The performance of a single cylinder gasoline engine (0.375L) was improved by optimizing the structures of intake port and combustion chamber to achieve the purpose of downsizing. The CONVERGE software was used to simulate the steady state air flow in the intake port at different valve lifts and the combustion process at 3000r/min with full load. Four optimization schemes of intake port and three optimization schemes of combustion chamber were proposed respectively. Considering flow coefficient and tumble ratio comprehensively

the first scheme of intake port was selected. With the selected intake port

the average flow coefficient was increased by 22.26%

and the average tumble ratio was increased by 14.41%. The flow distribution

turbulence kinetic energy and mixture distribution of the second combustion chamber scheme could accelerate flame propagation speed and shorten fast combustion period after comprehensively analyzing the flow distribution

mixture distribution

temperature distribution

cylinder pressure and combustion parameters of different combustion chamber schemes based on the first intake port scheme. The indicated power of the second scheme of combustion chamber was increased by 14.1% compared to the base combustion chamber

and the power performance reached the level of the base engine (0.400L).