Mack Trident Shines as B-Double Hauler

Keen to take Mack’s latest pooch on the prowl, PAUL MATTHEI recently slid behind the wheel of a Trident hauling a B-double for a run from Melbourne to Newcastle. Fitted with Mack’s flagship 535 hp MP8 engine coupled to the new mDrive automated shifter, high expectations were met with equally high results.

Bow WOW!

It’d been a few years since I’d driven a Mack on an interstate run. In fact, the last time was back in early 2005 between Adelaide and Sydney, steering a Super-Liner LT with a 550 hp Cat stirring through an Eaton AutoShift box.

Of course, much has changed since then. For starters, Mack’s much vaunted ‘New Breed’ of pups was born in Australia in late ’07, and following a few tough teething issues has matured into what is widely considered to be the finest and most comprehensive  collection of new bulldogs in the company’s long and proud history.

Furthermore, there’s no longer the option of having a hairy-chested Cat engine prowling beneath a bulldog snout, while Eaton’s underwhelming AutoShift has been largely superseded by the slicker, smoother, smarter UltraShift two-pedal automated transmission.

So while comparing the Super-Liner LT I’d driven back in ‘05 with the new Trident might seem akin to lining up chalk against cheese, there is at least one similarity that bears comparison.

That is, peak power and torque figures delivered by the latest iteration of Mack’s 12.8 litre MP8 engine with selective catalytic reduction (SCR) emissions control are within a bulldog’s bark of those produced by Cat’s C15. And remember, back in 2005 the C15 hadn’t yet been lumbered with the complicated and costly ACERT (Advanced Combustion Emissions Reduction Technology) emissions control system.

For the record, the Cat C15 produced 550 hp compared to the latest Mack’s 535 hp. In the torque department, however, the tables are turned with Mack pipping Cat at the post, notching 1920 lb ft compared to the yellow engine’s 1850 lb ft, both produced at a low 1200 rpm. The salient point about this comparison is that until its withdrawal from the on-highway truck engine business, Caterpillar was a leading powerbroker in the heavy-duty B-double business in a mix of Kenworth, Freightliner and Western Star chassis.

And herein, with its own engine now delivering such ample outputs, rests the reason why Mack can finally lay claim to having a serious contender for the hotly contested linehaul B-double market. Put simply, B-double operators generally want engines producing more than 500 hp and at least 1850 lb ft of torque, and the top rated version of Mack’s MP8 SCR engine now ticks both boxes with bold, thick ink.

It’s no secret, of course, that the MP8 engine is a canine clone of Volvo’s (Mack’s parent company) 12.8 litre D13C engine introduced some years back to provide the Swedish manufacturer with a powerplant to comfortably compete in the B-double arena. Before that, Volvo had used a complex turbo-compound system to coax 500 hp from an aging 12 litre six which was never designed to achieve such a high output. Ensuing durability issues provided resounding proof that a larger displacement engine was needed for B-double roles and the D13C with SCR emissions control has since acquitted itself remarkably well with ratings of up to 540 hp.

However, it was Mack’s insistence to remain with EGR (exhaust gas recirculation) emissions controls that precluded the MP8 from ratings above 500 hp – the main reason being the extra cooling capacity required for EGR engines. But with the introduction of ADR 80/03 emissions standards earlier this year, most manufacturers including Mack proceeded to offer SCR simply because it is now the most efficient method of mitigating harmful oxides of nitrogen (NOx) to the prescribed level.

Interestingly, it was possibly Mack’s proud American heritage that drove the company’s decision to stay with EGR – traditionally favoured by US operators – during the reign of the previous ADR 80/02 emissions regulation rather than convert to SCR. It seems the general consensus at the time was that US (and Australian) operators would be none too happy about having to regularly top up an AdBlue (liquid urea) tank as a necessary part of SCR operation. However, this assumption has proved something of a furphy on both continents as in most cases it appears drivers have taken to the new task without much fuss at all.

Indeed, our US correspondent Steve Sturgess who writes DIESEL’s State of the Union column has focussed on this issue a number of times of late with one of his most recent reports concluding that American operators are not finding SCR the terrible technology it has been regularly painted.

Anyway, back on Mack: Thanks to its Volvo parentage, switching to SCR was not particularly difficult and with its MP8 engine now punching out much the same performance standards as its Swedish counterpart, Mack is finally able to have a serious shot at the B-double business. What’s more, it can do it with its own fully automated 12-speed transmission called mDrive which, of course, is a suitably ‘Mackanised’ version of Volvo’s stunningly smooth I-shift box.

Bringing mDrive to market has been an extremely long-winded exercise and many wonder why it needed to take so long when the need, in fact, was so great. Whatever, it’s now here and best of all, it was worth the wait.

Taming the tiger

It was a blustery Melbourne morning as the cavalcade of new Macks was readied for the next leg of its Australian tour, moving from CMV’s Laverton (Vic) dealership to the NSW industrial hub of Newcastle.

As a Volvo, Mack and UD dealership, CMV is well versed in the supply of AdBlue (liquid urea) for SCR engines and even has a mini-tanker to dispense the product. Thus, filling the 200 litre AdBlue tank of a Mack Trident took just a few minutes, which sure beats trying to slosh it in using 10 or 20 litre containers!

While the Trident was the prime focus for this report, my first drive was a Granite day cab prime mover pulling a drop-deck semi with a Granite rigid tipper sitting on the deck.  Designed for urban distribution roles and with a gross combination rating of 45 tonnes, the Granite prime mover had the MP8 engine rated at 435 hp with 1655 lb ft of torque, coupled to an mDrive automated transmission and driving into a Meritor RT40-145 tandem running a 3.42:1 axle ratio.

Riding on a wheelbase of 4460 mm and with its steer axle set back 1297 mm from the bumper face, this Granite boasted a remarkably tight turning circle of 15.9 metres. It also sported a bumper to back of cab (BBC) measurement of 2960 mm and an overall length of 7272 mm, while fuel and liquid urea tank capacities were 700 and 125 litres respectively.

Apart from the mDrive experience, probably the most pleasing aspect of this drive was that it demonstrated just how well Mack engineers have tuned the MP8 engine to differentiate it from its Volvo counterpart. Quite simply, if I hadn’t known any different, I would not have suspected there was anything other than a traditional Mack six humming away under the hood.

Perhaps it’s due to a slightly freer exhaust system, but throughout the drive there was the distinct impression of a decidedly deeper engine note than what comes from a Volvo engine, which I believe is exactly what most Mack drivers would want to hear. And that’s not to say it was noisy; on the contrary these new bulldogs are quieter than their forebears by a country mile. No, it’s simply a familiar nuance that perhaps even subconsciously reinforces the fact that you’re driving a Mack.

And speaking of driving, although my stint in the Granite was short, it at least provided the opportunity to see how mDrive performed hauling away from traffic lights and such. Grossing just 25 tonnes or thereabouts, the unit certainly wasn’t working hard but the fact that the transmission software recognised this and would often skip one or sometimes two gears during upshifts was a solid recommendation for the intuitiveness of the system. I also noticed that it adapted quickly to a gentle driving style, keeping engine speed within the most fuel efficient band between 1200 and 1600 rpm.

Trident’s turn

Then it was time to park my butt in the comfortable sheep-skin covered driver’s chair of the Trident, hauling a loaded B-double set and grossing around 60 tonnes, well under the model’s 70 tonnes gross weight rating. My co-pilot for the trip was Mack driver-trainer Paul Munro and as we both scribbled in our logbooks, it struck me that there were three major departures from Mack tradition in this Trident and the Granite I’d just driven. First, of course, is the SCR emissions system while second and third are the absence of a clutch pedal and shift lever due to the mDrive automated transmission.

That’s right, there’s no shift lever at all, with gearbox functions controlled by large push buttons housed in a neat flush-fitting panel just to the left of the steering wheel, with a similarly large and easily read LED display at the top showing which gear is selected. Vitally, due to the wrap around cockpit style dash, this panel is well within fingertip reach of the driver and along with the normal selector functions, there’s another marked ‘PERF’ denoting a performance mode which allows revs to run higher on long climbs and provides better engine braking during descents.

Besides, not having a shift lever of any description beside the seat proved a boon when I decided it was time to test out the bunk for a few hours. Seriously, being able to swing both legs around the seat completely unimpeded is pure joy. And yes, the sack is extremely comfortable too!

Meanwhile, in the constricted confines of a roadhouse parking area it was similarly easy to appreciate the manoeuvrability afforded by a steer axle set back 1297 mm from the bumper which, combined with a 4885 mm wheelbase, provides a relatively compact turning circle of 17.2 metres.

At the other end, the Trident ran Meritor RT46-160 drive axles with a final drive ratio of 3.07:1, riding on Mack’s AP460 air suspension. Fuel and liquid urea capacities are 1400 and 200 litres respectively while the BBC dimension is 3775 mm with a 36 inch (914 mm) sleeper berth attached.

Pulling onto the highway, the Trident immediately flexed its considerable muscle and the 1920 lb ft of torque was put to good use as the mDrive box progressed through the gears as smoothly as any automated unit I’ve driven. Particularly impressive was the precise engine speed control that enabled crisp, fast shifts, keeping the turbo up to speed and minimising road speed drop off during each change.

Once up to the 100 km/h limit, at which the Trident’s tacho was indicating a relaxed 1500 rpm, Paul Munro proceeded to describe the cruise control operation and I soon discovered a very useful feature of the system. After setting the desired road speed and with the engine brake switched on, pressing another ‘set’ toggle switch allows the engine brake to activate when the vehicle speed exceeds the set speed by more than three km/h, such as on a downgrade. However, having the three km/h tolerance means slight variations in speed are allowed for without the annoyance of the engine brake coming on when it’s not needed. And on the subject of engine braking, Mack’s Powerleash unit is good for 315 kW (495 hp) of retardation at 2100 rpm.

After this, it was simply a matter of sitting back and enjoying the drive, with the Trident taking the task of hauling a 60 tonne B-double combination up the Hume well in its stride. For instance, on the first serious northbound climb near Glenrowan, it only dropped one gear and crested the rise at 65 km/h and 1300 rpm. Then further on at the steeper Aeroplane and Woomargama ascents it managed both in eighth gear, falling to 28 km/h and 1200 rpm on the former and 33 km/h and 1300 rpm on the latter.

The day progressed comfortably and smoothly, and with midnight approaching after skirting around Sydney and joining the F3 for the final leg to Newcastle, the Mack seemed to relish the cooler night air. Indeed, the truck romped up the Joll’s Bridge climb from the HawkesburyRiver, settling into 9th gear and holding 40 km/h at 1400 rpm on the sharpest pinch. Similarly, the run over Moonie Moonie saw the Mack cling tenaciously to 8th gear with the speedo steady at 30 km/h and the tacho registering 1250 rpm.

By any estimation it was a gutsy effort considering the all-up weight of 60 tonnes. However, in both cases the mDrive transmission wasn’t left entirely to its own devices. I found the best results were achieved by leaving it in auto but selecting performance mode at the commencement of a climb. This enabled single gear downshifts at about 1400 rpm rather than letting engine speed fall to 1200 rpm where the transmission would perform a skip downshift to compensate for the loss of road speed. Then once it had settled on the right gear for the pull, deactivating the performance mode allowed revs to drop to 1250 without a ratio change to make best use of the low down torque. This also allowed upshifts to occur sooner as the terrain levelled out which once again kept engine speed in the fuel efficient band between 1200 and 1600 rpm.

All up, the strategy seemed to work and arriving atNewcastle, a quick flick through the driver info system revealed the Trident had averaged a respectable 1.7 km/litre (4.8 mpg) on the trip fromMelbourne. What’s more, according to Paul Munro, the unit’s overall average consumption since the beginning of Mack’s cavalcade was 1.77 km/litre (5.0 mpg), achieved with a consistent 60 tonne gross weight and a wide variety of drivers.

At the end of the test, the overwhelming impression was that Mack has done a fine job of incorporating the necessary SCR technology and desirable mDrive automated transmission into its product line without compromising the traditional character of the brand.

This is perhaps best underscored by the conclusion that with this latest Trident, Mack finally has an entirely competent B-double prime mover propelled by a highly responsive six cylinder engine and automated transmission package.

Arguably the most pertinent point of all though is that none of this would have been possible for Mack without its Volvo parentage. For those who still yearn for the old days, it’s a point certainly worth thinking about.


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