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Francesca Saporiti edited this page Dec 6, 2019 · 1 revision

Are CO2MPAS and DICE mandatory for small-volume manufacturers?

Yes. Emissions data should be reported for all newly registered vehicles, i.e. also for manufacturers with a very low number of registrations in a calendar year. Such manufacturers, i.e. those which alone or together with its connected undertakings are responsible for less than 1000 new registrations in a calendar year are however exempt from meeting a CO2 emission target. However, as several of those manufacturers nevertheless apply for and are granted derogations, Article 3(2) of Regulation (EU) 2017/1153 should apply also in the case of them, i.e. they have the choice to report NEDC values that are determined either in accordance with type approvals granted prior to September 2017 or in accordance with Regulation 2017/1153.


Should CO2MPAS be used for each car or for each vehicle’s family?

For each vehicle’s family.


Is it possible the use of an alternative method for NEDC’s road load calculation?

No. The correlation regulation EU 1151/2017 sets out how the NEDC road loads are to be derived from the WLTP ones.


Which is the maximum CO2MPAS deviation for accepting the NEDC declared values?

4%. The NEDC declared values are accepted when CO2MPAS deviation is less than 4%.


Should CO2MPAS be used also when an NEDC physical test is already performed?

Yes. The NEDC test (High or Low) to be performed is set according to the CO2MPAS NEDC results and the DICE random number.


Does the same vehicle need to be used for the WLTP and NEDC (random testing)?

No, the vehicle does not have to be the same, but it must belong to the same interpolation family and be representative of that family. For WLTP testing, if you have the CO2 interpolation family and vehicles L and H, you don't need to bring TWO physical vehicles to the lab. The regulation says to take a representative vehicle from that interpolation family and test it both under L and H conditions (RLs and test mass).


Is it possible to use different Ki factors for NEDC and WLTP?

No. They must be those of WLTP.


What is the maximum CO2 extrapolation for the interpolation family?

The maximum CO2 extrapolation is 3 g/km.


How should we calculate the NEDC sub-phase values?

Follow point 3.3 of correlation regulation EU 1151/2017.


Is the optional equipment mass included in vehicle mass for NEDC?

No. For further details, check point 2.3.1 of correlation regulation EU 1151/2017.


What should the user do after running the NEDC tests?

According to point 3.2.8 of Annex I to the Correlation Regulations, it is for the type approval authority to ensure it has the relevant documentation which will allow it to calculate and include the deviation factor in the type approval certificate at the time of its issue. That is, if a vehicle is sampled for a physical NEDC test, the test result must be documented following Annex VIII to Directive 2007/46/EC. Based on the test results, the type-approval authority must record any deviation seen between the CO2 value declared by the manufacturer and the physical test value in the type approval certificate – i.e. the deviation factor as calculated following point 3.2.8 of Annex I to the Correlation Regulation. The test results must, therefore, be submitted to the type-approval authority in due time before the type approval certificate is issued.


How is the vehicle family identified?

Follow the requirements of the regulation EU 1151/2017.


Are the data in demo files based on real vehicles?

No, the data are representative of plausible vehicles.


What is the initial state of charge for the calibrated/simulated test?

In the WLTP CO2MPAS assumes 90%, while for the NEDC it uses 99%.


What does engine_speeds_out_hot mean?

It is the engine speed [RPM] minus the extra RPM due to clutch/torque converter and after treatment warm up.


Are the data marked as target used by CO2MPAS model?

No. They are just used as a reference to calculate some metrics that are added at the end of the summary sheet.


Is the prediction influenced by the data inserted into the prediction.WLTP sheet?

Yes. The data provided are used to simulate and predict the WLTP results.


Is brake energy recuperation related to conventional internal combustion vehicles?

Yes. If the battery charges during coasting conditions/overrun, this is considered to be brake energy recuperation. In the case of hybrids, it does not apply.


What does it mean that "Probably 'alternator_currents' have the wrong sign"?

CO2MPAS checks the data provided according to some basic criteria. For alternator and battery currents, it respects the following sign criteria:

  • Alternator current is negative when the alternator is supplying power to the low-voltage electrical system. Note that the alternator for the conventional internal combustion engine cannot contribute to the vehicle motion, therefore it is always <= 0.
  • Battery current is positive when the battery is being charged, negative when discharged.

What does it mean that some models fail the calibration?

The failure should not be taken as proof of real failure but rather a warning that something is not going well with the specific model and its calibration inputs. This is raised according to some score limits that are specified for each macro-model. For more details, visit the link.


What does it mean "n_dyno_axes(1) < n_wheel_drive(4) / 2"?

The NEDC can be performed on:

  • 1 dyno axis: the transmission is disconnected, so n_wheel_drive for NEDC is 2 (i.e., a 4x4 becomes 4x2).
  • 2 dyno axes, but synchronous (i.e. only one is applying the loads). If the transmission is not disconnected, the warning can be ignored. Otherwise, n_wheel_drive for NEDC is 2 because the transmission is disconnected.

How to increase the electrical loads in the simulation?

To set higher electrical loads, you can add a new data named prediction.service_battery_loads into the input sheet.


Should engine_idle_fuel_consumption be set to zero when vehicle has stop-start?

No, but you can measure it at the end of the WLTP cycle, disabling the stop-start function, keeping the engine on for two minutes.


What exactly is the engine load signal?

It is a standard OBD (On-Board Diagnostics) signal and it is defined in the UN Addendum 82: Regulation No. 83 (see annex 11, page 219, par 2.13).


What exactly is the start-stop activation time?

You can find the description here. If during TA the vehicle is subjected to double testing, the authority overseeing the test will check that the start-stop activation time declared in CO2MPAS is not lower than the time elapsed from the start of the NEDC test until the engine stops for the first time. If the engine stops for the first time at t_test > t_declared, there might be severe implications for the manufacturer’s entire fleet.


How to set a custom fuel type?

You can select the most similar fuel_type present in the CO2MPAS input file and specify fuel_carbon_content_percentage, engine_fuel_lower_heating_value, and fuel_heating_value relative to your custom fuel type.


Which WLTP vehicle mass should be used?

The inertia applied to the dyno. In the case of 1-axle testing, you should include the rotational mass.


Are we allowed to use internal/development signals?

No. You must use the signals prescribed by the regulation.


What are the required parameters for the T1 map?

The required parameters are engine speed [RPM] and engine power [kW]. They must include idle and maximum engine speeds and the speed at max power.


Are gears a required input for WLTP?

For manual transmission, it is a mandatory input, but it is not used in the calibration/prediction phases since it is set as a target. Instead, for automatic vehicles, it is not required.


How does CO2MPAS deal with capped and downscaled cycles?

They are not supported. Hence, you should provide the theoretical velocity profile and the bags phases, filling velocities, bag_phases, and gears into the time-series sheets.


Can final_drive_ratio be set to 1 and provide the gear ratios multiplied by it?

No, because it causes errors in the power calculation.


How to input two batteries for conventional vehicles?

You should insert the service_battery_nominal_voltage of the main battery and fill the service_battery_currents and service_battery_capacity using the following formula:

1 / service_battery_nominal_voltage * ∑(current or capacity of batteryi * nominal voltage of batteryi)


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