At Tier 4 Interim 2011 emissions levels, the QSX15 and QSX11.9 engines can achieve up to 5 percent improved fuel efficiency compared to Tier 3, depending on duty cycle and machine optimization. Fuel efficiency will be further increased for Tier 4 Final 2014 by an additional 3 percent to 4 percent.

CPF-SCR ultra-clean aftertreatment

The SCR system developed by Cummins for Tier 4 Final is a next-generation design that moves beyond the SCR technology currently in use for Tier 4 Interim. The system incorporates a copper zeolite-based catalyst capable of up to 95 percent NOx conversion and able to operate more efficiently at lower temperatures. The system features advanced sensors to provide full closed-loop control. Diesel Exhaust Fluid (DEF) dosing levels are minimized with enhanced mixing in the decomposition pipe.

The Cummins Particulate Filter is retained from the Tier 4 Interim aftertreatment used by the QSX engines. The CPF incorporates both a diesel oxidation catalyst and the wall-flow filter, providing an additional margin of PM emissions control at the higher engine loads and power outputs of heavy-duty engines.

With this higher PM filtration efficiency, the engine combustion can be formulated to increase power density and lower fuel consumption. The integration of SCR into the exhaust aftertreatment allows the CPF to reduce the frequency and duration of active regenerations below 1 percent of equipment operating time, creating a virtually full-time passive device.

The Tier 4 Final QSX15 at CONEXPO-CON/AGG 2011 is showcased as a fully integrated power unit manufactured by Cummins Power Products. The self-contained unit carries forward the same packaging size from Tier 3 to Tier 4 Interim and Tier 4 Final.

This package-proof capability is enabled as the QSX15 and QSX11.9 engines for Tier 4 Final 2014 will be almost identical to the QSX engines introduced to meet Tier 4 Interim in 2011. This ability to move forward to meet the near-zero emissions standards is pre-designed into the existing engine platform, with no significant change to engine system architecture.

The QSX engines retain a single Cummins Variable Geometry Turbocharger (VGT), avoiding the complexity of needing two turbochargers to achieve this level of power output.