How Do Natural Gas Class 8 Trucks Work?

Heavy-duty compressed natural gas (CNG) vehicles work much like gasoline-powered vehicles with internal combustion engines. Many heavy-duty vehicles use spark-ignited natural gas systems, but some systems use a diesel compression injection. In a spark-ignited system, the engine functions the same way as a gasoline engine. Natural gas is stored in multiple fuel tanks, or cylinders, typically behind the cab of the vehicle. A CNG fuel system transfers high-pressure natural gas from the fuel tank to the engine’s intake manifold or combustion chamber. The pressure is then reduced to a level compatible with the engine fuel injection system, and the fuel is introduced into the intake manifold or combustion chamber, where it is mixed with air. The fuel-air mixture is then compressed and ignited by a spark plug. Learn more about natural gas vehicles.

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Key Components of a Natural Gas Class 8 Truck

Battery: The battery provides electricity to start the engine and power vehicle electronics/accessories.
Electronic control module (ECM): The ECM controls the fuel mixture, ignition timing, and emissions system; monitors the operation of the vehicle; safeguards the engine from abuse; and detects and troubleshoots problems.
Exhaust system: The exhaust system channels the exhaust gases from the engine out through the tailpipe. A three-way catalyst is designed to reduce engine-out emissions within the exhaust system.
Fuel filler: A nozzle from a high-pressure hydrogen dispenser attaches to the receptacle on the vehicle to fill the tank.
Fuel filter: This filter traps dirt and other particles to prevent them from clogging critical fuel system components, such as fuel injectors.
Fuel injection system: This system introduces fuel into the engine's combustion chambers for ignition.
Fuel line: A metal tube or flexible hose (or a combination of these) transfers fuel from the tank to the engine's fuel injection system.
Fuel tank (compressed natural gas): Stores compressed natural gas on board the vehicle until it's needed by the engine.
High pressure regulator: Reduces and regulates the pressure of the fuel exiting the tank, lowering it to an acceptable level required by the engine 's fuel injection system.
Internal combustion engine (spark-ignited): In this configuration, fuel is injected into either the intake manifold or the combustion chamber, where it is combined with air, and the air/fuel mixture is ignited by the spark from a spark plug.
Manual shut off: Allows the vehicle operator or mechanic to manually shut off the fuel supply.
Transmission: The transmission transfers mechanical power from the engine and/or electric traction motor to drive the wheels.


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