During the development of a CN Ⅵ light vehicle equipped with a GDI gasoline engine, the phenomenon of high PN appeared. In response to the operating conditions of the engine running in the WLTC cycle, a corresponding SOI sweep was performed on the dyno bench. The PN emissions of the engine has reduced by optimizing of SOI. The results show that when the SOI is sufficiently advanced, the oil film formed by the collision of the spray and the piston causes the PN emissions to increase significantly. In order to avoid the deterioration of the PN emissions, the SOI should be appropriately postponed. In the low load conditions, it is more appropriate to calibrate the SOI at 295°CA and 290°CA. In the medium speed area, it is more suitable to set it at 300°CA or later. The SOI in the higher speed area can be slightly advanced if necessary. And the impact of SOI on fuel consumption is more obvious at low speeds, but it is not obvious at the conditions of medium to high loads and speeds.
During the development of a model equipped with dual VVT engines, a higher temperature of the catalyst was discovered. Therefore, the sweep point of VVT is optimized under low speed and high load conditions. The test results show that VVT has a significant effect on the temperature of the catalytic converter, and the temperature of the catalytic converter has decreased after optimization. At the same time, the VVT opening has little effect on the dynamics. In addition, VVT has an effect on the knocking tendency of the engine. When the knocking tendency increases, the temperature of catalytic converter and power performance of the engine are deteriorated. On the contrary, if the ignition angle can be advanced, the performance of the engine can be optimized.
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