23 August 2014
Mercedes-Benz has equipped their luxury sedan model S500 with a gasoline particulate filter (GPF). The vehicle was apparently launched a few months ago, representing the first-ever series production application of the GPF technology.
The installation of a GPF on the Mercedes S500—rumored for several months—has been confirmed in the Auto-Umweltliste 2014/2015 report published by the Verkehrsclub Deutschland (VCD, German Traffic Club).
A solid particle number (PN) limit of 6.0×1011, numerically equal to the limit already in place for diesel cars, will become effective for gasoline direct injection (GDI) vehicles from September 2017. A relaxed PN limit of 6.0×1012 1/km becomes effective for GDI vehicles beginning next month.
Car manufacturers have been developing methods to control PN emissions in-cylinder, such as by advanced fuel injection strategies. Mercedes, for example, introduced GDI injection systems with piezo-based injectors. In-cylinder control strategies, however, are tailored for the applicable emission test cycle and may be less effective under real driving conditions. Particulate filters, on the other hand, can provide effective PN emission control under all operating conditions.
Gasoline particulate filters utilize the same type of wall-flow substrates that is used in diesel particulate filters. A GPF can be included in the exhaust system in addition to the three-way catalyst (TWC), or a TWC coating can be applied onto the GPF substrate.
VCD estimates that the added cost for the GPF can vary from 20 to 50 euro per vehicle, when in mass production.