Test Drive: Mercedes-Benz Actros Rigid

Mercedes-Benz introduced the new generation Actros prime movers to the European market in 2013. Three years later, the Australian trucking community could hardly wait to get its hands on the new generation when it was finally introduced locally in late 2016. The initial launch unveiled the prime mover range, with the rigid range following some months later at the Brisbane Truck Show this past May.

Both the rigid and the prime movers underwent a comprehensive Australian testing program, which involved more than 35 customers, 20 trucks and in excess of 1.8 million kilometres. Though the extensive assessment regime kept the local transport industry waiting eagerly, the German truck manufacturer said the wait was necessary to get the new generation ‘just right’.

Having already driven the pre-series 2658LS in a B-double set up last September, this month Prime Mover took a rigid model for a test drive to see if it could measure up to its bigger brother. Straight away, it seems so – the Actros rigid models feature many of the components from the suite of new technologies found in the prime movers. This includes Euro 6 emission ratings, fuel economy savings, reduced AdBlue consumption, advanced safety technology and a focus on interior refinement and driver comfort. 
The new rigid model line-up runs from a 12-tonne city distribution unit through to a 32-tonne 8×4 model that can be used for palletised freight, tilt tray equipment haulage or waste and hooklift applications.

New engine families have been introduced to provide the power. Depending on the model, the eight-litre can be fitted with one or two turbochargers using asymmetrical turbo technology and high-pressure fuel injection. The 11-litre engine uses a single asymmetrical turbocharger and X-Pulse variable high-pressure injection combined with a higher static compression ratio to deliver higher torque at lower engine revs. All of the engines have high torque uptake from idle, and need just a gentle application of the accelerator to start off on all but the steepest of inclines.

Instead of forged or cast aluminium pistons, all of the new engines use one-piece steel pistons attached to reinforced connecting rods, and have a more rigid crankcase than the engines they replace. The turbo has fixed turbine geometry and varies the intake flow by using a simple valve, reducing parts compared to a variable geometry turbocharger. 

The eight-litre engine is available with either 299hp or 354hp, while the 11-litre unit is available with ratings of 394hp, 428hp or 455hp. The engines incorporate a powerful new engine brake with up to 340kW of power, and an optional water retarder can increase the available braking force to a total of 750kW.  

While the eight- and 11-litre engines will cover most applications, customers are also able to select the OM 471 13-litre and OM 473 16-litre engines for specific rigid models. The Euro 6 range uses Selective Catalytic Reduction with AdBlue fluid, Exhaust Gas Recirculation and a Diesel Particulate Filter to meet stricter emissions requirements.
In line with most other OEMs, Mercedes-Benz has invested heavily in transmission technology. The fully-automated PowerShift 3 transmissions in either eight or 12-speed configurations are standard across the rigid range. This latest generation changes gears 20 per cent faster than the previous units, and has a new creeper gear function for low speed work. The crawl function also allows the truck to start easing forward when the transmission is in Drive and neither the brake nor accelerator pedals are depressed.
The transmission’s control electronics actually take into account what weight is on the vehicle after an initial start and stop. The next time the truck comes to a complete stop, the driver can remove their foot off the brake pedal and the truck will start to creep away slowly. This initial momentum makes the transition from stationary to movement very smooth, with advantages on driveline wear and fuel efficiency. On our test we found it works particularly well in reverse gear. The automated clutch release system has been changed so that it pushes rather than pulls, which the engineers claim further assists in smoother starts.

Like the prime movers, the new rigids’ transmissions have the ‘EcoRoll’ function which saves fuel by automatically disengaging the drivetrain in overrun mode in certain circumstances, including when the transmission is in full automatic mode and is travelling in excess of 55km/h. It returns to normal operation if the accelerator, brake pedal or engine brake is applied.

When it’s operating, a large letter ‘E’ is displayed on the screen at the centre of the dash. It’s remarkable just how far a truck can coast with no power from the engine. This 21st century version of ‘angel gear’ incorporates fail-safe technology and the default condition re-engages the driveline. First time drivers need to remember to have the engine brake in the ‘off’ position for the EcoRoll to be activated if the other parameters are met.

The gear lever control is mounted on the right-hand stalk, which doubles as the engine brake control function. Gear selection is initiated by simply twisting to the forward or reverse positions. The driver can manually override the automation by paddling the lever up or down, although the only time we did this during our test sessions was to downshift an extra gear or two in order to increase the effect of the engine brake on descents when the engine was operating at higher revs.
Mercedes-Benz has upgraded the engine braking across the range, with 300kW for the eight-litre and 340kW for the 11-litre unit. The engine brake also is activated automatically when the service brakes are engaged.

Three engine cylinders are used in phase one, six-cylinders are used in phase two, while six-cylinders, the EGR valve and the turbo wastegate are used in phase three for optimum braking power. Engine brake noise could not be called obtrusive inside the cab, and is almost negligible from the outside. An optional water retarder offering maximum braking force of up to 750kW is available.

By setting the speed limiter function when going downhill the truck progressively brings on the engine brake through its three stages to help maintain the selected road speed. Loaded to around 80 per cent of Gross Vehicle Mass (GVM), we set the speed limiter to 40km/h at the top of the Toowoomba range and did not have to touch the brake pedal once throughout the descent. This function does not involve activating the service brakes, which must still be applied by the driver if required.

The service brakes on the new generation rigid models feature a full Electronic Braking System with a back-up pneumatic system, as well as anti-locking brakes. Key models also incorporate Stability Control Assist, Hill Hold Assist and Traction Control. Models 18 tonnes and above are available with optional advanced safety systems including Active Brake Assist 4, which automatically performs emergency braking for most obstacles and can now initiate partial braking for pedestrians. When the vehicle brakes heavily at speeds above 50km/h, fast flashing hazard taillights – in addition to the brake lights – come on to warn other road users.

Other features of the optional Safety Pack include Lane Keeping Assist, Proximity Control Assist and Attention Assist. Proximity Control Assist helps the driver maintain a pre-determined distance from the vehicle in front. It is now effective from standstill and includes the ability to come to a complete stop and start again, as long as the truck is not stopped for more than two seconds. In that event, the driver needs only to tap the accelerator, and the system will engage again. Active Brake Assist 4 has the ability to perform emergency braking when it senses a road hazard. It now has the ability to perform full emergency braking for stationary objects and is also active from standstill. It can even automatically begin partial braking when it detects pedestrians in front. 
Attention Assist monitors the driver’s attentiveness based on steering behaviour, lane keeping and driver activity. It activates Lane Keeping Assist as a first warning (even if that system is deactivated) and issues another warning after 15 minutes if the inattentiveness worsens.

As with its latest prime movers, Mercedes-Benz has developed new cabs and chassis for the rigid range, delivering better stability and roadholding as well as improved comfort. The new driver-focused interiors deliver a big improvement in refinement levels, with controls located well within reach of the driver. This includes multiple controls mounted on the steering wheel. Customers can also option up the cabins with interior style packs, and are able to choose the wood-look/velour ‘Home Line’ treatment or the metal-look chrome ‘Style Line’ treatment.  

The reinforced cab exceeds the tough Swedish cab strength test standard, as well as ECE R29, while a driver’s airbag is standard on all models. Access steps are deep, and the grab handles are solid. The steering wheel tilts out of the way, and the driver’s seat has fine pneumatic adjustments that will defer fatigue during extended driving shifts.
The rigid models of the new generation Actros certainly hold their own against the prime movers, giving Mercedes-Benz a bit of backing to making the Australian trucking community wait for the launch. The next move from the German company will see the latest models of the construction and all-wheel-drive rigid trucks launched – and with the rigids living up to the example set by the prime movers, expectations are high.

Fast Fact
Mercedes-Benz has introduced its new Australian developed telematics system for its trucks, which uses the Telstra 3G network. The onboard memory can store up to three months of data when not in range, and has a battery backup and a secure encrypted Cloud portal. The Android and iOS app allows the driver to conduct pre-inspections and upload comments and photos that are immediately transmitted to the fleet manager.



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