Analysis of Mercedes-Benz’s fourth-generation plug-in hybrid technology, supplemented by large-capacity batteries, 2.0T will become a supporting role

In the past 2022, in the luxury mid-size car market, the iron triangle is still formed by the familiar BBA. Compared with the competing BMW 3 Series and Audi A4L, the Mercedes-Benz C-Class, which still has outstanding sales after the replacement, seems to be missing a piece of the puzzle in terms of basic displacement. The launch of the Mercedes-Benz C 350 eL fills in this puzzle. However, with the wave of electrification, the most eye-catching thing about this plug-in hybrid model using a 2.0T engine is probably not its internal combustion engine. So today we will use our experience of this car to analyze the technical performance of Mercedes-Benz’s fourth-generation plug-in hybrid.

The code names are the same, but 2.0T is the displacement justice

At a price that is 30,000 yuan higher than the current guide price of the top model of the 2023 Mercedes-Benz C-Class fuel version, the Mercedes-Benz C 350 eL has also become the only model in the entire series (except AMG) with a guide price that exceeds 400,000 yuan. But on this basis, you can get a larger-displacement internal combustion engine (2.0T), a larger-capacity battery in a plug-in hybrid structure, and even an air suspension system.

We first focus on the internal combustion engine. Although the displacement has been upgraded, there is not much change in the parameters of this 2.0T. Judging from the data, its maximum power is 150kW and maximum torque is 320N·m. Compared with the 1.5T version of the Mercedes-Benz C-Class, it is only slightly larger in terms of maximum torque, but the maximum power performance is exactly the same. However, the powertrain is always a complete set. Since the Mercedes-Benz C 350 eL has a plug-in hybrid structure, the internal combustion engine will not assume all driving functions. On the contrary, internal combustion engines need to pay more attention to the cooperation with electrification systems. This is also a common state of current hybrid, plug-in hybrid and other technical products.

In terms of system parameters, the comprehensive system power of the Mercedes-Benz C 350 eL reaches 230kW, and the comprehensive system torque reaches 440N·m. This also helps this plug-in hybrid model, which has a curb weight that is nearly 390kg higher than the fuel version (approximately equal to the level of the fuel version with a full load of passengers), the official acceleration from 0 to 100km/h is still 0.8 seconds faster, achieving 100km/h in 7 seconds. .

However, it would be a bit exaggerated to say that this is all due to the electric drive. In fact, this 2.0T engine code-named M254 is a flagship product with the same code name as the 1.5T version of the Mercedes-Benz C-Class. From M274 to M264 to M254, Mercedes-Benz completed the succession of three generations of engines in just 10 years. Judging from the specific form, Mercedes-Benz is obviously accelerating its electrification layout. The most intuitive expression is that this M254 engine does not even have a belt structure. Technically, processes such as NANOSLIDE cylinder coating and CONICSHAPE cylinder honing are also used to reduce friction, improve efficiency, and are compatible with low-viscosity engine oil to further improve fuel economy.

ISG + big battery = easy plug-in?

As the protagonist of the Mercedes-Benz C 350 eL power system, its electrification part is actually not unfamiliar to us. Although it uses a plug-in hybrid structure, it is logically the same as the current 48V mild hybrid system of the Mercedes-Benz C-Class. Even thanks to the existence of plug-in hybrid, it is said that the Mercedes-Benz C 350 eL is a "full-blooded version" of the Mercedes-Benz C-Class. This is not just based on its engine displacement, but based on the performance of this entire set of power.

Specifically, this plug-in hybrid system continues the 48V light hybrid setting of canceling the traditional starter and belt. Everything, including the air-conditioning compressor, is driven by pure electric power. In terms of the use of in-car equipment, we can almost treat it as a pure electric vehicle.

What's even more exciting is the drive part. Since it loses the constraints of belts and other structures, the traditional internal combustion engine only needs to focus on output work, and the overall efficiency is naturally higher. The essence of electrification is the ISG motor integrated between the engine and gearbox. This structure can also be called the P2 structure. In addition to being able to undertake engine starting, start-stop and other functions, it can also drive and energy recovery.

Theoretically, the main disadvantage of this architecture is that it requires high adjustment skills, that is, the power switching between the engine and the motor. And the axial space is obviously occupied, but this is not a big pressure for models with longitudinal structure. Of course, the former does not seem to be a problem with the Mercedes-Benz C-Class. Taking the 48V light-hybrid version of the C-Class as an example, the adjustment of its power connection is mature. In the plug-in hybrid version, both the internal combustion engine and the electric motor have richer power reserves, so the adjustment pressure is smaller.

However, in addition to the structural problems that need to be avoided, the ISG motor at the P2 position also faces a practical challenge, which is the charging and discharging logic. This is even more clear on 48V light hybrids, because this motor architecture can be equipped with more powerful motors for driving and more efficient kinetic energy recovery. However, higher power charging and discharging performance also puts pressure on battery capacity. In short, if a larger-capacity battery is not carried and the vehicle is in a discharge condition for a long time and it is difficult to replenish energy, the motor will not be able to play its role, leading to logical confusion.

This challenge is obviously perfectly avoided by the plug-in hybrid structure. The Mercedes-Benz C 350 eL is equipped with a power battery pack with a capacity of 25.4kWh. As a medium-sized car with a pure electric range of 105km under WLTC operating conditions, the battery capacity it carries is larger than the plug-in hybrid BYD Tang 112km pure electric range version (NEDC). And considering the information on vehicle weight, battery life and battery capacity, it is more reasonable to boldly guess that Mercedes-Benz has made some "reservations" for the power battery. This capacity reservation not only protects the battery pack, but also maintains the basic logic of motor operation under extreme conditions.

At the same time, the plug-in hybrid structure also makes energy replenishment no longer dependent on objective working conditions, but can directly pick up the charging gun. Under 7kW AC slow charging, the Mercedes-Benz C 350 eL can be fully charged from 10% to 80% in about 3 hours, while 55kW DC fast charging can charge it from 10% to 80% in about 21 minutes. If conditions permit, it is not difficult to use it as a pure electric model.

Written at the end: In fact, ever since Mercedes-Benz began to apply the 48V technology of ISG motors, I have repeatedly speculated that its ultimate goal is to add a large battery to form a plug-in hybrid structure. Now the plug-in hybrid on the C-Class has finally completed an important piece of the puzzle on Mercedes-Benz's electrification path. It is expected that this technology will also be installed on the upcoming new Mercedes-Benz GLC without any surprise. However, with the addition of larger displacement, larger motors, larger batteries, and compatibility with fast charging, how Mercedes-Benz controls the cost of this plug-in hybrid system has also become an important issue for it to further promote electrified products. .