22 September 2010
Cummins commenced production and supply of the first US EPA Tier 4 interim and EU Stage III B certified engines for early installation by off-highway equipment customers. The latest generation QSB6.7 and QSL9 engines are built at the Cummins Rocky Mount plant in North Carolina for customers in North America and East Asia, with the Darlington plant in the UK supplying European customers.
The Tier 4i/Stage III B emission regulations take effect from 2011 for engines at and above 175 hp (130 kW). The new PM standard is 0.02 g/kWh (0.015 g/bhp-hr)—a 90% reduction from the Tier 3 PM standard. Among the available Tier 4i NOx emission compliance options, Cummins chose to certify their engines to the alternate NOx emission standard of 2 g/kWh, which represents nearly 50% NOx reduction from the Tier 3 standard. The actual NOx emissions from the QSB6.7 and QSL9 engines were 1.2 and 1.1 g/kWh, respectively.
The new QSB6.7 engine delivers up to 300 hp (224 kW) of power, while the QSL9 engine has outputs up to 400 hp (298 kW). The engines are intended for all types of construction, agricultural and industrial equipment. The new engines achieve up to 5% improved fuel efficiency and faster engine response, according to Cummins.
Emission technologies used by Cummins on engines above 130 kW are similar to those used on 2007 highway engines: exhaust gas recirculation with variable geometry turbochargers and wall-flow diesel particulate filters.
In Tier 4i/Stage III B engines below 130 kW, PM emissions will be controlled using “Cummins Compact Catalyst”, a device “specifically designed for the QSB6.7, QSB4.5 and QSB3.3”. The catalyst is a flow-through device that works by “passively oxidizing PM from the exhaust stream”, a description that can fit both a flow-through filter (FTF) and a diesel oxidation catalyst. For engines below 130 kW, the new emission standards become effective from 2012.