Magnetorheological (MR) fluids are materials that change their rheological behavior in the presence of an applied magnetic field. Devices using MR fluids have an ability to provide high torque, low inertia, be a safe device and have a simple interface. We have developed an MR-fluid actuator, which consists of an input component, an output component and an MR-fluid clutch between the two. In this paper, we investigate the dynamic characteristics of an MR-fluid actuator and aim to improve its response. Transient magnetic analyses are examined and experimental results are shown in the case of the proposed approaches. Finally, we realize a much faster MR-fluid actuator.