Internal combustion engines

There is no question that, in the long term, we will all be driving electric vehicles. The internal combustion engine remains a key pillar of mobility and finances the development of electric drive systems. All the more important, then, to continue to focus on economy, low emissions and efficiency.

1. Where we stand …

Reduced: consumption & emissions

  • Halved: Mercedes-Benz has continuously improved its internal combustion engines, mastering the balancing act between cutting consumption and emissions and increasing overall output. In the past two decades, the average consumption of our passenger car fleet in Europe dropped by almost half, from 9.2 l/100 km (230 g CO2/km) in 1995 to 5.0 l (123 g CO2/km) in 2015. Today, 62 models from Mercedes-Benz Cars already emit less than 120 g CO2/km. And 104 models carry the efficiency label A+ or A. With 88 models, diesel-powered vehicles account for a disproportionately large number of the efficiency champions.

Increased: even more efficiency in the latest diesel engines

  • 13 percent lower consumption and emissions: Our new OM 654 four-cylinder passenger-car diesel engine is more economical and more powerful, lighter and more compact than its predecessor, the OM 651: Thanks to the near-engine positioning of the exhaust aftertreatment, the all-aluminium construction and the new stepped bowl combustion process, its consumption and CO2 emissions have been reduced by 13 percent compared to its predecessor.

  • Up to 15 percent less fuel since 2011 in our Mercedes-Benz Actros: Our commercial vehicles are also fitted with cutting-edge diesel engines. One example is the OM 471 in-line six-cylinder heavy-duty truck engine. Thanks to modifications to the engine, the powertrain and the vehicle's aerodynamics, when fitted in the Actros, the latest generation of the truck diesel engine consumes up to 6 percent less fuel than its predecessor. Its smaller counterpart is following suit, with the latest generation of the OM 470 benefiting from the internal modifications to the OM 471: the asymmetrical turbocharger, enhanced exhaust gas recirculation and asymmetric injection have reduced emissions and improved the exhaust gas quality.

2. Still to come …

A new family of petrol engines:

  • New developments aren't restricted to diesel, however. "The petrol engine too has undergone remarkable developments in the last ten years, internal friction, variable valve timing, direct injection and turbocharging, just to name a few. And it will make further progress," states Thomas Weber, Head of Development. A completely new family of petrol engines is to follow in 2017. The aims here are the same as with our diesel engines: modular design, a reduction in variants and standardisation of the interfaces between drive unit and vehicle. The first representative will be an in-line six-cylinder engine (M256) with integrated starter generator (ISG). A four-cylinder engine (M264) with belt-driven starter generator (RSG) is also planned from 2017.

Particulate filter for petrol engines:

  • The particulate filter will soon no longer be the preserve of diesel engines alone: we are the first manufacturer to plan its wide-scale use for petrol engines too. After more than two years of positive field experience in the S 500 (Fuel consumption, combined cycle: 8.9-8.2 l/100 km; CO2 emissions, combined: 206-192 g/km), additional variants of the S-Class powered by a petrol engine are to be equipped with this new technology as part of the model update as early as next year. The filter will then be introduced in other, new vehicle models, model updates and new engine generations. Thereafter, the use of the particulate filter is also planned for the current model series.

More power for lower consumption: the new 48-volt on-board power supply

The key to future mobility lies in electrifying the car. And that begins not with the drive system itself but with the engine's ancillary components. Going forward, the plan is to electrify every Mercedes-Benz passenger car - with the new 48-volt on-board power supply.

The 48-volt on-board power supply offers a whole range of advantages: alongside savings when it comes to fuel and emissions, the new low-voltage network ensures enhanced ride comfort.

The key characteristics of the new 48-volt on-board power supply:

  • Compatible: retain existing systems, extend performance. The new on-board power allows two voltages. Smaller consumers are supplied with 12 Volt via a DC voltage converter. Consumers with high power requirements are designed for direct use with 48 Volt, which, specifically where electric motors are involved, allows a significantly higher efficiency to be achieved.
  • 4x more powerful: With the same current strength, the new 48-volt low-voltage on-board power supply offers four times the performance of its 12-volt predecessor - without the additional safety architecture of a high-voltage power supply. The new system allows consumption savings on a level which we have only been able to achieve to date through the use of high-voltage on-board power supplies in our hybrid vehicles.
  • Thinner & lighter: The integration of a 48-volt on-board power supply also offers advantages for ancillary consumers in the vehicle such as the air conditioning, electric heating elements or the extractor fan. At identical power, the electric currents are only one fourth of those in conventional systems. Cables can be made thinner and therefore lighter; and every gram less weight also means lower fuel consumption.
  • Smoother & quieter: Apart from reduced fuel consumption and CO2 emissions, the 48-volt on-board power supply also brings increased comfort. This is because the system is able to rev up an internal combustion engine to idle speed very quickly and smoothly. This benefits the NVH characteristics (Noise, Vibration, Harshness): the engine starts running so imperceptibly that it's as if it had never been switched off.

48 volts - only in combination with starter generators

The key hybrid functions that every future passenger car will have as a result of the 48-volt on-board power supply are: "energy recovery", "boost" and "starting off and manoeuvring in electric mode". The full potential of 48-volt starting systems can only be exploited if the starter and generator are integrated in a single unit. With the aid of extended functionality, this allows reductions in fuel consumption and improvements in starting comfort. In conjunction with a 48-volt on-board power supply, two basic solutions are available: the belt-driven starter generator (RSG) and the integrated starter generator (ISG).

  • RSG: The belt-driven starter generator with an output of around 10 kW is integrated in place of the generator which has featured to date. It is coupled with the internal combustion engine like the generator is today. The combination of starter and generator assists the combustion engine with starting, acceleration and energy recovery.
  • ISG: The integrated starter generator (ISG) combines the starter motor and the generator in one powerful electric motor that is installed between engine and transmission and is also used for cold starts. It replaces both the existing alternator and the starter motor. The more compact construction in comparison with the RSG allows a higher power-to-size ratio. The integrated electric motor assists the internal combustion engine, for example when accelerating, and supplies the battery with power by means of high-efficiency energy recovery.

With an RSG or ISG it is not necessary to wait until the vehicle is stationary before switching off the engine. The conclusion: 48-volt systems allow a great degree of the functionality of a fully hybrid system but with lower costs.

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