Methods and systems for improved engine speed control during engine starting

A system for controlling engine speed during an engine start of a vehicle, comprising:

• an engine coupled to an automatic transmission of the vehicle;
• a first battery in electrical communication with an engine starter during an engine start;
• an alternator mechanically coupled to the engine, the alternator having a field coil excitation circuit that is electrically buffered from the first battery during the engine start, the field coil excitation circuit in electrical communication with a power source other than the first battery during the engine start;
• and
• a control system having non-transitory instructions stored in memory to vary a strength of a magnetic field produced by a field coil via adjusting a voltage or current supplied to the field coil excitation circuit responsive to inputs received from the engine, and to automatically stop and restart the engine during idle-stop conditions.

A method of controlling engine speed, comprising:

• during an engine restart from an automatic engine idle-stop,
• electrically buffering a field coil of an alternator from a battery supplying power to an engine starter;
• and
• varying an electrical property supplied to the field coil to control engine speed during the engine start responsive to inputs received at a controller from an engine, the electrical property supplied to the field coil supplied via a substantially constant voltage source.