Stop-start systems are standard in most (if not all) European cars. This feature is also becoming common in other makes, too.
If you’re a new car owner or are still learning about cars, stop-start systems might be a mystery. How exactly do they help you save petrol?
STOP-START: IT’S ALL ABOUT FUEL EFFICIENCY
The internal combustion engine is inherently inefficient, which is why carmakers and engineers have always prioritised fuel efficiency.
Efficiency is also affected by drivetrain designs and aerodynamic considerations.
THAT’S WHERE STOP-START COMES IN
Stop-start switches off the engine when the car comes to a standstill, say, at a traffic light junction. Some drivers find this feature annoying, but its fuel-saving effect is indisputable.
Think about it for a moment: When stationary, any motor vehicle with an internal combustion engine that’s running does exactly zero kilometre per litre of fuel.
In certain on-board computers, the displayed value changes from km/litre to litres/hour when the engine is idling.
This lets the driver know that the fuel is still flowing/combusting even though the vehicle isn’t moving.
Stop-start shuts down the engine when the car comes to a complete stop.
As soon as the brake pedal is released (or clutch pedal is depressed for a manual car), the “sleeping” engine is restarted immediately.
The stop-start system includes a dedicated control unit that monitors a variety of parameters, including the battery’s state, air-conditioning demand and even the position of the crank.
If the combination of factors is not ideal for stop-start operation, the function will not be activated.
For example, when the battery is not fully charged up yet, or if the air-con needs to stay on, the controller will not shut down the engine.
SPECIAL COMPONENTS AND BATTERIES
The starter motor, alternator and battery in a car with stop-start have been specified/ modified accordingly.
This is so that the high frequency of starts/restarts won’t reduce their life cycles. Or, require shorter service intervals compared to a car without stop-start.
The fully sealed lead-acid battery in a car with stop-start is a special one, which cannot be substituted with a regular 12-volt unit found at tyre and battery shops.
An important element in every stop-start system is the automatic/automated transmission’s ability to allow the engine to start and engage drive in less than half a second.
Stop-start alone has been proven to reduce average fuel consumption by around 8 percent, although this varies depending on the extent of urban driving.