G420E/G424E Tier LP Engine System Operational Overview 18
MI-04 N-2001
Regulator/Converter
After passing through the electric fuel lock-off, liquid
propane enters the N-2001 regulator/converter
(Figure 13). The N-2001 functions as a fuel vaporizer,
converting liquid propane to vapor propane and as a
two-stage negative pressure regulator, supplying the
correct vapor propane fuel pressure to the mixer.
The regulator is normally closed requiring a vacuum
signal (negative pressure) to allow fuel to flow. This is
the second of three safety locks in the MI-04 system.
If the engine stops, vacuum signal stops and fuel flow
will automatically stop when both the secondary (2
nd
stage) valve and the primary (1
st
stage) valve closes.
Unlike most other regulator/converters, the N-2001
primary valve closes with fuel pressure rather than
against pressure, extending primary seat life and
adding additional safety.
Liquid propane must be converted into a gaseous
form in order to be used as a fuel for the engine.
When the regulator receives the desired vacuum
signal it allows propane to flow to the mixer. As the
propane flows through the regulator the pressure is
reduced in two stages from tank pressure to slightly
less than atmospheric pressure. As the pressure of
the propane is reduced the liquid propane vaporizes
and refrigeration occurs inside the regulator due to
the large temperature drop inside the regulator from
the vaporization of liquid propane. To replace heat
lost to vaporization, engine coolant is supplied by the
engine driven water pump and pumped through the
regulator. Heat provided by this coolant is transferred
through to the fuel vaporization chamber.
(Figure 14) shows the heat chamber and the coolant
passage in the N-2001.
Coolant
Passage
Figure 14
Figure 13
N-2001
Heat Transfer
Chamber
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