Interstate Clean Transportation Corridor


According to NGVAmerica, vehicular natural gas use has nearly doubled since 2003, in large part because of increased NGV product availability. Natural gas vehicle use is growing in the United States, supported reliable engine product, factory-direct vehicle options, and dozens of businesses that are skilled in converting conventionally-fueled vehicles to run on natural gas.

Generally speaking, there are two types of heavy-duty natural gas trucks available in today’s marketplace: spark-ignited engines in the 250 to 300 horsepower range and a larger 15-liter 400 to 450 horsepower plus dual fuel (natural gas with diesel pilot ignition) engine.  There are two spark ignited engine products available today:  one is the 8.9 liter ISL G engine from Cummins Westport, and the other is the 7.6 liter Phoenix engine from Emission Solutions Inc. (ESI).  Both of these engines are capable of using either an LNG or a CNG on-board fuel storage system.  The heavy-heavy duty Westport ISX engine is only available in an LNG platform.

The ISL G is shared with the Cummins ISL diesel engine block and has met 2010 U.S. EPA and CARB emissions standards since 2007.  The 8.9-liter ISL G is offered in ranges from 250-320 hp and has a peak torque of 1000lb-ft. The ISL G technology uses stoichiometric cooled Exhaust Gas Recirculation (SEGR) combustion, leveraging Cummins proven EGR technology to create a high-performance natural gas engine. These engines are currently operating in thousands of vehicles across the nation, predominantly in transit buses, school buses, refuse trucks, municipal and utility trucks, food and beverage delivery trucks, port drayage trucks, and other trucks and tractors manufactured factory-direct by Freightliner, Peterbilt and Kenworth.

The ESI 300 horsepower/900 lb-ft torque engine is available in several medium-heavy-duty Navistar WorkStar and DuraStar chassis, in horsepower ranges from 175-300 and peak torque of 900 lb-ft. This 7.6L engine has been successfully used in factory-direct and repower operations for beverage delivery fleets, school bus fleets, dump trucks, refuse trucks, delivery trucks, and municipal fleet applications. ESI is also working with Navistar to certify a 9.3 Liter 350 horsepower engine and factory-direct truck product. ESI’s engine technology can also be used to repower older International products going back to MY 2000.

The Westport ISX GX Engine is a 15-liter 400-475 horsepower heavy-duty engine available from either Kenworth or Peterbilt in several heavy-duty tractor and truck configurations.  The ISX GX uses the Cummins ISX engine base and a High Pressure Direct Injection (HPDI) fuel delivery system that compresses LNG to 4,000 psi for delivery into the engine.  The HPDI engine technology utilizes pilot diesel injection in order to create a “liquid spark” to ignite the high pressure natural gas.  The system delivers diesel like efficiency in a natural gas engine.  The ISX GX is available factory-direct from Kenworth.