DAF Trucks unveiled its first Euro-VI compliant vehicle, the DAF XF heavy truck, at the recent IAA Hanover Show and has now revealed further details.
Under the skin, the XF cab is an intensive reworking of the heavy truck cab that DAF has used since 1987, originally developed with ENASA of Spain. Under the cab floor sits the 12.9-L Paccar MX engine, revised to meet the forthcoming emissions limits. To accommodate the changes, DAF has developed a new chassis to provide flexibility in the mounting of ancillary components.
The trademark triple windshield wipers suggest which section of the cab has been carried over from the current XF105 range. Even so, there are extensive alterations. The cooling module of radiator and charge intercooler needs a 30% larger surface area than for Euro-V limits. To make space for that triggered a string of detailed changes to the chassis and cab.
Significant redesign of chassis, cab, and interior
As far as the cab is concerned, housing the bigger cooling pack involved redesigning the cab floor by effectively folding it around the front end of the chassis. It also meant that the cab floor had to be raised by some 30 mm (1.2 in) to a height of approximately 1470 mm (57.9 in), while still meeting impact requirements.
To integrate all these changes, DAF redesigned the cab suspension system, as well as turned attention to frame, cab floor, and firewall stiffness. The effect has been to reduce interior noise levels by around 2 dBA. The changes have also led to improved ride and handling and impact performance. The cab suspension has been designed to ensure that the cab remains attached to the chassis in a rear-end collision but is pushed backward with crumple zones at the front and rear of the cab, absorbing the impact energy.
The cab suspension is coil-sprung as standard with electronically controlled air suspension (ECAS) as an option. Roll has been reduced by placing the cab suspension mounts wider apart and fitting a new stabilizer. The bridge-shaped rear cab suspension allows space for the optional engine power take-off (PTO).
Externally, the new cab is distinguished from its predecessor in a number of ways. H7 headlights are the regular offering, but DAF claims a first in offering LED headlights as an option on a truck. Cornering lights are also available for the first time, incorporated in the new steel front fender and combined with the fog lamps. Inspection panels improve accessibility for all the front lamps. The headlamp bulbs can be changed without the need to tilt the cab.
Improving aerodynamic flow around the vehicle was important to ensure that the efficiency losses associated with Euro-VI emissions could at least be offset. The XF cab benefits from revised cab corner air deflectors, which help to keep the door handles clean. Concealing two of the three cab access steps behind the door helps to improve airflow.
The cab has been widened from 2500 to 2550 mm (98.4 to 100.4 in), and the mudguards, side fenders, and side skirts have been redesigned to reduce air resistance. The roof spoiler is now approximately 25 kg (55 lb) lighter than before. As an option, the height of the spoiler can be adjusted from beside the cab using a simple mechanical adjuster, to ensure that the spoiler height can be accurately matched to the trailer for the best aerodynamic performance.
The side windows in the doors are now in one section without a false quarter light, which helps to improve side visibility.
Inside, DAF claims that like the current XF 105 cab, the XF Super Space Cab offers more interior space than its rivals with a total volume of 12.6 m3 (445 ft3). There is 2250 mm (88.6 in) of interior height, and the cab includes around 1000 L (35.3 ft3) of storage space.
Features in the interior include new seats, with the option of a split backrest at shoulder height and integrated height adjustable seatbelts. Options include two-stage ventilation and heating.
The same basic dashboard architecture has been retained, but the instruments and switchgear have been redesigned to include a 5-in TFT screen, which provides information in 32 languages regarding vehicle and engine functions. It also incorporates DAF’s Driver Performance Assistant to give drivers feedback on how efficiently they are driving and offering tips on improvement.
To help accommodate the larger cooling system, the chassis has been redesigned with a Y-shaped front end. To ensure rigidity is maintained, the front of the Y-section gains a new crossmember fitted across the ends of the chassis, as well as a cross beam below the cooling system and a front under run protection bar.
For 4x2 tractor units, the chassis is made of KF600 high-tensile steel and features a central K-beam to help maintain rigidity. Side members are 6 mm (0.24 in) thick as standard or 7 mm (0.28 in) for special applications.
The front axle suspension is new, featuring 1750-mm (68.9-in) long parabolic steel springs. These are wider than before at 90 mm (3.5 in) compared with 80 mm (3.1 in) for current models. The new leaf width is applied to the two-leaf suspension for the standard 8-t (8.8-ton) capacity front axle and three-leaf spring used on the optional 9-t (9.9-ton) axle.
The rear axle suspension has also been redesigned using a Stabilink design. The antiroll bar and reaction rods are combined, helping to optimize stiffness while reducing weight by around 60 kg (132 lb).
The XF will be fitted with a new 13-t (14.3-ton) capacity rear axle for combination weights up to 44 t (48.5 ton) and engine torque outputs of up to 2300 N·m (1696 lb·ft). The axle is approximately 40 kg (88 lb) lighter than that used on the XF 105 and needs less oil than its predecessor, contributing to lower fuel consumption. DAF will offer rear axle ratios of up to 2.38:1, meaning that the engine will be operating between 1100 and 1200 rpm at highway cruising speeds. The 4x2 tractors will be fitted with four bellow ECAS as standard for the rear suspension.
The redesigned chassis means that DAF can offer more flexibility in the mounting of components on the chassis. For example, the battery box is mounted at the rear of the chassis, freeing up space on the rails. As a result, the XF is available with fuel tanks of up to 1500-L (396-gal) capacity. AdBlue or Diesel Exhaust Fluid capacity is 90 L (24 gal) or 140 L (37 gal) as an option on long-haul trucks fitted with a sleeper cab.
Paccar MX-13 engine tweaked to meet Euro-VI
The Paccar MX-13 has been meeting U.S. EPA ’10 emissions limits since 2010, with over 30,000 Kenworth and Peterbilt models sold since then equipped with the engine. Further development has been necessary to meet Euro-VI limits.
DAF has adopted a combination of selective catalytic reduction (SCR) and enhanced exhaust gas recirculation (EGR) for exhaust gas aftertreatment, similar to the technologies used to meet EPA ’10. For Euro-VI, the engine will use common-rail fuel injection in place of the electronic unit pump (EUP) system used for EPA ’10. This offers fuel injection pressures up to 2500 bar (36.3 ksi).
The block has been stiffened to handle the higher injection pressures and, like the cylinder head, is now cast in compact graphite iron (CGI). Fuel feed pipes are cast into the block and head. The two high-pressure pumps used to charge the fuel rail are integrated into the block and driven from the same camshaft that operates the valvetrain.
DAF has also adopted a variable geometry turbocharger for Euro-VI in place of the single-stage device for Euro-V to ensure effective rates of EGR, particularly at lower engine speeds. DAF also claims improved performance from the engine brake, which can apply up to 270 kW (362 hp) of braking power from 1500 rpm.
The Euro-VI variant of the Paccar MX-13 engine differs from the Euro-V version in several ways, including the use of a single auxiliary drive belt, a fan mounted directly on the crankshaft, a larger crankcase to extend service intervals to 150,000 km (93,200 mi), and the adoption of a composite sump. Other features include combining the fuel filter and water separator in a single unit mounted directly on the engine. The oil cooler is now fabricated from stainless steel to improve durability. The engine has been designed for a B10 design life of 1.6 million km (1.0 million mi).
The engine will be available with three power outputs: 410 hp (300 kW), 460 hp (340 kW), and 510 hp (375 kW). Corresponding torque output is given as 2000 N·m (1475 lb·ft), 2300 N·m (1696 lb·ft), and 2500 N·m (1844 lb·ft) between 1000 and 1425 rpm.
The XF is available with a range of ZF manual and automated transmissions. A 12-speed synchromesh manual transmission is the regular offering, but some markets are likely to opt for the automated AS-Tronic transmission as regular equipment. Vehicles specified with this transmission will also be equipped with EcoRoll, a system that automatically selects neutral on gentle downhill gradients. Potential fuel-consumption savings of between 0.5 and 1.0% are possible with the system.
DAF has also developed a quick gear change for the automated 12-speed AS-Tronic between the more frequently used gears 11 and 12. This is achieved by keeping the clutch engaged and reducing the torque interruption as a consequence.