Cummins Westport ISL G

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The Cummins Westport ISL G is an 8.9-litre, six-cylinder inline natural gas engine for shuttle and school bus, urban transit, vocational and medium and heavy-duty truck and tractor applications. It was introduced in late 2007 and replaced the Cummins Westport C Gas Plus and Cummins Westport L Gas Plus in 2008. The ISL G is based on the diesel-fueled Cummins ISL and shares 80 percent of its heavy duty components with its diesel counterpart.

The ISL G 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 also features cooled exhuast gas recirculation (EGR), and stoichiometric combustion. The ISL G meets the Environmental Protection Agency (EPA) and California Air Resources Board (CARB) 2010 and 2013 emissions regulations. The European ISL G meets Euro 5 regulations.

In 2016, Cummins Westport introduced the ISL G "Near Zero" (NZ). This version of the engine, as the name implies, achieves Near Zero NOx Emissions as defined by the Environmental Protection Agency and California Air Resources Board. The ISL G NZ, as well as its Euro 6 counterpart, have a closed crankcase ventilation (CCV) system and upgraded electronic controls to manage On-Board Diagnostics. The ISL G and its 'Near Zero' counterpart were replaced by the L9N in 2018.


Model Max. Power Max. revs Max. Torque Emmissions Certifications
ISL G 250 250 hp 2200 rpm 730 lb-ft @ 1300 rpm EPA 2010
ISL G 260 260 hp 2200 rpm 660 lb-ft @ 1300 rpm EPA 2010
ISL G 280 280 hp 2200 rpm 900 lb-ft @ 1300 rpm EPA 2010
ISL G 300 300 hp 2100 rpm 860 lb-ft @ 1300 rpm EPA 2010
ISL G 320 320 hp 2200 rpm 1000 lb-ft @ 1300 rpm EPA 2010
Cummins logo.png
Current products
Diesel B4.5 / B6.7 - L9 - X12 / X15
CNG B6.7N - ISB6.7 G - ISX12 G - ISX12N - L9N
Former products
Diesel ISB6.7 - ISL9 - ISX12 / ISX15 B5.9 - C8.3 - ISC - ISM - L10 - M11 - NH Series - VTB-903
CNG B5.9G - B Gas Plus - C8.3G - L10G - C Gas Plus - L Gas Plus - ISL G
Propane B LPG Plus