The heavy-duty QSX engine from Cummins has been revamped to displace 16 L, and will be available with a fully integrated air intake to exhaust aftertreatment system to meet U.S. EPA Interim Tier 4 and European Stage IIIB off-highway emissions regulations in January 2011. The QSX uses the XPI high-pressure common-rail fuel system and a Cummins particulate filter that reduces particulate matter emissions by 90%, and NOx is reduced by 45%.
These additions increase power to a top rating of 650 hp (485 kW), 50 hp (37 kW) more than the current Tier 3 QSX. Power can be extended down to 400 hp (298 kW) to meet varying needs. Torque is increased also, up 12% to 2150 lb·ft (2915 N·m).
The power increases were accomplished by increasing displacement, incorporating a high-pressure fuel rail, and using a variable-geometry turbocharger (VGT) and direct-flow air-filtration system.
“While cooled EGR is primarily employeed to reduce NOx emissions, we can also utilize this process to influence the combustion formula and realize fuel efficiency improvements. This will achieve up to 5% higher fuel efficiency for the Tier 4 QSX compared to Tier 3,” said Ric Kleine, Vice President, Cummins Off-Highway Business.
The common-rail system provides high fuel-injection pressure at all engine speeds, enabling cleaner combustion and improved engine response. Working in synchronization is the VGT with a sliding-nozzle design. The nozzle varies the airflow boost to match the engine rpm and load.
The particulate filter replaces the muffler and offers similar noise reduction, while also catching particulate matter and oxidizing it. The direct-flow air-filtration system is made specifically for Tier 4 applications and offers 35% smaller size while maintaining the same capabilities. The shape change of the filter from cylindrical to rectangular saves space.
Integrating the entire package, from air intake to exhaust, was a Cummins priority with the QSX. “Reducing Tier 4 installation for complexity for the equipment manufacturer has been a key aim of our QSX development program and we have focused on keeping the engine and particulate filter envelope as space efficient as possible,” said Susan Harrison, Executive Director, Cummins Industrial Engineering.
“A further benefit of Cummins integration capability is that we can electronically manage the engine and aftertreatment as a single system driven by the electronic control module. The engine ECM will integrate with equipment electronics, including the CAN bus common area networks for [SAE] J1939 and ISO multiplexing. This allows electronic systems to talk to each other along a serial datalink and is set to become a more significant feature as we look ahead to equipment designs for 2011,” added Harrison.