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The stop/start function automatically shuts off the engine when the vehicle is stationary. This not only saves fuel, thus reducing the associated costs, but also reduces CO2 emissions by 3-8%.
Background
Toyota began offering this system following the oil crisis of the 1970s, when the engine would automatically shut off after 1.5 seconds of idling, but the technology was not very widely adopted. Audi and VW worked on advanced systems in the 1980s but these failed to achieve any greater success. Only under the pressure of increasingly strict standards governing CO2 emissions have manufacturers continued to develop this ‘function’ to reduce fuel consumption. The systems used today, however, have been improved using modern battery technologies and measuring instruments.
How it works
If the brake pedal is pressed when the vehicle is not in gear, the engine shuts off. With automatic transmissions and newer vehicles in general, even a minimum speed is enough to trigger this. Simply release the brake pedal or press the clutch to start. The automatic start/stop system is monitored by a series of sensors to ensure that it is working as it should, with one device checking the battery charge status, for example, while the neutral device checks whether a gear is engaged. An intelligent crankshaft sensor enables the engine to start up immediately, wheel speed sensors detect when the wheels are stationary and a temperature sensor provides engine temperature information. All of this data is recorded by the engine control system so that the engine always stops and starts at the right time. The vehicle’s electrical systems do, however, remain active, even when the engine is switched off.
Examples of situations where the automatic start/stop function is not required
The engine will not cut out if it has not reached its operating temperature. This avoids repeated cold starts, which could damage the engine in the long run. Furthermore, the start/stop function will be automatically disabled when the power management system detects that the battery voltage is too low. There are other cases in which the system detects that you do not need this function, such as when you turn the wheels, indicating that you want to park. The automatic start/stop function will also not work when the air-conditioning system is used in high outdoor temperatures.
In summary
Modern motor vehicles tend to be fitted with heavy-duty starters, AGM batteries and intelligent sensor technology that mean that they’re well prepared for countless starts. If you find the constant stopping and starting of the engine annoying, such as in traffic jams, for example, you can disenable the system at any time by pressing a button. The same is true after long motorway journeys, when a sudden engine shutdown could cause long-term damage to the turbocompressor. As a car driver, you're probably wondering when exactly the automatic start/stop function is useful? The answer is pretty obvious when you consider that starting with a hot engine uses as little fuel as around 0.7 seconds’ worth of idling, meaning that it is in your interest to automatically switch off the engine when stationary for more than a second.