Advanced 6.7 Liter Natural Gas Engine Development

Cummins Westport Inc. developes advanced 6.7 Liter Natural Gas Engine

Institute of Gas Technology dba Gas Technology Institute


Des Plaines, IL

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Amount Spent



Project Status

Project Result

The project successfully completed the prototype engine design, build, and validation testing. Through analytical models, calculations, and testing, initial verification of performance targets as stated in the work scope have been achieved. Preliminary emissions, fuel consumption, and GHG data from the engine test cells indicate that the engine design achieves the design targets for the program. The learning gained from the engine operation helped to optimize and to create a production intent 6.7 liter natural gas engine and engine component designs. The development focused on unique designs for major engine subsystems.

The Issue

There are limited natural gas engines available that are ideally suited for Class 3 through 7 commercial vehicle markets including pickup and delivery trucks, utility trucks, school buses, shuttle buses, yard tractors, and specialized municipal works vehicles such as street sweepers. The ability to maximize natural gas penetration in these markets is compromised by the lack of a natural gas engine technology with the required combination of attributes to satisfy customer requirements for the duty/purpose of this size vehicle.

Project Innovation

GTI partnered with Cummins Westport, Inc. to develop and validate a prototype engine design for a new, high-performance, spark-ignited, dedicated natural gas 6.7 liter engine. The development project was based on the 6.7 liter Cummins ISB6.7 diesel engine platform, which is widely used in a diverse range of medium- to heavy-duty vehicles, particularly in the Class 5 to Class 7 truck and bus markets.

Project Benefits

The project results will lead to a commercialized natural gas engine with improved emissions and performance in medium- and heavy-duty natural gas vehicles, improved air quality, and decreased dependence on petroleum. The project developed a natural gas engine with fuel economy improvement of 5 percent to 10 percent over the older Cummins Westport 5.9 liter engine, and will be a key enabler for natural gas adoption in school bus and shuttle bus markets.



Cummins Westport, Inc.


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