There is a wide choice of powerful petrol and diesel engines for the E-Class Coupé and Cabriolet. All are highly efficient and equipped with the ECO start/stop function. Six petrol engines are available, ranging in output from 135 kW (184 hp) to 300 kW (408 hp) together with three diesel engines ranging from 125 kW (170 hp) to 185 kW (252 hp).

The BlueDIRECT petrol engines from Mercedes-Benz, which to date have comprised the familiar V6 and V8 engines, boast the very latest technology. A new addition is a six-cylinder engine which is being offered for the first time in the E-Class Coupé and Cabriolet not only as a naturally aspirated engine, but also as the E 400 with a displacement reduced to three litres but with a biturbo drive to compensate. With its power potential and formidable torque at low engine speeds, this six-cylinder model sets new standards in its segment. It produces 20 kW more power compared with the E 350. Its torque has increased by 110 Nm and is on tap between 1400 and 4000 rpm. On top of this, the new, efficient six-cylinder engine also fulfils the EU6 emissions standard. The E 500, meanwhile, not only promises sports-car-like performance – it is also making a name for itself as the most economical model in the V8 segment.

Another new addition to the BlueDIRECT petrol engine family is the four-cylinder petrol unit. With a combined fuel consumption in the E 250 Coupé of 5.7 litres and CO₂ emissions of 132 grams per kilometre (Cabriolet 6.2 litres and 144 g CO₂ per km) and producing 155 kW (211 hp) from a displacement of just two litres, plus 350 Nm of torque across a wide range from 1200 to 4000 rpm, it redefines standards in the four-cylinder segment. Producing a 0 to 100 km/h acceleration time of 7.1 s (Cabriolet 7.5 s), it really underlines the sporty temperament of the E-Class Coupé and Cabriolet.

Lean-burn process with stratified charge operation

Depending on the operating conditions, the new four-cylinder engine operates in stratified charge or homogenous mode. With stratified charge operation, the high-compression engine runs with significant excess air. To achieve this, the fuel is only sprayed into the air, which has already been compressed by the pistons, during the compression phase. A precisely controlled electronic multiple injection system helps to ensure that a fuel/air cloud builds up in a limited area around the spark plug, precisely at the time of ignition. The spark plug lights the ignitable fuel/air mixture around it, while only a very lean mixture with a high proportion of excess air is to be found in the remainder of the combustion chamber. This enables extremely efficient combustion. 

A prerequisite for stratified charge operation is fast piezo injectors. They spray the fuel into the combustion chambers several times in succession per power stroke, and as such enable specific control of the mixture formation and thus the flammability.

The new four-cylinder petrol engine from Mercedes-Benz also sees the world's first use of this stratified lean-burn process in combination with exhaust-gas turbocharging and external high-pressure exhaust gas recirculation. As a result, the E 250 Coupé is the only vehicle in this segment to achieve efficiency class A. In addition, the new BlueDIRECT four-cylinder petrol engines already meet the EU6 emissions standard which will apply from 2015. The new four-cylinder unit also meets the EU6 emissions standard in the guise of the homogenous variant for countries with different fuel qualities.

Advanced technology makes engines more efficient

The BlueDIRECT four-cylinder petrol engines combine spontaneous response and exemplary power delivery with high efficiency and best-in-class emission performance. To achieve this goal, Mercedes-Benz transferred the BlueDIRECT technology from the V6 and V8 engines into the four-cylinder models. Direct petrol injection with spray-guided combustion, which Mercedes-Benz was the first car manufacturer to introduce in series production, has been developed further by the engineers into third-generation direct petrol injection with spray-guided combustion. The system pressure is now up to 200 bar and is adjusted to the optimum level based on the engine's performance map. Completely newly developed piezo injectors allow up to five injections per power stroke for the best possible mixture formation.

The third-generation direct injection system also features "rapid multi-spark ignition" (MSI). Following the first spark discharge and a brief combustion period, the coil is quickly recharged and a further spark is discharged. The MSI system enables up to four sparks to be discharged in succession within one millisecond, creating a plasma with a larger spatial expansion than conventional ignition.

The rapid multi-spark ignition can be actuated to vary both the timing of the sparks and the combustion period to suit the relevant operating point. This provides scope for the best possible centre of combustion and improved residual gas compatibility. This in turn reduces fuel consumption. The result of this is excellent utilisation of the fuel with minimum emissions.

A new thermal management system has also been developed: in a cold state, a switchable water pump with flow-optimised ball valve ensures that no coolant flows through the engine, providing for swift heating-up of the combustion chambers after starting up the engine. The thermostat is electronically controlled and the coolant temperatures are adjusted according to driving style and ambient conditions. The thermostat itself is also a flow-optimised ball valve. In the interest of high efficiency, the volumetric flow of the oil pump is also controlled as in the V engines.

All engine variants are designed for operation with E10 premium petrol and an octane number of 95 RON.

The petrol engines

All figures based on 7G-TRONIC PLUS (figures in brackets apply to Cabriolet)

Powerful diesel engines in the best efficiency class

The six-cylinder diesel unit for the Coupé and Cabriolet comes in the guise of a BlueTEC model with further improved SCR (Selective Catalytic Reduction) technology, which allows it to comply with the EU6 emissions standard.

The diesel engines

All figures based on 7G-TRONIC PLUS (figures in brackets apply to Cabriolet)

ECO start/stop function with direct-start

The ECO start/stop function included as standard in all models operates with starter-supported direct-start. This means that when the engine is switched off, the attitude of the crankshaft is registered by a new crankshaft sensor so that the engine control unit knows the positions of the individual cylinders. On restarting, it can then select the cylinder that is in the most suitable position for first ignition. After the starter has briefly turned over the engine, reliable injection, ignition and combustion is immediately possible in the ideally positioned cylinder.

Optimised drive train

Mercedes-Benz will continue to offer two transmissions for the E-Class Coupé and Cabriolet in future: a 6-speed manual transmission with extremely smooth shifting and short shift travel, and the 7G-TRONIC PLUS automatic transmission with DIRECT SELECT lever and DIRECT SELECT shift paddles. The features of the latest version of the 7G-TRONIC PLUS to emerge include a new torque converter with reduced slip, an ECO shift mode with an improved ratio spread and an auxiliary oil pump to maintain the operating pressure during automatic stops. Low-friction components and low-viscosity oil help to reduce the operating pressure.

A new feature is Momentary M mode. The benefit here is that if the driver has shifted up or down manually, the transmission independently switches back to the fuel-efficient, automatic shift mode after a set period of time. This period of time is lengthened under specific conditions (no accelerator pedal use, e.g. on downhill gradients, high lateral acceleration, e.g. when cornering, or if the speed falls below a minimum threshold when coming to a stop), preventing the return to automatic mode.

Both in Momentary M mode and "fixed" M Mode included with the Sports packages, the driver will in future receive gear recommendations on the instrument cluster's multifunction display to foster an efficient driving style.