Overall output from the diesel hybrid is up to 165 kW (224 hp) with torque of more than 580 N·m (428 lb-ft). The E 300 BlueTEC HYBRID consumes 4.1 liters of fuel per 100 kilometers (57 mpg US) on the NEDC, with CO₂ emissions of 109 g/km. It will be launched at the end of 2011. Mercedes-Benz is currently selling two hybrids: the S 400 Hybrid and the ML 450 two-mode Hybrid—the first two hybrid passenger cars to be produced by a European manufacturer.

The basis for the E 300 BlueTEC HYBRID is the engine from the E 250 CDI. The electric motor draws its energy from a high-voltage, lithium-ion battery, which has already proven itself in the S 400 Hybrid. (Earlier post.)

The E300 BlueTEC Hybrid offers all the driving characteristics of a full hybrid, such as purely electric driving, stop/start function, recuperation, boost effect and, for the first time, “sailing” and silent starting of the internal combustion engine by the high-voltage electric motor. The operation strategy incorporates the following principal features:

• Even at low revs, the electric motor assists the diesel engine with high torque (boost effect). The result is high, clearly noticeable agility.

• When driving for longer distances or on the motorway, the intelligent electronics recognize the driving situation and automatically adjust the load point of the internal combustion engine to achieve a lower specific fuel consumption, thereby helping to save fuel and reduce emissions.

• Thanks to a clutch between the engine and the electric motor, the E 300 BlueTEC HYBRID can cover short distances at speeds of up to 35 km/h (22 mph) using electric drive alone. Consequently, the internal combustion engine does not even need to be started in most cases when driving in stop-and-go urban traffic or manoeuvring in parking spaces.

• The internal combustion engine in the new diesel hybrid is switched off as soon as the vehicle starts to coast down from 80 km/h; in this case, the electric motor just keeps the road speed constant (i.e., “sailing”).

• The diesel engine is started smoothly as soon as the driver releases the brake pedal, hits the accelerator pedal or reaches a defined limit speed during acceleration.

• Recuperation starts as soon as the driver releases the accelerator pedal. In this case, the electric motor functions as an alternator and converts the kinetic energy into electrical energy, which is stored in the high-voltage battery.

The air conditioning compressor and the steering are powered electrically, meaning that both systems operate even when the internal combustion engine is not running. All of the hybrid technology, including the high-voltage battery, is housed in the engine compartment.

The New C 220 CDI and E250 CDI BlueEFFICIENCY

Mercedes-Benz also presented two new BlueEFFICIENCY diesel models with lowered fuel consumption and CO₂ emissions. The new C 220 CDI now consumes 4.5 liters per 100 kilometers (52 mpg US)—0.3 of a liter less than previously. This cuts its CO2 output from 127 g/km to 119 g/km.

The E 250 CDI with an automatic transmission will require 4.9 litres of diesel per 100 kilometers (48 mpg US), resulting in 129 g/km CO₂, as opposed to 5.8 liters currently (154 g/km CO₂—all provisional, combined figures).

In the E 250 CDI, the four-cylinder engine achieves 150 kW (204 hp) and develops torque of 500 N·m. The C 220 CDI develops 125 kW (170 hp) and a maximum torque of 400 N·m.

Further improvements to the four-cylinder diesel engine formed one of the focal points of the optimization measures. The characteristic features of this powerplant include a lighter crankshaft (it now has only four balance weights as opposed to eight previously), optimized oil pressure regulation and belt drive plus an exhaust gas turbocharger with a self-regulating compressor.

Both the C 200 CDI and the E 250 CDI have been given a special automatic stop-start system—in conjunction with an automatic transmission for the first time in the case of the E-Class.

Enhancements to the 7-speed automatic transmission in the E 250 CDI include a new transformer with reduced slip, a newly developed ECO shift program with better kingpin inclination and an additional oil pump which maintains the operating pressure during an automatic stop. Friction-optimized components in conjunction with fuel-efficient engine oil enable the operating pressure to be lowered. A different rear axle ratio (2.47 instead of 2.65) also contributes to the good consumption figures.

The Mercedes-Benz C 220 CDI and E 250 CDI models will be available this autumn, and further BlueEFFICIENCY models from Mercedes-Benz will follow suit.