Control of SCR system operation

Current regulations (EEC 88/77-EC1999/96-EC 2001/27) allow registration of Euro 3 vehicles and also those with Euro 4 or Euro 5 emission levels, however, they don't establish any other constraints for the emission control system. The European Commission therefore focused on the problem of emission control system efficiency and effectiveness over time. It then prepared the Directive concerning Euro 4 emissions, due for publication halfway through 2005. The Euro 4 Directive not only establishes emission levels, it also defines the characteristics of the emission control system, independent of the technology adopted.

Euro 4 vehicles coming into service after October 1, 2006 (October 1, 2005 for new type approvals) will have to be fitted with a diagnostics system (On Board Diagnostics) covering operation of the emission reduction system. So in the case of SCR a telltale will have to light up when the AdBlue level drops below a certain value (minimum 10% of the tank capacity). An 'irregular engine operation' telltale will light up when the tank is empty. Iveco Stralis Euro 4 models offered this year will already be fitted ahead of time with both these telltales and an AdBlue level gauge, which can be consulted using the OBD menu on the instrument panel display. The OBD is already able to identify and store details of system malfunctions.

One year after introduction of phase one – from October 1, 2007 for new registrations (starting October 1, 2006 for new type approvals) – all Euro 4 vehicles must be equipped with a system 'encouraging conformity with the law', again, independent of the technology adopted. If the nitrogen oxide content exceeds the maximum permissible value by a certain measure the warning 'irregular engine operation' will appear on the instrument panel and this anomaly will be recorded by the onboard computer. If the pre-alarm level is continuously exceeded (or for SCR vehicles, if the tank is empty) this will initiate a procedure governed by the electronic fuel injection management system to reduce engine torque. This reduction will take place after the vehicle's ignition is next turned off. Again in accordance with the new Euro 4 regulations, the manufacturer must ensure that N3>16t category vehicles comply with polluting emission levels for 500,000 km or 7 years (N3<16t, 250,000 km - 6 years).

Governments in the various European countries will have to introduce a control procedure to be carried out by authorised operators who will check the on-board computer's memory to ensure the engine has always operated in conformity with Euro 4 regulations.