The simulation model of the 4-stroke secondary expansion mode can be verified by the results of the experiment. However, without the in-cylinder pressure data, the simulation model can only be verified by engine performance data. Because the studies mainly focused on the fuel economic performance, the simulation results of the brake specific fuel consumption(BSFC) were verified by the experimental data. Fig. 9 shows the comparison of the BSFC between simulation and experimental data at different operating conditions The results show reasonable agreements between simulation and experimental data, so the simulation mode can be used to the following studies.