Advanced technology calling card for new E-Class

  • 29-Apr-2009 03:51 EDT
Merc E_class 3.0908C1142_110.jpg

High technology, weight control, and aerodynamics mark out Mercedes-Benz's new E-Class sedan.

Advanced technology has been the essence of Mercedes-Benz for many decades, and the new E-Class demonstrates the point yet again. The spread of its new technology is broad, embracing a subtle headlight operating regime, automatic emergency braking, a very rigid bodyshell, and significant powertrain advances with the prospect of a diesel hybrid version. It is also highly aerodynamic, achieving a Cd of 0.25 without the aid of overt and aesthetically intrusive airflow hardware. And it even has a driver drowsiness detection system.

The most significant engine for the new car, which has previously been described in detail in AEI, is a 2.1-L four-cylinder turbodiesel with three power levels. The most interesting is the 250 CDI, the salient features of which include 150-kW (201-hp) output complemented by 500 N·m (369 lb·ft) torque and an NEDC combined fuel consumption of 5.3 L/100 km.

The V6 E350 CDI Blue Efficiency with 170 kW (228 hp) tops the E-Class diesel lineup. Later this year, it will be available in BlueTEC form with 155 kW (208 hp) and will meet EU6 exhaust emissions requirements slated for 2014 application.

Gasoline engines for the E-Class include the direct-injection, turbocharged, 1.8-L Blue Efficiency with variable intake and exhaust camshafts, while the E250 CGI, also with four cylinders, produces 150 kW and 310 N·m (229 lb·ft)—26% above that of the previous comparable V6 unit—with fuel consumption cut by some 20% to 7.3 L/100 km and CO2 emissions at 173 g/km.

V6 and V8 gasoline models (E350 CGI Blue Efficiency and E500) both show reduced fuel consumption. The most powerful E-Class, the E63 AMG, produces 386 kW (517 hp). A new-generation all-wheel-drive system is available on some variants.

Significant in achieving overall performance figures has been Mercedes’ high-priority attention to aerodynamics; a Cd of 0.25 is impressive and betters the previous model’s already impressive figure by 4%. Although the new car has a larger frontal area, Cd x A has increased only from 0.57 to 0.58.

Computer simulation engineers can claim much of the credit for this. Airflow analyses refining the new car’s detailed design were applied well in advance of wind-tunnel testing and prototype build. Flow analyses of the original digital prototype involved computers solving differential equations comprising some 30 million fluid elements. Significant finer points of the car’s aerodynamic design include the use of a controllable shutter that allows the quantity of cooling air ingress to be limited according to requirements. If it were possible to totally obviate the need for cooling air into the engine compartment, a Cd of 0.20 would be feasible, estimated Mercedes specialists.

Keeping weight under control is a constant challenge for vehicle builders. The new E-Class sees 72% of all bodyshell parts made of high-strength steel, while the hood, fenders, and trunk lid are of aluminum. The front end is a hybrid construction of alloy and glass-fiber-reinforced plastics. Curb weight of the E250 CDI Blue Efficiency is 1735 kg (3825 lb).

Weight may be increased by the use of enhanced crashworthiness and safety systems, but the pluses of the technology are huge. Mercedes has a plethora of such technology and the E-Class benefits from some of those fitted to the S-Class range. Significant among them is Brake Assist PLUS, which automatically calculates braking pressure to prevent, or mitigate the effects of, a collision. The development of the E-Class involved more than 150 high-speed crash tests with the increased use of high-strength steel alloys helping to improve results.

The new car gets an active hood to help improve pedestrian-protection effectiveness. It includes three impact sensors and hood hinges pretensioned and held by springs. In the event of impact with a pedestrian, the sensors send information to an electronic control unit (ECU), which triggers a pair of solenoids in the hinges, releasing them and allowing the trailing edge of the hood to rise by 50 mm (2 in) as the springs activate. If the system operates unnecessarily, the car user can reset it without the need to visit a dealer.

Another safety area concerns lighting. The E-Class is offered with a system that does not just automatically switch from high to low beam but does so in gradations, selecting optimum headlamp range giving improved visibility without dazzling oncoming drivers. The low-beam range has been designed to be increased from 65 to 300 m (210 to 985 ft) without risk of dazzling. It takes into account steering angle to anticipate tight corners.

The technology is camera-based and operates at speeds above 55 km/h (34 mph). The camera is positioned on the windshield and uses an intelligent algorithm to assess the range to target (oncoming vehicles) and vary it accordingly. New data is sent to the headlights every 40 ms. The system comes as part of an optional package that also includes bi-xenon headlamps, an Intelligent Lighting System, and LED daytime driving lights.

Detecting driver drowsiness and taking action to counter it has been the subject of experiments for decades. Mercedes’ solution, called Attention Assist, was developed through a four-year program and uses steering behavior as the essential indicator; Mercedes’ engineers discovered that drowsy drivers make minor steering errors that are corrected abruptly. The Mercedes system records some 70 parameters that are assessed for drowsiness detection.

The technology calculates an individual driver profile in the first few minutes of a journey that is then compared to the prevailing driving conditions and current sensor data—on lateral and longitudinal acceleration, the use of turn indicators, pedals, road surface unevenness, sidewinds, and, most significantly, steering input. If the system decides there is a problem, a tone sounds and a coffee-cup image illuminates on the instrument panel.

This AEI Editor experienced the system’s analysis of a situation at the end of a long day of driving the new E-Class in Spain. A passenger was recounting an interesting but lengthy anecdote when the Attention Assist warning triggered.

Could this useful piece of technology therefore be made available with driver control, to be triggered surreptitiously to reduce anecdote fatigue? The Mercedes technology team maintained a diplomatic silence.

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