Revealed: Why Audi launched an electronic turbocharged engine

This year, the electronic turbocharger installed on the Audi SQ7 has become popular. In the past, we often heard of turbocharging, mechanical supercharging or dual supercharging. In the past two years, Mazda has developed an air wave supercharging. What is this electronic turbocharger? Today, I will talk about this "fresh" electronic turbocharger.

The reason why we put a question mark on the word "fresh" is that the concept of electronic turbocharging is not a new invention that has only recently appeared. In fact, including Mazda's air wave supercharging, it can be found in the textbook "Internal Combustion Engine Structure" before 2000.

What is electronic turbocharging?

So, what exactly is the structure of this electronic turbocharger? Why has its concept been proposed a long time ago, but has never become a mainstream technology, and is now being promoted by Audi as an advanced technology?

From the name of "electronic turbocharger", we can know its basic principle. Compared with the common exhaust gas turbocharger, its turbine driving force does not come from the exhaust gas emissions of the engine, but from an electric motor. This is the fundamental difference between them.

The principle is simple, so what is its advancedness?

We all say that the future development trend of automobiles is four-fold: intelligence, electrification, lightweight and automation. Electronic turbocharging is a kind of electrification of automobile development. Compared with the mechanical exhaust gas turbocharger, the core advantage of electronic turbocharging is that its control can become more free: the exhaust gas turbocharger can only achieve supercharging at a certain speed, while the electronic turbocharger is driven by an electric motor and is not limited by the exhaust gas volume and speed, so the intake supercharging we want can be achieved at various speeds.

But as the saying goes, "the simpler, the harder it is." Although electronic turbocharging is more advanced in principle, the reason why it has not been put into mass production is that it is very difficult to implement.

First of all, the turbo motor needs to be very reliable. The turbine speed of a conventional turbocharger can reach 300,000 revolutions per minute. Such a high speed is a great test for the motor. Although Audi has mass-produced electronic turbochargers, its maximum speed can only reach 90,000 revolutions, and it cannot run at high speed for a long time. The fundamental reason is that the reliability of the motor cannot work all the time like a turbocharger.

Secondly, the control of electronic turbocharging is also more complicated. The brain of the car, the ECU, needs to determine how to increase the pressure and how much to increase the pressure according to the various working conditions of the vehicle. Correspondingly, a series of questions such as when to open the intake and exhaust valves, when to inject fuel, how to inject, and how much to inject, etc., all require a lot of time and repetitive work to match and adjust.

It is precisely because of the above two points that the electronic turbocharger installed on Audi is not as powerful as we imagined. Due to the limitation of the maximum speed, Audi has equipped the engine with two types of turbochargers: electronic turbocharger and exhaust gas turbocharger. The electronic turbocharger is responsible for solving the power problem at low speed, while the turbocharger is responsible for solving the power problem at medium and high speed.

The consequence of these two solutions is the increase in cost, but it also has the benefit of being more energy-efficient than single turbocharging. Of course, more importantly, the scope of use of electronic turbocharging is narrowed, which is an insurance for its reliability, durability, and matching difficulty.

Why is electronic turbocharging suddenly popular?

As mentioned above, electronic turbocharging technology is not new, so why is it so popular now? In addition to its ability to make up for the poor low-speed power of turbocharging, are there other reasons? Yes.

Electronic turbocharging can further improve fuel consumption and emissions.

The reason why new energy vehicles are recognized as the future trend today is mainly due to environmental pressure. Today, the global oil price is only US$50 per barrel, but the popularity of new energy has not decreased. This is because the average fuel consumption and emission level requirements in the future are very high, whether in Europe, the United States or China. It is difficult to meet the requirements with traditional internal combustion engine technology alone.

Therefore, any technology that can effectively improve emissions will be considered for inclusion in the car, and electronic turbocharging is one of them.

Compared with other manufacturers, Volkswagen and Audi have a more urgent need to improve emissions. So Audi launched the concept of electronic turbocharging a few years ago, but the first mass-produced one was the diesel engine installed on the SQ7.

Behind the electronic turbocharging is the overall 48V upgrade plan of European manufacturers.

Many people overlook a data, the electric turbocharger motor is powered by 48V voltage instead of the conventional 12V voltage. Why is this "48V" important? Because it represents the foundation of the European new energy development strategy.

In 2011, Audi, BMW, Daimler, Porsche and Volkswagen jointly released the 48V voltage specification and began to develop automotive electrification with the on-board voltage increased to 48V. Subsequently, many European car companies have successively developed new standards.

Why do they increase the vehicle voltage to 48V? The reasons given by European manufacturers are energy saving and safety considerations. However, in Yumo's opinion, the more important reason behind this is to compete with Japanese hybrid technology.

When it comes to hybrid power, people who know cars will definitely think of Toyota and Japanese car brands. Toyota Prius is now the world's best-selling hybrid model. Other models include Camry Hybrid, Honda Accord Hybrid, etc., which are also the most popular hybrid cars in the market.

German and American manufacturers are not necessarily behind Japanese manufacturers in hybrid technology, but Japanese manufacturers have already taken the lead in the market and reputation, and it is very difficult for German and American manufacturers to surpass them. Therefore, the new 48V voltage standard was proposed.

In Japanese hybrid models, the power supply voltage of the drive motor is basically above 100V. The advantage it can bring is that the motor has high power and strong performance, and can drive the vehicle forward alone. However, it does have certain safety risks, and foolproof anti-leakage measures must be taken. At the same time, it cannot be shared with other electrical appliances in the vehicle.

The 48V voltage is the maximum limit of the safe voltage, but if it is used for hybrid motors, it can only serve as an auxiliary power for the engine, and it is somewhat incapable of driving the vehicle alone. Its advantage is that it can be shared with other on-board electrical appliances. At the same time, because the motor is only auxiliary, the size and weight of the battery are not large, and the weight of the whole vehicle is easier to control. In addition, the cost increase caused by the 48V power supply is also much lower than that of Japanese hybrid technology.

European manufacturers hope to use these advantages of 48V, combined with their own technical reserves in traditional internal combustion engines, to achieve a double improvement in power and fuel efficiency, compete with Japanese hybrid technology, and ultimately achieve a transition to pure electrification.

At present, in Audi cars, the power supply of the electronic turbocharger is still separate from the power supply of other on-board electrical appliances, but in the near future, I think it will be an inevitable trend to combine the two in terms of power supply.

In fact, after the five major European manufacturers proposed the 48V voltage standard, a number of international parts suppliers including Valeo, Bosch, Delphi, Continental, etc., began to intensively develop related accessories, and electronic turbocharging is one of them. Then there will be a series of new electrification technologies such as electronic air conditioning - the air conditioning can be turned on without starting the engine, and electric drive VVT ​​- variable intake and exhaust valves that do not rely on camshafts.

The actions of European manufacturers are actually worth thinking about for Chinese automakers: What is our new energy strategy path in the future? Before the arrival of pure electrification, if traditional internal combustion engines cannot meet the fuel consumption and emission requirements, what transition technology should we use? Should we wait until the technology of international suppliers matures before following suit?

The answers to these questions will determine whether Chinese automakers’ powertrain technology can match that of foreign automakers in the next five to ten years. We will have to wait and see.