Stop/Start System Description and Operation: Notes

The Stop/Start System is used to improve fuel efficiency in stop/start driving. The vehicle automatically shuts down the engine in appropriate conditions at a traffic light, for example, resulting in zero tail pipe emissions and saving fuel which otherwise is used idling the engine when stationary. The engine instantly restarts when the driver is ready to move away.

As soon as the driver prepares to move away (depress the clutch pedal), the engine starts quietly and almost instantly; it only takes the system around 0.3 s to start the engine. The process is near unnoticeable, and happens before gear selection is completed.

To support the increased number of engine starts, the starter motor is upgraded with a high performance electric motor and a stronger pinion engagement mechanism with reduced noise levels.

Along with the upgraded starter motor, advanced battery technology is required to ensure the vehicles battery can handle the frequent charge and discharge cycles common with stop/start operation. There is an intelligent battery sensor connected to the battery which continually monitors the battery charge and healthy state. The engine control module (ECM) uses this information from the intelligent battery sensor to determine if the battery charge and health is sufficient for an Stop/Start condition.

The Stop/Start system can reduce fuel consumption and carbon dioxide (CO2) emissions by up to 5% in mixed driving conditions. In an urban environment and in heavy traffic with frequent stops the savings may increase to as much as 10%.

There are also sophisticated controls in place to help ensure the Stop/Start System does not compromise the needs of either the driver or vehicle. For the engine to shutdown, the vehicle must be below 5 km/h (3 MPH), the manual transmission in neutral and the clutch pedal fully released. To restart, the driver simply depresses the clutch pedal and the enhanced starter motor engages the engine, ready for when first gear is selected. When the engine has been shut down by the Stop/Start System, the tachometer needle will rest at the Autostop indicator icon (500 RPM point) indicating the engine has been shut down by the Stop/Start System.

To ensure neither the needs of the driver or vehicle are compromised the engine will not shut down in the following circumstances:

• Ambient and coolant temperature correlation does not match specified values.
• Ambient temperature is less than -10°C (14°F)
• Battery temperature is less than 0°C (32°F) or greater than 55°C (131°F)
• Driver seat belt is not fastened and the drivers door is not fully closed (not applicable to vehicles in North America)
• Clutch or accelerator pedal is pressed
• HVAC system demand is high
• HVAC defrost has been selected
• Battery charge is low

Likewise the engine will automatically restart if:

• Driver door opened and driver seat belt unbuckled (not applicable to vehicles in North America)
• Engine hood opened
• Battery charge is low
• HVAC demand increases
• Vehicle speed increases
• Brake booster vacuum has been reduced
• Engine coolant temperature is greater than 125°C (257°F)
• Economy mode turned OFF by driver
• Autostop time exceeded 5 min

When the Stop/Start System has shut down the engine, and the ambient temperature is below 15°C (59°F), the ECM will activate the Stop/Start auxiliary relay which controls the electric engine coolant pump motor to continually circulate the engine coolant through the engine while the engine is off. This is to ensure the engine and passenger compartment temperature is maintained while off. Once the Stop/Start System has restarted the engine, the ECM will turn off the electric coolant pump motor, thus allowing the engines internal coolant pump to circulate the engine coolant. The Stop/Start System is automatically activated each time the ignition switch is turned on, although there is an ECO Switch on the instrument panel to disable the system, if the driver so desires.