The M-Class is a story of success. With more than 1.2 million vehicles sold, it is the best-selling SUV in its segment and also enjoys the most loyal customer base. We will be continuing this success with the new M-Class, which will make an important contribution to our sales growth over the coming years. The new M-Class has the potential to set standards in the SUV world once again: on average it consumes one quarter less fuel than its predecessor and as such will be the most economical vehicle in its segment—whether fitted with or without a hybrid drive.

—Dr. Joachim Schmidt, Board Member of Mercedes-Benz Cars, Sales & Marketing

BlueTEC diesel units. On the diesel side—now available solely as BlueTEC units with SCR aftertreatment technology) , the focus is on downsizing and the new version of the V6 CDI engine. In the ML 250 BlueTEC 4MATIC, the 3.0-liter V6 of the previous ML 300 CDI BlueEFFICIENCY 4MATIC model is replaced by the 2.2-liter four-cylinder unit already applied in the S-Class. (Earlier post.) The NEDC consumption of 6.0 l/100 km is 28% lower than that of the previous model.

The ML 250 BlueTEC 4MATIC delivers maximum torque of 500 N·m (369 lb-ft) at 1600 rpm and a rated output of 150 kW (204 hp) with acceleration from 0 to 100 km/h in 9.0 seconds before going on to a top speed of 210 km/h (130 mph).

Two-stage turbocharging produces high torque even at low engine speeds. The compressor package —already fitted in the compact GLK 250 CDI 4MATIC SUV—made up of a small high pressure (HP) and a large low pressure (LP) turbocharger contributes to the high output on a par with the 6-cylinder unit in the predecessor model ML 300 CDI BlueEFFICIENCY 4MATIC.

The two turbochargers are connected in series, and each has a turbine and a compressor driven by this turbine. The HP turbine is located directly at the exhaust manifold and initially allows exhaust gas to flow through it; it then rotates at up to 215,000 revolutions per minute. The HP turbine housing features an integral bypass duct, which can be opened or closed by means of a charge-pressure control flap. If the flap is closed, the whole exhaust stream flows through the HP turbine, so that the exhaust-gas energy is available solely for the HP turbine drive. This means that the optimum charge pressure can be built up at low engine revs.

The two compressors are likewise connected in series, and are in addition connected to a bypass duct. The combustion air from the air filter first flows through the low-pressure compressor, where it is compressed as a function of the LP turbine's output. This pre-compressed air then passes into the high-pressure compressor, which is coupled to the HP turbine, where it undergoes further compression.

The result is a genuine two-stage turbocharging process. The major advantage of this demand-based control of the combustion air supply using two turbochargers is improved cylinder charging, and therefore high torque even at low engine speeds. Fuel consumption is also reduced.

The ML 350 BlueTEC 4MATIC features an extensively revamped 3.0-liter V6 which offers far better performance coupled with a substantial reduction in fuel consumption. This version offers an NEDC figure of 6.8 l/100 km (35 mpg US), a 24% improvement compared to the previous ML 350 CDI 4MATIC model.

The V6 develops 190 kW (258 hp) and torque of 620 N·m (457 lb-ft).While delivering performance on a par with the older ML 450 CDI 4MATIC with V8 diesel engine, the new unit offers 36% lower fuel consumption.

With AdBlue emission control technology, both diesel models meet the EU6 standard slated for introduction in 2014.

BlueDIRECT gasoline unit. The ML 350 4MATIC BlueEFFICIENCY gasoline-engine model features the technology of the new generation of Mercedes V engines. At the heart of the BlueDIRECT technology package lies the enhanced third-generation spray-guided direct gasoline engine with piezo injectors. In combination with multi-spark ignition, this technology offers further possibilities for fuel savings.

The V6 engine in the ML 350 4MATIC BlueEFFICIENCY utilizes a new stratified combustion process with a considerably extended characteristic map and fuel-efficient lean-burn technology (“homogeneous stratified mode” or HOS). HOS is a combination of homogeneous lean-burn and classic stratified combustion. The first injection is sprayed into the intake stroke, forming a homogeneous basic mixture. Actual stratified injection takes place during the compression stroke before ignition, and is a single or double injection depending on the characteristic map.

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 rapidly 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.

Controlling this rapid multi-spark ignition enables both the time lapse before the next spark and the combustion duration for the relevant operating point to be optimally adjusted. This provides scope for optimizing the center of combustion and improving residual gas compatibility, especially during stratified charge operation.

The 3.5-liter V6 unit has been designed as a naturally aspirated engine. As a major distinction from the preceding engine in the ML 350 4MATIC, the V-angle between the cylinder banks has been reduced from 90 degrees to 60 degrees. This has enabled the balancer shaft compensating primary vibrations to be omitted.

The design highlights of the 3.5-liter V6 include a completely new air intake and exhaust system in conjunction with a variable resonance intake manifold and optimized inflow and outflow. With the same displacement, the output compared with the previous 200 kW (272 hp) model is increased by 12.5% to 225 kW (306 hp), while maximum torque has increased by 5.7% to 370 N·m (273 lb-ft) and now is available over a broader engine speed range from 3500 to 5250 rpm.

In parallel with this increase in power, Mercedes engineers have reduced fuel consumption (NEDC combined) some 25% compared to the predecessor model.

The re-engineered 7G-TRONIC PLUS boasts an integrated ECO start stop function, lower converter slip and optimized efficiency. A central role is played by the new torsion damper, which eliminates torsional eccentricities and vibrations in the transmission even more effectively. Click to enlarge.

BlueEFFICIENCY. The engines’s fuel economy is supported by a package of BlueEFFICIENCY measures. The re-engineered 7G-TRONIC PLUS, standard on all M-Class models, has an integrated ECO start/stop function, lower converter slip and optimized efficiency. A central role is played by the new torsion damper, which eliminates torsional eccentricities and vibrations in the transmission even more effectively. The lower the rpm and the lower the number of cylinders, the more severe these can be. This results in a conflict of aims between comfort and fuel-efficient operation.

Mercedes-Benz developers resolved this by using a twin-turbine damper, which is also fitted with a centrifugal pendulum on the diesel models. Depending on the rpm, this moves the center of mass and allows comfortable operation even in the most economical operating range. Furthermore, the optimized damping allows a marked reduction in the slip of the torque converter lockup clutch even under low loads, which also contributes to fuel savings. In addition, the optimized damping of rotational irregularities and vibrations in the transmission allows an even faster response to driver commands via the accelerator pedal. Friction-optimized bearings and new transmission oil thermal management also help reduce fuel consumption.

The optimized belt drive system with decoupler, together with intelligent, on-demand control of all ancillary components and pumps, also helps to reduce the energy requirements of the new M-Class. The oil and water pumps in the engine, as well as the fuel pump in the rear section of the vehicle, are only activated according to actual need. The same control logic is used in the THERMATIC and THERMOTRONIC air conditioning systems. In these, the coolant compressor only runs when necessary.

An internal heat exchanger and the sophisticated sensor system including a demisting sensor on the front windscreen ensure optimum efficiency of the air conditioning systems in the interior. A key factor in the diesel engines is also the optimization that has been undertaken of the flow and counterpressure in the exhaust system with its SCR emission control technology.

A consistent use of lightweight construction techniques has enabled the development engineers to keep the weight of the new M-Class on a par with that of its predecessor, despite more equipment. The links on the front and rear axles, for example, along with the bonnet and wings, are made out of light and yet very strong aluminum alloys, while the cross member for the instrument panel is made of magnesium.

Aerodynamics. The most aerodynamic SUV in its class With a Cd figure of 0.32, the new M-Class (ML 250 BlueTEC) sets a new best figure for this vehicle class (total aerodynamic drag Cd x A = 0.92, predecessor 0.94). Simulations undertaken with the digital prototype, along with final touches added in the wind tunnel, optimize flow of air around the vehicle. The key factor determining the low wind resistance is the aerodynamic efficiency of the basic bodyshell, including the optimized design of the front bumper with its integrated spoiler, of the A pillars and of the roof spoiler, plus numerous other detailed improvements. These include:

• Sealing around the radiator section with adjustable fan shutter
• Sealed joints between the bonnet and the headlamps
• Front wheel spoilers
• Air outlets in the front wheel well liners
• Redesigned exterior mirror housings
• Optimized roof spoiler
• Side spoilers on the rear window (ML 250 BlueTEC 4MATIC)
• Underfloor and engine compartment paneling
• Aerodynamically optimized light-alloy wheels for the diesel models

Energy-transparent vehicle development tool. The “energy-transparent vehicle” development tool, created in-house by Mercedes-Benz, was piloted as part of the M-Class development process. Mercedes-Benz says that it will exploit the opportunities presented by this method, which can detect the possibilities for optimization in even the most minute component, on all new model series in the future.

An exacting examination of the flow of energy throughout the vehicle (tank to wheel) helps the development engineers to optimize every single assembly that has an impact on fuel consumption, right down to individual components, such as wheel bearings.

The idea for the energy-transparent vehicle stemmed from the failure in the past to verify or demonstrate clearly the many factors affecting consumption and the interaction between fuel-saving measures. Using the energy-transparent vehicle tool, the engineers can now detect detailed potential optimization measures by breaking down energy flows into cause and effect and analyzing energy interactions within the entire vehicle.

The process draws on complex, highly precise metrology which records some 300 energy-relevant measurement points with a sampling rate of up to 1,000 measured values per second. Every minute some 2.4 million measured values are generated, which can subsequently be analyzed to reliably pinpoint optimization potential. The process is complemented by energy simulation models which are validated by means of the measured variables. This enables the energy efficiency of individual major assemblies and components as well as the entire vehicle to be analyzed and quantified.

Once the specialists have identified a vehicle component with energy shortcomings, they team up with the relevant specialist departments to devise solutions. This cooperation focuses on design, or the properties of the materials used in individual vehicle components such as wheel or axle bearings. In addition, modified control strategies can also produce the desired outcome.

Daimler says that its energy-transparent vehicle process enables the development engineers to highlight and leverage optimization potential both for cars with conventional internal combustion engines as well as hybrid, electric or fuel-cell drives.

In the future, this process may even give rise to a generally applicable development tool for all machines and help boost energy efficiency across the board. A wide range of applications are conceivable. Whether in industry for power stations, (wind) generators, pumps or conveyor systems, in the home for refrigerators, washing machines, dryers and lawnmowers, or for transportation applications involving ships, trains or planes—the optimization potential of disparate technologies to save energy could be analyzed in detail with the consistent usage of this technique and implementation recommendations made.