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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 procedures 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.

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 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

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