812996 2 Mercury COVER

Electronic Controls
The engine's electronic system consists of the ECM, the engine sensors, the fuel injection system, and the vehicle interface. The ECM is used to control the operation of the engine. The ECM flash file contains the software that is used to program the ECM. The flash file contains the operating maps that define the following characteristics of the engine:
Horsepower
Torque curves
Engine speed (rpm)Engine Governor
The ECM provides the functionality of the engine governor.The ECM determines the timing, the duration and the pressure of injection. The amount of fuel that is delivered to the cylinders is precisely controlled by the ECM. This control is based on the actual conditions and the desired conditions at any given time during starting and operation of the engine.An accelerator pedal position sensor is used to determine the desired engine speed. The ECM compares the desired engine speed to the actual engine speed. The actual engine speed is calculated from signals that are generated by the engine speed/timing sensors. If the desired engine speed is greater than the actual engine speed, the ECM adjusts the signal that is sent to the injectors and the fuel system's high pressure oil pump in order to reduce the engine speed. The ECM continuously monitors the engine for actual conditions in order to adjust for desired conditions.
Illustration 1 g01120999
Typical exampleThe desired engine speed is typically determined by one of the following conditions:
The position of the accelerator pedal
The desired vehicle speed in cruise control
The desired engine rpm in PTO controlTiming Considerations
The ECM determines the fuel injection timing. In addition to desired engine speed and actual engine speed, the following inputs are used by the ECM in order to calculate the engine timing:
Coolant temperature
Intake manifold air temperature
Atmospheric pressure
Boost pressureThe signal from the engine speed/timing sensor is used by the ECM to determine the orientation of the crankshaft. This signal is used by the ECM to calculate an output for the injector solenoids relative to the top center position of each piston. The injection signal is adjusted for optimum engine performance, for fuel economy, and for the control of white smoke. The injection signal is output to each injector solenoid at the optimum time.Fuel Injection
The ECM controls the injection timing and injection duration by varying the output signals to the injectors. The injectors pump fuel into the cylinder only while the injector solenoid is energized. The ECM outputs a high voltage signal to the injector solenoid in order to energize the solenoid. Energizing the injector solenoid actuates a seated pin inside the injector. The pin is seated and the injection actuation pressure increases within the fuel injector body. The hydraulic force that is provided by the actuation pressure is used to move an intensifier piston in the body of the injector. The intensifier piston multiplies the hydraulic force that is transfered to the fuel. As the force of the pressurized fuel overcomes the spring tension that is used to seat the nozzle check, fuel injection occurs.Precise control of the injection actuation pressure and of the injector solenoid allows the ECM to deliver fuel over a varied rate during a single injection. This strategy provides the engine with optimum fuel economy and with strictly controlled emissions.The software that is used to control the ECM provides instructions for the amount of fuel that can be injected into the cylinder. The "FRC Fuel Limit" is a limit that is based on the boost pressure. The "FRC Fuel Limit" is used to control the air/fuel ratio for the control of emissions. When the ECM senses a higher boost pressure, the ECM increases the "FRC Fuel Limit". A higher boost pressure indicates that the density of air that is entering the cylinder is being increased. When the ECM increases the "FRC Fuel Limit", the ECM also adjusts the signals to the fuel system. This adjusts the delivery of fuel to the cylinders.The "Rated Fuel Limit" is a limit that is based on the power rating of the engine and of engine rpm. The "Rated Fuel Limit" is similar to the rack stops and the torque spring on a mechanically governed engine. The "Rated Fuel Limit" defines the power curves and the torque curves for a specific engine family and for a specific engine rating. All of these limits are determined at the factory. These limits are contained in the ECM software and these limits cannot be changed. Injection Actuation Pressure Control System
The ECM controls injection actuation pressure by controlling the output current to the injection actuation pressure control valve (IAPCV). The IAPCV utilizes the movement of spool valves that are inside the high pressure oil pump to control pump outlet pressure. By adjusting flow of control oil to the spool valves, the IAPCV controls the injection actuation pressure that is provided to the injectors. This determines the pressure of the fuel that is injected into the cylinder by the injectors.The injection actuation pressure sensor provides a signal to the ECM that represents the pressure of the oil that is in the high pressure oil manifold. The injection actuation pressure sensor's signal is compared by the ECM to the desired injection actuation pressure. The desired injection actuation pressure is a calculated value that is based on sensor inputs, on control maps, and on power demands of the engine. The difference between the actual pressure and the desired pressure is used by the ECM to calculate adjustments to the control current that is output to the injection actuation pressure control valve. The ECM provides continuous monitoring and precise control of the pressure that is in the high pressure oil manifold.High pressure oil is routed from the high pressure oil pump to the high pressure manifold through a steel tube. From the manifold, the oil is routed into each injector. All injectors have a constant supply of oil while the engine is running. Disabling the electrical signal to the injector solenoid does not interrupt the flow of high pressure oil that is available to the fuel injector."Basic" Systems and "Full Feature"