October 2018
ECE Adopts Updated Requirements on Selective Catalyst Reduction Systems for Light Duty Vehicles
To comply with the Euro 5 and Euro 6 light duty vehicle emissions requirements, most modern diesel engined vehicles are equipped with a selective catalytic reduction (SCR) system. The SCR system reduces the nitrogen oxides in the vehicle's exhaust gases by injecting a reagent fluid, sometimes referred to as diesel emissions fluid or by its most common trade name, AdBlue, into the exhaust stream ahead of an SCR catalytic converter. The chemical reaction which takes place within the SCR catalyst, converts virtually all of the oxides of nitrogen in the exhaust stream into nitrogen, water and carbon dioxide (CO2).
Due to the fact that reagent fluid is being consumed whenever the vehicle's engine is in operation, it is necessary for the reagent to be replenished at regular intervals for the SCR system to work correctly and comply with the exhaust emissions limits. Therefore, since the introduction of the Euro 5 and Euro 6 emissions limits, the United Nations Economic Commission for Europe (UN ECE) Regulation of light duty vehicle emissions, UN ECE Regulation No. 83, has included specific requirements to ensure that reagent tanks are replenished when required.
To achieve this goal, the current version of UN ECE Regulation No. 83.07 requires that vehicles equipped with an SCR system must be fitted with a driver warning system to warn the driver when the reagent level is low and a driver inducement system which actively encourages the driver to replenish the reagent tank, e.g. by restricting the vehicle’s performance until the reagent tank has been refilled. In the current version of ECE 83.07, the driver warning system must be activated when the predicted driving range before the reagent tank becomes empty is at least 2400 km, and the driver inducement system must be activated when the predicted driving range before the reagent tank becomes empty, is less than the average driving range from one complete tank of fuel.
To ensure the customer acceptance of SCR systems when they were first introduced, most vehicle manufacturers fitted their vehicles with a reagent tank whose capacity was sufficient to ensure that refilling of the reagent tank was only necessary at the vehicle's regular service intervals. This avoided the need for the vehicle owner to refill the reagent tank themselves as the refilling process could be undertaken by the dealership / garage as part of the vehicle's regular servicing. However, as part of their ongoing efforts to reduce overall vehicle weight, many vehicle manufacturers are now considering fitting their vehicles with smaller reagent tanks, which is now felt to be more acceptable to vehicle owners due to the greater awareness and greater availability of reagent fluid.
To cater for vehicles fitted with smaller reagent tanks, draft amendments to ECE 83.07 were adopted at the 175th session of the UN ECE World Forum for Harmonisation of Vehicle Regulations (WP.29) in June 2018, and have recently been allocated a provisional entry into force date of 29th December 2018. These draft amendments, which will become Supplement 7 to ECE 83.07, introduce two alternative strategies for initiating the driver warning system and the driver inducement system. This will allow vehicle manufacturers to choose from one of the following three activation strategies:
- Activate the driver warning system when the predicted driving range before the reagent tank becomes empty is at least 2400 km, and activate the driver inducement system when the predicted driving range before the reagent tank becomes empty, is less than the average driving range from one complete tank of fuel.
- Activate the driver warning system when the predicted driving range before the reagent tank becomes empty is 150% of the average driving range from one complete tank of fuel, and activate the driver inducement system when the predicted driving range before the reagent tank becomes empty is 75% of the average driving range.
- Activate the driver warning system when the reagent level falls below 10% of the reagent tank capacity and activate the driver inducement system when the reagent fluid level falls below 5% of the reagent tank capacity.