Evolution not revolution 07 January 2013

The procession of new models from Europe's heavy truck makers continues. Latest to set a match to its touch paper is DAF. Ian Norwell reports from Andalusia

With the Euro 6 emissions deadline now less than a year away and the closing date for orders a good deal earlier, there's plenty of choice. While some have manipulated their product replacement cycles to bring forward new vehicles, others have essentially stuck to extensive modifications. Both help to soften the blow of increased costs that comes with Euro 6 – €14,000 more for the new DAF XF tractor unit.

DAF's choice has been to make best use of existing components and re-develop others only where they provide significant operational advantages. A relative latecomer to the Euro 6 party, this OEM has spent the time refining its already successful XF heavy tractor (5,000 on the road in the UK) so it's a tale of cumulative improvements that make the whole.

Driving force
Isolating the true cost/benefit from Euro 6 engines is difficult: all the truck makers have honed not just their engines, but also the drivelines, vehicle construction, aerodynamics and their ways of operating and interfacing with drivers. For DAF, however, in terms of fuel consumption, operators won't have anything to complain about.

Speaking at the driving launch of the new XF in Andalusia, DAF's president Harrie Schippers put it thus: "Customers who operate our ATe XF tractors at Euro 5 will see their levels of fuel performance maintained by the new XF." And he added that operators running pre-ATe vehicles can look forward to an improvement of 5—8%, depending on cycle.

Where does Schippers' confidence come from? In common with most major truck makers, DAF can draw on experience gained elsewhere in its global operations – and 25% of its sister brands (Kenworth and Peterbilt trucks supplied in the US since mid-2010) have been EPA10 compliant for some time. While the US emissions regulations are not an exact match with Euro 6, they require the same technologies so DAF has good hard field data on EGR (exhaust gas recirculation), VGT (variable geometry turbo), active soot filters and so on.

In fact, the Euro 5 version of the six-cylinder, 12.9-litre Paccar MX-13 engine has already taken advantage of this experience, with revised engine internals as part of DAF's ATe programme. Further refinements for Euro 6 include not just the after-treatment plumbing, but also a new CGI (compacted graphite iron) engine block and high-pressure common rail pumps integrated into the block to limit hydraulic losses. Elsewhere, a single auxiliary drive belt, and a fan mounted directly to the crankshaft both save on maintenance costs, and cut weight and fuel usage.

Unlike most other OEMs, DAF seems to feel under no pressure to produce outputs in the 600bhp or even 700bhp bracket. Asked why there is a choice of just three – 410, 460 and 510bhp – and nothing chunkier, Ron Borsboom, director of product development at DAF, says: "We feel that up to 2,500Nm, available over a wide engine speed range, is sufficient and allows operators the most economic solution. Significantly higher outputs are indefensible on CO2 grounds." And no doubt in part, it's keeping stresses to sensible levels that must be responsible for DAF's claimed service life of 1.6 million km, with service intervals up to 150,000km.

Transmission
Downstream from the flywheel, changes are more incremental. The latest version of ZF's AS Tronic has some DAF-specific functions. New software and sensors controlling clutch engagement make starting off and manoeuvring smoother – certainly noticeable on the test drive – and EcoRoll, the coasting function in cruise mode, is now standard. This alone gives a claimed 0.5% to 1% economy edge to add to the pile.

Meanwhile, dedicated software for long distance, heavy haulage and off-road work will help fleet engineers tailor orders. Whichever you choose, with higher rear axles seeking out economies from lower average rpm, the shift down one ratio from top gear on inclines is becoming more common. And to avoid wasting the lower rpm advantage, 'Fast shift' is used, meaning that moving between 11th and 12th does not involve opening the clutch – so preserving energy and momentum.

Unlike other OEMs, some of which have deleted the option of a manual box altogether in favour of AMTs, DAF's standard for the new XF is its 12S2840 12-speed manual, with a 16-speed for heavy applications. With the tide now running fiercely against manual gearboxes in this class of truck, this is an interesting strategy. Fully 77% of XF customers in the UK ordered the AS Tronic as an option in the last year, so it can't be long before DAF comes clean and reverses the standard versus options listing.

The MX engine brake and the intarder built into the AS Tronic are both highly effective, but these are also cost options. Ticking neither on the order sheet would be a certain mistake, both from a maintenance viewpoint and a safety one. Either will more than pay its way, in terms of reduced friction material usage. Just check the prices.

To our surprise, DAF's Borsboom discounts taking ZF's forthcoming TraXon dual-clutch AMT – at least until it has "lost some weight." Surely the potential economy gains of an unbroken drive would be worth a few kilos? Unless Iveco wants to take it, Volvo will be unopposed in offering this technology when its I-Torque comes on stream in 12 months.

Between the rails
Moving on, chassis improvements exemplify the philosophy of gaining incremental advantage. The inevitable weight gain from the after treatment metalwork has been mitigated by a few simple redesigns that allow the chassis to drive away from the Euro 6 scrutineers only 90kg worse off than a Euro 5 model. Lightweight fifth wheel mounting plates, a lighter rear closing chassis beam, and a redesigned four-bag stabilink rear suspension, with anti-roll bar and reaction rods combined, all help cut kilos.

The new 4x2 chassis has a modular layout with options for fleets to arrange their major space needs. Fuel capacity can be maximised by moving the locations of SCR/DPF (selective catalytic reduction and diesel particular filter) equipment, the battery box and the spare wheel (if you carry one). However, latitude on right hand drive 6x2 chassis – due to start production in October this year, six months after the two-axle tractors – will clearly be a lot less.

From the driver's perspective, the cab has had a useful re-work an now offers improved visibility. Drivers will also notice new instruments with an even stronger accent on economy. Most apparent will be the lower noise levels. A claimed reduction of 2dB is more than believable. Even working hard on a 7% gradient at 40kph in 9th gear, it remained impressively quiet.

DAF may not have invested the vast sums that other manufacturers have, but what it has spent has been in places where it counts. For those with an eye to operational efficiency, this tractor unit offer less glitz and more grit.

Author
Ian Norwell

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