Principle of Operation

Principle of Operation





Ignition Management provides ignition to the combustion chambers with the required voltage at the correct time. Based on the combination of inputs, the ECM calculates and controls the ignition timing and secondary output voltage by regulating the activation and dwell of the primary ignition circuits. The ECM controls and monitors the secondary ignition output including Misfire Detection.
The ECM has a very broad range of ignition timing. This is possible by using a Direct Ignition System, or sometimes referred to as "Static Ignition System" (RZV). Reliability is also increased by having separate individual ignition circuits.
The Ignition Control is determined by the ECM (load dependent). The ECM will calculate the engine load based on a combination of the following inputs:
^ Battery Voltage
^ Air Temperature
^ Camshaft Positions (Cylinder ID)
^ Accelerator Pedal Position
^ Engine Coolant
^ Knock Sensors
^ Air Flow Volume
^ Crankshaft Position / RPM
The dwell time will be regulated based on battery voltage. When cranking, the voltage is low and the ECM will increase the dwell to compensate for saturation "lag time". When the engine is running and the battery voltage is higher, the ECM will decrease the dwell due to faster saturation time.
The Crankshaft Position/RPM signals the ECM to start ignition in firing order (153624) as well as providing information about the engine operation. This input is used in combination with other inputs to determine engine load which advances/retards the ignition timing. Without this input, the ECM will not activate the ignition.





Cold start is determined by the ECM based on the engine coolant temperature and rem during start up. A cold engine will crank over slower than a warm engine, the ignition timing will range between top dead center to slightly retarded providing optimum starting.
When starting a warm engine, the rem is higher which results in slightly advanced timing.
If the engine coolant and intake air temperature is hot, the ignition timing will not be advanced reducing starter motor "load".





Multiple Ignition Pulses ensure good spark quality during engine start up. The ECM will activate the ignition coils 9 times (voltage dependent) per 720° of crankshaft revolution.
The ignition timing will be progressively advanced assisting the engine in coming up to speed. As the engine speed approaches idle rem, the timing remains slightly advanced to boost torque. When the engine is at idle speed, minimum timing advance is required. This will allow faster engine and catalyst warm up.
The multiple pulsing switches to single pulse when:
^ Engine Speed >1350 RPM (varied with engine temperature)
The timing will be advanced when the ECM observes low engine rem and increasing throttle/air volume inputs (acceleration torque). As the throttle is opened, the ECM advances the timing based on engine acceleration and at what rate. The ECM will fully advance timing for the "full throttle" position indicating maximum acceleration (torque).

MS45 Emission Optimized Ignition Key Off





Emission Optimized Ignition Key Off is a programmed feature of the MS45 ECM.
After the ECM detects KL15 is switched off, the ignition stays active (ECM Relay/voltage supply) for two more individual coil firings.
This means that just two cylinders are fired not two revolutions.
This feature allows residual fuel injected into the cylinders, as the ignition key is switched off, to be combusted as the engine runs down.





When KL15 is switched off the I ECM operating voltage is removed.
The ECM will maintain a ground to the Engine Control Module Relay for a few seconds to maintain ignition coil activation.
The HEM signal represents the amount of intake air volume. This input is used by the ECM to determine the amount of timing advance to properly combust the air/fuel mixture.
The Air Temperature Signal assists the ECM in reducing the risk of detonation (ping). If the intake air is hot the ECM retards the ignition timing. If the intake air is cooler, the ignition timing will be advanced.
As the throttle is closed, the ECM decreases the ignition timing if the rem is above idle speed (coasting). This feature lowers the engine torque for deceleration. When the engine rem approaches idle speed, the timing is slightly advanced to prevent the engine from stalling. The amount of advance is dependent upon the engine temperature and the rate of deceleration.
Knock Control allows the ECM to further advance the ignition timing under load for increased torque. This system uses two Knock Sensors located between cylinders 1,2,3 and between cylinders 4,5,6. Knock Control is only in affect when the engine temperature is greater than 35°C and there is a load on the engine. This will disregard false signals while idling or from a cold engine.





Based on the firing order, the ECM monitors the Knock Sensors after each ignition for a normal (low) signal.
If the signal value exceeds the threshold, the ECM identifies the knock and retards the ignition timing (3°) for that cylinder the next time it is fired. This process is repeated in 3° increments until the knock ceases.
The ignition timing will be advanced again in increments to just below the knock limit and maintain the timing at that point.
If a fault is detected with the Knock Sensor(s) or circuits, the ECM deactivates Knock Control. The ignition timing will be set to a conservative basic setting (to reduce the risk of detonation) and a fault will be stored. The Malfunction Indicator Light will be illuminated when the OBD II criteria is achieved.