Service Manual

WEICHAI EMISSION-RELATED INSTALLATION INSTRUCTIONS
SYSTEM OVERVIEW
STOICHIOMETRIC, RICH BURN CONTROL
The 4G engine control module is the backbone of the EControls control system. Proven in a multitude of
applications around the world, the 4G based engine control system delivers reliable operation and
optimal engine operation no matter the environment. The 4G engine control system for highly regulated
emission countries enables operation at the stoichiometric air / fuel ratio with Rich Burn and a three-
way catalyst (TWC). Stoichiometric engine operation ensures that there is precise amount of air
delivered to completely burn all the fuel. The stoichiometric Air Fuel Ratio (AFR) for natural gas is 17.7:1
and for propane is 15.5:1. Figure 1 shows the required 4G engine control system configurations for
Propane (VPG), Natural Gas (NG) and Bi-Fuel (VPG and NG) with the TWC.
Figure 1 WP4GNA Non-Emergency Schematic
Bi-FUEL
The 4G Engine Controls System has full engine software control authority, therefore switching from
Natural Gas (NG) to Propane (LPG/VPG) fuel is a software command from the operator console or a
switch input into the 4G ECM. The Weichai WP04GNA engine is capable of operating in bi-fuel mode
starting from VPG/LPG and switching to NG after the NG pressure develops from operation. With the
proper valve and sensor arrangement the fuel supply transition can be made while in operation, under
full load, and automatically.
NG/VPG is WP04GNA standard configuration. With an add-on option, WP04GNA can also support LPG,
manual or automatic switching.
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