A computer simulation program was used to explore the concept of pressure compounding and turbopressure compounding a four-cycle diesel engine. Pressure compounding is a refinement of the Miller Cycle. Ralph Miller used early intake valve closing to reduce the peak compression temperatures of large natural gas engines, allowing them to operate at higher compression ratios without detonation. To maintain the same air flow, the inlet charge is boosted to compensate for the reduced inlet duration. Analysis demonstrates the shorter inlet event duration with the same mass flow results in added positive work during the inlet stroke. The overall result is a predicted 5% to 7% improvement in overall performance, depending upon the efficiency of the turbomachinery and the energy in the engine exhaust.