1. Towards RDE cold-start provisions Contribution to the RDE working group
25 January 2016
European Commission - Joint Research Centre (JRC)
IET - Institute for Energy and Transport
Sustainable Transport Unit

2. Background
• Current Type 1 (20-30 oC) and Type 6 tests (-7 oC) cover cold start; a dedicated cold-start test does not exist
Cold start emissions are recorded in RDE but excluded from calculations
Absence of vehicle conditioning
Low repeatability and reproducibility of test conditions may lead to high variability of warm-up durations and cold start emissions
Cold start contributes little to the overall emissions of comparatively long (up to 2h) RDE tests
Implementation of dedicated cold-start provisions as part of the 3rd RDE package

3. Addressing cold-start - Options
Option 1 – Status quo: Cold-start assessment via Type 1 and Type 6 tests; exclusion from RDE
Option 2: Cold-start inclusion in RDE data evaluation but no dedicated assessment
Option 3: Cold-start inclusion in RDE data evaluation with specific pre- conditioning requirements but no dedicated assessment
Option 4: Dedicated cold-start provisions (including preconditioning and dedicated evaluation of emissions as part of the RDE procedure)

4. RDE - Preconditioning Engine, tubing, and after-treatment
Parameter ranges rather than precise values
Parameters to be controlled:
Temperature range for vehicle storage
(Status of periodically regenerating after-treatment systems)
Others
Minimum duration of preconditioning
Standardization increases repeatability of tests but also the feasibility of defeat strategies

5. RDE - Driving Cold-start is typically followed by urban driving
Critical parameters:
Idling shares
Maximum uninterrupted idling duration
Maximum vehicle speed
Driving dynamicity (v*a+)
Test duration
Proposal:
RDE provisions could provide starting point for empirical assessment
Focus on real-world driving data

6. Definition of cold start
Options:
Current “protective” definition: 5 min or until coolant has reached 70oC
New definition for assessing cold start performance
Time or distance based; first MAW
Traces of coolant/oil temperature, etc.
Data evaluation (e.g., at cranking, at a given coolant temperature, etc.)
Applicability to hybrid vehicles
Average
speed
Distance travelled in 5 min
Distance travelled in 10 min
Time to travel 2 km
Time to travel 3 km
35 km/h
2.9 km
5.8 km
3:25 min
5:08 min
30 km/h
2.5 km
5.0 km
4:00 min
6:00 min
25 km/h
2.1 km
4.2 km
4:48 min
7:12 min
15 km/h
1.3 km
8:00 min
12:00 min
10 km/h
0.8 km
1.7 km
18:00 min

7. Empirical findings Empirical results of cold-start emission tests
Laboratory tests
Gasoline engines
Diesel engines
Vehicle ID G1 G2 G3 D1 D2 D3
Engine displacement [ccm]
2000
1200
3000
Number of cylinders 4
Engine rated power [kW]
155 90
110
100
Mileage [km]
11200
5000
13500
30000
14500

8. Empirical findings Normalized NOx emissions over the NEDC
Gasoline vehicles emit to 10 times more NOx during UDC1 than over the NEDC
Diesel vehicles emit 2 to 3 times more NOx during the UDC1 than over the NEDC
Three way catalyst appears to effectively reduce NOx immediately after UDC1 (195sec)
Between-vehicle variability of cold-start emissions is substantial – larger vehicle sample required

9. Evaluation of results
Weighing of cold-start vs. hot engine operation based on share of cold start operation in normal real-world vehicle operation
Assessment of typical trip durations in Europe
Assessment of daily frequency of trips and the occurrence of cold-start
Generic weighing factors

10. Evaluation of results Assessing the average length of on-road trips
Empirical insight to be added based on literature study
WLTP data base suggests trips in Europe cover on overage km
WLTP data in line with literature findings (analysis to be expanded)
Weighing time or distance based (e.g., relative to the average trip length
Source
Average trip length
WLTP data base (430,000 km and 35, 850 short trips; Steven, pers. Communication)
10.5 km (incl. trips <1,000 m)
12.0 km (excl. trips <1,000 m)
Pasaoglu et al. (2012)
15-25 km; 2-3 trips per day based on a web survey of 600 participants in 6 EU Member States
De Gennaro et al. 2014
5-20 km; parking duration 2-12 h in two Italian cities based on 28,000 vehicles and 36*106 km

11. Outline of activities Principle choice on Options 1-4
Prescription of vehicle preconditioning (thermal conditions, duration, status of regenerating after-treatment systems)
Decision on additional requirements regarding driving conditions during cold start (e.g., idling shares, driving dynamics)
Decision on a time/distance-based definition of cold-start
Evaluation of results:
Weighing factors combining cold start emissions and the hot emissions as determined through the RDE data evaluation

12. Conclusions and next steps
Measuring cold-start emissions does not present an analytical challenge
However, vehicle conditioning and controlling for driving dynamicity is important
Choice of cold-start distance to be supported by empirical data
Weighing with driving under hot engine conditions requires thorough data analysis
Hybrid vehicles demand attention

13. Contacts Pierre Bonnel pierre.bonnel@jrc.ec.europa.eu
Theodoros Vlachos
Barouch Giechaskiel
Francesco Riccobono
Martin Weiss