The 4-cylinder QSB3.3 and QSB4.5 engines from Cummins offers a simplified Tier 4 installation across a broad 75- to 160-hp (56-119 kW) power range

Cummins Inc. revealed on April 19 at the Bauma show the latest generation of its 4-cylinder QSB3.3 and QSB4.5 engines offering a simplified Tier 4 installation across a broad 75- to 160-hp (56-119 kW) power range.

With an air-intake-to-exhaust aftertreatment system specifically designed for highly flexible machine integration, the 3.3-liter and 4.5-liter QSB engines will lead the way for compact equipment to more easily meet low-emissions regulations in 2012, Cummins says.

The 4-cylinder QSB engines operate as integrated Tier 4 emissions systems with Cummins Compact Catalyst exhaust aftertreatment, shown for the first time at Bauma.

 Introduced for EPA Tier 4 Interim and EU Stage IIIB off-highway applications, the catalyst removes particulate matter (PM) by simple, flow through passive oxidation. With a smaller size than other types of aftertreatment, the Cummins Compact Catalyst can be installed in space-constrained equipment with the added flexibility of mounting separately from the exhaust muffler, or as part of a combined catalyst-and-muffler unit.

With no impact on equipment operation, the catalyst offers a robust and maintenance-free “fit and forget” solution, ideally suited for the rental-equipment market, according to the manufacturer.

Compared with Tier 3 applications, the QSB3.3 and QSB4.5 engines can achieve up to 5 percent improved fuel efficiency for Tier 4, depending on duty cycle.

Cleaner, more fuel-efficient combustion is achieved with a cooled Exhaust Gas Recirculation (EGR) system to reduce Oxides of Nitrogen (NOx) emissions. Extensively proven on Cummins 6-cylinder engines, the EGR system is scaled down for the 4-cylinder QSB configuration and driven by a variable-flow turbocharger. Using a simple variable turbine mechanism, the turbo improves boost across a wider engine speed than a wastegate turbo and avoids the complexity of dual turbochargers.

“By focusing on design simplicity, the 4-cylinder QSB engines reflect the need to maximize installation flexibility for Tier 4 compact equipment,” said Hugh Foden, executive director for Cummins Off-Highway Business in a press release.

“The Tier 3 QSB3.3 and QSB4.5 have earned an enviable reputation for durability and power productivity,” Foden continued. “Now, with the Cummins Compact Catalyst and upgraded performance systems, we are able to achieve low emissions without compromising the ability of these engines to perform at the highest load factors or in the toughest applications where they excel today.”

Equipment manufacturers looking to power a wide range of machines will benefit from Tier 4 installation commonality provided by the 4-cylinder QSB engines. The QSB3.3 extends across the 75- to 110-hp (56-82 kW) range, while the QSB4.5 extends from 110 hp to 160 hp (82-119 kW). For ratings up to 173 hp (129 kW), the larger 6-cylinder QSB6.7 engine will also be available with the Cummins Compact Catalyst.

The engines retain the impressive peak torque characteristics of the previous Tier 3 versions, with 306 lb-ft (415 N•m) peak torque available for the top-rated Tier 4 Interim QSB3.3 and 466 lb-ft (632 N•m) for the top-rated Tier 4 Interim QSB4.5.

Cummins Compact Catalyst

The Cummins Compact Catalyst represents the latest evolution of Diesel Oxidation Catalyst (DOC) aftertreatment, manufactured by Cummins Emission Solutions for over 15 years. The maintenance-free catalyst provides the installation simplicity needed for Tier 4 Interim and Stage IIIB engines below 174 hp (130 kW).

The Cummins Compact Catalyst achieves efficient PM reduction with a catalytic coating and substrate uniquely tailored to the QSB3.3 and QSB4.5 engines. By passively oxidizing PM from the exhaust stream with the simplicity of a small flow-through catalyst, Cummins is able to achieve Tier 4 emissions levels without compromising engine transient response or reliability.