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CWI ISL G natural gas engine to achieve 0.02 g/bhp-hr NOx

8 May 2015

Cummins Westport (CWI) announced it will begin field tests this year in California in transit buses with a spark ignited natural gas engine capable of producing “Near Zero” NOx emissions of 0.02 g/bhp-hr.

CWI believes its stoichiometric EGR spark ignited (SESI) natural gas engine technology as released on its ISL G and ISX12 G engines can provide an economic and efficient solution to California air quality improvement initiatives. The development of the low NOx ISL G engine has received funding support from South Coast Air Quality Management District (SCAQMD), SoCal Gas and California Energy Commission (CEC).

CWI has invested “significantly” into the SESI platform to develop a NOx technology pathway to achieve the 0.02 g NOx emission target. CWI said it has demonstrated this technology and will now field test a transit bus with the new ISL G that will reduce NOx emissions by 90% from the current EPA limit of 0.2 g/bhp-hr to 0.02 g/bhp-hr NOx while also meeting the 2017 EPA GHG emission requirements.

Heavy-duty engines can be certified to the 0.02 g/bhp-hr NOx limit under the California Optional Low NOx Standards. Regulatory work on a lower NOx standard at a national level could begin in 2016, potentially leading to a future mandatory federal NOx limit in the range of 0.05-0.02 g/bhp-hr.

The new ISL G is a turbocharged and aftercooled, spark ignited engine with cooled EGR and a three way catalyst (TWC) aftertreatment. The TWC is packaged as part of the muffler. Since it was first introduced in 2007, the ISL G 8.9 L engine has become the leading natural gas engine for transit buses and refuse trucks in California, said CWI.

CWI intends to announce the commercial availability of the Near Zero NOx technology in the ISL G engine later this year. The engine will be available as a first fit engine for transit bus and refuse OEMs, as well as as a replacement for existing ISL G vehicles.

The main technical challenges in achieving 0.02 g NOx emissions appear to include the control of cold start emissions, as well as emission durability.

Cummins Westport has also announced the availability of a new ISB6.7G dedicated natural gas engine in 2016. The engine uses a stoichiometric cooled exhaust gas recirculation technology, abbreviated SEGR. The two acronyms—SESI and SEGR—are used by CWI in an inconsistent manner, but they seem to indicate the same combustion technology.

Source: Cummins Westport