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Important Selling Points About Natural Gas Engines

Interest in natural gas engines continues to grow, and we want you to have the facts when selling the ISL G. Here is some important information about natural gas engines, plus links to the Cummins Westport Natural Gas Training Academy, where you and your customers can learn more about Cummins natural gas engines.

How Do Natural Gas Engines Work?

Cummins Westport natural gas engines operate on 100 percent natural gas, which can be in the form of compressed natural gas (CNG), liquefied natural gas (LNG) or renewable natural gas (RNG) made from biogas or landfill gas that has been upgraded to vehicle-fuel-quality. They feature spark ignition with Stoichiometric cooled Exhaust Gas Recirculation (SEGR).

Stoichiometric combustion is a process by which air and fuel are completely consumed, leaving no unburned fuel or oxygen in the exhaust. This allows for the use of a Three-Way Catalyst (TWC) for emissions control. The TWC is packaged in place of a muffler, and is maintenance-free. The use of cooled EGR lowers combustion temperatures, and improves power density and fuel economy. The system doesn’t require a particulate filter or Selective Catalytic Reduction (SCR).

Diesels Versus Natural Gas Engines

Power output and torque for comparable horsepower ratings are similar to those that drivers experience currently with diesel engines. Drivers will also notice that engine noise is reduced with natural gas engines.

Choosing the Type of Natural Gas

Natural gas can be carried onboard the vehicle in compressed (CNG) or liquefied (LNG) form.

Choosing CNG or LNG usually depends on fuel availability in the area of operation, space considerations for the vehicle, and the range requirements for the application – your customers can choose which option to use based on their needs. The number of fuel tanks required on a vehicle depends on whether CNG or LNG is used, the size and design of the vehicle chassis, daily mileage requirements, refueling station availability and configuration of the truck.

What About Biomethane?

Biomethane is a biogas – a mixture of methane and carbon dioxide produced by the anaerobic digestion of organic materials in landfills and the processing of waste products – that’s been upgraded to vehicle-quality to separate out the methane and increase the energy content. Biomethane can be processed into CNG or LNG fuel. Cummins approves the use of up to 100 percent biomethane as long as it meets Cummins published standard natural gas fuel specifications.

Safety Features

All natural gas fuel systems are equipped with a manual shutoff switch that stops fuel flow to the engine when necessary for maintenance or repair. CNG is infused with an odor agent so that leaks can be identified by smell. LNG has no odor, so methane detection systems are required on vehicles using LNG. Both CNG and LNG systems have an automated shutoff system activated by the ignition key.


There are two types of fueling stations for CNG: fast-fill and time-fill. Fast-fill stations operate at higher pressures, and take approximately 10 minutes for a fill. Time-fill stations are typically used when vehicles are parked between shifts, and can take several hours for refueling. These stations are often the choice for fleets that are not active overnight.

LNG is typically produced in a liquefaction plant, delivered via truck to refueling stations, and stored in tanks. So it can be offered in locations where the natural gas pipeline is not available. Because LNG is very cold, the person fueling the vehicle must wear protective eyewear, gloves and clothing. Fueling is done through a top-mounted cap, and takes about the same amount of time as filling a gasoline or diesel tank.

Finding Natural Gas Fueling Stations

The number of CNG and LNG fueling stations continues to increase as fuel providers build stations to meet the demand for natural gas across North America. The Alternative Fuels Data Center (AFDC) lists all public CNG and LNG filling stations around the country. Many fleets and carriers have their own fueling stations. For an up-to-date list of natural gas filling stations by city and state, visit the U.S. Department of Energy (DOT) AFDC website at

Online Training Videos – Natural Gas Academy

Cummins Westport has updated its Natural Gas Academy, and now has eight videos covering various topics on natural gas. Here’s a summary of what each video covers:

  • What Is Natural Gas? – A primer on natural gas, outlining the differences CNG, LNG and RNG, together with definitions of diesel gallon equivalent (DGE) and diesel liter equivalent (DLE). These apply to onboard fuel storage and range requirements.
  • Natural Gas Engines – This video covers the similarities and differences between natural gas engines and diesel engines, showing an actual installation of an ISL G. It also includes a comparison of the relative benefits of natural gas as an option to diesel.
  • Natural Gas Fuel Systems – CNG and LNG use unique fuel storage and delivery systems that are different from those of gasoline or diesel. This video showcases the various systems and options available.
  • How to Fuel a Vehicle – This video covers fast-fill and time-fill fueling station options, the difference between saturated and unsaturated LNG and the actual steps involved with fueling a vehicle with natural gas.
  • ISL G Engine Walk-Around – Take a closer look at the components and features of the ISL G engine, with a review of the differences between the ISL G natural gas engine and its ISL9 diesel counterpart.
  • Natural Gas Engine Maintenance – This video discusses maintenance items that are specific to natural gas engines, such as spark-plug replacement, natural gas engine oil and more. Maintenance intervals are outlined, and instructions are given on how to access training and reference materials through Cummins distributors, including Cummins Virtual College (CVC) and Cummins QuickServe® Online.
  • Upgrading Your Facility for Natural Gas Vehicles – This module covers key facility upgrades required in order to operate and maintain natural gas vehicles, such as facility modifications and safety procedures, and information on leak detection and alarm systems. You’ll also find handy reference links to the National Fire Protection Agency (NFPA), the Natural Gas Vehicle Institute (NGVi) and additional resources.

These video segments provide an excellent reference point that you can share with your customers. For more information on the ISL G, visit

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