In-depth analysis of the principles and operation of engine start-stop technology

"Stop at red light, go at green light" is a traffic rule that vehicles and pedestrians follow. It is now also applied to engines. The engine start-stop technology allows the engine to "stop at red light, go at green light" under certain conditions. This technology is a new way for automobiles to save energy and reduce emissions.

Nowadays, all slightly better cars are equipped with engine start technology. Some car owners use it every day, thinking that it can save energy and reduce emissions and save a lot of money. However, most car owners think that this function is too useless, and the frequent start-stop experience is very bad and also harms the engine, so they turn it off as soon as they get in the car.

In fact, engine start-stop technology is now very mature, and the tolerance of engines equipped with this function is high enough, so everyone can use it with confidence.

If you want to know more about it, follow us and take a deeper look at the engine automatic start-stop system.

Simply put, the engine automatic start-stop technology was developed in response to the traffic congestion in cities. Driving in urban areas is unavoidable, and the idling of the engine when the vehicle is idling not only consumes fuel, but also produces exhaust gas that is not conducive to the urban environment. With the engine automatic start-stop technology, the driver only needs to step on the brake pedal to stop the vehicle, and the automatic start-stop system will control the engine to automatically shut down. After releasing the brake pedal, step on the accelerator and the engine will automatically start.

The benefit of this function is that by automatically starting and stopping the engine, it can save fuel and reduce vehicle exhaust emissions without changing the driver's driving habits.

The principle of engine start-stop technology

The automatic start-stop system refers to an energy-saving system that automatically shuts down and restarts the engine according to the actual situation to reduce the engine idling time, thereby reducing fuel consumption and emissions. When the vehicle stops temporarily, it automatically shuts down, and when it needs to continue moving forward, the system automatically restarts the engine. This system is particularly suitable for vehicle use environments such as long waiting time at red lights and severe congestion.

For vehicles with automatic transmissions, the working principle of the automatic start-stop system is that when the driver steps on the brake pedal, the vehicle stops moving. At this time, the Start/Stop system automatically detects: the engine is idling; the wheel speed sensor of the anti-lock system shows zero; the electronic battery sensor shows that there is enough energy for the next start. When these three conditions are met, the engine automatically shuts down. When the vehicle starts again, as long as the driver releases the brake or turns the steering wheel, the engine will automatically ignite and enter normal driving state.

For vehicles with manual transmission, the automatic start-stop system works as follows: when the vehicle is stopped, put the gear in neutral and release the clutch, the vehicle will enter the shutdown state. If the vehicle moves during this process, the automatic start-stop system will not work. When the driver steps on the clutch and selects a gear, the car will restart.

The development of engine start-stop technology

In 1964, Toyota tested this type of equipment for the first time on the Crown sedan. As long as the vehicle came to a complete stop within 1.5 seconds, the engine would automatically shut down and shut down. This became the theoretical and design prototype for the development of automatic start-stop in the future. The Crown was tested for a long time in Tokyo's urban traffic, proving that this technology can bring about a 10% fuel saving effect.

But Toyota is not the first brand to put this technology into mass production. Fiat Regata and Volkswagen POLO took the lead in mass production of this technology in the 1980s. Volkswagen Group applied this technology to Golf and Lupo 3L in 1994 and Audi A2 in 1999 respectively.

Although this technology was not widely adopted by consumers in the early days because it was considered disturbing and expensive, the Lupo 3L car and Audi A2 did hold the world record for internal combustion engine fuel efficiency for many years.

Almost every mainstream brand on the market now has models equipped with automatic start-stop systems. Even many domestic brands have begun to equip them. This system is no longer as unattainable as it was in the past. However, each manufacturer has a large difference in the design and adjustment of the automatic start-stop system, which also leads to a large difference in the performance of automatic start-stop models of different brands.

Activation and operation of engine start-stop technology

Activation conditions

After the vehicle starts, once the speed exceeds 3km/h (about 2mph) and the time lasts for about 4 seconds, the engine start-stop function will be automatically activated.

How to operate

The engine automatic start-stop system can be used in both manual transmission models and automatic transmission models. The operation methods of the two models are different, as follows:

Operation of the automatic engine start-stop system for manual transmission vehicles

Engine shutdown procedure

If you need to stop the car, shift the gear to low gear and apply the brake to stop the car. Then shift the gear to neutral and let the engine idle before releasing the clutch. The auto start-stop function will automatically shut down the engine and the auto start-stop symbol light will come on.

Engine restart process

Need to start → press the clutch pedal → the start-stop function restarts the engine, the start-stop prompt symbol light goes out, → release the clutch after shifting gears to accelerate forward.

How to operate the automatic start-stop function of the engine in automatic transmission models

Engine shutdown procedure

If you need to stop the car, keep pressing the brake pedal. The start-stop function will automatically shut down the engine and the start-stop symbol light will come on.

Engine restart process

Need to start → Release the brake pedal → The start-stop function restarts the engine, and the start-stop indicator light goes out → Press the accelerator to accelerate forward

If you do not want to use this function, you can turn it off using the icon button, and the status prompt on the instrument cluster screen will disappear.

Types of engine start-stop technology

Depending on the cost and function, engine start-stop technology can be roughly divided into three categories: mild automatic start-stop, semi-automatic start-stop and fully automatic start-stop.

Mild automatic start-stop

The structure of the mild automatic start-stop system is the simplest and the cost is the lowest. Compared with the general power system, the engine with the mild automatic start-stop system only has a longer life of the starter and a higher output power of the battery used. Of course, in order to allow the engine to start immediately when the driver releases the brake or clutch and steps on the accelerator, the ECU control program also needs to be rewritten to determine the new ignition time, starter and gearbox working mode.

Most mild automatic start-stop systems have a manual switch that allows the driver to choose whether to turn on this function. To avoid the lights dimming instantly or the air conditioning fan speed decreasing when the engine is turned off or started, some mild automatic start-stop systems also add an auxiliary battery.

Since the function of mild automatic start-stop technology is too simple, and the starter and battery cannot provide assistance or power to the vehicle, it will not be used on hybrid vehicles. Also, because the system has simple functions and a simple enough structure, the cost is also low, with a price of about 1,800-2,400 yuan. Of course, the effect is also relatively low: the improvement in fuel economy is about 3%-5%. If the vehicle is driven in the city most of the time, and mostly during peak hours, this number will increase slightly.

Semi-automatic start-stop

Like the mild automatic start-stop system, the semi-automatic start-stop system also uses a longer-life starter and a more powerful battery, but it will be equipped with an auxiliary battery as standard. In most semi-automatic start-stop systems, the enhanced generator can recover the regenerative energy during braking and charge the auxiliary battery.

The price of semi-automatic start-stop system is mostly around 3000-4200 yuan, and the fuel saving effect can be improved by 7%-12%. Similarly, there will be additional bonus when driving during peak hours in the city.

Fully automatic start and stop

The fully automatic start-stop system has the most comprehensive functions. In terms of structure, it is based on the semi-automatic start-stop system, and the generator on the engine is replaced by a part-time electric motor. This part-time electric motor can be used as both a generator and a starter. When the engine is running, the engine drives the electric motor to rotate, and the electric motor converts mechanical energy into electrical energy to charge the battery; when the engine needs to be started, the electric motor becomes a starter, converting electrical energy into mechanical energy to drive the engine to rotate.

Different manufacturers currently choose different ways to place this part-time electric motor. Most car manufacturers put it as an accessory in the accessory belt drive system, generally called BAS. For this method, since the structural changes to the traditional engine are not too big, only a generator needs to be replaced, so it is relatively easy to implement.