Although Equation 300-3 is somewhat complex, it does not necessarily imply a high level of accuracy. It should only be used for estimating when pressure ratios range from two to five. Furthermore, the equation assumes the cylinder design provides ample valve flow area, the valve dynamics are satisfactory, and pressure pulsations are moderate. If any one of these conditions is abnormal, the Ev prediction is questionable.
Note that although Ev is a vital sizing consideration, it does not affect power consumption. Ev becomes an important factor, if the owner is considering a re-rate, or is troubleshooting a compressor capacity problem. Manufacturers may be consulted to determine highly accurate values of Ev based on proprietary information and programs.