What is Mercedes-Benz EQ Boost Engine Technology?

Jessica Shea Choksey | Sep 13, 2021

Although the shift to all-electric vehicles has become the main focus of the automotive industry and the world-at-large, hybrid vehicles—those that combine a combustion engine with battery-powered technology—are still alive and well. A prime example of an automaker employing hybrid technology is Mercedes-Benz, with its innovative EQ Boost system. Since making its debut on the S-Class a few years back, EQ Boost has made its way across the Mercedes-Benz product line, including the brand’s high-performance AMG models.

2021 Mercedes-Benz S-Class with EQ Boost Technology Black Front Quarter View

Full Hybrid vs. Mild Hybrid

There are essentially two types of hybrid vehicles: mild/light hybrids and full hybrids. Light or mild hybrid cars only use their electric motors to support the engine during acceleration and cruising. In other words, the electric motor cannot power the vehicle on its own. Conversely, full hybrid cars can drive on battery power alone for limited periods thanks to larger batteries and higher voltage output.

What is EQ Boost?

EQ Boost is a mild-hybrid system built around a 48-volt electrical architecture that increases the performance and efficiency of a conventional internal combustion engine (ICE). The technology consists of a rear-mounted 0.9-kWh lithium-ion battery (smaller than a full hybrid) and a powerful integrated starter generator (ISG).

The ISG is the centerpiece of this system. It is a compact-sized unit consisting of a starter, alternator, and electric motor and is uniquely fitted directly between the engine block and the transmission. The ISG acts as both a starter motor and a hybrid assist motor, adding horsepower for short periods of driving or enabling kinetic energy regeneration to be sent back to the battery.

This system also allows the powertrain to shut down under certain driving conditions in “Eco” mode to help improve fuel economy. Mercedes-Benz refers to this engine-free coasting as “sailing.” This capability brings EQ Boost closer to full hybrid technology compared to other light-hybrid offerings on the market.

On the performance side, this system integrates an electric compressor that supplies 8 pounds of boost to either the turbocharger or directly to the engine. It spools up almost immediately, eliminating virtually all turbo lag when the driver requires a power boost.

To further promote efficiency, the 48-volt system supplements the standard 12-volt electrical system to power auxiliary components such as lights, air conditioning, and the water pump. This setup eliminates the need for a separate 12-volt battery, reducing parasitic power loss and freeing up space.

Overall, an ISG combined with 48-volt power is a less expensive alternative to full hybrid technology.

How does EQ Boost Work?

Mercedes-Benz EQ engines utilize nanoslide cylinder wall coatings that reduce friction and power loss while increasing performance, the automaker says. Also, the combustion chambers themselves have a shape that maximizes efficiency.

Air enters the engine in the usual way, flowing to the turbocharger before heading into the combustion chambers. All EQ Boost engines feature direct injection, increasing engine efficiency and specific power output while reducing exhaust emissions.

The entire drivetrain runs more efficiently because the engine does not need to run all the components attached to it and receives additional power and torque from the EQ Boost electric motor system. As a result, more power gets sent from the engine, through the gearbox, to the wheels.

The magic really starts to happen when the car is in Eco mode. When the vehicle is not using cruise control, the engine can switch off to save even more fuel. At this point, the car is sailing and supplying the battery with power through high-efficiency recuperation. This level of efficiency and fuel savings was previously only possible with high-voltage full hybrid technology.

From the driver’s seat, the EQ Boost display in the gauge cluster shows whether the system is harvesting or using energy. The EQ Boost bar will move from left to right depending on energy flow as the vehicle drives along.

The overall result of the system is reduced tailpipe emissions, increased performance and fuel economy, and the ability to harvest and use energy that the system collects while driving.

The EQ Boost Driving Experience

The EQ Boost driving experience feels much like a non-electrically assisted engine, so there’s no need to change one’s driving style. Most of the time, the system is simply working in the background.

One of the things a driver may notice is a smoother off-the-line feel because the electric motor is delivering that extra power and torque boost on its own. Passing and speed-change maneuvers may also feel seamless due to the electric compressor’s ability to eliminate turbo lag.

When it comes to start/stop, EQ Boost is far less intrusive than other systems because the engine does not have to turn on each time the vehicle has to move slightly forward. The ISG serves as a buffer between the start/stop system and the engine, resulting in a quieter driving experience, even in heavy traffic and congested in-town driving.


Mercedes-Benz EQ Boost is a mild-hybrid technology that is helping to electrify vehicles intelligently and cost-effectively. This 48-volt system boosts fuel efficiency and power while lowering tailpipe emissions. It is something we will most likely see more of as we head into the future of sustainable mobility.

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