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A compact transient mini-tunnel (multi-tube type) inducing only a part of the exhaust gas, has been newly developed as a device for measuring the quantity of regulated exhaust emissions in the exhaust gas from diesel engines. This device allows measurement of exhaust emissions even for transient mode operating conditions of the engines, such as U.S. EPA FTP transient mode (FTP mode). The size of this mini-tunnel can be reduced to approximately twenty percent of the dilution tunnel (full-flow tunnel) specified by EPA and the flow rate in the mini-tunnel is a few percent thereof. The results have been demonstrated that the mass emissions of particulate, CO, NOx and HC measured with the mini-tunnel have good agreement to that measured with the full-flow tunnel under FTP mode and also steady state operating conditions of the engines (correlation coefficients of particulate, CO, NOx and HC are not less than 0.97).