At the opening reception at ACT Expo in Dallas, TX, Cummins Westport Inc. will unveil the ISB6.7 G, a 6.7-liter medium-duty, factory-built dedicated natural gas engine for school bus, shuttle bus, medium-duty truck and vocational applications. (Earlier post.) The new ISB6.7 G is currently in field trials with full production expected to commence in mid-2016.
The ISB6.7 G natural gas engine is based on the Cummins ISB6.7 diesel engine platform, the industry leader in the Cummins medium-duty engine family. The ISB6.7 G will operate exclusively on natural gas (CNG or LNG) utilizing Cummins Westport’s proprietary spark-ignited, stoichiometric combustion with cooled exhaust gas recirculation (SEGR) technology, first introduced with the 8.9-liter ISL G.
The SEGR technology was introduced with the ISL G in 2007, and was developed to meet 2010 EPA emission requirements. The cooled-EGR system passes exhaust gas through a cooler to reduce temperatures before mixing it with fuel and the incoming air charge to the cylinder. Stoichiometric combustion in combination with cooled-EGR offers increased power density and thermal efficiency. It also reduces in-cylinder combustion temperatures and creates an oxygen-free exhaust, which then enables the use of a three-way catalyst (TWC) for NOx control.
The ISB6.7 G TWC is packaged as a muffler and is maintenance-free. No diesel particulate filter or selective catalytic reduction aftertreatment will be required. The 6-cylinder ISB6.7 G will offer up to 260 hp (194 kW) and 660 lb-ft (895 N·m) of torque, and will be available with both manual and automatic transmissions.
The ISB6.7 G shares many base engine components with the ISB6.7 diesel engine and shares the emissions architecture of the ISL G and ISX12 G, including wastegate turbocharger, a high-energy ignition system controlled by the CM2180A Engine Control Module, and similar fuel module design.
The ISB6.7 G is expected to be certified at launch to meet the US Environmental Protection Agency and California Air Resources Board emission standards of 0.20 g/bhp-hr NOx and 0.01 g/bhp-hr PM and 2016 US greenhouse gas and fuel economy regulations.
Partial funding in support of the ISB6.7 G engine development has been received from California Energy Commission through its Public Interest Energy Research (PIER) Program in conjunction with the Gas Technology Institute.
The ISB6.7 G will be manufactured in Cummins’ medium-duty engine plant in Rocky Mount, North Carolina.