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A nano-sized PM and THC emission characteristics were investigated according to the fuel injection strategy such as a pressure and timing in the GDI engine. On the part-load condition, the particulate emissions exhibited a strong sensitivity to the injection timing. The fuel injection pressure also had a great association with the nano-particles and THC. A size of PM exhausted from the GDI engine located near 10nm on the part-load. In contrast, accumulation mode particles within 60 - 80nm mainly exhausted during the cold transient start phase. Increment of fuel injection pressure positively affected on the nano-particle and THC emissions during the start of the engine, as well.

Flow and wall guided gasoline direct injection engine was developed for decreasing fuel consumption in vehicle by operating engine in the stratified lean air fuel ratio and reducing Nitrogen Oxides by applying the system of exhaust gas recirculation in the part load. However, it needed an expensive lean NOx catalytic converter and low Sulfur gasoline. So, they are not successful because of higher cost of lean NOx catalytic converter and lower gain in fuel economy in the higher emission level. Yet, Homogeneous GDI engine fulfills demands for higher specific power output in full load over port injection gasoline engines by intake air cooling and shows the enhanced fuel economy by higher compression ratio and internal exhaust gas recirculation in part load. Also, Gasoline direct injection inside cylinder leads to the cost reduction of catalytic converter by reducing Hydro Carbon and NOx exhausted until catalyst light off from engine start and shortening light off time.