To study the secondary expansion internal combustion engine, a 4-cylinder traditional gasoline internal combustion engine.However, without the valve timing switching device, the expansion cylinders of this transformed engine cannot switch its operation between 2-stroke and 4-stroke. The prototype of a 2-stroke secondary expansion engine has been developed by ILMOR[11,12], which verified the fuel-saving potential of the 2-stroke secondary expansion mode. However, there is no prototype of the 4-stroke secondary expansion mode, so the experiment engine was transformed into a 4-stroke secondary expansion engine.