DAF XD PX-7 310 FA 4x2 with Powerline transmission review

It has been a busy couple of years for DAF trucks. First there was the arrival of the new XF, XG and XG+ in 2021, followed by the XD, and finally the XB. Along the way, the firm has picked up scores of awards for its new line-up, and was the first manufacturer to fully make use of the EU’s weights and dimensions allowances. It has been a successful overhaul, but now comes the so-called difficult second album – following the critically acclaimed new releases with new and exciting work. But there’s no change of genre or style; DAF is evolving its offering and adding to the foundations laid in 2021, with improvements to efficiency, safety and comfort.

Billed as the ‘next chapter’, the changes are actually more like a footnote to the story that came before, adding slightly to the Next Generation range with a few additions and alterations.

For example, the XF, XG and XG+ models now get the option of full side panels – improving aerodynamics and increasing efficiency. This builds upon the legacy of the Next Generation vehicles, which laid claim to a 19% aerodynamic improvement resulting in a 6.3% fuel consumption reduction compared with the outgoing XF range. That figure is boosted further with these new changes, pushing the figure as high as 13% thanks to revisions to the MX-11 and MX-13 engines, with revised engine timing, a dual-drive coolant pump for better low and high cooling performance, new air-compressors, a lower friction crankshaft, and improvements to the turbos, as well as exhaust gas recirculation. Revised valve timings, known as the Miller Timing Process, mean that the intake valve is left open for slightly longer on the compression stroke, allowing more air into the mix. Changing this combustion cycle yields an improvement in fuel efficiency. The cooling pump changes have resulted in both mechanically and electrically driven pumps, with an electric system for low cooling performance and a belt drive pump for high cooling. The system is therefore now more efficient, using either a mechanical or electrical system depending on demand.

A clutched air-compressor also increases efficiency, enabling it to be completely disconnected from the driveline, so when you don’t need air, a clutch disconnects and the compressor no longer operates. Both the MX-11 and MX-13 engines have also been given new design injectors to eliminate the problem of fuel contamination that some operators have been having. While these aren’t changes specific to the new vehicles, they are changes that are part of DAF’s continual reworking of the existing vehicles to create proactive change and improvements.

Further underlining the fuel-saving potential is a new more efficient 2.64:1 axle ratio, boosting efficiency by 1% alone. There’s also a new 2.05:1 ratio that reduces engine speed by 7%when cruising, heralding a new era of down-speeding to increase efficiency. On paper it’s a concern, but in reality it’s not.

It’s not just the tractor units, though, that have had an efficiency upgrade. Rigid chassis like the XD get the option of a new 6.7-litre Paccar PX-7 engine (as well as the MX-11), while the XB gets PX-5 and PX-7 options. 

As the newest addition to the range, many of the XB’s new features have been well documented, but there’s now the option of a new DAF XBc for construction, which gets a higher ground clearance of 255mm and improved approach angle of 25 degrees. Meanwhile, the low -entry cab (which can achieve a DVS 4-star rating) gets enhanced manoeuvrability thanks to an improvement in the steering lock, which has jumped to a 56-degree steering angle compared with the standard 49 degrees.

Comfort has always been a big selling point of the Next Generation vehicles – after all, the XG+ is all about size and space – but DAF is now trying to make drivers’ lives easier as well as more comfortable. Along with lower noise levels, some features have been made standard, such as the DAF Digital Vision System (the mirrorless cameras) and predictive cruise control. Along with standardfit low rolling resistance tyres. DAF says this produces a 9% fuel-saving over vehicles that don’t have these options.

There are also five new safety systems, with dual front cameras at the windscreen with two radars in the grille for short- and long-range detection, dual side radar, and a rear camera system. The side radar scans up to 7m to the front and 30m to the rear of the truck to detect vulnerable road users or other hazards, while the rear-view camera can be linked to a trailer connection. Together, the five new sensor systems have developed a huge amount of additional functionality, while other features like driver drowsiness detection – which creates awareness of your fit state to drive – and high beam assist – which now automatically dips the headlight beam when you come into a lit area like a village – make driving safer and easier. Other changes to the range include the addition of an XG Low Deck that can be specified with a fifth wheel height of just 91cm, making it more suitable for large volume trailers. Then there’s the new PX-7 engine that is constructed from a compacted granite iron block, has a new cast-iron cylinder head, low friction pistons and new turbocharger to develop 308hp at 2,300rpm, with 1190Nm of torque available between 1,200rpm and 1,500rpm. The smaller engine is also a significant 600kg saving over a similar driveline using the MX-11 engine. It has been paired to a ZF Powerline 8-speed fully automatic transmission that has been optimised for the high torque at low revs, with the option of a 276hp PX engine brake.

We drove the new driveline in an XD 310 FA 4x2 with a day cab and found the 6.7-litre engine to be a capable workhorse on a mixed terrain of country roads and highways. The smaller engine and low torque band immediately casts doubts over the truck’s cruising ability, but at 56mph the engine maintained a constant 1,300rpm in top gear and was far from being overly noisy. It also responded rapidly to the changing terrain. Our test route in the hills outside of Malaga gave us ample opportunity to see the PX-7 prove it can tackle steep inclines, and at roughly 80% of the 19-tonne GVW, we found no issues with performance and were surprised by the overall serenity of the engine noise.

Paired with the Powerline transmission, the rapid changes were almost unnoticeable, which meant the gearbox could easily make a couple of shifts to maintain momentum without the driver truly noticing the downshift. Aside from the initial interruption in drive as the transmission shifted from first gear into second, the rest of the shifts were smooth and barely noticeable – the only giveaway being the slight rise in engine revs once the change was complete. It’s an exceptionally pleasing combination and one that operators with gearshift-heavy urban multidrop routes would do well to consider. It was especially obvious how refined a package the PX-7 and Powerline gearbox are together when we changed to a smaller DAF XB 210 FA 4x2 with an extended day cab, powered by the smaller PX-5 and a different version of the ZF Powerline gearbox. While still delivering rapid shifts and capably getting us around the same test route without fuss, the slickness of the combination in the XD was missing. Engine revs were higher, shifts more noticeable. It was even more apparent in an XD 450 FAN 6x2 using the MX-11 and TraXon 12-speed gearbox. Although there was more power and the gearbox was less busy, the combination didn’t deliver the same effortless experience we found with the PX-7. It certainly made an interesting comparison and highlighted the abilities and strengths of the smaller PX-7 engine for operators that can make use of it.

Stepping up in size to an XG+ we were able to experience the newest axle ratio available for DAF’s tractor units.

Although geared with European operations in mind, operating at 40 tonnes with two axles, the concept of down-speeding and running a 2.05:1 rear axle ratio with 135/70 tyres is an interesting idea. Drivers would initially worry that with that set-up you’re likely to crawl up even the smallest of hills. However, because the engine rpm is so low – at around 950rpm at 85kph when running on the flat – there’s not far for the engine speed to drop to make a gearshift. Consequentially, when the terrain profile increases, the TraXon transmission shifts down from 12th gear to 11th and the truck’s climbing ability is maintained. The early change makes hill climbing no less stressful than in a truck with a higher ratio. The net result, however, is that on the flat for the MX-13 engine there’s a 7% drop in engine speeds at a cruise and therefore greater efficiency. While this notion does go slightly against the grain, it still means you can have good hill climbing ability simply by using the gearbox better, with a swift downshift as soon as you hit thehill. Not only does the principal work on paper, it works in reality too. On a long uphill drag, we lost very little in the way of speed. The only time it felt lacking was coming off a roundabout straight onto a steep incline for a motorway on-ramp. Without burying the throttle to demand more power and a downshift, we were left to crawl up the slope; however, the truck built momentum throughout and we barely felt disadvantaged. Once back to a cruising speed, the difference in engine speed then really became noticeable as the cabin descended into quiet. To say the silence was deafening is a cliché well suited, with far more wind noise noticeable than the engine revs.

The raft of new changes may well form the next chapter of DAF’s range development, but it feels more like an ongoing dialogue between efficiency and practicality. Rather than a whole new chapter, the updates feel like a series of ‘what if’ questions posed to their engineers. The resulting conversation then yields a set of truly unexpected and pleasantly surprising results, like the marriage between the PX-7 and Powerline transmission and the 2.05:1 axle ratio in a tractor unit.

Whether or not the latter will be suited to our heavier gross combination weight and additional axle, we will have to wait and see, because the next next chapter is that DAF Trucks UK plans to see if it’s something suitable for our shores. As ever, the conversation and the story will continue.