Cummins is expanding its on-highway natural gas engine lineup with the Cummins Westport natural gas ISX12-G.

The ISX12-G, built on the Cummins ISX12, uses the same base engine and key components as its diesel counterpart but will operate exclusively on natural gas, thus needing no diesel exhaust aftertreatment as does the 15-liter Westport HD. The ISX12-G features Cummins Westport's proprietary spark-ignited combustion technology with Stoichiometric cooled exhaust gas recirculation, first introduced on the 8.9-liter ISL G.

Westport says the new engine will be aimed at regional haul truck/tractor, vocational and refuse applications. Anticipated end-use applications in the regional haul market segment include intermodal and distribution operation and pickup and delivery.

The ISX12-G will feature three-way catalyst aftertreatment, which is packaged as a muffler and is maintenance-free. Preliminary specifications include ratings up to 400 horsepower and 1,450 pounds-feet of torque and an optional engine brake. The engine will run on either compressed or liquefied natural gas.

The ISX12-G is expected to be certified at launch to meet the U.S. Environmental Protection Agency and California Air Resources Board emissions standards of 0.2 grams per brake horsepower-hour oxides of nitrogen and 0.01 grams per brake horsepower-hour particulate matter. The company also expects the engine to be capable of meeting Euro VI and pending U.S. greenhouse gas and fuel-efficiency regulations.

The ISX12-G is entering the final stages of field-testing now and will be manufactured at Cummins Jamestown Engine Plant in Jamestown, N.Y. Production availability is scheduled for early 2013.

Partial funding for the ISX12-G engine development comes from the U.S. Department of Energy's National Renewable Energy Laboratory and the California Energy Commission in conjunction with the Gas Technology Institute.

Cummins and Westport Innovations Inc. also announced they have entered into an amended and restated joint venture agreement.

The joint venture agreement, Cummins Westport Inc., was amended to provide for, among other things, clarification concerning the scope of products within CWI. In addition, the parties have revised certain economic terms of the JVA. Additional terms and conditions of the agreement were not disclosed.

"Over the past 10 years, CWI has emerged as the pre-eminent supplier of high-performance natural gas engines for commercial vehicles," says David Demers, CEO of Westport Innovations. "With this new agreement, we have taken the necessary steps to provide CWI with a platform for continued growth and success over the next 10 years, while recognizing the dramatically increased interest in natural gas as a fuel."

Westport also said it has entered into a supply agreement with Cummins to allow manufacturing of the Westport HD 15-liter engine in the Cummins manufacturing facility in Jamestown. The new HD Supply Agreement gives Westport the ability to have its Westport technology-equipped heavy-duty engines produced in a Cummins manufacturing facility when a minimum threshold sales volume of at least 1,500 engines in any 12-month period has been achieved by Westport.