A LOT OF BOTTLE!
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• Although it was announced over a year ago, and has been on sale in Britain for a couple of months, the MercedesBenz 1644 with EPS gearshift has so far eluded our road testers (an omission which will shortly be put right); so the Opportunity to get some experience with a laden 1644 on an international run was accepted with alacrity — especially as the task set was to haul 1,500 cases of Beaujolais Nouveau from Beaune, in central France, to London.
Our route was rather different from that used for our full road tests. The run from Paris to Beaune down the A6 autoroute is largely flat, with gradients of only some 4% in either direction. From Paris to Calais the Al is similar, though with some extremely poor quality single carriageway for the last 40krn to the port.
Our route in Britain took us straight up the A2 and into our importer's North London depot via the M25 to the east and the North Circular Road.
This 1644 was one of the first righthand-drive examples to be built: as such it lacks some of the current specification refinements such as headlamp wipers, but it is otherwise representative. All 1644s are fitted with the hefty 14.26 litre 0M442 LA yee-eight engine, which in this guise is turbocharged and intercooled. This gives a power output of 320kW (435hp) at 2,100 rpm, and a massive 1,765Nm (1,300lb/ft) of torque between 1,100 and 1,600 rpm. Those outputs make the Mercedes the most powerful regular production on-highway truck built in Europe.
Of almost as much interest as the power of the 1644, however, is its gearbox, for it comes as standard with M-B's electronic power shifting (EPS) system. This is basically the ZF Ecosplit fourspeed, range-change/splitter gearbox used in other top-line Mercedes trucks, but with the mechanical linkages replaced by pneumatics controlled by electronics.
The driver uses what appears to be a conventional gear lever, but the awkward 'double H' shift pattern of the conventional boxes is replaced by a simple for ward-up, backwards-down pattern. While the gears are shifted pneumatically, the clutch is still foot-actuated with the splitter operated by a conventional toggle switch on the gear lever.
The EPS system is designed to cut gearchanging effort, which in many ways might be considered superfluous on such a powerful vehicle as the 1644. Running unladen, as it did from Paris to Beaune, the 1644 could have managed with a fourspeed gearbox. The green sector on the tachometer runs from 1,100 to 1,750 rpm, with a further 150rpm either side shaded green, which gives a vast working range, and in any case the engine is happy pulling on full 'throttle' outside this economical-operation band.
Even when running back to London with some 23 tonnes of wine on board, the 1644 never needed a gear lower than the low split on 7th for motorway running, except where we were severely baulked on the narrow two-lane section of the A6 north of Beaune. While the run up out of Dover docks needed fourth, the rest of the A2 towards London proved no greater challenge, the gear position indicator staying at '8' except for roadworks.
The exhaust brake, with its control button mounted in the usual Mercedes position on the floor in front of the driver's seat (where it can be a bit of an ankle-twister) is effective as a speed regulator when running light, even in high gears. At maximum weight, however, the 1644 will easily over-run the exhaust brake in the gears in the top half of the box. The big turbocharged and intercooled engine is not a quiet unit, and it has a distinctive gravelly gurgle at about 1,500rpm.
This engine and gearbox combination does seem, subjectively, to be fairly economical, however. With the combination of laden and unladen running, and the disadvantage of not being able to return to the same filling point to ensure consistent filling of the big (580I1t) tank, there was no point in trying to measure fuel consumption accurately. The truck used less than a tank of fuel in our ParisBeaune-London trip, however.
• TRANSMISSION
Like Scania's CAG and Eaton's SAMT systems, the Mercedes-Benz EPS system takes a bit of getting used to. Also like the CAG system, EPS requires intelligent driver input to achieve a quick and clean change, as it will only engage a gear when road and engine speeds have been synchronised. When that point has been reached, the control lever will click into place with the pressure of one finger: until then, even brutal ramming of the lever will not trigger a change.
That said, the system works faultlessly on upward changes, although the driver has to be careful to keep the 'block' button on the front of the lever firmly pressed in throughout the change if he is trying to skip gears.
The system will only skip gears one at a time, so the biggest single movement, even using the splitter, is 21/2 gears up or down. With a powerful, torquey engine, the logical change pattern from rest is 2,4,6,7,8, but on upward slopes this becomes uncomfortable because of the time it takes for the range-change to trigger. When pulling hard, it is much more satisfactory to include the extra gear at 5. This time-lag on the range-change was the most annoying feature of the gearchange when we got stuck in very slow-moving traffic on the Peripherique in Paris, where the other merits of EPS really shone.
EPS is not yet as pleasing a system to
use on downchanges. We found it all too easy to miss a downward change when slowing for roundabouts, for example, and end up in neutral. The solution is easy — knocking the lever sideways into the true neutral position and then either forwards or backwards will make the system select the gear which it thinks is best for the occasion.
Apart from wasting time, this process tends to leave the vehicle in a higher gear than that desired by the driver, and the whole process has to be repeated. Full-power downward changes under load are much easier to execute.
Apart from these problems EPS has a couple of quirks. Reverse (engaged by pressing the blocker button and changing down past neutral) is obtainable only in the low split. With the idle speed set at a high 600rpm on this vehicle, reverse was the only gear likely to crunch into engagement unless the clutch was held in for a long time prior to moving the lever.
The biggest quirk is driver induced, however: it is all too easy, especially when manoeuvring at low speeds, to drop back into usual habits and move the lever backwards from first for second gear. . .
• CAB COMFORT
The Mercedes 'G' cab is a pleasant place for a long-distance run; much wider than
the usual new-generation M-B cab, it has lots of room and is logically laid-out. Its width is a bit daunting at times. Care has to be taken with the mirrors when approaching toll booths at autoroute Peages, and the fact that the mirrors are further out than on just about anything else makes creeping between lines of trucks on a tightly packed ferry a challenge. Logically, the left-hand mirror is electrically controlled, which makes manoeuvring in tight spaces a little easier as it can be swung out to show the trailer wheels.
It is not controllable in the vertical plane, however, and the mirror itself is not convex enough, so that there is a significant blind spot along the left-hand side for British drivers abroad.
The combination of tilt-adjustable steering column and Isringhausen air seats makes a comfortable driving position easy to achieve. There is good internal stowage, but the cab is still austere by others' standards.
• CHASSIS
Hitched up to the latest Van Hool air-suspended triaxle trailer, the 1644 gave a superb ride unladen. It became distinctly more choppy once the trailer was loaded, but was still extremely good on all but the roughest French roads.
Romping along at around an indicated 100km/h (62mph) the whole vehicle felt relaxed, with just 1,609rpm showing on the tachometer. Wind noise was low, except from the ugly but effective add-on glare shield.
The brakes are powerful, but more importantly are delightfully smooth and progressive to use.
• SUMMARY
While definitive performance figures must await our full road test over a properly controlled route, we have no doubt from this exercise that the 1644 is as impressive in the flesh as it is on paper.
Its power and performance are prodigious, and the subjective evidence suggests that economy has not suffered.
Even after several days of familiarisation with the EPS, we have slightly mixed feelings: the ease and simplicity of gearchanging are a delight, especially in heavy traffic, but it would take even longer to be fully confident that it will do what the driver asks or expects every time.
by Allan Winn