City slicker

City slicker

The UK’s DAVID WILCOX got up-close and personal with the new, European, Euro-6 Mercedes-Benz Atego range – and is quite intent in reminding us what we’re missing in South Africa …

One of the key features of Mercedes-Benz’s Euro-6 range is its new modular cab system, a core design with a range of width, length, floor-height and roof-height options that create the right cab for the job. But the baby of the family, the Euro-6 Atego, has been given the cold shoulder. Unlike Actros, Antos and Arocs, its cab is not part of the modular programme and is, essentially, the same shell as when it was born 16 years ago …

Cabs

At 2,3 m wide it is the same size as the Antos cab, and only 50 mm shorter. When sampling the new Atego in Frankfurt recently, I asked Sven Ennerst, head of truck engineering at Daimler, why Mercedes needs both. He said that although the two cabs are similar in size, the Atego’s sits lower on the chassis, making access easier, and the cost of engineering the smallest modular cab to fit the Atego outweighs the benefits. Instead, Atego gets refreshed frontal styling similar to the Antos, Actros and Arocs family look.

The four cab sizes are unchanged, but have new names: S ClassicSpace (short day cab), S ClassicSpace Extended (180 mm longer), L ClassicSpace (low-roof sleeper) and L BigSpace (high-roof sleeper).

The facia features new switchgear and instruments, similar to the Actros and features a central colour display for vehicle data and driving-style information. The pod for a manual gear lever now sprouts from the front dashboard, relegating the park-brake lever to the floor.

DAF, Volvo and Renault Trucks have also all done this in their lightweight Euro-6 models. The justification is that a cable-shift eliminates the vibration evident in an engine-mounted lever. The pod reduces the gap between it and the front of the engine tunnel to just 10 cm, impeding access across the cab. The PowerShift 3 automated gearbox (which will be put to the test later on) is controlled via a steering-column stalk, the park brake moving to the dashboard.

There are three cab trim levels: classic, standard and comfort. Confusingly, classic is the standard trim, and standard and comfort are options. Surely Mercedes could have come up with three names that avoid the conundrum of standard being an option … ?

New chassis

Mercedes has carried out work on the Atego’s chassis to eliminate some of the additional weight of the Euro-6 exhaust after-treatment equipment and the larger engines. For example, there are new lightweight, single-leaf springs.

Interior space benefits from a 2,3 m-wide cab.  On a like-for-like basis, Mercedes claims that a new four-cylinder Atego is about
60 kg heavier than the previous model; the six-cylinder has gained about 90 kg. Although that’s commendable, it still leaves Atego as one of the heavier 7,5-tonners; largely because its 2,3 m-wide cab is aimed at the core German 12-tonne market.

Mercedes prefers to measure itself against arch rival MAN, claiming a recent weighing exercise found the Euro-6 Atego to be 12 to 20 kg lighter than an equivalent 12-tonne, Euro-6 TGL.

Attention has also been given to ride, handling and steering, with revised front-axle suspension geometry, a new steering system and improved drive-axle suspension mounts. New cab suspension reduces roll and pitch. Electronic stability control (ESC) becomes mandatory in November, so is standard on the Atego.

Smaller Ategos (with a single cab step) run on 17,5-inch wheels, the larger ones (two steps) are on 19,5-inch wheels. The cross-over is at 12-tonne gross vehicle mass (GVM), where operators can choose either wheel size.

The 12-tonne model I drove had 19,5-inch wheels, but you can specify 17,5-inch rims for a lower deck height. In Europe, the smaller wheels are popular for urban multi-drop distribution as well as with operators undertaking long-distance work.

Engines

The more important changes for Atego are in its powertrain. The three Euro-5 engines have been replaced by two all-new, Euro-6 engines. The 5,1-litre OM 934 four-cylinder engine is available in four ratings; there are three ratings of the 7,7-litre OM 936 six-cylinder engine. Between them, these seven options span
112 kW (150 hp) to 224 kW (300 hp), powering an Atego range from 6,5- to 15-tonne GVM – at which point the Antos takes over.

The increase in swept volume contributes to more power and, particularly, torque. The new OM 934 goes up to 170 kW/900 Nm, meaning fewer operators may feel they need a six-cylinder engine at 12-tonne GVM (the key weight for Atego in Europe, if not elsewhere).

Both engines have four valves per cylinder, operated by twin overhead camshafts. The exhaust camshaft is adjustable to vary the valve timing: An electromagnet at one end of the shaft opens a hydraulic valve, rotating the shaft to open the valves a little earlier than usual. This reduces engine efficiency, forcing it to work harder and allowing more hot gas into the exhaust.

Conscious that Ategos often work on low-speed urban routes with cool exhausts, Mercedes uses this technique to raise exhaust temperature to regenerate the diesel particulate filter (DPF) by burning the trapped particulates, thus avoiding the extra injector to spray and burn additional fuel just ahead of the exhaust after-treatment system.

The engines use a combination of cooled exhaust gas recirculation (EGR) and selective catalytic reduction (SCR). The addition of EGR means the SCR system does less work than at Euro 5, halving AdBlue consumption to between two and 2,5 percent of fuel consumption.

Manual Shifter now moves to a  dash-mounted pod.Delphi’s common-rail fuel-injection system provides injection pressures up to 2 400 bar. The lower two ratings of the OM 934 have a fixed-geometry turbocharger; the two higher ratings have two-stage BorgWarner turbochargers. An asymmetric turbo, with exhaust flow split 50/50 between the turbine and the EGR cooler, is used on all three versions of the OM 936. The new engine’s B10 design life (the point to which 90 percent should run without major rebuild) is 750 000 km,
150 000 km up on the Euro 5.

A rarity at this weight is an integrated engine decompression brake as standard, which is more effective than the usual exhaust brake. Other technology taken from heavier trucks is the hill-hold function of the EBS disc-brakes, which is standard.

Transmissions

We have often wondered why ZF and Volvo have never constructed a business case to develop syncroless, six-speed versions of their brilliant automated 12-speed gearboxes. Their offerings (essentially manual boxes automated with external shifters and clutch release) marketed as AS-Tronic lite (or I-Sync, when it is in a Volvo) are not as impressive, and nor was Mercedes’s six-speed Telligent box, previously offered in Atego.

Now though, Mercedes is showing ZF and Volvo the way, introducing a six-speed version of its PowerShift 3 gearbox, joining the eight-, 12- and 16-speed versions available in heavier models. Like its brethren, it is an automated box, using speed-matching technology rather than synchromesh rings. It is far superior to Telligent.

The six-speeder is paired with the four-cylinder engine and the bottom rating
175 kW (235 hp) six-cylinder, while the two higher ratings of the six-pot are mated with the eight-speed PowerShift 3, as in the 18-tonne Antos. The alternatives are six- or nine-speed manuals.

Apart from the clear driver benefits, PowerShift delivers driveline protection and fuel economy by keeping the engine in the green band (1 200 to 1 700 r/min) nearly all the time. You also get the EcoRoll function as standard, so now even 7,5-tonners can waft along with the engine at idle, saving fuel, emissions and noise.

All considered, Mercedes claims Euro-6 Atego is up to five percent more fuel efficient than the Euro-5 models.

On the road

I got to drive the 7,5- and 12-tonne models. The 7,5-tonner was an 818 model, rated at 130 kW (174 hp)/750 Nm. It has 11 percent more torque than the 4,25-litre engine in Euro-5 818 and more mid-range power, which Mercedes uses to lengthen the gearing. With a 3,417:1 drive-axle ratio, engine-speed at 80 km/h in top is 1 440 r/min, about 200 r/min lower than a Euro-5 818 with the standard 3,636:1 ratio. It is also in the middle of the torque plateau (1 200 to 1 600 r/min), so there is flexibility for accelerating or decelerating without needing a gearshift.

If extra power raises concerns about inappropriate driving styles, the logical solution is the PowerShift 3 box. Programmed to keep the engine working in the high-torque, most fuel-efficient part of its speed range, it maintains sensible progress without exploiting the engine’s power. It made no questionable shift decisions during our drive, although it is easy to throw in a manual shift by moving the right-hand control stalk up or down, with no need to switch to full manual control.

What works best? Shifts from PowerShift 3 are smooth and the box is not as ponderous as the previous six-speed Telligent autobox, or ZF’s AS-Tronic lite. When pulling out of a junction there is a slight time delay, but you learn to press the accelerator a tad earlier. What is more striking is the lack of noise as it moves off, demonstrating how sparingly PowerShift rations the revs, protecting clutch and fuel bill.

At higher GVM ratings, the new Atego is refreshed and ready to lead its segment.Choosing the six-speed manual box may save a bit of outlay, but you miss the valuable benefit of PowerShift 3’s EcoRoll function; that disengages the driveline to save fuel on even the slightest downhill gradient. This contributes to Mercedes’s claimed five percent fuel saving. It worked well on our test, engaging and disengaging almost imperceptibly.

Another notable feature of the Atego is the proper decompression engine brake integrated as standard into the four- and six-cylinder (7,7-litre) engines. Operated via a chunky stalk on the right of the steering, this brake – two-stage on the four-cylinder, three-stage on the six – gives more retardation than the simple butterfly valve exhaust brake typically found at this weight. The fact that it is standard is also a big plus for the little Atego, increasing safety and cutting brake maintenance. Mercedes says its maintenance contract prices for the Atego are up to five percent cheaper than the previous model.

While the combined PowerShift and engine-brake control is good to use, we can’t say the same about the park-brake lever; its contrived shape makes it awkward to grasp. Things are a bit better with manual models.

This Euro-6, four-cylinder model is said to be about 60 kg heavier than a Euro-5 model. That suggests it is about 200 kg more than DAF’s Euro-6 LF 7,5-tonner. This is the price you pay for the Atego’s 2,3-m-wide cab rather than DAF’s 2,1-m cab. This example, with a box body, had a quoted tare weight of 5,5 tonnes, leaving just two tonnes of payload capacity. It is also worth bearing in mind that Atego chassis cab weights are unusual, as they include extras such as side guards, underrun and rear mudwings/spray suppression.

Atego’s cab sits more happily on a 12-tonner where there is usually a little more weight tolerance. We drove a 1221 model, with 155 kW (208 hp)/850 Nm, which seems like a versatile specification without being unduly generous for most operations at 12-tonne GVM.

Performance on a hilly cross-country route was adequate and there is also a 179 kW (228 hp)/900 Nm rating of the engine for more performance, suggesting that one would turn to the six-cylinder engine only if planning to cover huge distances or run a lightweight drawbar.

The gearing – 3,909:1 drive-axle ratio and six-speed PowerShift box with 0,73:1 overdrive top – means the engine is on its 1 200 to 1 600 r/min torque plateau from 66 to 90 km/h in top gear. In practice, with a light foot and a flat road, the gearbox hangs on to top all the way down to 1 000 r/min.

Compared with the 7,5-tonner, the extra weight of the 12-tonne Atego suits it well, seeming to allow PowerShift’s EcoRoll function to work better.

We were impressed with this 12-tonner. It offers a payload potential of more than 5 100 kg in its box body, over twice that of the 7,5-tonner, and fuel consumption of most 12-tonners is typically only 0,5 to 0,7 km/l inferior.

The standard two-stage engine brake was supplemented by a third stage on this particular truck, using a Voith Magnetarder. It proved highly effective and is not unduly heavy at 39 kg. A proper retarder is another example of heavy-truck thinking made to work in a smaller package.

We wonder if the Atego is in danger of moving further away from what a substantial part of the 7,5-tonne market wants – something lighter and less sophisticated. Not so at the higher weights; at 12-, 13- or 15-tonne GVM, the Atego looks appealing, refreshed and ready to take on the task of challenging DAFs stranglehold on this neglected weight sector.

 


As regular readers of FOCUS know, this magazine has been appointed an associate member of the International Truck of the Year (IToY)! FOCUS is the sole South African magazine to have joined this prestigious body. One of the advantages of this association is access to exclusive articles, specially written for FOCUS by ITOY jury members. This is one such article.

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Andries Ndlehe and Sheldon Mayet with one of Leeu Transport’s 19 trucks.
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