Diesels evolve to improve efficiency

  • 11-Mar-2013 04:41 EDT
IAV Heavy Duty Test Cell 992.jpg

IAV developers monitor many aspects of engine performance and emissions during diesel engine testing.

While hybrid technology is helping some suppliers meet changing fuel and emissions expectations, engine makers are leaving no stone unturned as they attempt to reduce emissions and fuel consumption without reducing performance. Electronic controls, aftertreatment systems, and mechanical components are all being enhanced in response to demands from equipment buyers and regulators.

Engines must eke the most out of every drop of fuel to meet Tier 4 Final regulations. Many providers no longer focus solely on the engine, instead looking at all facets of machine operation. Working closely with hydraulics is an important factor, as is efficiency related to aftertreatment systems.

“Overall, where the industry is headed is to focus on full system controls instead of simply looking at engine controls or hydraulic controls as they have in the past,” said Mike Traver, Diesel Systems Business Unit Director for IAV. “That way, if the aftertreatment system needs a certain temperature and the engine needs fuel economy, it can take both into account. This approach also lets, say, a front end loader get a tremendous amount of torque to pick up a load while keeping the aftertreatment system at the right temperature.”

These aftertreatment systems now play a major role in engine development. Cummins focused on aftertreatment with its new four-cylinder, 4.5-L QSB4.5 engine, which meets Tier 4 Final near-zero emissions standards. To remove particulate matter, the Cummins Compact Catalyst aftertreatment is used to reduce space compared to DPFs.

Other suppliers are using different strategies to reduce emissions. Eaton is using exhaust gas recirculation to keep emissions low without sacrificing performance.

“Switchable (on-off) or modulated (0 to maximum) internal EGR helps decrease NOx at mid-low to mid-high engine loads without penalizing engine performance while delivering fuel efficiency at high engine loads,” said Majo Cecur, Engineering Manager Technology for Eaton’s Valvetrain Division.

As broad system approaches become more intertwined, it’s more challenging to develop controls. That’s prompting more companies to partner for expertise in focused areas of powertrain design.

For example, Ricardo and Doosan Infracore are collaborating to meet U.S. Tier 4 emissions regulations. Ricardo’s clean combustion technology lets Doosan meet requirements without a DPF. That technology is moving into wider production. Bobcat recently announced plans for Tier 4 solutions that include Doosan-built engines.

Electronic controls aren’t just focusing on aftertreatment systems. They’re also helping engines achieve the same power levels while reducing fuel consumption. For example, variable valve technology is moving into the off-highway market.

“Discrete late intake valve closing was developed for specific off-highway applications where the engine operates about 80% of its time in two load/speed conditions—low speed and low engine load, and high load and high speed,” Cecur said. “Proven fuel economy improvement is approximately 7%.”

While design teams are focusing on fuel economy and emissions, they can’t forget the reliability requirements of the rugged environments these vehicles serve in. Any change in technology must undergo stringent testing to minimize the potential for failure.

“Off-highway users have a strong preference for robustness and durability over increased fuel economy,” Traver said. “A guy doing threshing in wheat fields across several states is very unhappy if the check engine light comes on. That tends to drive OEMs to reduce the number of sensor inputs they need and reduce electronic complexity.”

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