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Electronic Controls
Electronic Control Module
The ECM consists of two main components, the control computer (hardware) and the flash file (software). The control computer consists of a microprocessor and electronic circuitry. The flash file contains the engine's operational characteristics. The operating maps influence the engine's performance.Engine Governor
The engine ECM governs engine speed. The engine ECM and the flash file work together by controlling the amount of fuel that is delivered by the injectors. Desired engine rpm is determined by the throttle position sensor signal and certain sensor readings. Diagnostic codes may derate the engine. Actual engine rpm is monitored by the engine speed/timing sensor.Fuel Injection
The ECM controls the timing and the amount of fuel that is delivered to the cylinders. This determination is based on the actual conditions and the desired conditions at any given time.The ECM compares the desired engine speed to the actual engine speed. The actual engine speed is determined via a signal from the engine speed/timing sensor. If the desired engine speed is greater than the actual engine speed, the ECM injects more fuel in order to increase the actual engine speed.The ECM controls the amount of fuel that is injected by varying the signals to the injectors. The injectors will pump fuel only if the injector solenoid is energized. The ECM sends a high voltage signal to the solenoid. This high voltage signal energizes the solenoid. By controlling the timing and the duration of the high voltage signal, the ECM can control injection timing and the amount of fuel that is injected.FRC Limit
The flash file inside the engine ECM sets certain limits on the amount of fuel that can be injected. The FRC limit is a limit that is based on the boost pressure. The boost pressure is calculated as the difference in pressure between atmospheric pressure and turbocharger outlet pressure. The FRC limit is used to control the air/fuel ratio for control of emissions. When the engine ECM senses a higher boost pressure, the engine ECM increases the FRC limit. A higher boost pressure indicates that there is more air in the cylinder. When the engine ECM increases the FRC limit, the engine ECM allows more fuel into the cylinder.Rated Fuel Position
The rated fuel position is a limit that is based on the power rating of the engine. The rated fuel position is similar to the rack stops and the torque spring on a mechanically governed engine. The rated fuel position determines maximum power and torque values for a specific engine family and a specific rating. The rated fuel position is programmed into the flash file at the factory.Cold Mode Operation
The ECM limits engine power during cold mode operation and the ECM modifies injection timing during cold mode operation. Cold mode operation provides the following benefits:
Increased cold weather starting capability
Reduced warm-up time
Reduced white smokeCold mode is activated whenever the engine coolant temperature falls below 18 °C (64 °F). Cold mode remains active until the engine coolant temperature rises above 20 °C (68 °F) or until the engine has been running for 14 minutes.Once the ECM determines the amount of fuel that is required, the ECM must determine the timing of the fuel injection. The ECM determines the TOP CENTER position of each cylinder from the engine speed/timing sensor's signal. The ECM calculates the fuel injection timing relative to the top center position of the individual pistons. The ECM also provides the signal to the injector at the desired time. The ECM adjusts timing for optimum engine performance, optimum fuel economy, and optimum control of white smoke.Injection Actuation Pressure Control System
The injection actuation pressure control valve (IAPCV) that is internal to the unit injector hydraulic pump is a precision displacement control actuator. This actuator controls the swashplate angle for the variable displacement unit injector hydraulic pump. The swashplate angle controls the pump output flow to the injectors. The injection actuation pressure sensor provides a sensor signal to the ECM. The sensor signal represents the output pressure of the unit injector hydraulic pump. A desired pressure is calculated by the ECM and a control signal is sent to the IAPCV.Starting Aids
The following devices (if equipped) are used in order to improve the starting of the engine in cold weather conditions.
Air inlet heater
Ether injectionThe ECM maintains full control of the air inlet heater and of the ether injection system.