Traffic has been the talk of every town on the globe. With increased traffic density on roads, the time spent by travelers at the traffic signals has also gone up considerably. While waiting for the traffic light to turn green, almost all the drivers do not turn the engine off and this results in fuel being burnt for nothing. To aid saving fuel in this case, the concept of Start-Stop was introduced. The very basic principle behind Start-Stop system is that the engine is turned off when the car stops and started when the driver decides to move without having the driver to crank the engine with keys. This might sound very simple, but in reality a lot of processing is taken into account for Start-Stop system.

In normal cases how would a driver at the traffic signal turn the engine off and re-start to move? The driver would first bring his vehicle to halt (0 kmph) by pressing the brake and the clutch. He would then use the key to turn off the engine and release the clutch. To move again, the driver will hold the clutch, crank the engine using key, release the brake and press the accelerator pedal. With start stop system the engine control unit uses these same steps to assist the driver in turning off and on the engine, with the driver not having to use the keys. The driver brings the vehicle to halt (0 kmph) by pressing the brake and the clutch, after vehicle stops the driver releases the clutch. The engine control unit detects the sequence of events and makes a series of checks in the car like, the battery charge, rail pressure, power demand on engine etc. If battery charge and rail pressure are low, the vehicle will not be turned off. If there is high power demand on the engine, because of for example Air Conditioning, the vehicle will not be turned off. But when all the conditions favor, the engine is turned off and the state of the engine is stored. To start the engine, the driver has to simply press the clutch. The ECU will sense it and crank, start and sync the engine with the help of the state stored. There is no stress on the driver to do anything special, He/She simply needs to press the clutch, engage the gear and move.

The disadvantage with start stop system is that with frequent use, the battery charge and life will deteriorate sooner. To overcome this, in some cases, 2 batteries were used in a car. One battery was only dedicated to crank the engine and the other served the electrical devices in the car.

It is always of interest to know if we really save fuel at the traffic signal. A study suggests that if a vehicle stops at a traffic signal for more 20 seconds, then it is worth to turn the engine off.

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