2012 Mercedes-Benz ML350

  • 10-Sep-2011 04:46 EDT
2012 M-Class_ (30).jpg

What looks like a minor styling refresh on the outside hides all-new powertrains and chassis upgrades underneath the skin of the 2012 ML350.

Mercedes-Benz has been tweaking the recipe for its midsize SUV since the introduction of the M-class in 1997. Then the target was the popular Jeep Grand Cherokee, and the object was to provide a functional off-roader.

But Mercedes buyers have different expectations for the company’s products, so when the M-class was revamped in 2005, it moved from a body-on-frame SUV to a unitized crossover in pursuit of improved ride, handling, efficiency, and cabin space. That platform, coincidentally, is now shared with the vehicle’s one-time target, the Jeep Grand Cherokee, a legacy of the years when the Mercedes and Chrysler brands were corporate siblings.

Now they are rivals again, and as Jeep has dramatically raised its game, so has Mercedes in a bid to preserve a gap between the mainstream Jeep brand and premium Mercedes brand.

To do that Mercedes engineers have packed more new hardware under the skin while designers have produced an opulent new cockpit meant to coddle occupants as never before.

The company’s engineers got an early start testing the new model using computer simulations to conduct virtual test drives of digital prototypes as early as December 2007, reported Ewe Ernstbertger, Vice President of Program Management for the ML. “This allowed us to make a wholesale evaluation of the chassis,” he explained. Then, when the company began testing physical prototypes in June 2009, those vehicles were already close to production specifications, making the 4.375 million miles of testing performed since more productive.

Advancing the M-class from the outgoing model, and from Jeep’s version, the company has added structural improvements to the platform and has upgraded some of the suspension components. Ultrahigh-strength steel in A- and B-pillars along with the roof rail contribute to increased rigidity and crash safety, while a cast magnesium crossmember behind the dashboard weighs 40% less than the old steel cross brace while increasing stiffness, according to Hans-Peter Reifenrath, Director of NVH, ride comfort, and aerodynamics.

Diesel models get a cast aluminum crossbrace that serves as the transmission mount with an integrated vibration damper specifically tuned to the frequencies produced by the diesel engine. Diesels also get a centrifugal pendulum in the torque converter that is designed to dampen vibration as well as map-controlled active engine mounts.

The new ML350 also gets upgraded suspension, as the Airmatic air-suspension system with adaptive damping gains a new computer-controlled anti-sway bar that is only active when the vehicle is turning. While driving over rough terrain or in a straight line on the highway, the Active Curve System disconnects the front anti-sway bar, allowing the front wheels to react independently for maximum off-road grip and optimal on-road ride quality.

Additionally, the standard-issue steel spring suspension is now available with optional adaptive damping for improved ride and handling on models that lack the Airmatic system. Electric steering is another change from the outgoing model, providing the fuel efficiency benefits of eliminating the engine-driven hydraulic steering pump.

U.S. drivers will initially see a direct-injected gasoline 3.5-L V6 producing 302 hp (225 kW) and 273 lb·ft (370 N·m). European models will feature a more efficient stratified charge fuel injection system using piezo electric injectors from Robert Bosch GmbH. U.S. gasoline, especially in the Midwest, contains too much sulfur for the piezo injectors, according to Peter Luckert, Director of diesel engine powertrain. The system requires gas with less than 30 ppm of sulfur, which is only available consistently on the coasts in the U.S., he said.

As much as sulfur was previously an issue for diesels, so it will be for gasoline engines as engineers seek ever more precise control of combustion, he said. The stratified system is 10% more fuel efficient than the homogeneous combustion engine coming to the U.S.

The twin-turbo 3.0-L V6 diesel engine is rated at 240 hp (179 kW) and an astonishing 455 lb·ft (617 N·m), promising exciting acceleration to match its fuel economy. This aluminum-block diesel employs twin-wire-arc spraying to coat the aluminum cylinder walls with a durable lining in place of pressed-in iron sleeves used previous. This cuts friction and saves 4.3 kg (9.5 lb) of mass, contributing a 3% reduction in fuel savings, the company says.

A turbocharged 4.8-L V8 gas engine will be available optionally after launch, according to the company. A new seven-speed automatic transmission contributes a 14% improvement in fuel economy over the old five-speed unit. The transmission contributes to the M-class’s off-road prowess with a revised shift program for off-road driving that increases the slip thresholds and raises the shift points to higher rpm.

For additional off-road capability, the M-class offers an on- and off-road package that features six different transmission programs; automatic, offroad 1 (light terrain), offroad 2 (more challenging terrain), winter, sport, and trailer. The package includes an underside skid plate, a two-speed transfer case, a center differential lock, and additional ground clearance.

Mercedes has dressed up all these improvements with new exterior styling and, more significantly, a substantially plusher interior featuring premium woods, metals, and leathers. “Our customers keep telling us this is what is appreciated,” said Hartmut Sinkwitz, Director of Interior Design. “You can see and feel the high quality of the materials,” he said, "and we are convinced this will set new quality benchmarks.”

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