The formula for efficiency.

  • The formula for efficiency.

  • However, the powertrain developers don’t work alone to achieve this goal, as approximately 200 employees at Mercedes-Benz in Sindelfingen are directly or indirectly involved in the hybrid powertrain project.

    The C 350 e is a true wonder of efficiency. It boasts 205 kW of output but only needs 2.1 litres of fuel to travel 100 kilometres. This corresponds to CO₂ emissions of 48 grams per kilometre. Despite all this efficiency, the comfortable sedan is as lively as a sports car: In its Sport Plus mode, the vehicle accelerates from 0 to 100 km/h in 5.9 seconds. A premium sedan that is as dynamic as a sports car and as environmentally friendly as a compact — how can that be?

    We asked someone who should know the answer: Uwe Keller, who has a Ph.D. in engineering and is also the Project Lead for the centrepiece of the C 350 e: the hybrid powertrain. “Ultimately, the secret lies in perfect interaction,” says Keller. “We matched all of the systems, parts, and components down to the last detail in order to ensure that the combustion engine, the transmission, and the electric drive work together perfectly. In combination with our intelligent drive system management concept, this results in a high level of efficiency and outstanding handling.” Efficiency is also the main objective of the project team led by Keller.

    The C 350 e is a true wonder of efficiency. It boasts 205 kW of output but only needs 2.1 litres of fuel to travel 100 kilometres. This corresponds to CO₂ emissions of 48 grams per kilometre. Despite all this efficiency, the comfortable sedan is as lively as a sports car: In its Sport Plus mode, the vehicle accelerates from 0 to 100 km/h in 5.9 seconds. A premium sedan that is as dynamic as a sports car and as environmentally friendly as a compact — how can that be?

    We asked someone who should know the answer: Uwe Keller, who has a Ph.D. in engineering and is also the Project Lead for the centrepiece of the C 350 e: the hybrid powertrain. “Ultimately, the secret lies in perfect interaction,” says Keller. “We matched all of the systems, parts, and components down to the last detail in order to ensure that the combustion engine, the transmission, and the electric drive work together perfectly. In combination with our intelligent drive system management concept, this results in a high level of efficiency and outstanding handling.” Efficiency is also the main objective of the project team led by Keller.

    However, the powertrain developers don’t work alone to achieve this goal, as approximately 200 employees at Mercedes-Benz in Sindelfingen are directly or indirectly involved in the hybrid powertrain project.

    These include experts for control devices, electrical functions, electronic systems, and batteries, as well as the individuals responsible for the various model series. “Every unit or department works with the others to make a contribution to the overall result; success is always the success of many,” Keller explains. Perfect interaction is not required from the technical systems alone, nor is the complexity limited to the technological aspects. After all, what the hybrid powertrain team does is to bring together two worlds that each have their own laws: the worlds of combustion engines and electric drive systems.“ If greater efficiency is to be achieved in such a system, everyone must be aware of the fact that a change to even the tiniest detail will impact the entire system,” says Keller.“ Getting this type of systemic thinking embedded in people’s minds was one of the biggest challenges we faced.”

    The most efficient powertrain.

    Regarding the powertrain, the main goal was – and still is – to achieve the highest degree of efficiency. That is because there is always a certain amount of loss whenever energy is transferred to the wheels via the transmission, regardless of whether the energy comes from a fuel tank or a battery. This is due to towing and friction effects, for example. The developers lower the losses with the help of sophisticated micromechanical measures. “The good thing is that everything we achieve in terms of powertrain efficiency has double the impact in hybrids – when they are driving and when they recover energy,” Keller says.

    Individual efficiency gains often amount to just a few percent, but when taken together they have a major effect on the system. “For example, we achieved CO₂ emissions of 109 grams per kilometre with the E-Class BlueTEC HYBRID in 2012,” he adds. “Today, we’re down to 99 grams – just through optimization measures alone.” This is also not the first success the powertrain specialists have been able to celebrate. Indeed, Daimler has launched a whole range of hybrid models on the market since 2009, and the drive system technology has been improved with each vehicle launched. New records for fuel efficiency and CO₂ emissions have been achieved nearly every time.

    With CO₂ emissions of 94.99 and 115 grams per kilometre, respectively, the diesel hybrids from the C-Class and S-Class series were recently rated at the top of their segments in benchmark studies. This is mainly due to an advantage that competing brands have been unable to match to date: “We have the most efficient powertrains in all model series,” Keller explains. Which brings us to an exceptional aspect of the Daimler approach here: The Group is not seeking to serve just one segment with its hybrid concepts. That’s why Daimler doesn’t build “special-purpose design” vehicles but instead utilizes a modular concept. The basis consists of customized powertrains that can be combined with different engines and used in all model series. Such a powertrain also includes a special hybrid transmission with an integrated electric motor. The combustion engine is linked to the transmission in a manner that allows it to be completely disconnected when it is not needed, in which case it stops running. Such a setup makes it possible to combine different types of engines and transmissions, including everything from front or rear-wheel drives for cars to all-wheel drive systems for SUVs.

    The result is a broad range of variants and a high degree of flexibility. This, in turn, enables Daimler to respond more effectively to customer requirements and offer a more extensive range of products.

    That’s why Mercedes-Benz developers implemented innovative operating strategies and driving programs streamlined for efficiency in the C 350 e. These features make the vehicle even more efficient in real driving situations.

    2.1 litres per 100 km — in the real world as well?

    The Group therefore has good reason to believe plug-in hybrids will be successful on the market. Regardless of the variant in question, the combination of a high level of dynamic handling and low fuel consumption is an attractive feature for many customers. Nevertheless, can consumption values such as those measured on a test rig with the C 350 e actually be achieved in practice? After all, it’s no secret that real-world fuel consumption is generally higher than official consumption figures. Still, Keller says, “Our 2.1 litres can definitely be achieved – and consumption can even be lower than that. For example, I drive to the office in the all-electric mode with a fully charged battery – that’s 13 kilometres. I then drive home in the evening on a full charge and with zero emissions. In other words, I don’t use any fuel whatsoever for my commute. When I take other trips where I need the combustion engine, my fuel consumption is pretty much exactly the same as the NEDC value without the electric drive.”It can thus be concluded that actual fuel consumption is variable and depends in large part on the use profile – and even more on the way the driver operates the vehicle.

    2.1 litres per 100 km — in the real world as well?

    The Group therefore has good reason to believe plug-in hybrids will be successful on the market. Regardless of the variant in question, the combination of a high level of dynamic handling and low fuel consumption is an attractive feature for many customers. Nevertheless, can consumption values such as those measured on a test rig with the C 350 e actually be achieved in practice? After all, it’s no secret that real-world fuel consumption is generally higher than official consumption figures. Still, Keller says, “Our 2.1 litres can definitely be achieved – and consumption can even be lower than that. For example, I drive to the office in the all-electric mode with a fully charged battery – that’s 13 kilometres. I then drive home in the evening on a full charge and with zero emissions. In other words, I don’t use any fuel whatsoever for my commute. When I take other trips where I need the combustion engine, my fuel consumption is pretty much exactly the same as the NEDC value without the electric drive.”It can thus be concluded that actual fuel consumption is variable and depends in large part on the use profile – and even more on the way the driver operates the vehicle.

    That’s why Mercedes-Benz developers implemented innovative operating strategies and driving programs streamlined for efficiency in the C 350 e. These features make the vehicle even more efficient in real driving situations.

    Efficiency through intelligence.

    Like the S 500 PLUG-IN HYBRID, the C 350 e was imbued with a lot of intelligence by Mercedes-Benz engineers. A sophisticated drive system management concept ensures that the efficiency benefits from the powertrain are fully exploited. In addition, intelligent strategies enable maximum driving efficiency. “A predictive and route-based operating strategy, a haptic gas pedal with radar-controlled energy recovery, and a radar-based shifting strategy – our people developed solutions that are truly unique,” says Keller proudly. The predictive operating strategy Keller referred to uses information on road topography from the navigation system to optimize the battery-charge state. For example, if a hybrid is approaching a long downhill gradient where braking energy can be recovered, the operating strategy will take energy from the battery in advance in order to lower fuel consumption and will then fully recharge the battery on the subsequent downhill stretch.

    Daimler has been using this operating strategy in selected hybrid vehicles since 2013. The route-based operating strategy is a C 350 e specialty. This strategy also uses data from the navigation system, but the goal here is to ensure the most efficient use of the combustion engine, the electric motor, and the battery along a given route. For example, a trip from Hamburg to Munich begins with all-electric driving in the city. Once the vehicle gets on the highway, the combustion engine takes over. The traction battery is then charged as needed during the rest of the trip, thereby ensuring that the vehicle can be driven completely emission-free once again when it arrives in Munich. The haptic gas pedal emits a double impulse to indicate to drivers when they should remove their foot from the accelerator. This occurs, for example, if the radar system in the C 350 e determines that the car is approaching a slowermoving vehicle on the highway. If the driver releases the gas pedal, the system switches off the combustion engine and the car begins to virtually “sail.” However, if the vehicle is still moving too fast, the system will turn on the electric motor to brake the car – and recover energy during braking.

    Please find the sustainability brochure here.

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