1. WLTP Correlation measurement
BMW,
Christoph Lueginger
WLTP Correlation measurement
Analysis of 328iA xDrive Dekra-measurements

2. Analysis of Dekra measurements 328iA xDrive Agenda
Introduction
Applied corrections (RCB, road load).
NEDC and WLTP measurement results.
WLTP-NEDC delta.
Check against the test procedure list.
Missing points for the WLTP-NEDC delta.
Additional results: 1-axle / 2-axle dyno influence of warm-up for chassis dyno setting.
Summary.
WLTP Correlation Measurements 328iA xDrive, BMW,

3. Analysis of Dekra measurements 328iA xDrive Introduction
Vehicle: BMW F34 328iA xDrive, 159 g/km.
Following the SGS from at Munich Airport:  We propose using one representative measurement each (instead of using mean values).  We checked the measurements against the "test procedure checklist".  We show transparently the applied corrections.
WLTP Correlation Measurements 328iA xDrive, BMW,

4. Analysis of Dekra measurements 328iA xDrive Quickcheck results
Calculation of times not understood (factor 1.03 / should be applied, but factor 1 found). Influence on NEDC-WLTP-Delta assumed to be small, but for absolute value not negligible.
If understood correctly, first run was used and only one run was performed. It is recommended to make 2-3 runs, and ignore the first run, as vehicle is not stable normally (to be equivalent to chassis dyno setting!).
Quickcheck results between NEDC 2WD, NEDC 4WD and WLTP "NEDC" comparable, no correction needed.
Quickcheck result of WLTP "High" shows relevant deviation to other tests. It is recommended to correct the WLTP "High" to get the right CO2-Delta between the cycles.
CO2-influence of error in "High"-test: Approx N  g/km  Correction g/km.
-21N
-21N
-21N
WLTP Correlation Measurements 328iA xDrive, BMW,

5. Analysis of Dekra measurements 328iA xDrive
Road load setting on chassis dyno
High
Error
Virtual High F0
confidential
19.76 F1
0.0677 F2 1 2 3
Deviation: g CO2 / km
 Correction: g / km
Road load delta High – NEDC. This would be also the expected chassis dyno setting delta.
Delta of chassis dyno setting (abc-values) between High and NEDC (both based on WLTP warm up).
Error due to chassis dyno setting also observed in quickcheck data.
Recommended correction of WLTP High measurements of g/km (to be simulated by LAT as well).
Recommended to use virtual F0F1F2 values as input, if "High"-measurements are used to compare or calibrate with simulation  see table.
WLTP Correlation Measurements 328iA xDrive, BMW,

6. Analysis of Dekra measurements 328iA xDrive Road load
NEDC
WLTP "Low"
WLTP "High"
WLTP "virtual High"
Audi Tool
WLTP "High" Audi Tool
F0, F1, F2, TM
confidential
Delta CO2 [g/km]
Basis
1.4
23.9
20.4
6.6
33.3
simulated by LAT
22.9
19.7
6.3
31.1
COMPAS by JRC
1.2
22.8
19.5
6.1
31.6
WLTP "Low" was measured with NEDC road load, which is reasonable to get e.g. the influence of warm-up or to separate road load from cycle influence.
But WLTP "Low" is not equivalent to NEDC road load (e.g. payload factor, inertia classes).
The provided WLTP road load values were calculated with BMW internal input parameters for that specific vehicle (similar to the Audi tool).
Delta-CO2 is simulated in WLTP with this vehicle parameters, confirmed by LAT-simulation and JRC COMPAS model calculation.
WLTP Correlation Measurements 328iA xDrive, BMW,

7. Analysis of Dekra measurements 328iA xDrive Corrections
cycle
WLTP cold
date
measured raw CO2-value [g/km]
167.6
165.7
166.7
185.2
186.6
186.1
186.2
road load
NEDC
High
correction chassis dyno [g/km]
+ 3.6
RCB balance of battery [Ah] Ah Ah Ah Ah Ah Ah Ah
RCB correction [g/km]
+ 4.5
+ 3.9
+ 4.7
+ 4.3
corrected CO2-value [g/km]
172.1
169.6
171.1
193.4
195.0
194.4
194.1
road load "Low"/"High" [g/km]
+ 1.4 / +23.9
173.5 / 196.0
171.0 / 193.5
172.5 / 195.0
If temperature is considered to be representative enough for NEDC and WLTP, it is not corrected.
No corrections for NEDC necessary.
WLTP High to be corrected due to obviously wrong chassis dyno setting.
Calculation of RCB correction:  according GTR Annex 6 -Appendix 2.  measurement of RCB: Details in backup. ΔCO2 = ΔRCB * U / 1000 * 1/alternatorefficiency * Willans * 1/distance WLTP from : 8.68 Ah * 12 V / 1000 * (1/0.67) * 668 gCO2/kWh * (1/ km) = 4.46 gCO2/km.
WLTP Correlation Measurements 328iA xDrive, BMW,

8. Analysis of Dekra measurements 328iA xDrive NEDC measurements
and appear to be outliers and are not considered in the average value.
Proposed NEDC 2WD reference measurement, "Favorite": : Justification: 12. and 13. are practically identical, 12. closer to correct engine temperature at start and closer to engine speed average.
Proposed NEDC 4WD reference measurement, "Favorite": : Justification: and are practically identical, no engine speed signal in
WLTP Correlation Measurements 328iA xDrive, BMW,

9. Analysis of Dekra measurements 328iA xDrive
WLTP "Low" and "High" measurements
With "High" RL-correction for wrong dyno setting, With "NEDC" RL-correction to High to be able to compare "NEDC" and "High" measurements.
Proposed WLTP "NEDC" reference measurement, "Favorite": : Justification: Close to the average and engine temperature close to desired value.
Proposed WLTP "High" reference measurement, "Favorite": : Justification: Close to the average and engine temperature close to desired value. Additionally engine speed signal only for and available.
WLTP Correlation Measurements 328iA xDrive, BMW,

10. Analysis of Dekra measurements 328iA xDrive WLTP-NEDC Delta
Dekra (corrected): ΔCO2 High-NEDC 26.4 g/km (26.2 – 27.0 g/km)
BMW (corrected): ΔCO2 High-NEDC 26.1 g/km
CO2 [g/km]
WLTP High
ΔHigh-NEDC
NEDC
Measured CO2-delta is only valid, as long as the proposed corrections are applied (RCB, road load)!
Recommended to take delta of single measurements ("Favorites") where the smallest corrections are applied (from WLTP High measurements)  26.4 g/km.
This is not the final delta, as some points from the testprocedure list are missing!
WLTP Correlation Measurements 328iA xDrive, BMW,

11. Deviation (Y/N/value)
Analysis of Dekra measurements 328iA xDrive
Test procedure checklist
No.
Subject
NEDC
Deviation (Y/N/value)
WLTP
Delta [g CO2 / km]
Notes
Measured values
, corrected
168.0
, corrected
194.4
26.4
Single , representative measurement
Version of roadload calculator (V1 or V2)
Tyre tread depth: 50-90% -
Tyre tread depth: % if V1: declaration of delta_RR + Interpolation OR F0-Change if V2: no changes N
0.8
from Audi-Tool: 6 N ==> extimated with 0.8 g/km CO2 1
soak temperature
25°C set point ± 3°C
23°C set point ± 3°C 2
oil and coolant temperature at start of the measurement
± 2°C to soak temperature
small
23°C ± 2°C 3
test temperature
23 °C ± 3 °C 4
test mass
Mass in running order + 25 kg (OEM data)
TMH (additionally TML (instead of TML also NEDC-inertia-class may be used))
if NEDC-inertia class was used for Low -> add CO2 for payload-mass and stepless inertia
same interpolation formula as in CO2-interpolation can be used 5
inertia
Stepwise inertia class at NEDC test mass.
Step-less approach: inertia mass = test mass. TML and TMH
Important: Measurement AND simulation in NEDC should use inertia class as inertia, as this is the physical impact on CO2 (not kerb mass + 100kg). 6
aerodynamics
aerodynamics as type approval car (resulting from weight, tyre-choice, no other options)
"High" / worst-case (for some cars also "Low" should be measured) 7
rolling resistance
RR resulting from widest tyre
"High": worst RR-class (for some cars also "Low" should be measured) 8
cold start
Yes 13
Dynamometer road load setting
NEDC and R83 tolerances
WLTP GTR with tolerances of the GTR
How to consider if not measured? (Annette) 14
Dynamometer road load: inertia of rotating parts
Always 0%
+1.5% of (Miro+25kg) single axle, 0% twin axle.
not relevant (2-axle dyno!)
Single axle dyno is treated differently on NEDC by 1.5%. Road load issues always use 3%. 15
4WD vehicles
1-axle dyno allowed
2-axle dyno mandatory
effect on Road Load hopefully taken care of in f0,f1,f2; effect on dyno setting in WLTP (2nd axle warm); effect on increased cold-friction on 2nd axle 16
Rechargable Energy Storage System (RESS)
Legislation does not require monitoring or correction.
Monitored and the delta energy balance is taken into account for fuel consumption
Battery fully charged overnight. On both test cycles the RCB must be monitored. 18
gear shift strategy
Fixed speed
not relevant
Obtained from engine speed and power curve of the vehicle, GSI for MT-hybrids
with the Gear Shift tool provided by Heinz Steven. 22
DPF regeneration
As prescribed in R83
As prescribed in GTR 31
RLD procedures
NEDC warm-up RLD Calculation (average of times)
WLTP warm-up (procedure differences to NEDC) RLD calculation difference (harmonic average of times) Y
open
F0F1F2 for High only calculated as delta, procedure difference not included, e.g. averaging of force vs. times in NEDC. Determination only with coast down testing. 33
RLD vehicle chracteristics
OEMs to provide data
Vehicle characteristics differences: mass, aero-drag, tyre rolling resistance (incl. tyre tread depth, RR-classes instead of tyre-width). If this cannot be measured, solution see "RLD procedures". 34
optional equipment
weighted average needed for weight, RR, aerodynamics. To be provided by OEMs 35
CO2 correction with Europe average temperature
as new EU regulation
Necessary in order to correlate with all test elements which are planned to enter for EU. Applicable in (EU) WLTP: [14°C] setpoint and time [9h] not decided yet. 36
Normalisation corrections
open, not defined yet
CO2 family tolerance
up to 4%
Final NEDC->WLTP Delta
27.2
[g CO2/km]
WLTP Correlation Measurements 328iA xDrive, BMW,

12. Analysis of Dekra measurements 328iA xDrive
Missing points in measured delta
corrected
measurement
not included in measurement
and additionally open points
CO2 [g/km]
issue
incl.?
road load "High" Y
warm-up WLTC
check list executed ?
WLTP High Delta CO2
X g/km ?
GTR updates
phase 1b,
EU WLTP
deviations
new ? ?
family tolerance
type approval
up to 4%.
EU WLTP issue
normalization
new
0.8 + X?
ATCT 14°C
point. 35 TP-list
coast down
process, e.g. tire
thread depth or
calculation error
point TP-list
1.5% rot.
masses
 not relevant,
2-axle dyno
point 14 TP-list
Dekra, corrected measurement:
g/km
All road load issues are covered,
if OEM WLTP type approval values
are used in a meta model.
NEDC
Many of the agreed points are already included in the corrected measurement delta.
The calculated delta of approx. 27 g/km also does not include all issues.
Final delta cannot be determined without final GTR / EU WLTP and additional measurements.
WLTP Correlation Measurements 328iA xDrive, BMW,

13. Analysis of Dekra measurements 328iA xDrive
Influence of 1-axle / 2-axle dyno mode
Result of 2.5 g/km matches BMW experience.
The measured CO2-delta may be dependent on 4WD technology and therefore OEM dependent.
This delta cannot be simulated and has to be added additionally in the correlation meta model.
WLTP Correlation Measurements 328iA xDrive, BMW,

14. Analysis of Dekra measurements 328iA xDrive
Influence of warm-up cycle for chassis dyno
Derived from abc-values of NEDC and WLTP "NEDC".
Possibly wrong as WLTP High chassis dyno setting was not correct  effect should not be based on this measurement only.
Clear influence on abc-values visible, as WLTP leads to warmer conditions and therefore a higher chassis dyno load.
Effect is between N (velocity dependent), at small speeds most likely disturbed by measurement tolerances.  Proposed influence: N (2-3 g CO2 / km).
This delta cannot be simulated and has to be added additionally in the correlation meta model.
WLTP Correlation Measurements 328iA xDrive, BMW,

15. Analysis of Dekra measurements 328iA xDrive Summary
Chassis dyno setting wrong for WLTP "High", but can be corrected.
Some small signal-errors (e.g. battery current).
From the measurements we gain the following main results:
The corrections should be crosschecked (e.g. CO2-effect by road load already checked by JRC and LAT, also RCB correction to be checked).
From now on only "Favorite" measurements are used (same delta but better as simulation input and easier to discuss)
For WLTP High calibration simulation use "virtual High" road load to compensate the wrong chassis dyno setting.
Results
328xiA High
corrected measurement
additional points
final
Influence of warm up WLTC instead of NEDC
Influence of 2-axle dyno instead of 1-axle dyno
Delta CO2 [g/km]
26.4
27.2 ?
2-3
2.5
WLTP Correlation Measurements 328iA xDrive, BMW,

16. Analysis of Dekra measurements 328iA xDrive Backup
WLTP Correlation Measurements 328iA xDrive, BMW,

17. WLTP GTR Rotating Masses Clarification for road load
inertia setting
1-axle: m + mr (1.5%)
2-axle: m
 on road on dyno 
Coast down
times measured
Calculation
times to forces
Road load
F0F1F2
Calculation
forces to times
Chassis dyno setting
Road load
Vehicle speed
m + mr (3%)
m + mr (3%)
to be consistent
same mass to be used
If "3%" is mentioned in this presentation, it includes also individually determined values.
The 3% are used to consider rotating masses.
Only wheels are relevant, drivetrain influence is very small compared to the wheels.
To get the same times measured at the coast down the same mass has to be used in both calculations and is therefore independent of 2WD/4WD or 1-axle/2-axle dyno mode…
Note: mr always refers to "Miro + 25kg", not to TM!
WLTP Rotating Masses, BMW,

18. WLTP GTR Rotating Masses Clarification for dyno setting
2-axle dyno
1-axle dyno
+ 1.5 % of (Miro+25kg)
for not driven axle
inertia setting: TM
inertia setting:
TM + 1.5% * (Miro + 25kg)
In case of a 1-axle dyno, the effect of the non-rotating axle has to be compensated by the additional mass of 1.5% * (Miro + 25kg).
The 3 % / 1.5 % regarding inertia are the same values as used for calculating the road load, but for a complete different reason. Therefore these two issues should not be mixed up.
(Miro = mass in running order)
WLTP Rotating Masses, BMW,