Third-gen Actros gets automated manual

  • 24-Apr-2008 04:15 EDT
Actros1.jpg
The third-generation Mercedes-Benz Actros features a higher-pressure air system speeding up parking-brake-release times, a revised steering system, and two-stage coolant pump.

Mercedes-Benz has launched the third generation of its Actros European heavy-truck range, featuring a series of changes while retaining the same basic cab and V6 and V8 powertrain options. The most significant change is the adoption of the PowerShift 2 twelve-speed automated manual transmission (AMT) as standard equipment. Mercedes claims to be the first truck manufacturer to standardize with a twelve-speed automated transmission. This gearbox is based on the same AMT available as an option on the Actros since 2006, but incorporating several modifications.

Among these is the inclusion of tilt sensors and revised gear-change software. The tilt sensors measure the incline of the road surface continuously and the transmission ECU compares the data with that from the accelerator-pedal-position and vehicle-speed sensors to provide the best gear-change strategy for driving conditions.

Drivers can also make manual changes by using the shift lever if they wish. PowerShift 2 does not provide a selectable “manual” mode. The driver simply makes a manual shift and the system will default to automatic if no further manual changes are made.

Modes from the original PowerShift are retained. These include “power” mode, when maximum power is needed; “eco-roll” mode for normal driving conditions; “maneuvering” mode for maneuvering, coupling, and uncoupling trailers; and “rocking” mode to help gain traction on slippery surfaces. Maneuvering mode has been developed to include a new torque buildup and reduction process. Mercedes claims that maneuvering on ramps, in confined spaces, or at gated entrances is now better controlled.

Smoother, faster gear changes are among the claims that Mercedes is making for the transmission, as well as near elimination of vibration in the powertrain and reductions in cab pitch and roll during gearshifts. The PowerShift 2 transmission features direct-drive top gear ratios, compared with the previous overdrive PowerShift transmission. The only exception is for trucks with a 6x4 double drive layout, which retain overdrive gearboxes.

Other new Actros features include a battery status indicator, which will be fitted as standard from the end of 2008. Included in the instrument cluster, the bar chart display shows the state of charge and the expected lifetime of the battery. Sensors continuously monitor voltage, current, and ambient temperature to produce an estimate of battery life.

Another standard fitting is what Mercedes terms an electronic air processing unit (E-APU). This effectively applies modern technology to the compressed air system on board the truck, which operates the brakes and supplies power assistance to the clutch. Raising the air pressure in the system has enabled the elimination of the air reservoir in the spring-brake circuit used to release the trailer parking brakes, reducing weight by about 20 kg (44 lb). Mercedes also claims that it reduces spring brake-release times by up to 20%. The engine-driven air compressor, which recharges the system reservoirs with compressed air, will only operate when it can draw the least power, notably in downhill running and deceleration, when the compressor is least likely to make fuel-consumption demands.

A two-stage coolant pump will be introduced from 2009, fitted initially to the 320-kW (430-hp) engine. Fitted with an electromagnetic clutch sourced from German manufacturer Linnig, it will run at a lower operating speed under partial load, but feeds direct drive and therefore maximum operating speed to the pump under full load. Mercedes claims a reduction in fuel consumption of 0.7% for the two-stage water pump and a combined savings of 1% when also considering the E-APU.

Modifications to the steering for air-suspended tractor units are aimed at providing more steering “feel.” These Actros models are equipped with a smaller-diameter torsion bar, modified control arms, revised hydraulic valve opening, and a reduced steering ratio.

Subtle exterior changes distinguish the latest Actros model from its predecessor. Mercedes has borrowed from the limited-edition Black Edition for the new door mirrors and chrome headlamp surrounds, while the larger front grille and, inside, the new instrument cluster are said to be inspired by its SpaceMaxx concept truck. At night, the Mercedes three-pointed star on the grille is backlit with LEDs. This badge sits in the center of the new front lifting panel, which features fewer, redesigned louvers than before. Above the windscreen is a new three-piece sun visor with winged outer sections. Bi-xenon headlamps are offered for the first time with the Actros, as are the optional light-sensing headlamps and rain-sensing wipers.

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