SHAFT 8C2252 - Caterpillar

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 engine ECM controls the timing and the duration of the fuel that is injected. The engine ECM varies the signals to the fuel injectors. Fuel is injected only while an injector solenoid is energized by a 105 volt signal from the engine ECM. The timing of the injection signal determines the engine timing. The length of the injection signal determines engine speed. By controlling the timing and duration of the 105 volt signal, the ECM controls the engine speed.Injection timing depends on the desired engine rpm and load. The ECM detects the top center of each cylinder. The ECM sends an injection signal at the desired time.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.