Solid competition

| April 02, 2008

New MaxxForce engines from International a success.

Competition is a wonderful thing. For truckers, two recent products that best exemplify this claim are the 11- and 13-liter MaxxForce engines from International, first announced two years ago and formally introduced in late January.

The big-bore MaxxForce duo, with a combined horsepower span from 330 to 475, offers users impressive fuel economy, solid low-end pulling power, quiet operation and, as if that weren’t enough, an overall package that weighs several hundred pounds less than comparable engines.

MaxxForce engines are the results of an alliance between International and MAN Nutzfahrzeuge, headquartered in Munich, Germany, to collaborate on design, development, sourcing and manufacturing of components and systems for commercial trucks.

The benefits of the pairing were demonstrated two months ago when International summoned a group of trade press members to the Las Vegas Motor Speedway for a drive test of the new engines and an informational blitz focused on the features contributing to their performance.

Given a choice of vehicles to drive, I selected a bright red ProStar powered by a MaxxForce 13, set at 430 hp and 1,550 lb.-ft. of torque, and geared through a 10-speed Eaton transmission. The tractor was hitched to a flatbed loaded with Jersey barriers. The combination weighed about 61,000 pounds.

The initial thing first-time drivers will notice about the MaxxForce engine is its sound, or lack thereof. I wasn’t packing a decibel meter at the event, but I could tell the engine was noticeably muted. In their pre-trip orientation, International officials stressed this point, warning test drivers that they probably wouldn’t be able to “shift by ear” because of the lack of audible cues. That wasn’t quite the case for me, but I did need to listen more carefully.

Several factors help quell the noise, according to Dave Schaller, senior program manager for International. “The high-pressure Bosch common rail fuel system [capable of an eye-popping 26,000 psi] is one of the reasons the engine is quiet,” he says. Full pressure and maximum torque occur at very low rpm, so there’s no need to rev up just to achieve more power. Also, in on-highway applications, all of the front-end accessories are turned with a single belt. The fan is gear-driven. Fans in severe-service trucks, however, are belted to help dampen shock loading during clutch engagement.

Our test route was fairly short – a mere 23 miles – and didn’t include much terrain diversity. We ran north from the speedway on I-15 to the intersection with US 93 North, then returned to our starting point. The only real display of the MaxxForce’s much-touted low-end torque occurred during the short climb up the ramp to the interstate’s southbound lanes. Accelerating up this brief, roughly 7 percent climb, I was grabbing gears in reasonably rapid succession, and each time I did, the engine dipped to about 1,100 rpm then spooled steadily higher until the next shift point. This engine is operating in a zone that was once dominated by the low-lugging Mack Maxidyne.

Obviously, the Bosch fuel system is an integral part of this capability, but so are the engine’s dual turbochargers – one for the low end, the other for high – which provide full boost across the rpm spectrum. This combination should satisfy the power needs of most on-highway operators, excluding heavy haulers and others who really need a full 15 liters under the hood. Equally important, though, the turbo and common rail systems are delivering good fuel economy, according to a few of the fleet managers who’ve been testing the engine for International.

“We started running a MaxxForce 13 last April, and it’s averaged about a half-mile per gallon better than the other engines we have, ” says Larry Mead, service manager for Cliff Viessman Inc. in Marshall, Minn., a 400-truck food-grade tank operation headquartered in Gary, S.D. “At first, we had it set at full power [475 hp and 1,700 lb.-ft. of torque], but we later cut back to 410 hp and 1,450 lb.-ft. of torque, and that really bumped the mileage.”

Mead’s comments were similar to those of the other fleet people who attended the event in Las Vegas. As the only tank operator, though, he was likely the one who benefited most from the MaxxForce’s lower weight.

International officials attribute much of the reduction in poundage to the compacted graphite iron from which the block is cast. “CG iron,” as it’s called in the trade, is reportedly much stronger yet lighter than other metal used in heavy industrial forging. MaxxForce is the only large diesel made from the material, although “nearly all of the NASCAR race teams use it,” says Steve Perkins, big bore specialist for International. There are other benefits, too. “Because of the structural strength of CG iron, we were able to build a rear PTO drive right into the block,” Perkins says. “That adds to operating efficiency.”

By the time I’d returned to the speedway, I was sold on the many advantages the MaxxForce offers. Nevertheless, I did have one gripe: the engine brake. I think it needs more oomph. I’d activated it, at full power, on my descent to Speedway Blvd., but found its slowing assistance to be minimal. Later, during one of the informational sessions, I learned that this isn’t a standard compression-type device. Instead, it’s a hybrid system that starts with an exhaust baffle, gradually building enough backpressure to override exhaust valve operation, yielding something similar to compression braking. These tandem forces are supposed to generate up to 300 braking horsepower. Perhaps the unit in my test truck simply needed some tuning.

The big bore MaxxForce just went into production a few months ago, so some adjustment can be expected as more units start populating the nation’s roadways. Quite honestly, if internal-brake performance is the only nettlesome issue people have with these engines, I believe International is on the cusp of a huge product success story.


MaxxForce 13: Specifications
Engine Type: Diesel, 4-cycle
Configuration: In-line 6-cylinder
Displacement: 12.4 liters (757 cu. in.)
Bore and Stroke: 126 mm x 166 mm (4.96 in. x 6.54 in.)
Compression Ratio: 17:1
Aspiration: Twin-series turbocharger, air/liquid intercooled
Governed Speed: 1,900 rpm on-highway, 2,100 rpm vocational
Combustion System: Direct injection
Cooling System Capacity: 49 liters (52 U.S. qt) (engine only)
Lubricating System Capacity: 42 liters (44.5 U.S. qt)
Total Engine Weight (dry): 2,244 lbs (1,018 kg)
Dimensions: 1,365 mm L x 930 mm W x 1,239 mm H (54 in. x 37 in. x 49 in.)
Valves: 4 per cylinder, overhead cam actuated
Horsepower Range: 410-475 horsepower (306-354 kW)
Torque Range: 1,450-1,700 lb.-ft. (1,964-2,302 Nm) @ 1,000-1,200 rpm
Clutch Engagement Torque: 830 – 960 lb.-ft. @ 800 rpm

MaxxForce 11: Specifications
Engine Type: Diesel, 4-cycle
Configuration: In-line 6-cylinder
Displacement: 10.5 liters (641 cu. in.)
Bore and Stroke: 120 mm x 155 mm (4.72 in. x 6.10 in.)
Compression Ratio: 17:1
Aspiration: Twin-series turbocharger, air/coolant intercooled
Governed Speed: 1,900 rpm on-highway, 2,100 rpm vocational
Combustion System: Direct injection
Cooling System Capacity: 49 liters (52 U.S. qt) (engine only)
Lubricating System Capacity: 42 liters (44.5 U.S. qt)
Total Engine Weight (dry): 2,244 lbs (1,018 kg)
Dimensions: 1,365 mm L x 930 mm W x 1,239 mm H (54 in. x 37 in. x 49 in.)
Valves: 4 per cylinder, overhead cam actuated
Horsepower Range: 330-390 horsepower (246-291 kW)
Torque Range: 1,250-1,450 lb.-ft. (1,693-1,964 Nm) @ 1,000-1,200 rpm
Clutch Engagement Torque: 660-830 lb.-ft. @ 800 rpm

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