A mathematical model of Bosch 3rd generation Common Rail fuel injection system with piezoelectric injector has been created. The numerical calculations for third different accumulator pressures (30, 80 and 160 MPa) and third energizing times ET (0.5, 1 and 2 ms) have been carried out. The results of calculations of total injected mass per cycle have been compared with the experiment with good agreement. The maximum error for ET=0.5 ms is 10.4% and for ET≥1 ms is less than 5%.