Electronic System
Overview
i07797269
System Overview
The engine is designed for electronic control of most
engine operating functions. The electronic system
consists of an Electronic Control Module (ECM), the
wiring harness, switches, sensors, and fuel injectors.
The engine ECM receives information from the
sensors and the switches on the engine. The engine
ECM processes the information that is collected to
control the engine. By altering the fuel delivery with
the fuel injectors, the engine ECM controls the speed
and the power that is produced by the engine. The
aftertreatment system is controlled by the engine
ECM.
The following information provides a general
description of the control system. Refer to the
Systems Operation manual for detailed information
about the control system.
System Operation
Engine Governor
The ECM governs the engine. The ECM determines
the timing, the injection pressure, and the amount of
fuel that is delivered to each cylinder. These factors
are based on the actual conditions and on the
desired conditions at any given time during starting
and operation.
For variable speed engines, the ECM uses the
throttle position sensor to determine the desired
engine speed. The ECM compares the desired
engine speed to the actual engine speed. The actual
engine speed is determined through interpretation of
the signals that are received by the ECM from the
engine speed/timing sensors. If the desired engine
speed is lower than the actual engine speed, the
ECM allows more fuel to be injected, increasing
engine speed.
Timing Considerations
Once the ECM has determined the amount of fuel
that is required, the ECM must determine the timing
of the fuel injection.
The ECM adjusts timing for optimum engine
performance and for the fuel economy. Actual timing
and desired timing cannot be viewed with the
electronic service tool. The ECM determines the
location of top center of the number one cylinder from
the signals that are provided by the engine speed/
timing sensors. The ECM determines when injection
should occur relative to the top dead center position.
The ECM then provides the signal to the injector at
the correct time.
Fuel Injection
The common rail fuel system is controlled by the
ECM. The ECM gathers data from several sensors
on the engine. The ECM then uses this data to adjust
the quantity of fuel being delivered as well as the
timing of the injection event. The injection event
begins when the ECM sends a signal to the injector
solenoid to actuate the valve inside the injector. As
the valve opens, the fuel flows from the fuel rail,
through the fuel line, and into the injector. As the
valve opening pressure is reached, the valve is lifted
and the fuel is delivered at high pressure into the
combustion chamber.
The flash file inside the ECM establishes certain
limits on the amount of fuel that can be injected. The
“Smoke Limit Fuel” is a limit that is based on the
intake manifold pressure. The “Smoke Limit Fuel” is
used to control the air/fuel ratio for control of
emissions. When the ECM senses a higher intake
manifold pressure, the ECM increases the “Smoke
Limit Fuel” . A higher intake manifold pressure
indicates that there is more air in the cylinder. When
the ECM increases the “Smoke Limit Fuel” , the ECM
changes the control signal to the injector. The signal
will allow more fuel into the cylinder.
The “Torque Limit Fuel” is a limit that is based on the
power rating of the engine and on the engine rpm.
The “Torque Limit Fuel” is like the rack stops and the
torque spring on a mechanically governed engine.
The “Torque Limit Fuel” provides the power curves
and the torque curves for a specific engine family and
a specific engine rating. All these limits are
determined at the factory. These limits cannot be
changed.
Other ECM Functions for
Performance
The ECM may also provide enhanced control of the
engine for functions such as controlling the cooling
fan. Refer to Troubleshooting, “Configuration
Parameters” for supplementary information about the
systems that can be monitored and controlled by the
ECM.
10 UENR4469-36
Electronic System Overview
Copyright of Perkins Engine Company Limited. NOT FOR REPRINTING OR RESALE
To Next Page
Loading...
