OICA/Euromot proposal on NOx Control
The editorial group has already integrated the proposal into the main REC document.

Mr Stein summarised the proposal. The industry insists that there should be a minimal NOx control diagnostic system. The definitions therefore include ones for scan tools. The requirements include sampling from the reagent tank to be possible. The proposal includes a 25 ppm NH3 limit, which is less stringent than the Euro VI requirement.

Following a discussion of manufacturers’ responsibilities and the scope of type approval it was agreed that the phrase “when used by the driver or operator” should be deleted from para. 7.4.6 because the regulation can only set an obligation on the manufacturer to provide such documentation. A similar, more general requirement, may also be needed so as to apply also to particulate control systems.

Section 7.4.8 covers the provision of maintenance information. It was agreed that providing the information to the installer would satisfy the manufacturer’s obligation providing that it has been made clear that the information has to be passed on to the operator.

Section 7.5 covers reagent freezing protection. Reagent level monitoring must operate under all conditions. Details of the diagnostic system are provided in Annex 10. Provisions for a NOx Control Diagnostics (NCD) family are included. This allows the NCD system to be used across different engine/REC families.

The operator warning and inducement systems are described in paragraphs 4 to 6 of Annex 10. This requires a counter and visual and audible warning systems. The proposal for inducement is that starter current will be interrupted if failures are not rectified after a certain time. Stein said that the requirement had been discussed with retrofitters and was felt to be feasible. The proposal avoids the problem of engine shutdown during operation. Paragraph 7 covers reagent availability and related inducement requirements and paragraph 8 covers reagent quality monitoring, for which a NOx sensor or regent quality sensor will be needed. It is recognised that some sort of computer capability will be required to meet the requirements. Only 2 demonstration tests are required.

In further discussion about responsibility for failures that result from another part of the supply chain (dealer, installer etc.) it was noted that this is similar to the supply of loose engines for NRMM, and the text is based on these requirements, where the manufacturer is not considered to be responsible for such issues. In particular the problem was discussed of the engine stalling in a critical situation and then not being able to be restarted because of the inducement system. Mr Eberhardt commented that this had been discussed with safety authorities and the system provides very adequate warning. In worst case the effect is no different from the vehicle/machine running out of fuel.

Mr vHimmen raised a concern that the coolant temperature parameter for operation of the NOx Control Diagnostics system does not cover air-cooled engines.

For the NOx threshold (paras. 8.2 and 10.3) it was proposed that the threshold should be that NOx emissions do not exceed [twice] the limit value with a cap on the maximum g/kWh. Eberhardt agreed to work on this proposal with Stein.

The obligation on contracting parties to accept RECs approved to the regulation was discussed. This does not imply an obligation to accept only such systems – national requirements could still be applied. The situation across the EU will depend on whether the regulation is adopted as an obligation for all Member States.

TNO data on generic simulation of a retrofit SCR
TNO presented the results of their modelling based on data on generic Euro III engines to evaluate the effects over the WHTC and enable the group to propose NOx efficiency requirements using the WHTC for HD engines. The engine and SCR parameters used were described. A number of simulations were run with different engine temperatures and SCR heat-up times. Idle temperature and SCR efficiency were the dominant effects on engine-out NOx emissions. Overall, the results of the modelling indicated that the worst-case efficiency over the whole WHTC would be about 50% compared to around 85% on the ETC.

Members then discussed the level of these efficiencies compared to those obtained in specific retrofits using various bus cycles. It was commented that experience has shown that not all systems that work well on the ETC perform well in urban driving, even if efficiencies of tailored bus applications achieve efficiencies similar to those on the ETC; the regulation has to cover a much wider range of situations including single retrofits. The proposed process was re-iterated: the emissions performance is assessed first on the bare engine and then on the engine with retrofit, on the cycle to which the engine was approved. The reduction efficiency is calculated from WHTC (HD) or NRTC (NRMM) emissions levels before and after retrofitting. There is no g/kWh limit for the efficiency tests, only the percentage reduction is important in that case.

In answer to a question on whether, adapting a system to optimise performance for a particular set of buses, it would still be considered as meeting the standard, it was stated that it is clear that this would be the case providing it still met the emissions and efficiency requirements on the appropriate tests. In discussion most participants felt that such situations were unlikely to give worse performance than on the WHTC.

After further discussion, participants agreed that the WHTC provides the only acceptable option for the HD efficiency test (NRTC is agreed for NRMM & Tractors). The efficiency requirements then need to be determined. The current proposals are 50% for Level 1 and 70% for Level 2 (on a weighted cold+Hot WHTC). Tremayne commented that the dosing strategies that would have been used in the TNO simulations were perhaps more aggressive than would be used for retrofit and data previously presented by AECC was noted. It was agreed that participants would give further thought to the figure and review proposals during discussion of the text.