Cummins Westport ISB6.7 G

The Cummins Westport ISB6.7 G is a 6.7-litre, six-cylinder inline natural gas engine for school bus, shuttle, transit, medium-duty truck, and vocational vehicle markets. The engine was announced in 2012 and launched in 2015. Production and sales began in the middle of 2016.

The ISB6.7 G is based off of the diesel-fueled Cummins ISB6.7. The engine may be fueled by compressed or liquefied natural gas and features spark-ignited, stoichiometric combustion with cooled exhaust gas re-circulation. Like the Cummins Westport ISL G, the ISB6.7 uses a three-way catalyst which works by introducing a catalyst to convert the nitrogen oxides to nitrogen gas and oxygen gas, carbon monoxide to carbon dioxide, and hydrocarbons to carbon dioxide and water.

The engine meets the Environmental Protection Agency (EPA) and California Air Resources Board (ARB) 2016 emissions regulations. It also meets ARB's optional low oxides of nitrogen (NOx) standard of 0.1 g/bhp-hr and 2017 EPA greenhouse gas (GHG) requirements. For the European market, the ISB6.7 G meet Euro 6 regulations.