Hitting the road

John Baxter | May 02, 2010

Mike Jeffress, vice president of maintenance of Maverick Transportation, says his company has had no issues with drivers not being able to operate the truck normally because of frozen DEF, in spite of having a cold winter in Michigan. The fleet runs DD15s in Cascadias.


Cummins’ 2010 ISX substitutes a common-rail fuel injection system for the larger camshaft and fuel injectors on early ISX engines. This, along with the ability to split each injection cycle into several parts, means quieter operation.

Cummins has given the ISX a new injection system. Both the familiar 15-liter ISX and the 11.9-liter version, available in August, sport the XPI (extreme pressure injection) common-rail injection system. Its ultra-high-pressure injection pump delivers a continuously regulated supply of the juice to a rail. This large pipe supplies each of the six injection nozzles with fuel at whatever pressure is needed, even below 1,100 rpm.

Cummins’ Steve Charlton, director of heavy-duty engineering, says of the new system: “You can dial in the pressure for the next combustion event, or create a five-piece event to help with emissions. That means you can use pilot injection to reduce noise. You can also increase the exhaust temperature to keep the SCR catalyst working or to help regenerate the DPF.” He says the system can create 35,000 psi or more.

Since XPI provides high-pressure fuel without unit injectors, the 2010 ISX engines no longer need the second camshaft that used to operate them. This helps the engine run quieter.

Customers say their drivers are happy with the overall performance, from startup to full bore down the highway, says Lou Wenzler, Cummins on-highway market communications director. Road testing a SmartPower 425-hp ISX that jumps from 1,450 lb.-ft. torque to 1,650 in the top two gears, one driver refused to believe the engine was only a 425, Wenzler says.

Charlton says the ISX engines also have a greatly enhanced EGR cooler that does a much better job of turbulating the exhaust and coolant as they pass through, enhancing its cooling capabilities, and thus reducing engine stress. And Charlton says the engine is tuned so the sweet spot is considerably larger.

Fleets commonly see a 0.3 mpg improvement, which is 5 percent better than last year’s engines, say Wenzler and Jim Kelly, senior vice president of heavy-duty marketing.

Ray Redmon, maintenance manager of Calex of Pittston, Pa., says his fleet runs Volvos with 2007-spec ISX engines rated at 450 hp. He’s looking forward to purchasing some 2010 ISX-powered trucks this year because he believes the lower levels of EGR should reduce the occasional oil filter plugging of his current engines. To virtually end such trouble, even on 2007 engines, Wenzler says Cummins Filtration has slightly altered the volumes of oil flowing through full flow and bypass sections of their filter.


Navistar’s MaxxForce 13 has a larger radiator, charge air cooler and EGR cooler, as well as more reliable twin wastegated turbos and an improved EGR valve for 2010.

With its MaxxForce 11- and 13-liter engines, Navistar has seen fuel economy improve 1 percent to 3 percent in its 2010 models, says Tim Shick, director of business and product strategy at Navistar Engine Group. This is due to improvements in chassis integration with the International trucks, adoption of a clutched air compressor and, in the case of the ProStar, excellent aerodynamics.

Also, oil analysis reports on the new engines have been as good as those on previous engines, Shick says.

He notes that competitors’ engines are also using EGR – in their case, to supplement SCR. “The MaxxForce 11- and 13-liter engines are using advanced EGR as an alternative to SCR,” he says. “Our EGR rate will go from 25 to 30 percent for ’07-’09 engines to 30 to 35 percent for 2010.”

The MaxxForce 13 engine has ratings from 410-475 hp, the 11-liter from 330 to 390 hp. Because EGR rates increase with power level, he says, Navistar increased the size of its cooling package and EGR cooler to shed more exhaust heat this year. And, engines have been shifted back a bit in the chassis to improve underhood airflow.

“Exhaust leaves the engine at 500 to 800 deg. F., but the EGR cooler can take it down to 200 deg. F. or less,” he says.

  • Rod Rimmer

    Please note that the PACCAR MX engine’s camshaft is mounted LOW in block.

  • Cory Russell

    Great information. If you have more info please send it to me.


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