Doosan D50S-5 Operation & Maintenance Manual page 83

EMS (Engine management system) of G643E EMS (Engine management system) of G643E
engine is a closed loop system utilizing a catalytic engine is a closed loop system utilizing a catalytic
muffler to reduce the emission level in the exhaust muffler to reduce the emission level in the exhaust
gas. In order to obtain maximum effect from the gas. In order to obtain maximum effect from the
catalyst, an accurate control of the air fuel ratio is catalyst, an accurate control of the air fuel ratio is
required. A small engine control module (SECM) required. A small engine control module (SECM)
The SECM makes any necessary corrections to the The SECM makes any necessary corrections to the
air fuel ratio by controlling the inlet fuel pressure to air fuel ratio by controlling the inlet fuel pressure to
the air/fuel mixer by modulating the dual fuel trim the air/fuel mixer by modulating the dual fuel trim
valves (FTV) connected to the regulator. Reducing valves (FTV) connected to the regulator. Reducing
the fuel pressure leans the air/fuel mixture and the fuel pressure leans the air/fuel mixture and
increasing the fuel pressure enriches the air/fuel increasing the fuel pressure enriches the air/fuel
mixture. To calculate any necessary corrections to mixture. To calculate any necessary corrections to
the air fuel ratio, the SECM uses a number of the air fuel ratio, the SECM uses a number of
different sensors to gain information about the different sensors to gain information about the
engine's performance. Engine speed is monitored engine's performance. Engine speed is monitored
by the SECM through a variable reluctance (VR) or by the SECM through a variable reluctance (VR) or
Hall Effect sensor. Intake manifold air temperature Hall Effect sensor. Intake manifold air temperature
and absolute pressure are monitored with a TMAP and absolute pressure are monitored with a TMAP
sensor. MI-07 is a drive-by-wire (DBW) system sensor. MI-07 is a drive-by-wire (DBW) system
connecting the accelerator pedal to the electronic connecting the accelerator pedal to the electronic
throttle through the electrical harness; mechanical throttle through the electrical harness; mechanical
G643 Electronic Controlled LP Engines (If Equipped) G643 Electronic Controlled LP Engines (If Equipped)
General Description General Description
uses two heated exhaust gas oxygen sensors uses two heated exhaust gas oxygen sensors
(HEGO) in the exhaust system to monitor exhaust (HEGO) in the exhaust system to monitor exhaust
gas content. One HEGO is installed in front of the gas content. One HEGO is installed in front of the
catalytic muffler and one is installed after the catalytic muffler and one is installed after the
catalytic muffler. catalytic muffler.
EMS schematic of G643E LP engine EMS schematic of G643E LP
cables are not used. A throttle position sensor (TPS) cables are not used. A throttle position sensor (TPS)
monitors monitors
accelerator pedal position sensor (APP) command. accelerator pedal position sensor (APP) command.
Even engine coolant temperature and adequate oil Even engine coolant temperature and adequate oil
pressure are monitored by the SECM. The SECM pressure are monitored by the SECM. The SECM
controller has full adaptive learning capabilities, controller has full adaptive learning capabilities,
allowing it to adapt control function as operating allowing it to adapt control function as operating
conditions conditions
temperature, fuel variations, ignition component temperature, fuel variations, ignition component
wear, clogged air filter, and other operating variables wear, clogged air filter, and other operating variables
are compensated. are compensated.
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engine
throttle throttle position position in in
change. change. Factors Factors such such
relation relation to to the the
as as ambient ambient
Operation Section Operation Section