The advent of electronic turbocharging
The inline 6-cylinder engine has reappeared in the latest Mercedes-Benz S-Class after many years. We know BMW has always been a staunch supporter of inline 6 engines, and Mercedes-Benz's shift puts it in direct competition with its rival once again. BMW's inline 6 engine (B58) now utilizes the latest modular platform, achieving a good balance between technology and cost control. Can Mercedes-Benz, returning to the inline 6 engine camp, prevail? Let's examine its capabilities through a key Mercedes-Benz technology.
● The Imperfections of Turbochargers
Due to global emissions regulations and displacement taxes, turbocharging has become a common feature in modern engines. Compared to naturally aspirated engines, it's easier to tune for greater torque output at low to mid-range RPMs, improving vehicle acceleration. However, it also has drawbacks. Turbochargers require a certain turbine speed to function, often resulting in turbo lag, requiring patience.
● BorgWarner Offers Mercedes-Benz a Solution
How to optimize the shortcomings of current turbocharging technology? BorgWarner offers Mercedes-Benz a solution. The latest Mercedes-Benz inline 6-cylinder engine (M256) utilizes BorgWarner's eBooster electric supercharger technology. This engine has two superchargers: a turbocharger and an electric supercharger.
The eBooster electric supercharger is connected to the rear end of the turbocharger. Compared to the turbocharger, it can actively control the supercharger's speed. At low engine speeds, before the turbocharger reaches its maximum boost efficiency, it helps increase the air intake into the cylinders, thus effectively reducing turbo lag. Mercedes-Benz engineers confidently claim that their inline 6-cylinder engine has no turbo lag.
● How does the electric supercharger act as the best partner for the turbocharger?
First, it's important to understand that the electric supercharger plays a supporting role in the supercharging system. It's a powerful partner to the turbocharger, but it's not always active. At higher engine speeds, when the turbocharger can obtain sufficient thrust, the electric supercharger stops rotating to conserve energy.
BorgWarner designed two separate boost lines for the electric supercharger and turbocharger, using a bypass valve to open and close the electric supercharger's line. The ECU determines when to activate the electric supercharger and open the other boost line based on the current engine speed and operating conditions.
Faced with increasingly stringent emission regulations, automakers must continuously push the limits of internal combustion engines with new technologies to meet the demands of the times. In Mercedes-Benz's new inline-6 engine, the electric supercharger not only improves some of the drawbacks of traditional turbochargers but also reduces emissions and saves fuel. Of course, to gain an advantage over increasingly formidable competitors, an electric supercharger alone is far from sufficient.
As mentioned earlier, the electric supercharger is driven by a 48V voltage system. In fact, in the Mercedes-Benz S-Class equipped with this inline-6 engine, the 48V voltage system is a crucial foundation for its energy efficiency and environmental protection. Based on the 48V voltage system, Mercedes-Benz has matched the inline-6 engine (M256) with a 48V mild hybrid system.
48V voltage systems are a future trend for traditional fuel-powered vehicles. Both German and Chinese brands have begun mass production of this technology, and even Japanese brands, traditionally focused on full hybrid systems, are now sourcing 48V mild-hybrid system components from suppliers like Bosch. Based on a 48V system, vehicles can support more high-power electrical systems, such as electric superchargers, electric power steering, active anti-roll bars, and electric brake assist systems.
● Summary
As 48V voltage systems become more widespread, electric superchargers may become a new trend. Mercedes-Benz has not only drastically changed its latest 6-cylinder engine to an inline layout but also applied this new technology, which is undoubtedly related to increasingly stringent emission regulations. How will the Mercedes-Benz inline-6 engine compare to the BMW inline-6 engine? Perhaps we will have to wait for a more detailed comparative analysis in the future.