What is automatic start-stop system and how does it run?

Stop-start technology increases fuel efficiency up to 3.3 percen
automatic start-stop system


In recent years, the technology of the “automatic start-stop system” has been widely used in various vehicles. A large number of European cars have begun to be equipped with automatic start-stop system.

This previous exclusive configuration of luxury cars will also enter the homes of ordinary people. However, many people are still confused about this technology, and some even think that frequent engine starts may affect the service life of the vehicle. Today, let’s find out if the automatic start-stop system hurts the engine? How much fuel can be saved? How does it work?

Whats the automatic start-stop system?

As early as the 1970s, Toyota Crown began to use this technology. The thinking behind the start-stop system is very simple: When the engine is stopped for a short time, such as while you wait for traffic lights or traffic jams, the fuel consumption and emissions will be reduced. The automatic start-stop system will save fuel and protect the environment like this way. CO2– emissions can be reduced by 2 – 9% if using this technology. The benefits to the environment and improved efficiency have caused a rapid spread of automatic start-systems to all classes of vehicles. In view of the more stringent EU regulations on pollutant emissions of motor vehicles, many car manufacturers have gradually begun to popularize this technology.

What are the reasons for frequent engine stalls/restarts?

Classically, when an automatic transmission vehicle depresses the brake deeply until the vehicle stops, the engine will automatically turn off immediately and restart automatically when the brake is released. The manual gear car is put into neutral gear and the engine is turned off when the clutch is released, and it restarts automatically when the clutch is stepped on at the start. However, every manufacturer has different considerations, most cars do not provide steering wheel assistance when they are turned off, and a strong brake on the steering wheel will start the engine. However, a few models are exceptions. For example, when the Chevrolet Cruse is turned off, the steering wheel is still assisted and you can turn the direction.

In addition to the basic condition of whether to step on the brakes deeply, sometimes when the battery power is too low, the front windshield is defogging, the car is rolling, the cold weather, or the lower brake pressure, etc., in these special circumstances, the automatic start and stop will not work. It is precise because of such “thinking” that there are many opportunities for the engine to start and stop frequently. Many people find it troublesome and worry about it. In fact, many times they don’t understand the characteristics of the car’s start-stop system and can’t use it.

When is the proper usage for automatic start-stop system?

The automatic start-stop system is automatically turned on by default when the key is energized, and you only need to press a button to turn it off. It is understandable that while the automatic start-stop system saves fuel, its comfort will be decreased and the starting speed will be half a beat slower, and there will be some jitters at the start.

So it depends on how you choose, whether you want economy or comfort? If you encounter a big traffic jam, travel slowly for a long time, or frequently stop and start, you’d better turn off this function. It is best to also close when encountering wading sections or when it is raining. However, if it’s just a daily walk in the city, you can always open this function.

street cars by night 1

How much fuel can the automatic start-stop system save?

Different displacements and models of different manufacturers have different fuel savings. Take for instance a 1.8L displacement car, when the vehicle is idling in place, it consumes about one liter of fuel per hour, and it consumes about three to five seconds of idling gasoline for one start. Therefore, stopping the engine for more than 5 seconds, and the fuel saving effect is the most obvious.

Will frequent start and stop damage the life of the engine and battery?

We must know that for vehicles equipped with automatic start-stop system, their starters and batteries have been improved. Like Spaceflight power’s AGM technology was specially designed for vehicles, which not only with the start-stop technology, as well as an energy recovery system and other fuel-saving systems technology. A battery with AGM technology will accept the energy which it receives by energy recovery with high efficiency. By comparison, batteries with EFB technology are only designed for cars with entry-level automatic start-stop system.

AGM battery 2
EFB battery 3

With the usage of this powerful and high efficient technology AGM battery, good fuel savings will be reached and emissions will be reduced further. In order o improve the whole efficiency even further, in some vehicles, the starts, which normally run all the time are decoupled during acceleration phases. So, the entire motor power is available for acceleration and the engine can work especially efficiently.


Most modern vehicles with the technology of “automatic start-stop system” have been widely used. All electrical functions are powered by the battery – which again shows the importance of a powerful AGM or EFB battery that is fully matched to the energy management system of the modern vehicle.

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