Article

Mack Pinnacle

It might look the same, but there are plenty of changes under the skin.

September 2006, TruckingInfo.com - Test Drives

by Steve Sturgess, Executive Editor

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The new Mack Pinnacle with its all-new MP7 engine is a prime example of what the '07 emissions regulations have wrought. What we have in this Mack is an all-new engine platform in an effectively all-new truck. But it doesn't look a whole lot different, because nearly all the changes are under the skin.

These changes add up to a whole new model for Mack, as they do for most of the truck makers previewing 2007 models at the Mid-America Trucking Show earlier this year. Doubtless there will be a bunch more announcements as we head toward the Jan. 1, 2007, deadline.

Driving the changes are modifications to the chassis to accommodate engines with higher-flow exhaust gas recirculation and diesel particulate filters required to meet the stringent emissions regs of 2007, as well as the need to be prepared for even tougher regulations in 2010. Higher EGR flow rates mean more heat rejection, and the DPF requires moving chassis components to free up the necessary real estate on the truck.

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Wholesale changes mean rugged testing in the lab, on the test track and, as in this case, in-fleet testing. This particular Mack development truck is being used by the Polman Transfer fleet, based out of Wadena, Minn., a general freight hauler that is an existing Mack account. Polman has some high-mileage accounts, ideal for gaining real-world experience and duty cycles to find those problems that don't show up in the lab.

Polman transfer is a family company going way back. In fact, Duane Polman started out with a 1946 Chevrolet, but quickly shifted to Mack with the 1950 LJ and B Models. Early freight was wood pulp, hauled south to the Twin Cities, with up to 20,000 pounds on a two-axle.

Over time Duane Polman has tried other brands, but remains a staunch Mack account.

Duane still goes in to the office every day, but the company is now run by his sons, D.J. and Nick.

Wally Anderson runs the shop, and chooses trucks, components and all mechanicals. He has overseen test units for previous Mack engine/electronic changes over the 26 years he has been with the company.

Today, Polman's freight is lots of French fries (the local soil produces a particularly white potato much favored by McDonald's). Polman also hauls "four wheelers," ATVs from Roseau up close to the Manitoba border, which is where we're heading on this evaluation. The run up is with an empty to stage there. The haul back is 20 of the recreational machines. Approximate weight: 50,000 pounds GVW. Total mileage: just shy of 400 miles.

THE TRUCK

The Pinnacle is the latest evolution of the CH, although really, only the basic cab structure remains. The CH had a major styling change with the introduction of the Vision over-the-highway trucks and, more recently, a ruggedization with the modifications for the launch of the vocational Granite.

More recently, the Granite has had a revision to the back-of-cab to address the front-to-back room of the old cab, along with running changes to dash and seat slides that make the cab an acceptable driver environment. New doors with lowered beltline toward the front aid visibility, as does a one-piece windshield option for the Pinnacle.

The Pinnacle also sees styling changes that have their basis in the need for more cooling for the 2007 engines.

The new engine, the MP7, is shorter than the old – very old – E7, and sits back in the frame. This allows for the critical air handling under the hood that was the subject of much research and development for the new models for 2007. As in 2002, cooled EGR requires heat rejection to the cooling system; 2007 sees higher rates of EGR with finer, closed-loop electronic controls for even tighter NOx control. And more heat rejection.

Underhood temperatures are expected to be an issue again with the greater heat, so underhood air management is highly desirable.

Another major change, although it's one that carries over from the latest Vision models, is the Mack Advantage frame. This is a new frame, developed with the latest engines in mind and sharing a number of features with the Volvo frame. The original concept was to have as much in common as possible – but, to preserve the Mackness, it shares only about 50 percent of its components.

As well as an economy of scale, this brings two important benefits: lighter weight, in strength-to-strength comparisons with the previous Mack frames; and a much better turning radius with the steering gear position optimized. It also appears to offer some ride benefits, based on our previous experience with the Vision on the Advantage chassis. Steering is good – something I've come to expect from a Mack – and front end ride with the steel suspension is as good as you could want. There is the Hendrickson AirLink air suspension option, though I like the taper-leaf steel Mack setup as an excellent compromise between ride and steering feel.

The frame accommodates the MP7, available in limited production as an '06 and in full production from January as an EPA '07. The MP8 comes along a little later.

Another entry in this all-new, three-model engine range is the Volvo D16 (and, later, the Mack MP10).

Volvo and Mack refer to these engines as the new platform to meet the emissions requirements of North America and Europe for the foreseeable future. I find that confusing, for while the base architecture is the same, the castings, physical size, bore centers, weight, go up in size with each displacement. I like to think of that as three engine ranges, since they all have varying horsepower. The Volvo companies have made sure that the horsepower ratings do not overlap, so if a customer is spec'ing horsepower, the engine choice is made. Mack expects the 11-liter MP7 to be its bread and butter, and given Mack's strength in vocational applications, that is entirely reasonable.

The engines are based on the Volvo VE D12, a single overhead camshaft design surprisingly like the Series 60, and the biggest selling diesel in the world, says Volvo. However, to sustain ever higher injection pressures, generated by unit injection off the overhead camshaft, the valvetrain gearing has been moved to the rear of the engine on all displacement "platforms."

This is to damp out the severe torque fluctuations that the camshaft sees pumping up the injectors. Instead of feeding the torsional vibrations to a front drive and then back through the crankshaft (which introduces variability in the injection timing), the cam drive torque variations are fed directly into the engine's flywheel.

A new feature on this – and other brands of '07 engines – is the electronically controlled Holset variable geometry turbocharger. Holset is a wholly owned subsidiary of Cummins Engine Co. and in the '02/'04 emission step, the turbochargers were proprietary to Cummins. The company has made a strategic decision to make the technology available to competitors – as it has the DPFs manufactured by its Fleetguard division – that will be used by Mack and Volvo starting in January.

The Holset VGT is a simple and elegant design that has proven very robust. For '07 it gets electronic, in place of earlier pneumatic controls. This enables closed-loop control through the engine ECU that is claimed to give even snappier throttle response.

An MP7 395C MaxiCruise, rated 395 horsepower, was the fleet test unit that Polman was out to break if anything was to break. It arrived with 40,000 miles and to date, nothing has broken, but in getting to the 120,000 miles at the time of our evaluation, fuel economy had improved markedly. The engine is basically to full 2007 standards but, because of lack of access to the ultra low sulfur diesel fuel essential for particulate filter life, it had no aftertreatment device.

The presence of a DPF makes hardly any difference to performance up until the maintenance interval, which could be at 300,000 to 400,000 miles. So running without the DPF had no impact on the baseline performance of the MP7 on this test.

The transmission was a Mack T-310 10-speed pushing Meritor rear ends with a 3.90 ratio and 22.5-inch Goodyear rubber.

ON THE ROAD

Setting out unloaded with veteran Polman driver Shawn Thoennes at the wheel, the truck had that electronic-engine smoothness where you can feel every cylinder pulling its weight. Thoennes was easing up through the gears in a perfect progressive shifting sequence, nicely matching engine speed to shift and getting the truck under way very smartly. I was to find later that this was made easy by the excellent throttle modulation due, in part, to the electronic VGT control.

You feel the smooth torque, but you can't hear the engine working hard. The injection system features the latest Delphi injectors that rate-shape the fuel injection, giving pre and post events either side of the main injection event. This goes a long way to eliminate the distinctive diesel "knock." Later in the day, when I was driving, I was particularly interested to see if I could hear the valve/accessory gear train, just inches ahead of the toeboard instead of being up by the radiator. There were times at idle that I could hear what sounded like a little gear rattle, but nothing like the noise you get, for instance, from an old transmission. And that may be an idiosyncrasy of this particular early production engine, because torsional dampers are on the geartrain to address noise.

This overall quietness of the engine is helped by the extensive floor deadening. Mack says this is truly a hose-out interior, with a rubber tub floor covering. That's a plus, but it's the insulation beneath that makes the Pinnacle so quiet.

Outbound with an empty trailer, the tractor felt tight and quiet. Cruise noise levels were only 68-69 decibels. The 11-liter ran with the usual electronic immediacy, never missing a beat and with exhaust completely clear. At the first break, the dash display showed we had run 6.2 mpg. Thoennes said in the initial stages of testing the engine would only give 5 mpg, but with 120,000 miles on it, he was regularly in the 6s.

Picking up a loaded van, there seemed hardly any difference in performance, the engine pulling the 33,000-pound load easily away at idle and cruising comfortably over the few hills on this northerly run.

As noted earlier, throttle response and modulation were excellent, and I found it very easy to match shift speeds despite the minimal familiarity with the Mack transmission. Gearing allowed for a fairly relaxed cruise speed of 1,625 rpm at 60 mph. That's maybe a little higher than we are used to, but the engine is right on top of the horsepower curve, which is flat between 1,500 and 1,700 rpm. And the lower overall gearing helps performance with a maximum 1,570 pounds-feet peak torque at 1,200 rpm.

The engine is equipped with a retarder (referred to as a PowerLeash in Mack's Bulldog-speak) that is very effective, so there was almost no need to use the service brakes on the run back down to Wadena.

The truck rode very nicely in both directions, with the front taper-leaf suspension working well and the truck maintaining lane well on the largely two-lane trip. In fact, the steering was up to the standard Mack has set in the past. There was a bonus, too, that driver Thoennes commented on: The turning circle was a major improvement over the other Macks – mostly CH – in the Polman fleet.

OPERATIONAL FACTORS

It will be a while before we know for sure about the reliability and durability of the new engines. But Mack customers will doubtless be pleased to see an end to the E7, which had its fair share of trials and tribulations after 2002. These new engines are based on the highly successful VE D12 that has served Volvo so well throughout the world. So there's every expectation that the MP7 will be as good.

And as economical. Or perhaps more so. According to the engineers at the launch of the engines late last year, the new platforms are more fuel efficient than the old, eliminating the 1-2 percent loss of Btu in the ultra-low diesel fuel and then some.

Then there is lube oil. Current opinion is that oil change intervals will remain as they are today, and there may well be the opportunity to stretch intervals with experience. But the engine oils used must meet the low-sulfur, low-ash CJ-4 category, and indications are that these will cost more, if for no other reason than the new additive chemistry uses more expensive materials.

The reason for the CJ-4 category is to protect the DPFs. These highly expensive components – replacement of the whole can could be as much as $5,000 – will require some maintenance. And mechanics are going to have to deal with the ceramic-filter elements. Banging them on the garage floor to clean them won't work and could easily damage the very expensive element.

The good news is that the DPF maintenance interval can be 300,000 miles and more, meaning just one service in the first ownership of many trucks.

CONCLUSION

We have driven several of the '07 engines to date, and all the engine manufacturers seem to be on track for the Jan. 1 deadline.

Mack is there, with field test units like the Polman truck running without major problems and delighting drivers while the engineers track their progress and fine-tune the electronics.

Certainly, Mack should be proud of this 11-liter. It performs very well – nearly 400 horsepower and 1,560 pounds-feet is a pretty strong rating out of the box. And it drives like a strong engine, rewarding the driver with good throttle response, substantial low-end torque and a nice quiet environment in the cab.

If all the '07s are going to be this good, then American truckers – owners and drivers – are going to have little to worry about.

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