Sunday 26 May 2019

DAF unveils MX-11 Euro 6 engine

workhouseThe wraps have been thrown off DAF’s new 10.8-litre engine as the Paccar subsidiary rises to the challenges posed by operators nervous of Euro 6 technology.

While DAF’s current MX-13 Euro 6 engine represents a European adaptation of an American reworking of an engine originally designed to meet a previous European standard, the MX-11 is all new and was designed from the sump upwards to meet and beat the hurdles of Euro 6.

Although most MX-11 production is expected to go into the ‘midrange’ DAF CF models, where it will replace the existing 9.2 litre PE engine, DAF is expecting it to appeal to buyers of the XF long-haul trucks too.

It is available at three ‘distribution’ ratings: 290 hp/1200 Nm, 330 hp/1400 Nm and 370 hp/1600 Nm; and two ‘haulage’ ratings: 400 hp/1900 Nm and 440 hp/2100 Nm. In comparison with the Euro 6 version of the MX-13, which covers the 410 hp – 510 bhp band, it offers ‘like-for-like’ fuel savings of three per cent and a weight saving of over 180 kg.

DAF’s UK marketing director Tony Pain expects that while 80 per cent of XF customers will remain loyal to the MX-13, 20 per cent will choose the MX-11. The percentages will be reversed for the CF.

Although, ultimately, the engine may not be as durable as its larger stablemate, it may actually prove more reliable in to day-to-day transport tasks than its larger counterpart.

Presenting the engine, DAF’s chief engineer Ron Borsbroom (pictured) ointed out that for maximum reliability and minimum fuel consumption the engine had to maintain a working temperature in its exhaust system over a wide range of conditions. It was easier for a smaller engine working harder to do this than for a larger, ‘lazier’ engine.

“The new MX-11 engine fits completely in the trend towards achieving high efficiency at lower displacement volumes. Eleven litres is the ideal displacement volume for achieving outputs of 290 hp to 440 hp within the requirements of the Euro 6 legislation and using reliable single-stage turbo technology.”

Built in Eindhoven, Holland, the engines will be exported to Britain, where they will be fitted into DAF trucks built at Paccar’s Leyland Assembly works. All right-hand drive DAFs, including those destined for export markets, are built in Britain.

Delphi provides the fuel injection system, designed and made in England, and the variable-geometry turbo is supplied by Cummins from its Huddersfield factory. The complete exhaust aftertreatment system is made by Cummins too.

A block-mounted camshaft is dedicated to driving the twin-pump common-rail ‘distributed pump’ fuel injection system at pressures of up to 2500 bar, meaning that the relatively unstressed double overhead camshafts can be of hollow construction. A genuine Jacobs engine brake, which opens one of the two exhaust valves of each cylinder, is controlled by a third cam.

The wiring that controls both the engine brake and the fuel injection is integrated into a reusable rocker cover gasket. This remains in situ on the block when the composite (for quietness and lightness) cover is removed to adjust the valve clearances, meaning that the electrical connections do not need to be disturbed.
Other electrical connections on the engine are very robust, and a fully-sheathed and foam-filled wiring harness is used.

Controlling airflow through the engine is vital in maintaining Euro 6 engine performance. There are three mechanical controllers: a back-pressure valve, an exhaust gas recirculation valve and the variable geometry turbo.

The common rail fuel injection allows for diesel to be added to the cylinder before and after the main injection/combustion ‘event’ if required and a seventh injector is positioned in the exhaust system to spray fuel onto an oxidation cat to burn accumulated soot off the particulate filter if needed. However, given the smaller size and harder-working nature of the engine, this ‘regeneration’ is required less often than on larger engines.

Careful control of engine oil consumption means that the filter cleaning intervals can be stretched to 500,000 km. While most competitor trucks have all exhaust aftertreatment elements (filters and catalysts) contained in a single module, DAF will supply the SCR and the soot filter as separate units should bodybuilding requirements dictate this.

Particular attention has been paid to reducing the parasitic load imposed on the engine by items such as the air compressor, oil and water pumps.

A PTO at the traditional one o’ clock position at the rear of the engine is joined by another at 11 o’ clock. For operators of rigid refrigerator trucks, a belt-driven air or water-cooled Frigoblock generator can be fitted directly to the engine, and there is an option at the front for driving a hydraulic pump.

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