Synchronize Fuel Injection And Firing Order Function - GF07.10-P-1006KJ
ENGINE 281.910 in MODEL 453.0/3/4
Function requirements synchronization of fuel injection and firing order, general points
- Circuit 87 (Engine management ON)
- Engine runs
Synchronization of fuel injection and firing order, general points
Synchronization of the injection and firing order is achieved by the ME-SFI [ME] control unit (N3/10) for actuation of cylinder 1 ignition coils (T1/1) to cylinder 3 ignition coils (T1/3) and the cylinder 1 injection valve (Y62/1) to cylinder 3 injection valve (Y62/3).
Furthermore, synchronization is required for knock control and fuel shutoff on the individual cylinders. The ME-SFI [ME] control unit synchronizes the injection and firing order using the following signals:
- Intake camshaft Hall sensor (B6/15), intake camshaft setting
- Crankshaft position sensor (L5), engine speed and crankshaft position
Function sequence for synchronization of the fuel injection and firing order
The function sequence is described in the following steps:
- Function sequence for synchronization
- Function sequence for coasting detection
- Function sequence for engine speed signal
Function sequence for synchronization
When starting the engine, the injection sequence is specified to match the firing order. To do this the voltage signals are read in by the crankshaft position sensor and by the intake camshaft Hall sensor. The ignition TDC (Top Dead Center) from cylinder 1 is detected by the crankshaft position sensor.
Function sequence for coasting detection
When the engine shut down coasting detection is started, which also evaluates the engine turn back shortly before standstill. During a computer run on from the ME-SFI [ME] control unit, the determined rest position of the crankshaft as a°CKA is stored and used for the next engine start. If coasting detection does not produce a result, or the engine has been turned while shut down, injection and firing order are synchronized at engine start.
Function sequence for engine speed signal
Using the signal from the crankshaft position sensor, the ME-SFI [ME] control unit generates the short circuit-proof engine speed signal (for example for cold testing and diagnosis) and outputs via the interior CAN (CAN B) to the driver-side SAM control unit (N1011).
When the crankshaft is turning, a voltage signal (AC voltage) is generated in the crankshaft position sensor by the webs on the sensor rotor. Here, each tooth generates a voltage pulse. No voltage is generated at the gap where there are 2 missing teeth. The engine speed signal is a square wave signal with a constant on/off ratio of 3 pulses per engine revolution (360°CKA) and a maximum current of approx. 20 mA.
direction recognition
If the engine rotates backwards, something which can only happen sporadically, briefly before standstill, after the engine has been stopped, then the pulse duration for the 0 V-pulse is altered. The ME-SFI [ME] control unit can thereby determine any change in direction of rotation and thus record the exact angular position of the crankshaft at any given time. This information is, in particular, needed for rapid starting of the engine using the ECO start/stop function (with code B03 (ECO start/stop function)).
If no voltage signal is received from the crankshaft position sensor, the voltage signal from the intake camshaft Hall sensor is used instead (for limp-home mode). For limp-home mode the max. rotational speed is 3000 rpm.
| Electrical function schematic, synchronization of the injection and firing order | PE07.10-P-2706-97BBA | ||
| Overview of system components motor electronics (ME-SFI) fuel injection and ignition system | GF07.61-P-9997KJ |