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To achieve this precise level of engine management, the computer code went from 350,000 bytes of information to over 550,000 bytes. Cummins also used an advanced computer program to test fuel maps and other engine-management strategies.

“This design is based totally off our ability to model an engine on the computer,” says McAvoy. “We can look inside the cylinder and combustion process and achieve a simpler approach to cutting emissions.”

The reduction in harmful emissions was achieved without adding exhaust gas recirculation (EGR) or after-treatment equipment. In fact, the “600” engine has only 43 new parts. But when 2007 rolls around, expect the next Cummins engine to have cooled EGR as well as particulate aftertreatment filters or traps.

In developing the new “600,” Cummins and Dodge made numerous other improvements or changes to the engine:

• Air inlet redesigned to block hot engine air from entering, reducing the intake charge by 30 to 40 degrees.
• Intake resonator re-engineered for increased airflow
• Larger compressor on Holset turbocharger
• Engine cooling improved with new fan assembly and mounting fan shroud to engine for more efficient airflow through radiator
• Upgraded intercooler
• Upgraded exhaust valves
• Tailpipe increased to 4-inch diameter
• Improved sealing and gasket materials
• Oil-change intervals are now 15,000 miles (vs. 7,500 for competition).
• Holset turbocharger gets bigger compression side
• Switch to electronic control of wastegate
• Upgrades to exhaust manifold
• Revised intake ports in cylinder head
• New piston bowl geometry
• Different spray pattern from injectors

The new Cummins “600” now gives Dodge the current numbers edge over the competition from Ford and Chevy/GMC. Just days after Dodge released its numbers in December 2003, Chevy announced the 6.6-liter Duramax would be boosted to 310 horsepower and peak torque of 590 lb ft. GM, working with Isuzu, added a new turbo charger, reworked the engine computer and installed an electronically controlled EGR. Ford did not announce any changes its 6.0-liter Powerstroke, leaving it at 325 horsepower and 560 lb ft.

Diesels and heavy-duty pickups are important to the manufacturers, especially at a time when Nissan, Honda and Toyota are poised to steal market share in the light-duty truck market. Heavy-duty trucks hardly ever need cash incentives and often sell for sticker price, and 2500/3500 accounts for a third of overall Ram sales. Customers are usually very loyal to their favorite brand, and many light-truck consumers look up to heavy-duty owners for advice and direction when shopping for a pickup. Dodge now has over 28% of the heavy-duty diesel market, recently passing GM and setting its sights on Ford’s dominating share. Considering that Ford sold nearly twice as many F-series pickups last year as Dodge Rams (845,586 units vs. 449,371, according to Automotive News), Dodge’s presence in the heavy-duty market is quite remarkable and continuing to improve. Now that Dodge can boast best-in-class numbers, that share is expected to increase.

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