Class 7 and 8 truck owners aren’t the only fleet managers concerned about the impact of 2007 diesel engine emissions compliance on truck design and performance. Medium- and light-duty fleet managers actually may face more limitations as a result of new after-treatment systems.
Medium- and light-duty OEMs met with buyers and body builders at the Work Truck Show Tuesday, Feb. 28 in Atlanta to discuss limitations and chassis changes that will result from lower-emissions engine designs. Among the challenges:
For some fleets, the changes largely will go unnoticed, except at purchase times when new hardware will increase truck prices by $3,500 to $5,000. “A compliant vehicle will cost more,” says Steve Matsil, vehicle chief engineer for General Motors.
For others, the changes could alter the way they approach spec’ing decisions. Body manufacturers will be forced in some cases to relocate mounting bolts and other equipment. Front-mounted PTOs, for example, might not be available in certain models due to new
cooling requirements. “There are concerns with radiator blockage from snowplows, hose reels, aerial device supports and PTOs,” says Bill Reed, manager of special vehicle engineering for Ford Commercial Trucks. “It is a potential problem for blockage to radiator, something we have to minimize.”
Also, hood size, engine designs, fuel efficiency and overall weight will change in many models. Radiators also are getting larger, as much as 20 percent, which will affect frame extensions, says Landon Grogan, engineering project manager for Freightliner. “Frame rails will be offset or splayed to accommodate larger cooling modules,” Grogan says.
Medium- and light-duty manufacturers are taking the same basic approach to treating diesel emissions, employing diesel oxidation catalysts and particulate traps to meet new government regulations. They also are beefing up their exhaust gas recirculation systems to improve emissions before they reach the exhaust system. And OEMs are using both passive and active regeneration in diesel particulate filters, or DPFs.
The temperature changes will occur mainly at the DPF and the tailpipe. As the after-treatment system burns off soot in the trap, exhaust temperatures will reach the range of gasoline exhaust systems – in some cases more than 750 degrees Fahrenheit for passive regeneration and 1200 degrees for active. Skin temperatures will be lower thanks to heavy insulation, but exhaust at the end of short tailpipes will be hotter than today’s engines, according to light- and medium-duty OEMs.
Most of the medium- and light-duty after-treatment systems will include the ability to dose the DPF with diesel fuel to raise temperatures when active generation is needed to clean out the DPF. International Truck and Engine Co.’s Greg Saele says manufacturers are taking three approaches to getting fuel into the exhaust system.
“They’re using in-cylinder dosing where diesel fuel is injected into the cylinder after combustion and then blown through the exhaust port into the exhaust system,” Saele says. Other approaches include downstream dosing where a smaller fuel injector squirts diesel fuel into the exhaust system after the turbo charger. Finally, Caterpillar’s Regeneration System injects fuel after the turbo and ignites it before it reaches the DOC, Saele says.
The location of the DPF and exhaust components are, for the most part, fixed on lighter-duty trucks, the OEMs said, but for medium-duty trucks, they can be changed to accommodate multiple PTO locations and other equipment. Freightliner, for example, has several cab and chassis mount options for its DPFs.
Truck and engine makers said that options, however, would be limited. George Bondor, a Kenworth applications engineer, told manufacturers that cab-mounted DPFs in T300s featuring Cat C7 and Cummins ISB and ISC engines likely will be located under the passenger door. “You may have used that space in the past for equipment, and that space may not be available anymore,” Bondor says. Other DPF mounting options exist, including a vertical back-of-cab mount option and frame mounts behind the cab, and Bondor says the company might offer more options later. “Body installations may have to change to accommodate exhaust systems.”
The OEMs say they will work with body manufacturers to address their concerns, but the emissions system changes that are coming will impact fleet operations. “These changes will result in cleaner air and a healthier environment by reducing diesel exhaust,” GM’s Matsil says. “There will be some impact on lifecycle cost and filter servicing. The packaging of emissions equipment will affect some vocational applications.”
