Abstract: The economic performance is a key to domestic medium truck. CA1092 truck with 6102 gasoline engine is one of the meium truck. In the paper, the performance of 6102 gasoline engine was studied through the volumetric efficiency analysis. The inlet systems of the engine and the matching carburetor were analyzed through experiment. By mean of cyclic simulation program, the factor influenced 6102 gasoline engine volumetric efficiency was investigated. The new inlet manifold was designed. Engine rig test and automoble road test were conducted on the engine which was installed new inlet manifold by changing compression ratio and conducting match adjusting of carburetor. The experimental results showed that the economic performance of current engine was increased 3%, and the engine had good dynamic performance on medium and low speed.