How Do Bi-fuel Natural Gas Vehicles Work?

A bi-fuel natural gas vehicle can use either gasoline or natural gas in the same internal combustion engine. Both fuels are stored on board and the driver can switch between the fuels. The vehicle is equipped with separate fuel tanks, fuel injection systems, and fuel lines for both fuels. Learn more about natural gas vehicles.

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Key Components of a Bi-fuel Natural Gas Vehicle

Battery: The battery provides electricity to start the engine and power vehicle electronics/accessories.
Electronic control module (ECM) - (gasoline): The ECM controls the gasoline mixture, ignition timing, and emissions system; monitors the operation of the vehicle; safeguards the engine from abuse; and detects and troubleshoots problems.
Electronic control module (ECM) - (natural gas): In a bi-fuel natural gas configuration, the natural gas ECM communicates with the gasoline ECM and controls the natural gas 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 (gasoline): This is a filler or "nozzle" used to add gasoline to the tank.
Fuel filler (natural gas): A filler or "nozzle" is used to add natural gas to the tank.
Fuel injection system (gasoline): This system inserts gasoline into the engine's combustion chambers for ignition.
Fuel injection system (natural gas): This system introduces fuel into the engine's combustion chambers for ignition.
Fuel line (gasoline): A metal tube or flexible hose (or a combination of these) allows for transferring gasoline from the tank to the engine's fuel injection system.
Fuel line (natural gas): A metal tube or flexible hose (or a combination of these) allows for transfering natural gas from the tank to the engine's fuel injection system.
Fuel pump: A pump that transfers fuel from the tank to the engine's fuel injection system via the fuel line.
Fuel selector switch: On bi-fuel vehicles, this dashboard switch allows the driver to select between fuels.
Fuel tank (compressed natural gas): Stores compressed natural gas on board the vehicle until it's needed by the engine.
Fuel tank (gasoline): This tank stores gasoline 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.
Natural gas fuel filter: Traps dirt and other particles to prevent them from clogging critical fuel system components, such as fuel injectors.
Natural gas sensors: These monitor the pressure of the fuel supply and relay that information to the electronic control module.
Transmission: The transmission transfers mechanical power from the engine and/or electric traction motor to drive the wheels.

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