In this paper, effect of intake process and uniform distribution on combustion process and fuel economy are made in vehicle engines. The transient parameters of gas flow of intake pipe in multi-cylinder engines are measured. The gas flow in intake pipe is calculated by means of the established induction model and multi-net method. The transient process of gas flow in intake pipe is described objectively in vehicle engines. The efficient research method is provided for improving the combustion process and reducing the fuel consumption in vehicle engines.