test Cycles

Class 3 Cycle

With the highest power-to-mass ratio, Class 3 is representative of vehicles driven in Europe and Japan. Class 3 vehicles are divided into 2 subclasses according to their maximum speed: Class 3a with v_max < 120 km/h and Class 3b with v_max ≥ 120 km/h. Selected parameters of the Class 3 cycles are given in Table 2, and the vehicle speed for Class 3b is shown in Figure 1 (in this representation, Class 3a trace would look very similar).

Table 2
WLTP Class 3 cycle: selected parameters
PhaseDurationStop DurationDistancep_stopv_maxv_ave w/o stopsv_ave w/ stopsa_mina_max
ssmkm/hkm/hkm/hm/s²m/s²
Class 3b (v_max ≥ 120 km/h)
Low 3589156309526.5%56.525.718.9-1.471.47
Medium 3-243348475611.1%76.644.539.5-1.491.57
High 3-24553171626.8%97.460.856.7-1.491.58
Extra-High 3323782542.2%131.394.092.0-1.211.03
Total180024223266
Class 3a (v_max < 120 km/h)
Low 3589156309526.5%56.525.718.9-1.471.47
Medium 3-143348472111.1%76.644.139.3-1.471.28
High 3-14553171246.8%97.460.556.4-1.491.58
Extra-High 3323782542.2%131.394.092.0-1.211.03
Total180024223194
Figure 1. WLTC cycle for Class 3b vehicles

Class 2 Cycle

Class 2 is representative of vehicles driven in India and of low power vehicles driven in Japan and Europe. Selected parameters of the Class 2 cycle are given in Table 3, and the vehicle speed is shown in Figure 2.

Table 3
WLTP Class 2 cycle: selected parameters
PhaseDurationStop DurationDistancep_stopv_maxv_ave w/o stopsv_ave w/ stopsa_mina_max
ssmkm/hkm/hkm/hm/s²m/s²
Low 2589155310126.3%51.425.719.0-0.940.90
Medium 243348473711.1%74.744.339.4-0.930.96
High 24553067926.6%85.257.553.7-1.110.85
Extra-High 2323780192.2%123.191.489.4-1.060.65
Total180024022649
Figure 2. WLTC cycle for Class 2 vehicles

Class 1 Cycle

With the lowest power-to-mass ratio, Class 3 is representative of vehicles driven in India. Selected parameters of the Class 1 cycle are given in Table 2, and the vehicle speed is shown in Figure 3.

Table 4
WLTP Class 1 cycle: selected parameters
PhaseDurationStop DurationDistancep_stopv_maxv_ave w/o stopsv_ave w/ stopsa_mina_max
ssmkm/hkm/hkm/hm/s²m/s²
Low 1589154333026.1%49.127.620.4-1.000.76
Medium 143348476711.1%64.444.639.6-0.530.63
Low 1589154333026.1%49.127.620.4-1.000.76
Total161135611428
Figure 3. WLTC cycle for Class 1 vehicles

Cycle Modifications

For some vehicles, it may not be possible to follow speed/time requirements of the cycle. The reasons for this are:

  1. Vehicles with power to mass ratios close to the borderlines between Class 2 and Class 3 vehicles or very low powered vehicles in Class 1 may not be able to achieve the accelerations required to maintain cycle speed. In these cases, a downscaling procedure can be applied to reduce the maximum acceleration rates to improve driveability. A consequence of this procedure is a reduction of maximum cycle speeds.
  2. Some vehicles may have a maximum speed limited to a value lower than the maximum speed of the downscaled cycle. In these cases, the vehicle shall be driven with its maximum speed in those cycle periods where the cycle speed is higher than the maximum speed of the vehicle. An example of vehicles for which this applies is Class 3a vehicles over the Extra-High 3 phase.
  3. Some vehicles may not be able to follow the speed trace of the downscaled cycle within the required tolerance for specific periods. In these cases the vehicle shall be driven with the accelerator control fully activated during these periods. In these cases, driving trace violations are permitted.

Tests for Hybrid & Electric Vehicles

The WLTP includes special provisions for testing of various categories of hybrid-electric and electric vehicles: OVC-HEVs (off-vehicle chargeable hybrid electric vehicles); NOVC-HEV (not off-vehicle chargeable hybrid electric vehicles); and PEV (pure electric vehicles).

All OVC-HEVs, NOVC-HEVs and PEVs are classified as Class 3 vehicles. Emissions and a number of other parameters are tested over the respective Class 3 (Class 3a or Class 3b) cycle, in both charge-depeting and charge-sustaining modes. In addition, certain parameters are tested over WLTC city cycles, composed of the low and medium speed phases only. The test matrix is summarized in Table 5.

Table 5
WLTC test matrix for hybrid and electric vehicles
WLTPWLTP city
Charge-depletingCharge-sustainingCharge-depleting
Criteria Emissions, FC, CO2, AER, EAER, RCDC, RCDA, EACCriteria Emissions, FC, CO2AERcity, EACcity
OVC-HEVClass 3aLow 3 + Medium 3-1 + High 3-1 + Extra High 3Low 3 + Medium 3-1 + High 3-1 + Extra High 3Low 3 + Medium 3-1
Class 3bLow 3 + Medium 3-2 + High 3-2 + Extra High 3Low 3 + Medium 3-2 + High 3-2 + ExtraHigh 3Low 3 + Medium 3-2
NOVC-HEVClass 3a--Low 3 + Medium 3-1 + High 3-1 + ExtraHigh 3--
Class 3b--Low 3 + Medium 3-2 + High 3-2 + Extra High 3--
PEVClass 3aLow 3 + Medium 3-1 + High 3-1 + Extra High 3--Low 3 + Medium 3-1
Class 3bLow 3 + Medium 3-2 + High 3-2 + Extra High 3--Low 3 + Medium 3-2
Abbreviations:
AER - All-electric range
EAER - Equivalent all-electric range
EAC - Recharged energy
FC - Fuel consumption
NOVC-HEV - not off-vehicle charging hybrid electric vehicle
OVC-HEV - off-vehicle charging hybrid electric vehicle
PEV - pure electric vehicle
RCDA - Charge-depleting actual range
RCDC - Charge-depleting cycle range