Browse Publications Technical Papers 2018-01-1819

Impacts of demanding low temperature urban operation on the real driving emissions performance of three European diesel passenger cars 2018-01-1819

In Europe, the development and implementation of new regulatory test procedures including the chassis dynamometer (CD) based World Harmonised Light Duty Test Procedure (WLTP) and the Real Driving Emissions (RDE) procedure, has been driven by the close scrutiny that real driving emissions and fuel consumption from passenger cars have come under in recent times. This is due to a perceived divergence between stated certification performance and measured on-road performance, and has been most pointed in the case of NOx emissions from diesel cars. The RDE test is certainly more versatile and relevant than CD test cycles, but certification RDE cycles will rarely include the most extreme low speed congested or low temperature conditions which are likely to be more challenging for NOx aftertreatment systems. To build understanding of the emissions and fuel consumption performance of latest available diesel passenger cars, Concawe has conducted a study of the CD and RDE performance of 3 vehicle types. Two of the vehicles featured urea-dosed Selective Catalytic Reduction (SCR) after-treatment, whilst the third was fitted with a Lean NOx Trap (LNT) and a downstream passive SCR catalyst. For each vehicle, triplicate tests were conducted over a moderate RDE on-road cycle, as well as CD testing of the Transport for London (TfL) Urban Inter Peak (UIP) cycle, developed directly from real-driving trips in the City of London, UK and considered a severe urban test. The vehicles were run under the TfL UIP with progressive low temperature intervals with temperatures ranging from -15°C to 23°C. The urea-dosed SCR equipped vehicles performed well from the TfL UIP under extreme urban conditions, and also at low temperatures, while for the LNT-equipped vehicle the conditions were more challenging, but this aftertreatment did show some positive traits.The data generated provides insights into the urban RDE emissions performance of Euro 6 diesel passenger cars, and their after-treatment systems, which can be used to better understand their on-road performance, including at the extreme low temperature boundaries of the urban section of the regulatory RDE test.


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