DAF tweaks its heavy trucks for diesel savings

UK market leader DAF has introduced a number of refinements to its Euro 6 XF and CF trucks and MX-11 and MX-13 engines, with the objective of achieving fuel savings of between four and five per cent.

The changes include engine tweaks and improved aerodynamics. There are also additions to the powertrain management software including the introduction of an Eco Mode, Predictive Cruise Control and Predictive Shifting. Engine brake power has been increased on the MX-13 engine, too.

On the 10.8-litre MX-11 engine, steps have been taken to reduce internal losses through specifying a lower-capacity oil pump and reducing internal friction by lowering piston ring height.

Combustion efficiency has been improved by a new piston design, changing the Delphi fuel injection to the seven-hole nozzle type used on the MX-13 and enhancements to the engine management software.

The 12.9-litre MX-13 gets a new camshaft with revised valve timing, and the low-height piston rings. Parasitic loss has been reduced by the addition of a two-stage water pump and engine management software enhanced.

The new water pump can also be found on MX11 engines installed in chassis with the XF cab and in single-drive CF trucks of 440 hp and above. DAF expects these changes to yield fuel consumption reductions of up to two per cent.

Engine-brake power on the big engine has been increased thanks to the revised valve timing: the brake, which uses Jacobs technology, delivers 20 per cent more retardation at 1,500 rpm, and maximum stopping power is now 360 kW at 2,100 rpm.

Braking power is controlled via a three-stage control on the steering column, with lower ratios being automatically selected as required; and DAF claims that it will now be sufficient for most operations which previously required a transmission retarder to dispense with it, thereby saving on weight, fuel and cost.

All Euro 6 XF and CF trucks with automated transmissions and MX-family engines will now have an Eco Mode switch, with the exception of those equipped with the on/off-road software.

When activated, Eco Mode cuts maximum engine torque by 10 per cent in the first 11 gears, which gives gentler acceleration and reduces typical daily fuel consumption by around one per cent. However, Eco Mode should be switched off if the truck is climbing a gradient that is steep enough to force it to drop out of top gear.

Predictive Cruise Control and Predictive Shifting, both of which use technology provided by Continental, make an appearance on the DAF option list for the first time.

Already well–proven in trucks built by other manufacturers, the systems use GPS mapping to determine the position of the vehicle and the nature of the terrain ahead, and adjust the vehicle’s speed and gear selection strategy to suit.

The aim is to hold a higher gear ratio where possible and let the vehicle’s momentum to carry it over hill summits.  These systems combined can save up to three per cent fuel consumption on hilly routes.

New aerodynamic kit has been developed for the CF cab. There’s a new roof deflector that is 10cm higher to suit British trailers and side collars that are 5cm longer to accommodate 2.55m-wide trailers. There’s also a new roof deflector to suit the 4mm overall height of low deck vehicles.

PM filter regeneration

DAF claims that once the MX engines are up to operating temperature, heat in the exhaust system should be sufficient to ensure constant passive regeneration of their particulate matter filters, with soot particles being combusted spontaneously.

Changes to the fuelling strategy on the new engines mean that the interval for periodic active regeneration has now doubled to 100 operating hours.

On the MX engines this is initiated by a low-pressure injection of diesel downstream of the hot side of the turbo, and is carried out without the driver’s intervention. However, a switch in the cab allows this process to be temporarily disabled if the rise in exhaust system temperature might pose a risk because of the truck’s surroundings.

Vehicles used in prolonged urban operations may require a manual ‘forced’ regeneration to be initiated. A four-phase warning lamp gives the driver prior notification that this will need to be done – typically within an eight-hour window.

The driver has to stop the vehicle in a suitable open space and trigger the forced regeneration by pressing the relevant switch twice. Engine revs rise to 1,100 rpm to force injected fuel into the filter and burn the accumulated soot.

If the warnings are ignored, then the filter will eventually become so choked that it has to be removed for professional cleaning.

Filter state is monitored by pressure sensors up and downstream of the PM filter. Once the difference between the two exceeds a preset value, active regeneration is initiated.

Silence speaks volumes

The features of DAF’s ‘Silent’ CF 4×2 tractor unit, which debuted at the IAA Show last Autumn, are now available on CF and XF models fitted with the MX-11 engine in 4×2 and 6×2 rigid and tractor chassis.

‘Quiet’ mode is activated when the driver presses a dashboard button. This increases the pre-injection rate in the engine, reducing combustion noise, and limits engine speed and torque.

The automated gearchange ‘short-shifts’ through the ratios to further reduce drive-by noise. Together with gearbox encapsulation, this enables the truck to meet the PIEK low-noise standard for urban night-time deliveries in Holland.

UK operators can specify the Silent option for operations requiring night-time deliveries in sensitive areas.

Rear-steer tractor launched

A new 6×2 tractor chassis featuring a single-wheel rear steering-axle with a capacity of 7.5 tonnes has been launched by DAF.

The FTN chassis is intended for applications where the truck may be operating in confined spaces and loads on the rear of the tractor are high, precluding the use of a tag axle. Typically, this would be on tractors featuring chassis-mounted cranes, or those working on maximum-weight tasks in support of agriculture.

The FTN chassis is available with the full range of CF and XF cabs, and the MX-11 and 13 engines.

There’s also now a 6×4 drawbar chassis variant of the XF: the FAT; designed for operations such as logging which combine long hauls with an off-highway mobility requirement.