Clearing the Air: Finding a happy medium

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Cummins’ ISB will be rated at 200-325 hp and 520-750 lb.-ft. of torque @ 1600-1800 rpm.

For 2007, Environmental Protection Agency regulations require that medium- and heavy-duty diesel engines meet the same rigorous emissions standards. Beginning in January, the truck and diesel engine industry will be required to provide more than a 50 percent reduction in nitrogen oxide (NOx) and a 90 percent reduction in particulate matter (PM) from the standards set in 2004, notes Dr. Helmut Endres, vice president of engineering for International’s engine group.

That’s no easy task, since older technologies used to reduce one pollutant tend to increase the other. So medium-duty engine manufacturers will have to use the same new emissions-reduction technologies that will be used on heavy-duty diesels.

New components
For ’07, diesels will use higher levels of exhaust gas recirculation (EGR), except for Caterpillar’s, which will use a second-generation of its Advanced Combustion Emissions Reduction Technology (ACERT) with Clean Gas Induction (CGI) – a lower-volume EGR system in which the exhaust gas is drawn aft of the diesel particulate filter (DPF).

EGR works to reduce NOx by cooling peak cylinder temperatures. Problem is, it results in less complete combustion, and partially burned fuel is a big source of PM.

So, like their big brothers, ’07 medium-duty engines also will use a DPF to remove PM from exhaust. That piece of equipment, in addition to manufacturers’ research and development expenses, will add to the average initial cost increase of somewhere around $5,000 per truck. The DPF also will require periodic cleaning at the same intervals as those used on heavy-duty diesels, according to Doug Ackerman, manager of marketing for Detroit Diesel.

Finally, as in heavy-duty engines, medium-duty diesels will require the use of ultra-low-sulfur fuel and new CJ-4 engine oil. For more specifics on how ’07 engines operate, see last month’s Special Report 2006, “Passing the Test.”

The rundown
As with their heavy-duty brethren, ’07 medium-duty diesels will continue to be available in a wide variety of brands, and horsepower and torque ratings. Here’s what we know so far:

  • At Caterpillar, the 7.2-liter C7 has taken over as the medium-duty powerplant, since “the (9.3-liter) C9 has moved up to more of a light, heavy-duty engine,” says Jason Phelps, who handles the company’s on-highway customer communications. The C7 has ratings of 190-300 hp @ 2500/2400 rpm, with torque at 520-860 lb.-ft. @ 1440 rpm.
  • While Cummins will offer medium engines in several application-specific ratings, general-purpose ratings include: The ISL, at 345-365 hp and torque at 1150-1250 lb.-ft. @1300/1400 rpm; the ISC, with 240-330 hp and 660-1000 lb.-ft. @ 1300/1400 rpm; and the ISB, with 200-325 hp and 520-750 lb.-ft. @ 1600-1800 rpm. Cummins also will supply private-branded engines to Dodge and Paccar.
  • For Detroit Diesel, it’s the Mercedes-Benz 7.2-liter MBE 900, rated at 190-300 hp @ 2200 rpm, and 520-860 lb.-ft. @ 1200 rpm.
  • At GMC/Chevy, there’s the home-built 6.6-liter Duramax V8, with 300-330 hp @ 3000 rpm, and 520-605 lb.-ft. @ 1600 rpm.
  • International, meanwhile, will offer its line of MaxxForce 5 diesels in I6, V6 and V8 configurations, ranging from 4.5 to 9.3 liters, and from 200 hp @ 2700 rpm and 440 lb.-ft. @ 1850 rpm, to 350 hp @ 2200 rpm and 1150 lb.-ft. @ 1440 rpm. International also supplies private-branded Power Stroke engines to Ford.
    Japanese engines also will be compliant with ’07 regulations:
  • Hino will offer its J-series engines with ratings of 175 hp @ 2700 rpm to 220 hp @ 2500 rpm.
  • Isuzu will offer its 4H-series engines rated at 190 hp @ 2600 rpm, and its 6H-series in ratings from 200 to 300 hp @ 2200 rpm. The company also supplies private-branded engines and trucks to GMC/Chevy.
  • Mitsubishi Fuso has its own line of 4.9- and 7.5-liter diesels rated at 147 hp @ 2700 rpm to 274 hp @ 2600 rpm.
  • Finally, UD Trucks will provide its own powerplants rated at 175 hp @ 2700 rpm to 230 hp @ 2500 rpm.

Making them fit
With extra components, and exhaust-aftertreatment devices and associated plumbing, a major challenge has been making the package fit into smaller medium-duty chassis.

“Correct sizing of the components has been very important,” notes Detroit’s Ackerman.

“Integration with the vehicle has been the biggest challenge,” agrees Jeff Weikert, Cummins’ executive director of midrange diesels. It seems the goals all along have been driveability, durability and fuel economy. “We want the new technology to be transparent to the end user,” he says.