Cummins Integrates SCR Clean Exhaust System to QSK Engine Range

SCR aftertreatment replaces muffler with drop-in simplicity while clean combustion increases fuel efficiency.

COLUMBUS, IN - Cummins Inc. (NYSE: CMI) announced that the QSK high-horsepower engine range will move forward to meet EPA Tier 4 Final off-highway 2015 emissions with a combination of clean in- cylinder combustion and a new Selective Catalytic Reduction (SCR) clean exhaust system.

For most applications, the Tier 4 Final QSK engine and integrated SCR aftertreatment offer the installation simplicity of a drop-in replacement for the current QSK engine and exhaust muffler, with a similar size and equivalent noise reduction. While achieving very low emissions levels, Cummins Tier 4 Final technology also reduces the overall cost of operation, with QSK fuel efficiency improved by 5 percent to 10 percent, depending on the equipment duty cycle.

The new SCR clean exhaust system will be utilized on the next generation of 19- to 60-liter QSK engines across a broad 800- to 3,000-hp (597-2237 kW) power range. The SCR clean exhaust system will be scaled-up for QSK engines above 3,000 hp, including the new larger-displacement engine platform, with details due to be released in September.

"Using SCR aftertreatment for high-horsepower applications means we are able to avoid any major change to the engine platform and retain the dependability and power performance of our current QSK engines," said Mark Levett, Cummins Vice-President and General Manager - High-Horsepower Business.

Cummins SCR clean exhaust system reduces oxides of nitrogen (NOx) emissions to 3.5 g/kW-hr for Tier 4 Final off-highway, representing a more than 40 percent reduction compared with the Tier 2 level.

By focusing NOx reduction within the exhaust rather than during in-cylinder combustion, Cummins avoids the need to make any major change to the external engine platform. Using SCR also leaves a much higher performance threshold in-cylinder in order to focus on Particulate Matter (PM) reduction and improve fuel-efficiency.

PM emissions are reduced by 80 percent to meet the 0.04 g/kW-hr level for Tier 4 Final. This is achieved by a clean-combustion formula utilizing higher-pressure fuel injection and enhancements to the power cylinder design. This inherent capability to achieve higher fuel injection pressure is a key feature carried forward from the fuel system on today's QSK engines. Highly efficient PM reduction in-cylinder eliminates the need for either a diesel oxidation catalyst or diesel particulate filter aftertreatment in the exhaust stream.

Cummins clean combustion for Tier 4 Final enables fuel-efficiency to be improved by 5 percent to 10 percent compared with Tier 2 engines, with DEF consumption to fuel held as low as 2 percent to 3 percent. Low DEF consumption is achieved by a series of advanced sensors monitoring the operation of the Cummins SCR clean exhaust system to match DEF dosing levels to engine load and duty cycle. Lower dosing also means that the on-board DEF tank is easily sized to meet fuel tank capacity, or can be increased in size for extended refilling intervals to match specific equipment operation.

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