Particulate Matter and Hydrocarbon Emissions Measurements: Comparing First and Second Generation DISI with PFI in Single Cylinder Optical Engines

A Spray Guided Direct Injection (SGDI) engine has been shown to emit less Particulate Matter (PM) than a first generation (wall guided) Direct Injection Spark Ignition (DISI) engine. The reduction is attributed to the reduced incidence of fuel-wall impingement and higher fuel injection pressure. The extent to which this is true was investigated by comparison between single cylinder SGDI and DISI engines. Both engines were also operated with conventional port injection to provide a baseline. Feedgas PM number concentration and size spectra were measured using a Cambustion differential mobility spectrometer for the fuels iso-octane and toluene with a range of Air-Fuel Ratios (AFRs), ignition and injection timings.

In addition to a reduction of the emitted PM mass, it was found that the PM emitted by the SGDI engine was dominated by nucleation mode PM, like a conventional Port Fuel Injection Spark Ignition (PFI-SI) engine, and the accumulation mode normally associated with DISI engines was not detected.