Direct injection gasoline engines have been gaining popularity for passenger car applications, particularly in the EU. It is well known that emissions of particulate matter are an inherent disadvantage of spark ignition engine with direct injection. Direct injection of gasoline can lead to the formation of substantial numbers of particulates, a proportion of which survive to be emitted from the vehicle's exhaust. EU legislation limits particle mass (PM) emissions; particle number (PN) is soon to be limited, although an opt-out means that dedicated filters will not be required immediately. A range of tests were conducted on a pool of Euro 5 passenger cars in BOSMAL's climate controlled emissions laboratory, using EU legislative test methodology. In addition, further measurements were performed (particle size distribution, tests at multiple ambient temperatures). Results were compared to legislative limits and order of magnitude comparisons were made with emissions from indirect injection gasoline and direct injection Diesel engines. Size distribution profiles showed sensitivity both to the ambient temperature and to the thermal state of the engine (both during the test cycle and varying with the ambient temperature for the cold start). A substantial proportion of the total particles measured by the particle sizer were of too low a diameter to be detected by the current legislative PN method. In general, emissions from the test vehicles showed high number, small size and relatively low total mass. Preliminary results from a global harmonized test cycle are also presented, both for cold and hot start conditions. Given ongoing concern regarding the toxicity of very small particles and the upcoming particle number limits, research on this type of emission is a necessity for automotive exhaust emissions research.
