M 264 and M256 - these abbreviations will have to be remembered , because they describe the new high-performance gasoline engines from Mercedes, which for the first time rely on a 48-volt electrical system and mutate into a mild hybrid with powerful power with a starter generator.
The displacement continues. As in previous years, Mercedes is expanding the smaller-volume units to replace the previous six and eight-cylinder units. This will be strikingly happening in autumn as a premiere in the E-Class Coupé, which is the first Mercedes model to offer the M264 a home.
The two-liter four-cylinder is basically based on the previous generation of the M274, but is nonetheless has been fundamentally redesigned. The conversion to a 48-volt on-board network creates the possibility of implementing a mild hybrid upgrade. A new starter-generator not only serves as an 'alternator' and starter, but also for recuperation when coasting and as a power source when accelerating.
The M264 has a starter-generator with a clever belt drive at the front of the Motor mounted. Mercedes calls the design 'pendulum belt tensioner': Depending on whether the unit is generating electricity and feeding it into the lithium-ion battery with a capacity of around 1 kWh, or whether it is supposed to help you accelerate vigorously, a tension pulley unit swivels the drive belt to one side or the other to ensure maximum power transfer.
160 Newton meters extra thrust
The starter generator recuperates a maximum of 12 kW, in the other working mode it can help with propulsion with 10 kW. More important than this number: The electric drive can contribute a proud 160 Newton meters of torque, so the two-liter gasoline engine can easily accelerate the six-cylinder predecessor in the 320 model. 5.9 seconds for zero hundred instead of the previous 6.6 seconds - that is clear.
A new development is the twin-scroll turbocharger with an electrically controlled wastegate valve, which guarantees high performance even at low speeds. With a maximum output of 299 hp, the engine is also a real hit in terms of liter output. Thanks to the 48-V on-board network, an electric water pump with 550 watts of power is now used, which can be controlled as required, thus enabling the engine to warm up as quickly as possible.
Another advantage of the starter generator over a conventional ring gear starter is the softer and fasterStarting process. This is not only a plus for reasons of comfort, it also enables the engine to be switched off if necessary in sailing mode and restarted as quickly as possible with practically no delay. Mercedes also wants to have brought the noise and vibration behavior to the level of a six-cylinder with numerous special insulation measures and new plastic engine mounts.
The new M256
The new one puts another shovel on top M256, in every respect. The three-liter in-line six-cylinder will celebrate its premiere in the facelifted S-Class and will replace the previous eight-cylinder in the S 500. With this machine, the developers were able to go to the full technically, as it is a completely new development without having to build on a previous architecture as with the M264. The starter generator, which is also used in the six-cylinder, was designed with a rigidly integrated stator at the crankshaft output to the transmission. This has a number of advantages, such as an even faster and practically jerk-free starting of the engine as well as no power losses via a belt drive, the new M256 is a belt-free motor. The electric motor contributes up to 16 kW of power if required.
Accordingly, not only the water pump, but also the air conditioning compressor is electrically driven. In the six-cylinder, the new 48-volt electrical system also provides an additional charger. In addition to the exhaust gas-powered twin scroll charger, there is also an electrically operated compressor, which provides sufficient compressed air in the combustion chamber even at low speeds. A maximum of 435 hp and 520 Newton meters can be called up in the high-performance version of the M256, and official acceleration is guaranteed here too: the future S500 six-cylinder accelerates in 4.8 seconds exactly as fast as the previous model with V8.
The reward for all the effort is not only significantly lower consumption values - minus 23 percent for the four-cylinder, minus 25 percent for the six-cylinder compared to the units to be replaced. The new engines are also considerably better than their predecessors in terms of pollutant emissions thanks to additional design features such as optimized injection with a new piston design. And: Both engines are fitted with a particle filter as standard.