However, fully closing the VGT during the transient resulted in high back pressure and low volumetric efficiency. Thus, both the torque response and the turbocharger acceleration were worsened. A trade-off between the torque rise in the first 0.5 second, T50, and the turbocharger speed at 1.5 second has been illustrated in this study. The optimum calibration depends on the requirement of the transient operation. Compared to a single-step-change VGT actuator trajectory, the torque rise in the first 0.5 second can be improved by 14.4 Nm (10.6%) at the expense of lowering the turbocharger speed at 1.5 second by 3.8 krpm (6.4%), and the T50 can be improved by 0.71 s (47.1%) at the expense of lowering the turbocharger speed at 1.5 second by 1.7 krpm (3.8%). If no turbocharger acceleration compromise was accepted, the T50 can be improved by 0.54 s (35.5%). The turbocharger speed at 1.5 second can be increased by up to 0.5 krpm (0.9%), while the T50 can still be improved by 0.25 s (16.5%). The VGT position in the first 0.5 second was crucial, because the achievable transient response was largely limited by the VGT setting at the first stage. Compared with a conventional boost pressure feedback controller, which may fully close the VGT during transient, a model based transient control strategy may be required to improve the transient operation and to avoid overshoot.