MAN D38 engine

It’s safe to say that European prime movers are a breed of their own in the Australian transport game, trying to set themselves apart by sophisticated electronics, driver friendly work environments and high attention to detail – and the MAN TGX is no different.

After testing the 540hp D26 model in autumn, we know that the updated cab-over from Germany has stayed true to the “more is more” philosophy we’ve come to know and appreciate – but can it combine its upmarket attitude with the grunt necessary for B-double work?

To find out, we organise a drive from Melbourne to Sydney in the highly anticipated top model, the D38. Named after the engine inside, the TGX D38 is not afraid to take on the challenge as we roll out of Derrimut with a weighbridge ticket showing 62,090kg GVM, including the 1,050 litres of fuel we have on board.

Our D38 is one of four ‘assessment vehicles’ brought to Australia over the course of 2015 and will be shared among media representatives and dealers, while the other three will be taking part in long term evaluations with national fleets including Toll and Lindsay Australia.

According to MAN, those real life assessments will involve some experimenting with final drive ratios, for example, to ensure the D38 is geared correctly for the job at hand. Our test vehicle is equipped with 3.08:1 rear ends, while the ones on fleet duty will initially be sporting a 3.20:1 ratio. 

Our unit has also been doing the truck show circuit and has just returned from Perth, so we get treated to a little more bling than usual: The MAN’s bright red paint is complimented by a platinum matte finish on the mirrors and some carbon fibre effect on the dash trim. The bikini bull bar, meanwhile, has been added just prior to our trip following a few scares from errant wildlife on the run across the Nullarbor.

What really counts on our trip is under the hood, though, and quite an engine it is.

Developing 560hp (411kW) and 2700Nm of torque (1991 ft-lb) the 15.2 litre single overhead cam six has 20hp and 200Nm more than the previous D26 engine – with the extra torque and its broad range being the key reason to employ a steeper diff ratio.

MAN says maximum torque is developed as low as 930 rpm – a very precise figure, even for a German make – made possible by the use of two turbochargers used in sequence, with the high pressure unit doing its work at low revs and increasing the boost from the low pressure turbo as revs increase. Two keep the set-up cool, there are two air-to-water intercoolers employed.

MAN’s innovative ‘top down’ cooling system has the coolant fluid travelling in the reverse direction of most typical engines in that it flows from the top to the bottom of the engine. MAN’s rationale for this is that by introducing the cooler fluid straight from the radiator to the hottest area of the engine around the cylinder head, heat stress will be reduced around the combustion chambers and head casting, which in turn will protect components such as the injectors and exhaust valves.

Interestingly, the engine produces a very un-European growl down low that is more reminiscent of American diesel engines than a current-day truck from Munich. The sound is not intrusive but seems to underline that this European has some real grunt under the hood.

To put the MAN to the test, we tend to manually hold a higher gear when tackling a steep climb and let the tacho needle dip below 950 rpm, but there seems to be no sign of driveline snatch or the engine running out of breath at sub-1,000 revs. You may rather see a driver downshift manually before reaching low-pull territory.

An evolution of MAN’s D20 and D26 engines, the D38 continues the trend towards six-cylinders and away from V8 and V10 configurations in an effort to reduce weight on the front axle, which is a particular issue under Australian regulations. In the new TGX, super single 385/65 Continental tyres are used on the steer axle to spread pavement pressure and contribute to the fuel saving task by minimising rolling resistance.

The fundamentally lighter six-cylinder architecture uses lightweight Compacted Graphite Iron (CGI) for the block and cylinder head castings. The sump and rocker cover are moulded in high impact plastic and the flywheel housing is cast from aluminium. The result is a 160kg weight advantage compared to the D38’s predecessor – a figure many a fleet manager will enjoy, especially since many of the ancillary engine components are common to the MAN D20/D26 family.

A Euro VI compliant engine, the D38 uses a combination of several technologies to meet the new standard – a diesel particulate filter (DPF), a cooled high pressure Exhaust Gas Recirculation (EGR) system and finally a Supplementary Catalytic Reduction (SCR) system that injects AdBlue urea fluid into the exhaust.
Such is the combustion efficiency of the engine and the DPF and EGR components that AdBlue consumption on the trans-nation trip for its appearance at the Perth Truck Show was measured at just 0.93 per cent of fuel burned.

On our 880km trip from Melbourne to Sydney, diesel consumption averages 1.88 kilometres per litre, which is a good result taking into account the high GVM and that the truck has less than 12,000km on the clock. What’s good to know is that the twin cylinder air compressor automatically disengages from the engine when not required, which equates to less fuel burn by reducing engine load.

Also interesting in that context is the exhaust brake. In a first for MAN, a Turbo Exhaust Valve Brake (TEVB) is an integral part of the engine braking system and can provide up to 600 kW of braking power. As opposed to MAN’s previous exhaust brake systems, with the TEVB the exhaust gas valve is located in front of the turbochargers and is able to develop greater back pressure for braking. On the road and with the cruise control active, the engine braking is impressive, with the transmission downshifting itself to increase the boost backpressure as the engine revolutions are kept high. 

On steeper declines, the trick to maintain legal speed without touching the service brakes is to decrease the cruise control speed by a couple of kph, which will result in the transmission downshifting a couple of gears and maximising the engine’s retarding abilities at up to 2,200rpm. 

The large amount of thermal energy produced when braking is not emitted into the engine cooling system, rather it is discharged directly via the exhaust. When using the higher stages of engine braking, the engine-cooling fan is also activated to contribute to the braking task and keep the vehicle safe.

A distinct feature of a modern European truck is the electronics package on board. In the MAN, an adaptive cruise control system uses forward facing radar technology to maintain a pre-determined gap between the front of the MAN and other vehicles in the same lane. A detailed readout is available on the dash that shows the exact distance as well as the road speed of the other vehicle, which comes in especially handy when approaching freeway exits. In addition to lane departure warnings and variable speed limiter settings, the driver is always alert and well informed.

Another driver-friendly feature is the familiar MAN TipMatic2 version of the ZF 12-speed automated manual gearbox, even though it won’t be fitted in the final production model. According to MAN, the final D38 is slated to be fitted with the revolutionary ZF TraXon modular transmission, whose Efficient-Roll mode will contribute further to the D38’s fuel efficiency. The function works by neutralising the driveline on slight declines when engine braking isn’t required and allows the truck to maintain road speed with the engine idling along and no load required of it. The feature will bring MAN to equal footing with other European OEMs that already have an electronic “angel gear” on board today.

A GPS-controlled cruise control is also planned for production models, which takes into account the upcoming terrain so that the truck accelerates as it approaches a hill and then coasts over the top. Again, the function will bring the MAN closer to the Scandinavian competition.

So, is the D38 ready for Australian B-double work? Without having tested the final version, and knowing that some technical features are yet to be added, the preliminary answer is yes. B-double work is tough and requires finding a good balance between efficiency and performance, but the D38 will be able to handle it all. It is capable of handling more than 60 tonnes GVM, should return good fuel efficiency and be relatively stress-free to drive, with a definite focus on the operator’s comfort and well being – making it a more-than worthy competitor and an interesting option for fleets open to European technology.


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