Balancing GDI fuel economy and emissions

Will OEMs have to adopt gasoline particulate filters (GPFs) in order to comply with stringent new emissions regulations? Top engineers discuss current developments.

Increasing concerns about airborne soot, or particulate matter (PM), are translating into vehicle emissions regulations. One of the more stringent of these, the Euro 6c, is scheduled to phase-in starting September 2017. For engine and powertrain developers, the clock is ticking. And they're preparing for the possibility that gasoline direct-injected (GDI) engines may have to use exhaust particulate filters in order to comply with the new standards.

A straightforward method to control soot is to use gasoline particulate filters (GPFs.) Like DPFs used in diesel engines, a GPF is placed in the exhaust stream and filters out soot with a wall-flow substrate. While likely effective, there are downsides including extra cost, vehicle complexity, and back-pressure effects on the engine. These changes in world regulations accompanied by changes in drive cycle tests complicate a decision to either use or avoid GPFs.