In order to ensure the measurement accuracy of an inlet port steady flow test rig

the error analysis theory and the measurement system analysis method were used to analyze the main sources affecting the measurement accuracy from direct and indirect factors. Results showed that the measurement accuracy of swirl momentum meter and intake flow meter had the greatest influence on the measurement results of swirl ratio and flow coefficient

accounting for 85.68% and 94.15% of total measurement error

respectively. For the valve lift deviation of 0.1mm

the measurement result would change about 1%. When the outward deviation of the measured cylinder head positioning reached 1.0mm

the swirl ratio may increased by 14.43%

but the flow coefficient would not change significantly. Moreover

the repeatability and reproducibility of the steady flow test rig could reach 28%

and the reproducibility of human factors would hardly affect the test results.