Compressed Natural Gas (CNG) System
Fuel from the compressed natural gas (CNG) fuel tank flows through the solenoid tank valve and coalescent fuel filter to the gas regulator. The gas regulator provides a consistent system operating fuel pressure of approximately 724 kPa (105 psia). The fuel is passed to the fuel rail solenoid and is then introduced into the fuel rails. The fuel in the fuel rails is introduced into the intake air system through the fuel injectors and fuel injector sleeve assemblies.
The alternative fuel control module (AFCM) meters fuel according to demand from the powertrain control module (PCM). The AFCM will enable the ALT fuel injectors and disable the gasoline injectors when in ALT fuel mode. The AFCM monitors the fuel tank pressure and communicates the fuel level to the instrument cluster on the SCP network. The fuel gauge, integral to the instrument cluster, will display the appropriate fuel level when in ALT fuel mode.
The PCM calculates the spark advance for maximum power. A combination of sensors and inputs from the PCM are used to monitor the engine and environment to provide closed loop fuel control. Through speed density calculations, the PCM determines fuel flow and air flow while adjusting the air/fuel mixture. The air/fuel adjustment is required for each spark event.