A powertrain has an internal combustion engine provided with an accessory transmission that includes a first pulley connected to a crankshaft of the engine, a second pulley connected to a shaft of an electric machine, and a belt connecting the first and the second pulleys to each other to rotate in the same direction of rotation (R). The electric machine is operated to supply an active torque to the second pulley during start-up of the internal combustion engine by means of a starter motor.

A method for controlling a start of a mild hybrid vehicle that includes an engine, a starter-generator starting the engine or generating electricity by an output of the engine, a starter starting the engine, and a battery supplying electric power to the starter-generator may include: determining, by a controller configured for controlling an operation of the vehicle, whether a start of the vehicle is requested; checking, by the controller, current limit data of the battery when the start of the vehicle is requested; checking, by the controller, start torque current data of the starter-generator according to state data of the vehicle; comparing, by the controller, the current limit data with the start torque current data; and starting, by the controller, the engine using the starter-generator or the starter according to a result of the comparing, by the controller, the current limit data with the start torque current data.

Systems and methods for starting an engine that may be started via two different electric machines are described. In one example, the method reserves an amount of torque that is based on a torque capability of a belt integrated starter/generator and the engine is started with the reserved torque if engine starting torque is greater than a torque capability of the belt integrated starter/generator.

Systems and methods for stopping an engine of a vehicle are described. In one example, the method anticipates when an engine is expected to stop and modifies engine operation so that less fuel is in the engine's intake ports when the engine is stopped so that the fuel may not escape the engine when the engine is restarted.

The disclosure is directed to a system and method for providing supplemental power to start one or more cranking motors. The supplemental starting system includes a starting-signal isolator configured to connect to one or more electrical starting-signal wires providing starting signal to one or more cranking motors, a resetting relay electrically connecting to the starting-signal isolator, a programmable logic controller (PLC) electrically connecting to the resetting relay, a supplemental battery relay electrically connecting to the starting-signal isolator and the PLC, a supplemental battery electrically connecting to the supplemental battery relay, and a positive output-terminal electrically connecting to the supplemental battery relay. When an output of the starting-signal isolator is higher than a threshold voltage, the resetting relay and the supplemental battery relay are configured to be in a close state, so that the supplemental starting system is configured to provide electricity to one of the one or more cranking motors.

Systems and methods for operating a hybrid vehicle are described. In one example, the automatic engine stopping may be inhibited so that an engine may be restarted during change of mind conditions without generating a large driveline torque disturbance. The engine stopping may be inhibited based on a inhibit engine pull-down torque threshold.

Systems and methods for operating a hybrid vehicle are described. In one example, a torque reserve for starting an engine via an electric machine is adjusted responsive to vehicle operating conditions. The torque reserve may set aside a portion of torque that an electric machine may produce for cranking and starting an engine.

Systems and methods for starting an engine of a hybrid vehicle are described. In one example, the method selects one or more electric machines to start an engine. The method may reference a data structure, such as a matrix or table, and the matrix or table outputs which of the one or more electric machines is applied to start the engine.

Systems and methods for starting an engine of a hybrid vehicle are described. In one example, the method uses the engine to generate larger amounts of thermal energy while the engine is rotated under power of an electric machine. The systems and methods described herein may be applied to series and parallel hybrid vehicles.

Systems and methods for starting an engine that may be started via an electric machine and a driveline disconnect clutch are described. In one example, the method estimates a maximum motor propulsive torque during engine starting. The maximum motor propulsive torque may be based on an estimated speed that a torque converter impeller speed will be when an engine cranking period ends.