The efficiency of a hydraulic pump tends to be high when it has a:

A hydraulic pump's efficiency is significantly influenced by its design and operational characteristics. A variable displacement pump is designed to adjust its output flow rate and pressure according to the system's needs. This adaptability allows the pump to operate at optimal efficiency across a range of conditions, only delivering the necessary flow rate and pressure for the task at hand.

As the hydraulic system operates under varying loads, a variable displacement pump can maintain high efficiency by reducing the displacement when the demand is lower, thus minimizing energy wastage. In contrast, fixed displacement pumps operate at a constant output, which can lead to inefficiencies as they may deliver more flow than necessary when the system demand decreases.

Furthermore, a pressure relief valve is primarily a safety device to prevent damage to the system by releasing excess pressure but does not inherently improve the pump's efficiency. A balanced port arrangement can enhance performance by reducing the load on the pump and improving the flow, but it is more about facilitating smoother operation rather than directly impacting the efficiency of the pump. Therefore, the design characteristics of a variable displacement pump are crucial in maximizing efficiency in hydraulic systems.