DSG-423 FUEL SYSTEM
04-8
drawn into the engine.
While the carburetor is designed to mix the fuel and air
and adjust fuel to match the speed and load of the
engine, it has only “ballpark” accuracy. This accuracy is
not fine enough to achieve emissions targets. To
achieve accurate fueling, the air inlet pressure to the
carburetor is controlled by an Electronic Pressure
Regulator (EPR).
The EPR serves two functions; to vaporize the liquid
propane and to control the vapor pressure to the mixer.
As the propane vaporizes, the EPR monitors and
controls the vapor pressure to the mixer in reference to
the inlet air pressure to the carburetor.
The EPR receives a pressure command from the GCP
called “Delta P” which is the difference between fuel
vapor pressure and the air inlet pressure. This has been
calibrated for all speeds and loads. There is a sensor
internal to the EPR that measures the actual “Delta P”
of the delivered fuel.
The actuator of the EPR will then drive the diaphragm of
the vaporizer to adjust the fuel pressure to the
carburetor so that the actual “Delta P” matches the
Delta P command from the GCP.
This provides an extremely accurate open loop type of
fuel control. There is also a dry fuel temperature sensor
for increased pressure command accuracy.
After a preset time has passed, the engine will go into
closed loop control, using information from the pre and
post oxygen sensors to allow further adjustement to
meet emissions regulations.
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