However, when the load was high, these two curves in Fig. 10 became closer. The BSFC of the test engine was even higher than that of the 4RB2 at the 2000 RPM condition when the torque was higher than 45 Nm. It is because that the effect of the above three points would be lessened in the high load condition. With the increase of the load, the in-cylinder pressure of the combustion cylinder in the exhaust stroke would increase, which reduces the extraction effect. The intake air amount is enlarged in the high load condition, so the burned gas trapped in the expansion cylinder would increase. More work would be needed to compress the burned gas for the expansion cylinder, which may decrease the thermal efficiency. In addition, the throttle valve opens large for the traditional engine 4RB2 in the high load condition, which may weaken the advantage of the throttle pumping loss for the test engine.