Mercedes-Benz B-Class engineered for alternative powertrains

  • 27-Sep-2011 08:16 EDT
Merc9-11BClass 1.jpg

A compact "sports tourer" from Mercedes, the new B-Class has efficient aerodynamics with a Cd of 0.26.

Mercedes-Benz’s new B-Class, which uses a fresh front-wheel drive platform, is now far more deserving of its categorization as a compact sports tourer. In fact, it is not as compact as it was, being some 90 mm (3.5 in) longer and 11 mm (0.4 in) wider than its predecessor, but significantly, it is almost 50 mm (2.0 in) lower at 1557 mm (61.3 in)—all of which gives it a sleeker appearance.

Seat height has been radically reduced by some 86 mm (3.4 in), mainly for easier entry and egress. Rear-seat legroom is 976 mm (38.4 in), which is greater than that of the Mercedes E-Class and S-Class.

It also has remarkably good aerodynamics, with a best per-model Cd figure of 0.26, which is attributable to some effective fine-tuning, including a patent-pending serrated wheel-arch spoiler. Airflow management is particularly focused on the B-Class’s underbody and system cooling.

The car, unveiled at the Frankfurt Motor Show, is available with a direct-injection turbocharged gasoline and a new diesel engine, a seven-speed dual-clutch transmission (DCT), and an electric oil pump for stop/start capability is standard on all versions. A six-speed manual gearbox is also standard, described by Mercedes as being “closely related” to the DCT.

The B-Class has also been designed to take non-conventional power sources. Engineered interfaces in the bodyshell facilitate the car’s main floor panel being modified to accept alternative drive systems, and an underfloor compartment covering part of the area beneath the back seat could be used for large battery installation. The car was designed from conception to integrate hydrogen fuel-cell technology, which was latterly available on the outgoing model.

The gasoline engines for the B-Class, designated M270, are a new series and use third-generation direct-injection technology introduced in 2010 for Mercedes’ BlueDIRECT V6 and V8 engines; they are expected to power other Mercedes models. The four-cylinder engines are designed for lateral or longitudinal installation and are initially available in 1.6-L form with two power levels, producing 90 kW (121 hp) and 200 N·m (145 lb·ft) or 115 kW (154 hp) with 250 N·m (184 lb·ft). Maximum torque is available from a remarkably low 1250 rpm.

The four-cylinder diesel is a development of the company's highly efficient 2.1-L unit downsized to 1.8-L with outputs of 80 and 100 kW (107 and 134 hp), the more powerful unit producing 300 N·m (221 lb·ft) of torque at 1600 rpm.

The engines have been packaged to optimize the B-Class’ turning circle, which at 11 m (36.1 ft) is good for a front-wheel drive car. Suspension includes a new four-link system at the rear. Sports suspension is optional, lowering the c.g. by some 20 mm (0.8 in) and incorporating active sports dampers. The electromechanical power steering has been re-designed for the new B-Class, with the motor positioned directly on the steering gear to improve packaging.

As usual with Mercedes, all transmissions and engines have been developed in-house and are manufactured at plants including Stuttgart-Untertürkheim and Stuttgart-Hedelfingen; Rastatt/Baden; Gaggenau/Baden; and Kölleda/Thuringia.

Majoring on safety, the B-Class gets extensive new driver-assistance systems, including radar-based collision warning technology with adaptive Brake Assist as standard, which Mercedes claims as a “world first” in the compact market segment. It gives visual and aural warnings and prepares Brake Assist, which operates if the driver exceeds a specific pedal force. A particular scenario for its operation would be reducing the risk of rear-end collisions in heavy traffic conditions.

Depending on specification, the car also offers adaptive headlight assist; blindspot and lane-keeping assist; Mercedes’ established Pre-Safe system; pelvis bags for driver and front passenger; active parking; hill-hold; and a reversing camera. The car’s optional Comand system allows internet access.

The available Easy-Vario-Plus system for optimum interior configuration includes 140 mm (5.5 in) longitudinal adjustment of the rear seats to increase luggage space from 488 to 666 L (17.2 to 23.5 ft³) and "horizontalizing" of the front passenger seat's backrest.

Dr. Thomas Weber, Daimler Board Member for Group Research and Head of Development at Mercedes, says he believes the new B-Class has the highest standard of safety that has ever been available in its class: “No model change in the history of Mercedes-Benz has ever seen so many new developments introduced in one fell swoop,” he added.

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