Various system level characteristics and parameters must be considered when incorporating an Integrated Starter / Generator (ISG) into the electrical architecture of a ground vehicle. Three techniques will be discussed in the context of system level performance and efficiency. Dynamic Field Weakening will be discussed as a method to shift the operating envelope of the machine / drive pair to dynamically manage operating efficiency with experimental data shown. Pulse Width Modulation – Rectification / Control (PWMRC) during generation mode will be with simulated and experimental results presented. Finally, the impact of low winding inductance machines, such as air core or iron-less, when operated in a field weakening mode will be discussed along with simulated operation.