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Through the paces

International’s reputation for building trucks has always had three main tenants: reliability, efficiency and economy.

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International’s reputation for building trucks has always had three main tenants: reliability, efficiency and economy.

In emphasizing these hallmarks, however, the company hasn’t necessarily attracted buyers who value a more luxurious trucking experience. This situation will likely change soon, as production of the new ProStar increases.

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Formally introduced at the 2006 Mid-America Trucking Show, ProStar was developed during the past five years – the initial designs actually date back to the late 1990s – at a cost of several hundred million dollars. ProStar replaces the venerable 9400, introduced in 1991, as International’s chief long-haul highway tractor, and in doing so it boosts the company’s vehicle standards at least several notches.

Truck buyers are an ever more demanding crowd to please. They want lower operating costs, more driver amenities and better resale value. ProStar is intended to satisfy these demands with a range of new features not yet seen on other International models. Among other things, ProStar offers:

• Smoother and more rounder body shape, which reportedly cuts aerodynamic drag by more than 8 percent, improving fuel efficiency if the truck is driven properly;

• A four-piece drop-down bumper that provides greater access to the front of the engine compartment; as a multi-section piece, it is reportedly less expensive to repair than a one-piece standard bumper;

• Much quieter cab interior, the result of a molded floor mat with extra noise control, better insulation, integrated dash panel wiring harness pass-through ports, better engine mount placement, and an optimized floor structure;

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• Longer maintenance intervals on a variety of components.

I recently drove a ProStar Limited, the fanciest of four model levels, on a short lap of Southern Minnesota, pulling a dry van partially loaded with spent brake shoes. My tour began at River Valley Truck Center in Mankato, where Carol Howard, the dealership’s leasing manager, explained some of the truck’s more salient qualities before handing me the keys.

Fully briefed, I departed for some behind-the-wheel research. Right out of the proverbial gate I noticed the truck’s maneuverability. It not only turns more tightly than its predecessor – the result of a 50º wheel cut compared with previous system’s 45º, but also the steering is nearly effortless. International officials say both of its vendors, Sheppard and TRW, developed new gears for the ProStar that offer “a positive center feel.” In other words, a “dead band” spans the middle of the turning range, and tension increases as the wheels are turned farther off center. The steering is also designed to reduce road vibration without creating a disconnected feeling.

Panoramic visibility is another immediately obvious benefit of the ProStar. Within the first few miles of my trip, I realized how much of my surroundings were in clear view. Several factors contribute to this broad vista: First, the 17.6 sq.-ft. single-pane, bonded-in windshield is 15.8 percent bigger than the dual-pane version it replaced. The 4.9 sq.- ft. side-window combinations (roll-up and vent) are also bigger – 39 percent – than the previous model’s. The new A-pillars are slightly thinner. And outside, the hood slope is angled 6.4º more steeply, to a total of 19.6º.

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Under that hood, a Cummins ISX engine, rated at 435 HP, powered my test unit. It easily handled the terrain and load I was pulling. Roughly 10 minutes into the drive, though, the diesel particulate filter went into auto-regeneration, a now-common event that lasted about a half hour. Perhaps more interesting was the disparity between oil and coolant temperatures. At several points along my route, the coolant registered 180 degrees F, but the oil was almost 40 points hotter, an indication of the increasing demands ’07 engines are placing on lubricant.

Temperatures were much more pleasant in the cab, where the HVAC system delivered excessive amounts of refrigerated air. The three controls for this unit seemed fairly straightforward, but a warning message on the dash display kept advising me to “Activate HVAC front blower.” I later discovered that this meant the sleeper’s air condition switch was turned on, but some other accompanying switch – the front blower’s, I suppose – was off. Despite my ignorance in these matters, everything seemed to work well.

The suspension systems (chassis, cab and seat) worked equally well. A good ride is, of course, key to driver comfort, and the ProStar excels in this category. Shortly after I jumped on I-90 at Alden, Minn., the surface of the eastbound lanes, so decrepit that it should be preserved and licensed for vehicle endurance research, provided a magnificent workout for the truck’s numerous air and leaf springs. The ride through this rotten stretch of roadway was supple without being mushy. Although I did feel the sharpest jolts coming through the steering column, they’d been miniaturized and hollowed out by the time they reached my hands. The seat was fully isolated from the violence below. At the same time, sway and pitch were controlled, providing a stable, firm driving experience.

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According to International’s engineering team, the exceptional ride was achieved “through computer dynamic simulation, cab mounting, cab rear strut optimization, frame modal analysis and stiffness. The primary suspension was tuned with the cab and seat suspensions to optimize ride and handling.”

I enjoy trucking after sundown, when a cab’s interior is awash with the glow of gauge lights. The ProStar shines here, too – literally. Its ivory-faced instrumentation – there were 13 dials in my test truck – is suffused with a gentle and sophisticated amber glow as soon as the headlights or clearance lights are activated. My only disappointment with this array of readouts was, oddly enough, the driver display console, a super-sized (4.6 x 7.7 in.) fount of truck and trip knowledge located on the dashboard’s B panel. Still in the factory default setting, it was programmed to go into screen saver mode after only a few minutes without human interaction. I appreciate energy conservation as much as anyone, but think that at least one screen – instantaneous fuel economy – should be visible at all times. I was also frustrated with the instant mileage accuracy. The meter bounced wildly between 2- and 10-mpg, with little or no change in acceleration or engine load. Officials at International later told me that algorithmic improvements are coming soon.

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Aside of these temporary issues, the display itself – one of two in the dash – was easy to see and operate, flanked on two sides by large buttons that would enable even novice user to navigate through various screens without taking their eyes off of the road.

My ProStar test trip lasted just six hours, but that was enough to experience the truck in a variety of locations and across a range of roads. I came away impressed with the vehicle’s features, design and construction. The interior, similar in size to that of the 9400, has a spacious and airy ambiance, yet seems to wrap comfortably around the driver’s seat. It’s also exceptionally quiet. The dash’s hefty rectangular rocker switches are well ordered and easily reached. The steering wheel, itself chockablock with buttons for lights, cruise control and the stereo, is luxurious in both feel and appearance. With a different logo it would not look out of place mounted in a Bentley. The ProStar’s boldly aero exterior is just as refined, with sleek body lines that flow up and back from the front bumper’s ever-present smile.

Those body lines should translate into operational cost savings for truck owners, says Ron Schoon, International’s chief engineer for aerodynamics. “Our studies show ProStar to be the most aerodynamic heavy truck among competing models,” he says. “Using the 9400 as our benchmark, we set out to improve drag coefficient by 7 percent. By the time we finished, though, we’d actually achieved an 8 percent improvement.”

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Schoon and his team focused much of their attention on the hood, mirror, windshield and side-skirt shapes. They also spent a lot of time sculpting a sun visor that is aerodynamically neutral. “I think we’ve been very successful in integrating the sun shades into the product designs,” he says. “Our styling people believe that this is a premium feature for the vehicle’s appearance. I’ve tested all of the competing vehicles, I haven’t found one yet where the sun shade offers any drag reduction or is even neutral.”

As mentioned above, the amount of money required to develop this truck was considerable, but truckers who spend any significant time behind the wheel of a ProStar will probably consider the investment to be worth every dime.

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