Research on reducing HC emission of turbocharged gasoline engine for passenger car

Analysis of a 1.5 L turbocharged port injection gasoline engine revealed that its HC emission was produced mainly in cold starting and idling, warming up stages resulted from poor combustion. Nozzle spray hole diameter, inlet port tumble ratio, valve overlap and piston cooling oil injection pressure were optimized to improve the HC emission and the effects were verified by actually measuring emissions of the original engine and whole car. Results indicate that the spray hole and valve overlap reduce by 17.6% and 83.3%, HC emissions lower by 17.6% and 9.3% respectively; and inlet port tumble ratio and piston cooling oil injection pressure increase by 77.3% and 27.8%, HC emissions lower by 4.8% and 1.5%, but leading to NOx emissions seriously rising by 35.6% and 47.4% meanwhile. Considering trade-off among engine emissions, the technical scheme of reducing spray hole diameter and valve overlap is selected. Combined to optimization of ECU parameters, whole car HC emission drops by 61.7% and all pollutants are low by 50% than limit values of China IV emission regulation.