The concept of piezohydraulic actuation is to transfer the reciprocal small stroke displacement of piezoceramics into one directional movement by frequency rectification through the media of hydraulic fluid. Our work in piezohydraulic actuation is focused on the development of systems that incorporate active valves for flow control. We present experimental results demonstrating the importance of fluid compressibility and valve timing in the optimization of the output power of the actuation system. An efficiency analysis is also presented. Results show the effective bulk modulus of the fluid is approximately linearly dependent on pressure. A linear bulk modulus to pressure model for the working fluid is developed and the data is compared to experimental results. An array of different timing tests are run on the inlet and outlet valves and the results show that their timing is crucial to the performance of the system. Also shown is that the optimal timing conditions change slightly under different loads. To analyze the power and efficiency, the system is considered as two sub-systems, the piezoceramics sub-system and the hydraulic component sub-system. The power and efficiency of each sub-system is measured and analyzed under different loads. As load increases, the results show that the efficiency of the piezoceramics decreases while the efficiency of the hydraulic components increases.