The market share of Gasoline Direct Injection (GDI) vehicles has been increasing, promoted by its positive contribution to the overall fleet fuel economy improvement. It has however been reported that this type of engine is emitting more ultrafine particles than the Euro 6c Particle Number (PN) limit of 6·1011 particles/km that will be introduced in Europe as of September 2017 in parallel with the Real Driving Emission (RDE) procedure.
The emissions performance of a Euro 6b GDI passenger car was measured, first in the OEM build without a Gasoline Particulate Filter (GPF) and then as a demonstrator with a coated GPF in the underfloor position. Regulated emissions were measured on the European regulatory test cycles NEDC and WLTC and in real-world conditions with Portable Emissions Measurement Systems (PEMS) according to the published European RDE procedure (Commission Regulation (EU) 2016/427 and 2016/646). Finally, tests were conducted on the chassis dyno to explore the impact of going towards the RDE boundary conditions (driving dynamics and ambient temperature as defined in the RDE legislation).
PN results showed that the vehicle was a state-of-the-art GDI as values on the regulatory test cycles were below the Euro 6c limit of 6·1011 particles/km in its original configuration using the reference E5 fuel. A maximum value of 9·1011 particles/km was measured during the on-road tests, increasing to 2·1012 particles/km when going towards the RDE boundary conditions. With the GPF, PN emissions were controlled well below 6·1011 particles/km on NEDC, WLTC and on-road RDE. With GPF, emissions stayed well below 9·1011 particles/km towards the RDE boundaries, demonstrating that the GPF enables well controlled real-world PN emissions.
No fuel penalty impact could be measured for the GPF during the tests and NOx emissions were always below the Euro 6d NTE (Not-to-exceed) limit that will apply from 2020 onwards.