Cummins Westport has introduced its new ISB6.7 G natural gas engine to the Type C school bus market.

The company launched development of the engine in 2012. It is currently in field trials, and Cummins Westport officials said that it will be in full production by mid-2016.

The 2016 ISB6.7 G is a 6.7-liter mid-range, factory-built, dedicated natural gas engine. It is based on the Cummins ISB6.7 diesel engine platform, which is reportedly the top-selling engine in the school bus market.

The ISB6.7 G is fueled by compressed natural gas (CNG), liquefied natural gas or renewable natural gas, utilizing Cummins Westport's proprietary spark-ignited, stoichiometric combustion with cooled exhaust gas recirculation technology.

Company officials said that a key feature of the ISB6.7 G is three-way catalyst aftertreatment, which is packaged as a muffler and is maintenance-free. No diesel particulate filter or selective catalytic reduction aftertreatment will be required.

Preliminary specifications include a range of ratings up to 260 hp and 660 lb-ft torque, and automatic transmission capability.

"The ISB6.7 G is the natural choice for Type C school bus customers desiring clean, quiet and safe operations with diesel-like power and performance," said Rob Neitzke, president of Cummins Westport.

Company officials said that the ISB6.7 G will be certified at launch to meet the U.S. Environmental Protection Agency and California Air Resources Board emissions standards of 0.20 g/bhp-hr nitrogen oxides and 0.01 g/bhp-hr particulate matter, and 2017 U.S. greenhouse gas and fuel economy regulations.

The ISB6.7 G will be manufactured at the Cummins Rocky Mount Engine Plant in Whitakers, North Carolina.

As previously reported, the ISB6.7 G will power Thomas Built Buses' new Saf-T-Liner C2 CNG school bus.