812935 1 Mercury SCREW, Pilot Adjust

Control System
The following components are included in the control system:
An Electronic Control Module (ECM) and an emergency stop button in an engine-mounted junction box
Optional remote control panel with either an Operator Control Panel (OCP) or Human Machine Interface (HMI)
Integrated Sensing Module (ISM)
Fuel metering valve
Gas Shutoff Valve (GSOV)
Ignition system that is controlled by the ECM
Detonation sensor for each two cylinders
A system for prelube or postlube that includes a solenoid and prelube pump
Actuators that are hydraulically actuated and electronically controlled for the air choke and the exhaust bypass (wastegate)
A system for cranking that includes the solenoid and starting motor
Air/Fuel pressure module (G3616)The ECM controls most of the functions of the engine. The module is an environmentally sealed unit that is in an engine-mounted junction box. The ECM monitors various inputs from sensors to activate relays, solenoids, and so on, at the appropriate levels. The ECM supports the following five primary functions:
Governing of the engine
Control of ignition
Air/fuel ratio control
Start/stop control
Monitoring of engine operationThe ECM does not have a removable personality module. The software and maps are changed by using the Cat ET to flash program a file.Governing of the Engine RPM
Desired engine speed is determined by these factors: status of the idle/rated switch, status of the desired speed input (analog voltage, 4 mA to 20 mA, or CAN) and of parameters that are programmed into the software. Actual engine speed is detected via a signal from the engine speed/timing sensor. Parameters such as idle speed and governor gain can be programmed with Cat ET, but the governor gain should not be programmed.The ECM monitors the actual engine speed. The ECM calculates the difference between the actual engine speed and the desired engine speed. The ECM controls the fuel metering valve to maintain the desired engine speed. The fuel metering valve is located in the gas line after the GSOV.If actual engine speed is less than desired engine speed, the ECM commands the fuel metering valve to move toward the open position to increase the fuel flow. The increase of fuel accelerates the engine speed.The speed governor gain adjustments Proportional (P) and Integral (I) are available in Cat ET. The speed governor gain adjustment Derivative (D) does not exist in the software.The air/fuel ratio control gains adjustment is not available in Cat ET for Adem 4 (A4) controlled engines.G3606, G3608, and G3612
The fuel flow is controlled by the desired air/fuel ratio until 500 rpm.
The airflow is calculated using the engine speed, IMAT, and Intake Manifold Air Pressure (IMAP).
The desired fuel flow is calculated based on the airflow and desired air/fuel ratio.The speed governor turns on at 500 RPM.
The speed difference drives change to the desired fuel flow.G3616
The fuel metering valve is in a fixed position until 250 RPM.The speed governor turns on at 250 RPM.
The speed difference between the actual speed and the desired speed drives the change in the fuel metering valve position.Control of Ignition
Each cylinder has an ignition transformer. To initiate combustion, the ECM sends a pulse of approximately 108 V to the primary coil of each ignition transformer. The pulse is sent at the appropriate time and for the appropriate duration. The transformer increases the voltage which creates a spark across the spark plug electrode.The ECM provides variable ignition timing that is sensitive to load, speed, and detonation. Detonation sensors monitor the engine for excessive detonation. The engine has one detonation sensor for each two adjacent cylinders. The sensors generate data on vibration that is processed by the ECM to determine detonation levels. If detonation reaches an unacceptable level, the ECM retards the ignition timing of the whole engine. If retarding the timing does not limit detonation to an acceptable level, the ECM shuts down the engine.Levels of detonation can be displayed by the OCP or HMI on the optional control panel. Alternatively, the "Cylinder X Detonation Level" screen of Cat ET can also be used. The "X" represents the cylinder number.An Ignition Multi-Strike feature is an option that is programmable. The Ignition Multi-Strike feature must be activated by a Caterpillar dealer.The ECM provides extensive diagnostics for the ignition system.Air/Fuel Ratio Control
The ECM provides control of the air/fuel mixture for performance and for efficiency at low emission levels. The system includes the following components: maps in the ECM, output drivers in the ECM, fuel metering valve, air choke actuator, exhaust bypass actuator (wastegate), and ISM. Illustrations 1 and 2 are diagrams of the system main components and of the system lines of communication.
Illustration 1 g03789900
G3606 and G3608
Illustration 2 g03795220
G3612 and G3616
The desired air/fuel ratio is based on maps that are stored in the ECM. The maps are specific for different applications, for engine speeds, and for engine loads.The engine load is calculated from the fuel flow. The load calculation starts at 500 rpm and the load reads zero below 500 rpm.Note: The calculated engine load varies. Several variables affect the calculated engine load, including timing, settings for emissions, fuel quality, and specific gravity of the fuel.G3606, G3608, and G3612The volume of fuel that is consumed by combustion is calculated by the TecJet measuring the following conditions:
Fuel inlet pressure
Fuel temperature
TecJet differential pressureG3616The volume of fuel that is consumed by combustion is calculated by measuring the following conditions:
Pressure differential between the fuel manifold and the inlet air manifold
Temperature of the fuel to the cylinder
Engine rpmThe system has three modes of operation for the air/fuel ratio:
Start-up mode (fixed actuator positions)
NOx feedback disabled mode (open loop and prechamber calibration operates in this mode)
NOx feedback enabled mode (closed loop NOx control)The relationship of the modes of operation to the speed and load and the transitions between the modes are represented in Illustrations 3 and 4.The modes of operation are explained in more detail below.
Illustration 3 g03807798
G3606, G3608, and G3612
Illustration 4 g03808256
G3616
The NOx feedback enabled mode and air system initialization thresholds have high and low speed (and high/low load for NOx feedback) values. If t