Mercedes is extending the two-door E-class range by introducing a high-output four-cylinder engine codenamed the "M 264" to the E350 Coupé and Cabriolet models. The new powerplant pumps out an impressive 299 hp (220 kW) and 296 lb-ft (400 Nm) of torque, rivaling the performance of some of Mercedes' high-capacity six-cylinder engines, while keeping emissions firmly in four-cylinder territory. Mercedes has achieved this by fitting the engine with a 48-V electrical system that debuted on the 2017 Mercedes S-Class.
The 48-V electrical system utilizes a 48-V belt-driven starter-alternator combo as well as a 48-V electric water pump. Combined with the engine's twin scroll turbocharger, CAMTRONIC variable valve timing and particulate filter, Mercedes is claiming a combined fuel economy figure of 36 mpg (6.7 L/100km) for the Coupé and 35 mpg (6.8 L/100km) for the Cabriolet. The CO2 emission figures are respectable as well, at 149 g/km and 154 g/km for the coupe and cabriolet, respectively.
Apart from the performance benefits that this system provides, Mercedes is highlighting further advantages in using a 48-V electrical system. Firstly, the starter-alternator is integrated into an electric motor that is fitted in between the engine and transmission. Combined with the electric water pump, this setup does away with traditional engine-driven ancillaries while providing easy cold starting, increased power and torque, and regenerative braking.
A 48-V setup also allows "stop-start" technology to be fitted and be a lot more durable. This means the engine can be switched off more frequently when it is not required, such as when coasting, decelerating or whenever the throttle is not being applied. Its "soft start" properties also allow the engine to be turned on and off without it being perceptible to the occupants.
One of the biggest advantages of using a 48-V electrical system is that the current draw from electrical components is a quarter of the amount required for a 12-V system, which means that the wiring can be made thinner and lighter to provide better fuel economy. While the 48-V system powers the drivetrain, the remainder of the components, such as the instrumentation and lighting, will be powered by a conventional 12-V system.
As well as the high-output four cylinder, two more frugal engines are now on offer from the E-class sedan – the 2.0-liter turbodiesel four cylinder (143 kW/194 hp) from the E220d and the 2.0-liter turbocharged four-cylinder gasoline engine (135 kW/184 hp) from the E200. The two-door E220d and E200 trim levels are not electrically boosted like the E350, but are available with 4MATIC 4WD. As part of the updates, Mercedes offers new paint finishes as well as an optional Night Package for the Cabriolet, which smartens up the exterior with a redesigned front bumper, diamond grille and 18 inch five-spoke alloy wheels.
Mercedes lists the starting price at €59,738 (US$69,600) for the E350 Coupé and 65,212 (US$75,980) for the E350 Cabriolet.