Article

Test Drive: Mack Pinnacle

The Pinnacle is Mack's latest- generation premium tractor for over-the-road fleets and owner-operators

September 2007, TruckingInfo.com - Test Drives

by Steve Sturgess, Executive Editor

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They also power Volvo's trucks around the world as well as Renault trucks in Europe and other markets. (In the Volvo products there's currently a bigger engine: the 16-liter D16 – see next month's Heavy Duty Trucking for Volvo VT880 test. Mack will get that big motor next year.)

The two new engines are significantly different from the earlier Mack power. They are physically a little longer, though narrower than their predecessors. They have integrated exhaust aftertreatment systems (diesel particulate filters). And they flow more exhaust gas in the recirculation so they need more, optimized cooling.

As a result, the new engines demand longer hoods and different "packaging" in the chassis. This means that while the Pinnacle may not look a whole lot different from the Vision it replaces, it most certainly is.

In fact, says David McKenna, the powertrain sales and marketing manager who rode along with me on this 500-mile test, only about 25 percent of the Pinnacle carries over from the Vision.

Mack's home city of Allentown, Pa., was the base for a two-day evaluation of the 2008 Pinnacle with the 13-liter, 800-cubic-inch, MP-8 diesel. Day one was spent in the Poconos, hauling up a series of sharp grades – mountains, even – as we negotiated I-78, I-81 and I-80 north of Allentown on a big loop of nearly 300 miles. We were in a truck specially built to honor U.S. servicemen killed or injured in battle, and it was a moving experience to drive this truck and get the thumbs-up from many other drivers, truckers and four-wheelers alike.

To make it work, we were loaded to 76,000 pounds GCW to feel the performance of the new diesel.

Day two saw us heading down I-78 toward Hagerstown, where the route settles out to more level running. I wanted to see what sort of fuel mileage potential the new engine has, cruising along at 58 to 60 mph, letting the truck run out on the down grades and keeping out of the engine brake as much as possible.

THE TRUCK

The Pinnacle was first announced along with the engine lineup in late 2005, but didn't really make much of an impression until 2006 when a few appeared with early MP-7 new generation engines. These were early production models from Mack's Hagerstown facility. The earliest Pinnacles were mostly demonstration units with the 11-liter, running in '04 configuration without the diesel particulate filter because low sulfur fuel was in short supply. In fact, we drove one briefly from the Poleman Transfer fleet out of Wadeena, Minn., about a year ago.

The Pinnacle is produced at the Volvo New River Valley plant in Virginia, alongside Volvo's VN. When the Mack production shifted there with the closing of the Winnesboro, S.C., plant several years ago, the opportunity was taken to combine the best of the frames between the two brands. But to satisfy the Mack design and performance criteria, only about 60 percent of the frames came out as common. Many compromises that would have diluted the Mack-ness of the end product were resisted, so there are significant differences amid the similarities of the Volvo and Mack products.

Another change that goes back a few years is the improved durability of the Pinnacle cab. This comes from the introduction of the Granite construction range that featured a severe-duty version of the cab, with extra gusseting, different sections and so on. These have now been incorporated into all the cabs on the Mack products, adding around 30 pounds to the Pinnacle, but gaining enhanced durability in exchange.

The interior space is better, especially on the daycab, where the B-pillar is extended and seat mountings have far more fore and aft travel. The hood is longer, so the cab sits a little further back from the all-new cooling package that has a fan ring. And, on the axle-forward Pinnacle, the "eyebrows" over the grille with the associated Mack "belt buckle" disappear, along with the big, bold M-A-C-K letters. Instead there's a rectangle grille and a subtle "MACK" down at the bottom right.

Under the hood of the test unit was the 13-liter (800-cubic-inch) MP-8. New for the 2007 emissions certification, the MP-8 shares the same architecture as the smaller MP-7 and the upcoming giant MP-10 (if you hadn't guessed, the numbers in the Mack designations refer to displacement in hundreds of cubic inches). They are all overhead cam, as was the Volvo D12 on which they are based, but with the camshaft and auxiliary drive moved to the rear of the engine. Injection pressure has jumped from the D12's 25,000 psi to 36,000 psi and, since the pressure is generated by Delphi Gen 3 unit injectors off the camshaft, there are major torsional fluctuations in the camshaft drive. These are now fed directly in to the flywheel instead of the nose of the crankshaft, allowing for better damping and stricter control of the injector timing.

The Delphi injectors are multi-event with pre- and post-injection for better combustion control, lower NOx and a significant reduction in diesel combustion knock.

The engines are different: The MP-7 is smaller and 360 pounds lighter than the MP-8 but peaks with 405 horsepower in its line-up (this MP-8 is a 485). Both engines are available with Maxidyne, Econodyne or MaxiCruise personalities. The three are differentiated by torque and rpm curves that deliver performance differently to suit different fleet or vocational needs. Ours was a 485/1,650 Econodyne designed for typical interstate and part load/part throttle application.

Backing up the engine, an air assisted two-plate clutch and a 13-speed Mack Maxitorque transmission completed the Bulldog part of the powertrain. Drive axles were by Meritor with 3.90 to one ratio.

With the double overdrive of the Mack 13-speed, triple-countershaft transmission, the gearing gave 1,370 rpm at 60 mph indicated. Calculating out the road speed with the Bridgestone 22.5-inch M726 drive tires gives us 1,360 at 60 mph. Mack's McKenna says he likes to gear for around 1,400 rpm at 65 mph, so we were turning a few extra rpms.

The engine and transmission sit lower in the frame than the earlier E7 did, which gets some additional cooling to the oil pan, as well as helping with underhood air management. The narrower engine also helps, and the general clean and compact EGR system make it a competent-looking install in the chassis. Downstream, the exhaust runs into a frame-mounted "teakettle" DPF that sits between the very typical Mack stack of air tanks and the fuel tank on the passenger side. From there, a splitter in the exhaust allows for two matching stacks up the outside corners of the back of cab.

The stacks were relatively short because the Pinnacle featured a mid-roof and no cab fairings of any kind. It did have some fine-looking step/storage boxes and checker-plate fenders, with polished tanks setting off the stirring murals.

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