SPROCKET GP 3A6604 - Caterpillar

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.The governor uses the throttle position sensor to determine the desired engine speed. The governor 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 greater than the actual engine speed, the governor injects more fuel in order to increase engine speed.
Illustration 2 g01860934
Typical example
The desired engine speed is typically determined by one of the following conditions:
The position of the throttle
The desired engine speed in Power Take-Off (PTO)Timing Considerations
Once the governor has determined the amount of fuel that is required, the governor must determine the timing of the fuel injection. Fuel injection timing is determined by the ECM after considering input from the following components:
Coolant temperature sensor
Intake manifold air temperature sensor
Intake manifold pressure sensor
Barometric pressure sensorThe ECM adjusts timing for optimum engine performance and for 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 top center. The ECM then provides the signal to the injector at the desired time.Fuel Injection
The ECM sends a high voltage signal to the injector solenoids in order to energize the solenoids. By controlling the timing and the duration of the high voltage signal, the ECM can control the following aspects of injection:
Injection timing
Fuel deliveryThe flash file inside the ECM establishes certain limits on the amount of fuel that can be injected. The "FRC Fuel Limit" is a limit that is based on the intake manifold pressure. The "FRC Fuel Limit" 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 "FRC Fuel Limit". A higher intake manifold pressure indicates that there is more air in the cylinder. When the ECM increases the "FRC Fuel Limit", the ECM allows more fuel into the cylinder.The "Rated Fuel Limit" is a limit that is based on the power rating of the engine and on the engine rpm. The "Rated Fuel Limit" is like the rack stops and the torque spring on a mechanically governed engine. The "Rated Fuel Limit" provides the power curves and the torque curves for a specific engine family and a specific engine rating. All of these limits are determined at the factory. These limits cannot be changed.Customer Parameters and Engine Speed Governing
A unique feature with electronic engines is customer specified parameters. These parameters allow the owner of the machine to fine-tune the ECM for engine operation.