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Start/Stop Function in Automatic Transmission

Start/stop systems are already available for different types of cars with automatic transmission. Since they started to be mass produced in late 2007, 1.5 million vehicles have already been equipped with Bosch’s start/stop technique, which reduces CO2 emissions by up to 8% and fuel consumption in urban traffic

So far, this system had been used mainly in cars with manual transmission.

In cooperation with car manufacturers, Bosh has successfully adapted this new technique for its use in cars with automatic transmission, so it is already assembled in some new models such as Porsche Panamera and Volkswagen Passat with DSG transmission, as well as Fiat 500, in combination with an automated manual transmission, and in Audi A8 equipped with an automatic converter

In vehicles with automatic transmission, the start/stop function works very simply. You only have to hit the brakes and when the car stops, the engine shuts off automatically. The car starts again when the foot is lifted from the brake pedal.

On the one hand, this is very comfortable for the drivers, because they only have to accelerate and brake but, on the other, it has been a major challenge for the engineers as the start process is even faster and more dynamic, because this eliminates the time required by the driver in a car with manual transmission to step the clutch and shift into drive.

To this end, Bosch’s development engineers have adapted the powerful electric engine as well as the silent one-way starter motor and fuel injection system. The regulation software has been modified jointly with the car manufacturers. The new system still comprises, among other components, the battery sensor, a DC converter and a battery highly resistant to stop/start cycles.

The start/stop systems that build on existing components such as the starter motor and the engine control electronic module can be adapted quickly and economically to different engines and vehicles.

For that reason, this starter motor-based technique has been imposed on almost all car manufacturers in Europe, often with Bosch as supplier.

The powerful alternators that can charge the battery quickly are an ideal complement to the start/stop systems. With this, the start/stop system can be used more times.

Bosch has included the alternators of the Efficiency line in its product catalog. “Both techniques are elements of Bosch’s Efficiency Plus solutions. Together, they make it possible to save up to a ten percent of fuel in the cities”, explained Ulrich Kirschner, president of Bosch’s Starter Motors and Generators Division

More developments and more technology…

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