The new Mercedes-Benz CLA-Class: Chassis, Suspension and 4MATIC AWD System

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XI. The chassis and suspension: In the service of dynamism

The chassis of the CLA features a McPherson front axle and an independent multilink rear suspension, featuring three control arms and one trailing arm per wheel. This means that longitudinal and lateral dynamics are virtually independent of one another. Direct Steer is standard for all versions.

A CLA-specific feature is the elastic decoupling of the rear axle carrier, which benefits ride comfort. The measures include rubber bearings vulcanised onto the anti-roll bar and the elastomer coating of the coil springs, which produces an effective noise de-coupling between the vehicle body and rear axle.

The connection of the damper to the vehicle body is via an aluminium bearing with a soft universal joint that contributes to reducing friction in the damper, and consequently helps responsiveness. Wheel carriers and spring links are made of aluminium, in order to reduce the unsprung masses.
Two suspension set-ups are available: the comfort suspension and the optional sports suspension for sporty yet comfortable handling. The latter entails lowering of the body by 15 mm (front) and 10 mm (rear).

Irrespective of the selected chassis, all CLA variants come with the Direct Steer system. This electromechanical power steering offers improved feedback to the driver in comparison to conventional systems and makes an important contribution towards overall efficiency, as the steering assist function only requires energy when the steering wheel is actually turned. Additionally it enables various steering assistance functions which are activated by the ESP® control unit. These include countersteering in case of oversteering, corrective steering when braking on road surfaces offering different levels of grip (split-friction braking), mitigation of the extent to which the front-wheel drive influences the steering and compensation for crosswind and road gradients.

With all engine variants, the CLA-Class comes with disc brakes on all wheels. The callipers on the rear axle and the brake boosters are made of aluminium. A particularly convenient feature is the HOLD function, which is familiar from the larger model series: when stopping, for example at traffic lights, the driver merely has to press the brake pedal slightly more firmly and the brake will remain engaged until they move off again. The brake is released automatically when the driver steps on the accelerator. On versions with manual transmission, the Hill Hold function automatically prevents the vehicle from rolling back unintentionally when moving off on a slope.

The CLA-Class is equipped with an electric parking brake, which operates by means of actuator motors acting on the callipers of the rear axle. The parking brake is activated via a button under the light switch on the left of the dashboard. This creates additional space in the centre console, as the handbrake lever is no longer required. When the button is pressed at speeds of over four km/h, the parking brake acts as an emergency brake, activating all four wheel brakes via the ESP®'s hydraulic unit.

In conjunction with the 7G-DCT automatic transmission, the parking brake offers a particularly convenient mode of functioning: when the driver accelerates sufficiently after fastening their seat belt, the parking brake is released automatically.

XII. The 4MATIC all-wheel drive system: Extraordinary agility and high traction reserves

The CLA from Mercedes-Benz is available with a new variant of the 4MATIC permanent all-wheel drive system featuring fully variable torque distribution. Similar to the other 4MATIC versions, this new development boasts high tractive power reserves and outstanding agility combined with superlative driving safety and energy efficiency.

The most innovative components of the new 4MATIC include the power take-off to the rear axle which is integrated in the 7G-DCT automated dual clutch transmission and the rear-axle gear unit with integrated, electrohydraulically controlled multi-disc clutch. This set-up enables fully variable distribution of the drive torque between front and rear axle. Additional benefits of this design are a lower system weight than is available from the competition and high efficiency. Similar to the front-wheel drive versions, all 4MATIC models also boast good energy efficiency.

The 4MATIC all-wheel drive system is a completely new development and was specifically adjusted to the requirements of the new front-wheel drive models.

Integrated power take-off unit (PTU) channels power to the rear axle

The new 4MATIC is combined with the 7G-DCT seven-speed automated dual clutch transmission. The power flow to the rear powertrain is provided by a compact power take-off unit (PTU) which is fully integrated into the main transmission and is supplied with lubricant from the latter's oil circuit. This configuration gives rise to substantial weight advantages of up to 25 percent over competitor systems which branch off power by means of an add-on component with its own oil circuit. Together with the friction-minimised tapered roller bearings, the PTU achieves an excellent level of efficiency.

Completely new development with torque-on-demand rear axle

The electrohydraulically actuated multi-disc clutch integrated into the rear-axle gear unit is responsible for fully variable torque distribution. Fundamental operating principle: when the multi-disc clutch is open, the car is driven almost exclusively by the front axle. When the clutch is closed, the rear axle comes into play. However, the drive torque can be shifted in fully variable mode between front and rear axle according to the given situation (torque on demand).

The system pressure to activate the rear axle is supplied in milliseconds by the rotor pump which is integrated into the rear-axle gear unit. The pump is activated automatically as soon as only minimal speed differences arise between front and rear axles. Pressure control is performed by a proportioning valve under the control of the ESP®.

Motoring enjoyment thanks to intelligent control systems

The 4MATIC is activated according to the basic principle of "as often as necessary, as rarely as possible". This means that when the underlying conditions allow, the all-wheel drive models run almost exclusively in particularly economical front-wheel drive mode. As soon as the driving situation requires, drive torque is channelled to the rear axle as appropriate. The reverse process takes place just as quickly: as soon as additional drive torque is no longer necessary at the rear axle – e.g. in case of heavy braking manoeuvres with ABS intervention – the rear powertrain is deactivated and torque is reduced to zero.

In case of impending understeer or oversteer under load, the drive torque is first of all distributed such as to stabilise the vehicle. Only if these measures fail to have a stabilising effect do the control systems adapted to 4MATIC conditions, such as ESP® or 4ETS, intervene to keep the vehicle on course.

With this strategy, the developers have managed to combine two key requirements defined in the performance specifications: optimum energy efficiency coupled with maximum driving dynamics and driving safety.

Individual: transmission modes to suit personal driving styles

The torque distribution ratio is also dependent on the activated shift program of the 7G-DCT dual clutch transmission. The ECO mode results in torque distribution of a conservative nature. Less torque is channelled to the rear axle, resulting in gentler handling and supporting an economical driving style at lower revs. In SPORT or MANUAL mode, the activation times are shortened and more torque is distributed to the rear axle in the interests of a dynamic, sporty driving style.

Credits: Daimler AG

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The new Mercedes-Benz E 63 AMG: Chassis, suspension and brake system

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Chassis, suspension and brake system: High-tech for maximum performance

High grip and exceptional agility are the defining characteristics of the AMG RIDE CONTROL sports suspension. The E 63 AMG features a steel suspension system at the front axle and a full air suspension system at the rear axle. This solution guarantees sensitive response by the front suspension, while automatic level control ensures that the vehicle height at the rear remains constant at all times – irrespective of the load. The electronically controlled damping system comes as standard. The three-link front suspension on the S-Model and the 4MATIC variants has been further optimised for superlative driving dynamics. Newly developed aluminium axle components result in markedly enhanced grip and agility during fast cornering, combined with a high degree of neutrality. The S-Model features elastokinematics which are geared even more emphatically to high cornering performance. This results in more direct feedback, further improved grip and maximum neutrality at the critical limits.

In the interests of enhanced lateral dynamics all E 63 AMG variants – rear-wheel and all-wheel-drive – are provided with independent front suspension geometry. In contrast to the other E-Class models, the three-link suspension on the E 63 AMG features a 48 mm wider track, independent wheel carriers, steering knuckles, wishbones, tension strut bearings and head bearings, plus increased negative camber. The combined effect of these measures is markedly greater stability at high cornering speeds and improved road feel. The AMG-specific rear axle also incorporates independent components: specific tie rods, tension struts and compressive members and the substantially more rigid carrier of the subframe on which the rear axle is mounted lead to higher cornering dynamics.

Selection of the suspension set-up on the AMG DRIVE UNIT

The AMG RIDE CONTROL sports suspension with electronically controlled damping system enables the driver to choose his personal suspension set-up in accordance with his individual driving needs. The button marked with a bumper is located on the AMG DRIVE UNIT to the left of the E-SELECT lever. The driver simply presses this button to switch the electronics from "Comfort" to "Sport" or "Sport plus". The currently active mode is indicated both on the lamp of the suspension button and in the AMG main menu.

"Comfort" delivers a sensitive response with soft damping characteristics, while the shock absorber response is an average 40 percent firmer in "Sport". "Sport plus" is ideal for challenging laps on a racetrack: in addition to the higher damping force, this mode comes with specific control algorithms that have been tailor-made for a decidedly sporty driving style on level road surfaces. The system also carries out instantaneous automatic adjustment of the damping characteristics and reduces the body roll angle according to the given driving situation, speed and vehicle load. This provides the driver with a means of infinitely variable adjustment between maximum agility and optimum ride comfort. For the E 63 AMG Saloon with rear-wheel drive an AMG RIDE CONTROL performance suspension is optionally available with more rigid spring/damper tuning.

Eleven sensors for electronic damper control

The electronic damper control utilises four sensors to permanently monitor the drive and brake torque along with steering angle and lateral acceleration. Four position sensors are also used to determine the ride height and to ascertain the direction of motion. Three acceleration sensors help identify the absolute body roll. Powerful control electronics that interact constantly with the engine and transmission control units instantly adjust the forces at the four shock absorbers.

Direct electromechanical AMG speed-sensitive steering

The electromechanical AMG speed-sensitive steering enables perfect control of the vehicle: the steering ratio is 20 percent more direct than on the other E-Class models (14 : 1), providing for extremely agile handling in bends in conjunction with the variable servo assistance geared to the given suspension mode. In suspension mode "C" the AMG speed-sensitive steering operates at a higher level of power assistance, with an emphasis on comfort. In "S" and "S+" modes the driver is provided with a lesser degree of steering assistance, which tends to result in improved road feel. The fixed characteristics programmed for the power assistance provide for enhanced feedback and steering precision.

In the electromechanical AMG speed-sensitive steering system the steering gear and the supporting servo-motor form a single compact unit and are mounted as previously on an extremely rigid and low-weight integral support frame made of high-strength steel which is positioned in front of the wheel's centre line. The high-performance control unit processes a variety of parameters captured by the sensors – including vehicle speed, steering angle, steering angle speed, lateral acceleration and also understeer/oversteer characteristics – and in a split second calculates the forces which the driver needs to input into the steering in different driving situations – from parking to high-speed motorway driving. Active damping enhances the feeling of safety when driving straight ahead at high speed.

Specific AMG light-allow wheels for each model variant

The E 63 AMG rolls off the assembly line with model-specific AMG light-alloy wheels. 10-spoke AMG light-alloy wheels painted in titanium grey with high-sheen finish come as standard, with front tyres in size 255/40 R 18 on 9.0 x 18 wheels and rear tyres in 285/35 R 18 on 9.5 x 18 wheels. The tyre/wheel combinations on all 4MATIC variants and the E 63 AMG S-Model are one size up: 255/35 R 19 (front) and 285/30 R 19 (rear) on AMG light-alloy wheels in 9.0 x 19 and 9.5 x 19 fit snugly in the wheel arches. Only the high-performance S-Model features exclusive 10-spoke light-alloy wheels painted in matt titanium grey with a high-sheen rim flange. A special option available from the AMG Performance Studio is particularly lightweight forged 5-spoke AMG light-alloy wheels with covered wheel bolts, painted in titanium grey with a high-sheen finish. Sizes: 9.0 x 19 with 255/35 R 19 tyres (front) and 9.5 x 19 with 285/30 R 19 tyres (rear).

A choice of two AMG high-performance composite braking systems
It goes without saying that all AMG high-performance automobiles guarantee spontaneous and fading-resistant deceleration and the shortest possible stopping distances. The front and rear axles on the E 63 AMG sport ventilated and perforated brake disks in 360 millimetre format. In view of the special stress to which they are exposed, the front discs feature composite technology that has been tried and tested in motor racing to help offset temperature peaks more effectively. The models rated at 410 kW (557 hp) are identifiable by brake callipers in silver painted finish with white AMG lettering featuring six-piston technology at the front and four-piston technology at the rear. The S-Model features red painted brake callipers.

AMG ceramic composite high-performance brakes are exclusively available as an option for the E 63 AMG S 4MATIC and are recognisable thanks to the "AMG Carbon Ceramic" logo on the brake callipers sporting the model-specific paint finish. Thanks to the special materials and production technology used to manufacture the discs from carbon-fibre-reinforced ceramic in a vacuum at 1700 degrees Celsius, the ceramic discs are much harder. This not only increases the service life many times over compared with a grey cast iron disc, but also enhances their resistance to extreme loads and heat. This results in extremely short stopping distances, an exact pressure point and much higher fade resistance even under extreme operating conditions. The larger ceramic discs – front: 402 x 39 millimetres; rear: 360 x 32 millimetres – feature a composite design all round and are connected with a floating radial mount to an aluminium bowl.

Compared with the conventional composite brake discs, the ceramic brake discs are around 40 percent lighter. The further reduction in unsprung masses not only boosts driving dynamics and agility but also improves steering response as well as ride comfort and contact characteristics. Six-piston fixed callipers are fitted at the front with a brake lining surface of 2 x 154 cm2; four-piston fixed callipers with a brake lining surface of 2 x 73 cm2 are used at the rear.

Overview of brake data:

~ Official photos and details courtesy of Mercedes-AMG GmbH ~

Copyright © 2013, mercedesgla. All rights reserved.

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The new Mercedes-Benz E-Class 2013: Engines, drive system, chassis and suspension

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I. Engine and drive system: Superior performance, economical consumption

"E" for "Efficiency": this is the well-proven success formula with which the E-Class is raising the bar and showing how the intelligent interaction between technical innovations throughout the drive train can reduce fuel consumption. 

The E-Class Saloon and Estate are available with a broad range of powerful and efficient petrol and diesel engines with optimised drive train. All are fitted with the ECO start/stop system.

The petrol engines: powerful, fast and clean

The BlueDIRECT petrol engines from Mercedes-Benz, which to date have comprised the familiar V6 and V8 engines, are characterised by the latest technology. A new addition is a six-cylinder engine which is being offered for the first time in the E-Class not only as a naturally aspirated engine, but also as the E 400 with a displacement reduced to three litres but also with a biturbo drive as a result. With its output potential and enormously high torque at low engine speeds, this six-cylinder model sets new standards in its segment. It produces 20 kW more compared with the E 350. Its torque has increased by 110 Nm and remains available in the engine speed range of 1600 to 4000 rpm. On top of this, the new, efficient six-cylinder engine also fulfils the EU6 emissions standard. The E 500 is making a name for itself as the most economical model in the V8 segment.

Another new addition to the BlueDIRECT petrol engine family is a four-cylinder petrol engine. With a combined fuel consumption in the E 250 of 5.8 litres (135 g CO2 per km) and producing 155 kW (211 hp) from a displacement of just two litres, as well as 350 Nm of torque across a wide range of 1200 to 4000 rpm, it sets new standards in the four-cylinder segment. Providing acceleration from 0 to 100 km/h in 7.4 s (Estate 7.8 s), it provides the E-Class with spirited performance.

Lean burn process with stratified charge operation

Depending on the operating conditions, the new four-cylinder engine features stratified charge or homogenous operation. With stratified charge operation, the high-compression engine runs with significant excess air. To achieve this, the fuel is only sprayed into the air, which has already been compressed by the pistons, during the compression phase. A precisely controlled electronic multiple injection system helps to ensure that a fuel/air cloud builds up in a limited area around the spark plug, precisely at the time of ignition. This lights the ignitable fuel/air mixture around the spark plug, whereas only a very lean mixture with high excess air is to be found in the remainder of the combustion chamber. This enables extremely efficient combustion.

A prerequisite for stratified charge operation is fast piezo injectors. They spray the fuel into the combustion chambers several times in succession per power stroke, and as such enable specific control of the mixture formation and thus the flammability.

The new four-cylinder petrol engine from Mercedes-Benz also sees the world's first use of this stratified lean burn process in combination with exhaust-gas turbocharging and external high-pressure exhaust gas recirculation. As a result the E 250 achieves a combined optimum consumption figure of 5.8 litres per 100 km (corresponding to 135 g of CO2/km), and is therefore the only vehicle in this segment to achieve efficiency class A. In addition, the new BlueDIRECT four-cylinder petrol engines already meet the EU6 emissions standard which will apply from 2015. The new four-cylinder engine also meets the EU6 emissions standard in the guise of the homogenous variant for countries with different fuel qualities.

Advanced technology makes engines more efficient

The BlueDIRECT four-cylinder petrol engines in the E-Class combine spontaneous response and exemplary power delivery with high efficiency and best-in-class emission performance. To achieve this goal, Mercedes-Benz transferred the BlueDIRECT technology from the V6 and V8 engines into the four-cylinder models. Direct petrol injection with spray-guided combustion, which Mercedes-Benz was the first car manufacturer to introduce in series production, has been developed further by the engineers into third-generation direct petrol injection with spray-guided combustion. The system pressure is now up to 200 bar and is variably optimised according to the engine's characteristic map. Completely newly developed piezo injectors allow up to five injections per power stroke for the best possible mixture formation.

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 quickly 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.

The rapid multi-spark ignition can be actuated to vary both the timing of the sparks and the combustion period to suit the relevant operating point. This provides scope for the best possible centre of combustion and improved residual gas compatibility. This in turn reduces fuel consumption. The result of this is excellent utilisation of the fuel with minimum emissions.

In conjunction with continuous adjustment of the intake and exhaust camshaft, the direct injection system also provides the essential basis for so-called scavenging. As a result of a partial overlap of the opening times of the intake and exhaust valve, part of the drawn-in cold fresh air conveys the hot exhaust gas contained in the cylinder into the exhaust manifold, thereby improving the filling level substantially in comparison with the conventional mode of operation. Due to the increased mass flow in the exhaust line, the turbocharger additionally responds considerably faster at low revs in particular, avoiding turbo lag.

A new thermal management system has also been developed: in a cold state, a switchable water pump with flow-optimised ball valve ensures that no coolant flows through the engine, providing for swift heating-up of the combustion chambers after starting up the engine. The thermostat is electronically controlled and the coolant temperatures are adjusted according to driving style and ambient conditions. The thermostat itself is also a flow-optimised ball valve. In the interest of high efficiency, the volumetric flow of the oil pump is also controlled as in the V engines.

All engine variants are designed for operation with E10 premium petrol and an octane number of 95 RON.

The petrol engines

In September 2013, the E 200 Natural Gas Drive with bivalent natural gas drive will complete the comprehensively updated range of drives for the E-Class. The 120 kW (163 hp) four-cylinder engine in this Saloon model can be run both on premium petrol and natural gas.

Powerful diesel engines in the best efficiency class

Some of the diesel models of the E-Class are available as BlueTEC models fitted with the established SCR (selective catalytic reduction) technology and as such meet the EU6 emissions standard.

The engine range is supplemented with the E 300 BlueTEC HYBRID. It combines the four-cylinder diesel engine (150 kW/204 hp) with an electric motor (20 kW/27 hp). The E 300 BlueTEC HYBRID consumes 4.1 l/100 km and produces CO2 emissions of 107 g/km. As such it occupies the leading position among the most economical models in the upper medium-size category.

The diesel engines

ECO start/stop function with direct-start

The ECO start/stop system included as standard in all models operates with the starter-supported ECO start/stop function. This means that when the engine is switched off, the attitude of the crankshaft is registered by a novel crankshaft sensor so that the engine control unit knows the positions of the individual cylinders. On restarting, it can then select the cylinder that is in the most suitable position for first ignition. After the starter has briefly turned over the engine, reliable injection, ignition and combustion are immediately possible in the ideally positioned cylinder.

Optimised drive train

Mercedes-Benz will also offer two transmissions for the E-Class in the future: a 6-speed manual transmission with high ease of shifting and short shift travel, and the 7G-TRONIC PLUS automatic transmission with DIRECT SELECT lever and DIRECT SELECT shift paddles. The features of the latest evolutionary stage of 7G-TRONIC PLUS include a new torque converter with reduced slip, an ECO shift programme with an improved ratio spread and an auxiliary oil pump to maintain the operating pressure during automatic stops. Low-friction components and low-viscosity fluid help to reduce the operating pressure.

A new feature is the short-term M mode. The benefit of this: if the driver has shifted up or down manually, after a set period of time the transmission independently switches back to automatic, fuel-efficient shift mode. This set period of time is lengthened in specific conditions (no accelerator pedal use, e.g. on downhill gradients, high lateral acceleration, e.g. when cornering, or if falling below a minimum speed when coming to a standstill), and return to automatic mode is prevented.

In short-term M mode as well as in "fixed" M Mode, the driver receives prospective gear change recommendations in the multifunction display of the instrument cluster, to enable an efficient driving style.

4MATIC all-wheel drive

Traction and driving stability can also be improved in the E-Class with the 4MATIC all-wheel drive system - particularly in difficult road conditions. As ever, the combination of the ESP® vehicle dynamics control system with the 4ETS electronic traction system makes regular differential locks superfluous. This saves weight and noticeably increases driving safety as well as ride comfort. The transfer case of the all-wheel drive is integrated into the main transmission.

The all-wheel drive models impress with:

- good traction characteristics, with a power distribution ratio on the front and rear axles of 45:55
- low fuel consumption due to the improved efficiency of the drive train
- additional weight of only 70 kg, compared with additional weight of up to 120 kg in the case of the competition
- unchanged bodyshell as well as unrestricted interior and luggage compartment space due to the compact design

The following engines are available with 4MATIC:

- E 250 CDI 4MATIC, 150 kW (204 hp), 500 Nm
- E 350 BlueTEC 4MATIC, 195 kW (265 hp), 620 Nm
- E 300 4MATIC, 185 kW (252 hp), 340 Nm
- E 400 4MATIC, 225 kW (306 hp), 370 Nm
- E 500 4MATIC, 300 kW (408 hp), 600 Nm

II. Chassis and suspension: The basis for superior handling

All of the models of the E-Class family will in future be fitted with an electromechanical Direct-Steer system as standard. This combines the speed-dependent power assistance of speed-sensitive steering with a variable ratio across the steering angle range. The power steering assistance provided by the rack and pinion steering gear is controlled on-demand and therefore contributes towards efficiency.

Advantages of the electromechanical Direct-Steer system:

- improved agility thanks to more direct steering response
- comfortable handling and high levels of steering comfort across all speed ranges
- considerable savings potential, since energy is only required when steering occurs
- enables the use of innovative assistance systems, such as Active Parking Assist

Four suspensions to choose from

For the E-Class, Mercedes-Benz is offering four refined suspension configurations:

- the standard model and ELEGANCE line are fitted with the DIRECT CONTROL suspension with selective damping system, configured for comfort
- the sportily configured DIRECT CONTROL suspension with selective damping system is positioned 15 mm lower and part of the AVANTGARDE line
- the DIRECT CONTROL lowered sports suspension is available in conjunction with the Exterior Sports package and AMG Sports package
- the AIRMATIC air suspension with electronically controlled damping system is fitted as standard on the V8 models. The Estate is fitted as a matter of course with rear-axle air suspension with integrated level control.

On the front axle, the established 3-link front suspension helps to ensure optimum driving dynamics. Both of the links (torque strut and cross strut) in the lower link plane determine the comfortable characteristics of the axle. The third link, the tie rod, forms part of the rack-and-pinion steering system.

At the rear is the familiar multi-link independent rear suspension, featuring a lightweight design. It provides good wheel control qualities for high levels of comfort and excellent driving dynamics.

All suspension variants feature impressive sensitivity and ride characteristics and help to ensure a high level of handling safety.

Excellent braking with ADAPTIVE BRAKE

The brake system in the E-Class is fitted with the ADAPTIVE BRAKE as standard. Depending on the engine variant, the following braking systems are used on the front axle with internally ventilated brake discs:

- 1-piston floating brake callipers with different sized brake discs for the 4-cylinder and V6 engine variants
- 4-piston floating brake callipers for the V8 engine variants

On the rear axle, the E-Class is braked by 1-piston floating brake callipers with different sized brake discs. In the case of the V6 and V8 engine variants, the brake discs are internally ventilated.

All of the engines have a foot-operated parking brake with integrated, automatic cable adjustment. The force applied by the driver is distributed to two additional drum brakes on the rear axle via the brake cable in the centre tunnel. Automatic adjustment helps to reduce the servicing costs.

Credits: Daimler AG

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