838811 Volvo.Penta Tachometer

Electronic Controls
Electronic Control Module
The ECM consists of two main components, the control computer (hardware) and the personality module (flash file). 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 personality module 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 measured by the engine speed/timing signal.Fuel Injection
The engine ECM controls the timing, the duration, and the pressure 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 following conditions: desired engine rpm and load. The ECM detects the top center of each cylinder. The ECM sends an injection signal at the desired time.Cold Cylinder Cutout
During a cold start or extended periods at low idle, the engine ECM will automatically turn off one unit injector at a time in order to determine if the cylinder is firing. If the ECM determines that the cylinder is not firing, the ECM turns off the unit injector. If the ECM determines that the cylinder is firing, the ECM turns on the unit injector. This strategy improves engine starting. This strategy reduces the following: white smoke, the use of ether injection and warm-up time.Cold Mode Operation
Cold mode controls fuel injection timing when the engine is cold. When the engine is cold, controlling the fuel injection timing reduces the possibility of engine damage. When the engine is cold, controlling the fuel injection timing helps minimize white smoke.Cold mode is activated whenever the engine coolant temperature is below 70 °C (158 °F). Cold mode remains active until the engine coolant temperature is warmer than 73 °C (163 °F).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 of the personality module at the factory."Multi-Torque" and "Dual Horsepower" Selection
This feature allows the use of a 3516B engine to be installed in a 793B Off Highway Truck. The feature permits the use of different torque maps for different transmissions. The feature reduces the number of software part numbers that are required for operation. The feature protects the transmission from excessive torque.The selection of "Multi-Torque" and "Dual Horsepower" is available through the Caterpillar Electronic Technician (ET). If you select "Dual Horsepower", the engine ECM will use the low power 1611 kW (2160 hp) torque map for all transmission gears. If you select "Multi-Torque", the engine ECM will request the serial number of the transmission from the transmission ECM.Note: If the transmission ECM does not communicate with the engine ECM, the engine ECM will use the default 1611 kW (2160 hp) torque map. You may think that the low power is an engine problem. The problem is really the failure of communications between the transmission ECM and the engine ECM. The Cat ET will continue to display "Multi-torque" on the Cat ET configuration screen in this circumstance. Power down the machine and then restart the machine. The ECM will then reset the display to the default "Dual Horsepower" configuration.If the transmission ECM responds with the 793C transmission, then the engine ECM will use the 1611 kW (2160 hp) torque map for the "CONVERTER DRIVE". In the "DIRECT DRIVE" gears 1 through 5, the engine ECM will use a 1716 kW (2300 hp) torque map. In the "DIRECT DRIVE" gear 6, the engine ECM will use a second 1716 kW (2300 hp) torque map with a different torque shade.Rating Selection 777D Only
This feature allows the 3508B to simulate the performance of the 3508A in the 777C.When you select "Rating Number" a window will open up allowing you to select the 745 kW (1000 hp) rating or the 686 kW (920 hp) rating. No password is required for this feature and no transmission serial numbers are checked. Block Diagram of Electronic Governor
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Typical schematicEngine Wiring Diagram
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Typical schematicEngine Wiring Diagram
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Typical schematicLocation of the 3508B Engine Sensors
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Front view (1) ECM connector J2/P2 (2) Atmospheric pressure sensor (3) Connector for the engine fan speed sensor (4) Turbocharger compres