Ford Details Stop-Start System for U.S.

Ford Motor Co. says it has taken several steps to make its engine stop-start system for automatic transmissions attractive to U.S. customers. The system is available as a $295 option on the 2013 Fusion sedan.

Ford estimates the system could boost fuel economy as much as 10% and save owners $1,100 over the life of their vehicle.

Like other stop-start devices for automatics, Ford's system uses an electric pump to maintain hydraulic pressure in the transmission when the engine stops. But the company says it has developed several unique control algorithms to ensure a smooth restart.

One algorithm monitors load on the electrical system and predicts how long the car's battery can continue to power accessories when the engine stops. If the load is deemed too high, the algorithm disables the auto stop-start feature.

The control software also determines when the electrical system should switch from the engine-driven alternator to the starter battery. Ford says the technology begins blending from the alternator's 14-15-volt output to the battery's 12 volts before the engine stops. The technique helps eliminate light dimming or momentary changes in vent fan speed.

Finally, the control system monitors cabin temperature and humidity. It also checks evaporate core temperature and, under hot conditions, allows the engine to restart sooner so it can resume power to the air-conditioning system.